Resolution – fotosaurier

Resolution of Lenses (Sharpness) on Analog Film – Compared to Digital Sensors

This article describes, how I made the resolution-power of lenses digitally measurable on analog film and COMPARABLE to the data, which are directly measured on digital sensors.

Since a long time I am looking for an experimental set-up, which allows me to understand, how the information content of the exposure on an analog film compares to the digital data from a digital sensor – looking through the same lens. Resolution being the main point of interest for me in this case.

FAZIT of this article is: I just found a method to do this … and it works!

Fig. 1 is an example of the resolution-chart, generated with Olympus OM Zuiko Auto-W 28mm f/2.8 lens on black and white negative film (Agfa APX100) at the lenses optimum aperture f/5.6. It shows the MTF30-resolution-values from center to corner (21,7 mm picture-circle-radius):

Spoiler-Bild-Imatest-on-Film — **Fig. 1**: Resolution measured digitally on analog 35mm-film: The maximum mean resolution value, measured in the center (1.237 LP/PH), corresponds to **100 lines/mm on Film.** At f/8.0 the resolution is even more uniform over the frame – but a bit lower in the center. – source: fotosaurier

1. Introduction: Quality of historical lenses.

Until the end of the last milennium, photographic lenses were designed to generate highly detailed images on film (or glass-plates coated with light sensitive layers).

When at the beginning of the millennium 2000 ff the radical change to digital sensors for the recording of photographic pictures happened within a few years, the photographic community sat on a huge number of phantastic and beloved lenses for the ancient analog recording method with film. We all could not believe, that all these wonderful and iconic lenses would become useless.

This was a strong motivation, to put the historical lenses in front of the sensor-driven digicams! Knowing very well …

… that for the very special needs of digital imaging sensors, new lenses had to be designed under consideration of some special optical features along the optical path behind the lens, before the light hits the light sensitive elements.

The older „analog“ glass is not perfectly fitting to these conditions! … but what are the artefacts on sensors and how important are they?

Measuring the Modulation Transfer Funktion (MTF) of a lens is a fundamental method to characterize the optical resolution of a lens itself – independant from the recording method (film or digital sensors): the direct optical measurement of the MTF-curve over the imaging circle of a lens shows the contrast as a function of the „spatial frequency“– these data today often being available from the lens-makers. Historically, the method was developed parallel to each other by Zeiss and Angénieux (during the 2nd world-war). Fig. 1 shows the certificate, which was delivered with my Angénieux zoom-lens as a qualitiy-proof (showing that this is an extraordinary example … above average expectations!).

Angén-Certificate_70-210_IMG_9574 — **Fig. 1**: MTF-curve and actually tested contrast-value (86% at 20 cycles/mm) in a certificate for the Angénieux-Zoomlens 70-210mm f/3.5. The graph shows in the lower curve the lowest contrast transfer-limit at which the lens is accepted for delivery – source: fotosaurier/Angénieux

Reminder: One „cycle/mm“ is two lines/mm! Two lines (one black + one white!) are the spatial (linear) cycle. We call this here in my article „Linepairs = LP„. In the systematics, which I personally use in the IMATEST-software, the resolution is always defined as „Linepairs per Picture Height = LP/PH„, where the picture height on film or sensor always is 24mm (for 35mm stills) … if not otherways stated. That means:

For 35mm stills (24mm x 36mm) the data in „LP/PH“ can be converted into „cycle/mm“ with division by 24, or into lines/mm with division by 12.

Fig. 2 shows the type of MTF-plots, which are today typically used as the contrast over the radius of the image-circle:

MTF-curves Fujinon 56f1,2_eng — **Fig. 2**: Modern version of a MTF-curve, showing the contrast of a lens over the picture-circle (APS-C-format!) for two different spatial frequencies – separated for sagittal and meridional rays – source: Fujifilm

These lens-specific-informations are perfect to characterize the lens – but do not help me, in the case of historical lenses, for which these data are mostly not available. For these I have to measure the performance myself – either using analog film or the digital sensor.

In historical times (1960s to at least 90s) tests of „Lens Performance“ were published in several US-publications like „Modern Photography“ and „Popular Photography“ and others targeting on amateur photographers.

These mostly used the „USAF 1951“ target, which was mounted on a flat wall and photographed at scale 50:1 on b&w negative film and read by inspection with a loupe of defined enlarging power directly on the film strip,

SilverFast_Resolution_Target_USAF_1951 — **Fig 3**: Resolution Target „USAF 1951“ – source: By LaserSoft Imaging – Eigenes Werk, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=12126324

Results from these test were as shown in the following picture:

AnalogResol_OM24f2,8_ModernPhotgr — **Fig. 4:** Unfortunately I did not find the analog test results of the 28mm f/2.8 Zuiko Auto-W, which I use as my test reference in this article – ths is the test of it’s sister-lens with 24mm focal length. I have tested both with IMATEST on A7R4 Sensor and found, that in the corners, the 28mm-lens is **much better** in resolution than this example – source: Modern Photography

I tried this method myself in the 1970s and can tell you: it’s a lot of work!

2. The digital IMATEST lens testing method and software for digital imaging:

Testing the optical performance on a digital sensor is facing several facts and influences, which are new and specific: pixel size, algorithm, problems of digital signal-processing systems like aliasing, additional optical elements in the optical path like glass-filters and micro-lenses!

The question: is there an essential influence of all these optical systems on the visual result in the picture over the picture-circle (Bildkreis), e.g. because of the varying angles at which the light-rays hit on the sensors between center and the farthest corner of the picture format or due to the additional optical elements introduced into the light-path?

In the case of RANGEFINDER-lenses we know that there often is a strong influence of this. These lenses are often made for a very short distances between the last lens and the film – especially for wideangle- and standard-lenses. Little was known to me about historical SLR-lenses, which were never planned and calculated for the use with modern digital sensors.

Since several years I do quite a few measurements on historical lenses, using a high-resolution digital sensor with 62,5 Mega-Pixels, resulting in 61 MP effectively on Full Format (35mm stills).

Until now I did not know, whether the measurement of my historical lens is falsified due to artefacts, genrated by the digital recording system. The work, described in this article, was done, to clearify this situation.

I just want to know: how does picture quality of historical SLR-lenses on the analog film compare measurably to that delivered by digital sensors?

Digital cameras are really big number-crunching-machines! And with the right software, I can use the numbers to generate a numerical picture of the optical quality of the lens-sensor-combination. IMATEST is such a software and it uses standardised TARGETS to do that. I use the following target:

DSC03033_Macr-Yashica_55f2,8_5,6-foc Kopie — **Fig 5**: **SFRplus** target for Imatest – it’s height is 783 mm between the horizontal black bars, which means, that the reproduction ratio on film is 33:1 – source: fotosaurier/Imatest – original information graphics from IMATEST

Over years I did – like many other amateur-photographers – compare real-world photos of analog vs. digital processing. But I was never satisfied, because this method gave me only subjective impressions – it did not create reproducible figures, to generate a precise description of the results!

I collected intensive experience with IMATEST on more than 150 lenses over meanwhile 5-6 years using the digital pictures generated by digital sensors (4,9 to 102 Megapixels) of seven different DIGICAMS. During this time, my Standard Digicam to compare lenses was (and still is) Sony A7R4 (60 Megapixels) – since it had arrived in the market (2018/19).

IMATEST (Studio) software delivers MTF-based resolution data – as it can do that separately in three RGB-channels, it also delivers lateral CA-data. Using the Target structure of Fig. 5, the software selects 46 local areas, and runs the MTF-measurement automatically for all these 46 areas. The following picture demonstrates the automatic areas, which are typically selected – but you could choose others as well:

ROI-chart (standard) — **Fig. 6**: The **46 magenta rectangles** (called „**ROI**„) frame the Edges in the target, at which the 46 MTF-measurements are made – source: fotosaurier/Imatest

These are the curves, which are generated from each digital picture (black&white):

Zusammenstellung_IMATEST_A7R4_OM28d2,8_2,8 — **Fig**. 7: Summary of the IMATEST-results for the **OM28mm f/2.8** at open aperture f/2.8 **on Sony 60 MP-sensor** (A7R4) – explanation see text beneath – the graph lower left corresponds to the type of graph in Fig 1., the right graph corresponds to the type of pictures in Fig. 2 – source: fotosaurier

The upper left curve shows the edge-profile at center of the target (ROI no. 1, which is the left (vertical) edge of the center square in Fig. 6). From this graph the edge-rise between 10% and 90% is taken from the x-coordinate in pixels. The lower left curve is the MTF-curve (contrast over spatial frequency) for the same location. From this graph the MTF30 value (Frequency at 30% contrast) is taken: follow the horizontal line at 0,3 MTF-value to its section with the curve and take the frequency on the abscissa. The right curve shows the MTF30-values of ALL 46 ROIs plotted over the distance from the center in the 35mm-fframe.

I have resumed the IMATEST test-method in more detail in this article here in my blog!

3. Digital measurement of resolution on analog film

Now I decided to make the following experiment:

Take a photograph of the IMATEST-target on analog film;
digitize the picture with a film-scanner;
analyse the resulting digital picture with IMATEST.

For the tests, which I describe here, I used the following hardware:

28mmf2,8-on-OM4Ti_DSCF1655_blog — **Fig. 8**: Analog SLR Olympus OM-4 Ti with Zuiko Auto-W 28mm f/2.8, loaded with „fresh“ Agfa APX100

Camera for the shooting on analog-film: Olympus OM-4Ti
Lens: Olympus Zuiko Auto-W 28mm f/2.8 (Ser.no. 232073)
Film: B&W negative film AgfaPhoto APX100, iso100, developed in Rodinal 1+25 (8′)
Scanner: reflecta RPS 10M film scanner

The OM-4Ti (about 25 years old) and the lens (nearly 50 years old) work still perfect. I let the OM-4Ti automatically generate the exposure time: from 0.4 seconds to 1/250 seconds. The densitiy of the negatives was very constant on the film-strip!

Why I chose the OM 28mm f/2.8 I will be explained in the next article „My crazy lenses – One Lens + Seven Cameras: Olympus OM 28mm f/2.8 – Analog vs Digital – Part I: Analog“ …

With this method I hope to use the full analyzing-power of IMATEST-software on a picture-frame, which is generated through the lens WITHOUT the typical artefacts, which digital sensors MAY generate in the optical path of a historical lens.

ON THE FILM we have now the IMATEST target-pattern, which allows to make a fast and powerfull analysis of optical data over the full picture frame – very close to the edges and into the corners. This pattern is superimposed by the typical grain-structure of the light sensitive layer – and potential light-diffusion-effects within the film thickness. Both (analog) effects LIMIT the resolution, which can be achieved on FILM.

My first and major interest was always focused on the observation of the enormous difference between the center-resolution (see Fig. 7), which is digitally measured on A7R4 with ca. 2,800 LP/PH or higher) and corner-resolutions of 400-600 LP/PH on the sensor .

With other words: are the low values on edges and in coners of the frame, measured with the digital sensors, an artefact, caused by the change of angle, under which the light-rays are hitting the sensor (or by the filter stack)? We know definitely about these effects with rangefinder-lenses, which have a very short back-distance between last lens and film, causing big trouble on sensors of mirrorless cameras. This is today well known, to be mainly caused by the thick filter-stacks in front of the sensors (creating field-curvature and cromatic aberrations with analog lenses).

It has been shown, that this can mostly be „cured“, by reducing or deleting the filter-stack, and/or putting a positive lens (so-called „PCX-filter“) in front of the lens-sensor-combination.

The 35mm-negative-films:

I made my first attempts to photograph the IMATEST-target on film parallel with

b&w-film Agfa APX100, iso 100 and
colour negative film EKTAR 100,

which are both still available as „fresh“ products.

I will report here mostly about the black-and-white film results, because the results on colour film were very low in resolution – in fact only about 2/3 of that with the b&w-film. The colour-neg-film had been externally processed by my photo-dealers lab – while I did the devellopment of the b&w-film myself with Rodinal. As a consequence, my confidence into the colour-results is not too high … it has to be reviewed definitely! The lateral CA-values, however, were very well on par with the measurements with the sensor. I will re-try! Maybe with a different color film.

The A/D-converting:

The negatives were digitized through my film-scanner reflecta RPS 10M,which offers a maximum linear resolution of 10,000 pixel per inch (PPI).

To me, this step seemed to be very important: to avoid new artefacts from the digitizing algorithm. So I chose a spatial frequency, which is higher than the expected limiting spatial frequency of the film: I set the scanner at 5,000 ppi. On pixel-level this corresponds to an imaging-sensor of ca. 33.7 MP (for 24mm x 36mm) -digitaly speaking it is an „8k-resolution“.

From my earlier estimations I had found, that a normal recording film for general imaging purposes should correspond to a digital FullFormat-sensor with 20-12 MP.

The picture height, which the scanner digitally delivers (24mm minus a bit of crop to frame the target safely), was 4,536 pixels and so the „Nyquist Frequency“ of the scanner set-up corresponds to 2,268 LP/PH – corresponding to an effective sensor-size of 30,3 Mpxls.

Fig. 9 shows the b&w-picture, which was generated with the scanner:

AGFA100_OM28f2,8_2,8_H4536 — **Fig. 9:** Scanner-output from the b&w negative-film Agfa APX100 from Olympus OM 28mm f/2.8 at full aperture f/2.8. **Picture-hight** of this original scan is 4.536 Pxls. You see, that the light-fall-off of this lens into the corners is very moderate … and the linear distortion with exactly 1% acceptable as well! – source: fotosaurier

Let’s have a closer look into the structure of this image – in Fig. 9a you get an impression of the grain structure of the films emulsion at about 200% enlargement of the 30,3 MP-image:

Enlargement-Film-200% — **Fig. 9a**: Overview of the grain-structure at ca. 200% enlagement of original scan in Fig. 7. The pixel-size here is 5,3 µm – the grains of the film are bigger than the pixels – source: fotosaurier

Following picture is the MTF-curve of the image „as scanned“ (in the center of frame):

Agfa100_OM28f2,8_4536_MTF — **Fig. 10**: **MTF-curve** (contrast over spatial frequency) **of the original b&w-scan** with 4,536 Pxls picture height in the center with OM 28f2.8 open aperture – source: fotosaurier

The „noise“ in the curve is caused by the film-grain, which is considerably bigger than the pixels.

I transformed these image data to a picture height of 3,024 pixels – of course by proportionally shrinking the pixel-count in the width as well.

Film_3024-pixel-height_at-800% — **Fig. 10a**: Here we look at about 1,000% into **the pixel-structure of the scanned and shrinked image**. At the edges of the dark rectangle (where the resolution is analysed!) the grain-diameter and the pixel-width (7,9 µm) are about the same size. Only some local „grain-clusters“ are considerably bigger- source: fotosaurier

Previous trials had shown, that with a film with this grain-structure, this digital image-size would give adequate results for MTF and resolution, what the following summary of the IMATEST-Data confirms:

Zusammenstellung_IMATEST_APX100_OM28f2,8_2,8 — **Fig. 11**: The reduction of the picture height of the SCAN to 3,024 pixels corresponding to 1,512 LP/PH leads to a much less noisy MTF-curve and a very smooth edge profile. Open aperture f/2.8 **the resolution MTF30 for this lens drops moderately by about 25% from center to corner**. – source: fotosaurier

With a pixel size of 7.9 µm we got a much smoother MTF-curve. The Nyquist-frequency of 1,512 LP/PH would allow to measure quite a bit higher MTF30-resolutions. On the same APX100-film-strip I had run the same test for three other lenses of the OM-system. In the following spreadsheet you see the highest MTF30-resolutions CENTER and CORNER (mean values) measured for for all three lenses:

Maximum MTF30 for OM-Lenses — **Fig. 12**: **Maximum** MTF30-resolutions for four Olympus OM-Lenses, **measured with my set-up with a scanner-resolution of 5,000 ppi, shrunk down to 1,512 LP/PH** – source: fotosaurier

Looking back to the results, which „Modern Photography“ and „Popular Photography“ published in analog lens tests of the 70s, 80s and 90s, measured on film (Plus-X from Kodak) and analysed visually with a loupe, we see, that the resolution-readings in the corners (sometimes called „far edge“ for the short edge of the frame) often started at 45/50 lines/mm with widangles and reached 75-90 lines/mm for the best lenses. This seems to be in fair correlation with the results of my method.

My interpretation of what we see here:

I. Looking first at the resolution-values in the center of the measurement on film we see something like a „barrier“ in the range of 1,350 LP/PH looking at different top-notch Olympus lenses.

With the A7R4-Sensor we measure two and a half times the resolution (2,767 LP/PH) compared to that on film (1,099 LP/PH) in the center of the OM 28f2.8 – at open aperture (f/2.8)! (See Fig. 7 / Fig. 11)

Conclusion 1: the maximum resolution-values, which we see with this method here on analog film are limited by the GRAIN of the film – and here they correspond to ca. 112 lines/mm. I estimate the MTF30-resolution-limit of the APX100 film to be 120 lines/mm respectively 1,440 LP/PH. For the (old?) Agfapan APX100 Professional film a resolution value of 100 lines/mm at 30% transfer factor value was given. (I do not know, wether the new APX100 emulsion (ADOX) matches with the former product exactly. Of course, the chart contrast of the used target has also influence – in my Imatest target it is 4:1.)

The (relatively small) differences with different lenses are probably caused by differences in contrast of each lens – which is also the reason, why in most cases the center-resolution rises by 10-20% from open aperture to f/5,6 and then drops again slightly. The width of the edge-profile in the center is also pretty constant (0.011-0.016 mm), which probably corresponds to the average film-grain diameter.

II. Looking at the corners we see the maximum corner-resolution on film typically lowered by 12-23% compared to the maximum center-resolution for these lenses – in the case of the OM 28 f/2.8 at f/2.8 the relative corner-drop (from 1,099 LP/PH at center to 734 LP/PH in corners) is exactly 33%. (see Fig. 9). The lowest corner values thus correspond to 50% of the grain-determined resolution-limit of this b&w-film.

Conclusion 2: The MTF30-corner-resolutions, measured with Imatest on the b&w-film APX100, delivers the REAL resolution values on film, because these values are far enough away from the resolution limit of the film, to be un-influenced by the grainyness!

Now we look at the results measured on digital sensor and on analog film, put together in one graph:

Resol_Film-Sensor_OM28f2,8_2,8 — **Fig. 13: „The proof“** (der Beweis!) – if the resolution is measured under 1.000 LP/PH, the **corner-resolution on sensor corresponds to the real resolution of the lens on film for this SLR-lens! –** source: fotosaurier

Fig. 13 shows principally the same Data, which were the basis of the graphs in Fig. 7 and Fig. 11 – right side (MTF over disxtance from center). Here the mean values of the MTF30-resolutions (center – part way – corner) are plotted over the distance from the center of the image.

The horizontal lines in Yellow and Green represent the Nyquist frequencies of the A7R4-sensor and the APX100-film respectively.

The blue line stands for the MTF30-resolution on film (734 LP/PH in corners).

The grey line shows the MTF30-resolution on the A7R4-sensor (784 LP/PH in corners).

Final CONCLUSION: yes, the enormous drop of resolution over the distance from the center, which is measured with high-resolution sensors, is real. This is no artefact, generated by the sensor in the corners but corresponds quite well with the resolution measured directly on film. Conclusion 1 has already shown, that the high resolutions, measured in the center of the image, are also real and the resolution-results on film are just limited by the grain of the film.

This seems to be widely valid for many historical SLR-lenses, which have an SLR-typical large back-focus. As we know, with RANGEFINDER-lenses having very short back focus to film, this may change dramatically – and that is covered widely in literature in the meantime. (Keywords: Sensor filter-stack; PCX-filter)

I have myself to-date researched the phenomenon on the example of the rangefinder-lens (LM-mount) Voigtländer VM Ultron 35mm f/1.7 in this article. Unfortunately until now available only in German …

My intention was, to find out, whether this corner-degradation-effect would also influence the picture quality with SLR-lenses:

… well – it obviously is NOT, even with wideangle lenses!

Another conclusion, which I draw from these results is, that the calibration of the film-scanner-resolution, set to 1.512 LP/PH (Picture-height of 3,024 Pixels), was a realistic choice for this type of b&w-film. It corresponds to a image-sensor with 13.5 Megapixels. That may need to be re-tuned with analog films with finer grain and higher resolution.

If we would use an ultra-fine-grain analog film (which exists!), we probably will measure very similar resolution curves as we get from the sensors! .. and I will definitely try to prove this hypothesis as well. (I have already tried to to this with the ADOX CMS 20 II – however, the development seems to be absolutly critical – I have to retry …)

–> It will also be interesting to extend this method an different analog films – and using the same lens for that, it may allow to characterize the film-emulsion with respect to its practical resolution power … of course with a specific calibration of the scan-process adapted to each film.

–> Last thought: I will try to find out, whether an innovative film pressure-plate, as it is used in the Contax RTS III (with vacuum!), can improve the variations of resolution, which are measured over the image frame …

At the end, you see in Fig. 14 + 15 the full resolution analysis of OM Zuiko Auto-W 28mm f/2.8 on 60 MP sensor and on b&w-film:

Ima-Graph_OM28mmf2,8 — **Fig. 14**: Resolution of Olympus OM Zuiko Auto-W 28mm f/2.8 **on 60 MP-sensor** (Sony A7R4) – source: fotosaurier

Imatest_OM28f2,8_APX100_Graph — **Fig. 15**: Resolution of Olympus OM Zuiko Auto-W 28mm f/2.8 **on analog film** (Agfa APX100) – source: fotosaurier

Finally, I want to tell you tell you a small anecdotal story about the early times of digital photography:

My own analog photograpy started in the mid-1950s (no error!) – and I was a busy hobby photographer, since then also developing my B&W-stuff on my own. So also my wife had a long pre-experience in seeing my film-enlargements on paper in sizes up to 50 cm x 70 cm.

When I made my first experiences with digital photography around 2002 with 6 MP (Canon EOS 10d), my wife was very critical about the results: „This does not look natural!“ she said. And she was right …

As a long-time enthusiast of the Olympus OM-System of 1972 I had realized of course, when Olympus tried something completely new in 2003 with the „E-1“ – a DSLR with the FourThirds format (17,3×13 mm). It had only 4,9 MP – less than the Canon, which I owned at that time. But surprise!: the pictures found grace in my wifes eyes … and my own! Since then I know: it takes more than just Megapixels, to tango!

Herbert Börger, Berlin, April 2023

My Crazy Lenses – Topcor R 30cm f/2.8 and its Modern State-of-the-Art Counterparts – „Supertele-Lenses“

Travel on my time-machine
The known Facts – Topcor 30cm f/2.8
Topcor 30cm f/2.8 – Optical Performance
The Reference: Canon EF 300mm f/2.8 IS USM
Three more 300mm f/2.8-teles

DSCF2458_Alle300f2,8-5_blog — **Fig1**: From left to right – Tropcor R 30cm f/2.8, Arsat Yashma 300mm f/2.8, Tamron SP LD (IF) 300mm f/2.8, Minolta AF Apo-Tele 300mm f/2.8, Canon EF 300mm f/2.8 L IS USM

1. On my time-machine:

I own the Topcor R 30cm f/2.8, which I am looking at here, since a few years – but I have not used it too often. It is very heavy, long and dark, giving the impression of a tank-breaking weapon: you definitely will get trouble at any security check nowadays … and in the best case you will earn compassion instead of admiration! Too bad, because it is an ingenious piece of optical engineering.

Information about Topcor lenses today are rare and not always reliable. I will restrict myself to reliable information and I will try to verify legends … or destroy them.

So I entered my time machine and travelled back into the year 1958. I was 13 years old at my arrival there – and at the Topcon (Tokyo Kogaku) factory I met a team of innovative engineers, who were fanatically burning for the QUALITY of their products – and really proud of it! The year before (1957) they had introduced a new SLR-camera (Topcon R), which was designed in Bauhaus-style, i.e. with clear and modern lines – and they were ready to ignit a firework of innovations around the SLR-concept within the next few years (from first-in-industry TTL-exposure-metering to first electric winder).

And they had introduced a line of lenses for this SLR-system-camera, among which the Topcor 30cm f/2.8 peaked out. Another „first-in-industry“-innovation.

I looked around in the photo-stores and could not find any Canon- or Nikon-SLRs there: the dealers told me, that both companies were just bringing out SLRs. It seemed, that the Topcon-people had considered the German SLRs, which were already on the market, as their competition. Personally at that time I was already a SLR-user (of my father’s Contaflex – which means, that from time to time my father was still allowed to use it himself).

Everybody, who is acqainted with the rules of the market, would have expected, that shortly after an innovation like the Topcor R 30cm f/2.8, the major competitors would bring out a similar product.

But that did not happen – so I returned in my time-machine. Finally I found out, that it took the new japanese competitors more than a decade! And there was no comparable Lens in Europe, as far as I could see. 13 years later Nikon presented a prototype, to be tested during the Olympic Winter Games of Sapporo in 1972.

The real next step was taken by Canon with a 300mm f/2.8 Lens for their new FD-System, using a lens made of FLUORITE in 1973 (some say 75)! This was finally 16 years after the arrival of the Topcor-lens … and just in that year, when Topcon stopped the production of their supertele-lens.

2. The known facts:

This Topcor R 30cm f/2.8 monster-tele-lens with 300mm focal length was presented to the world in 1958 („Topcon Club“ says 1957!) – one year before Canon or Nikon started to produce any SLR – and 13-16 years before any other lens- or camera-maker presented such a fast 300mm tele-lens. Not only at the 1964 Olympic Games in Tokyo but all the time until 1972 it was without any competition. As a consequence, there even was produced quite a number of lenses with Nikon mounts! Next to Topcon, Canon brought out its Canon FD 300mm f/2.8 S.S.C. Fluorite lens in 1973 – setting the level for professional superlele-lenses for the next decades and until today. Just a few years later Topcon went completly out of the business with SLR-cameras and lenses. Sad, but even the extensive book „Topcon Story“ by Marco Antonetto and Claudio Russo (1) does not answer the question „why?“. Today Topcon is a market-leader in geodesic instruments.

Stephen Gandy (3) estimates – cameraquest.com – that 700-800 lenses have been produced in total during 18 years of production.

Topcor-R-300f2,8_DSCF2335_blog — Fig. 2a:

R328cut — Fig. 2c: Lens scheme of Topcor 1:2.8 30cm – source: http://www.topgabacho.jp/Topconclub/lens3.htm

The lens is made of six single lenses in four groups – of which lens no. 6 (group 4) is the filter (diameter 39mm), which is, of course, part of the optical design! This filter is an early (maybe the first) example of a filter which is positioned in a slot in the rear part of the lens-body. In the book „Topcon Story“ (page 128) there is an error in the spreadsheet listing of the data of the R.Topcor-lenses: the data in the last line are the data of the „300mm 2.8“ and not of the f/5.6-lens. Here the no. of elements is „five“, which is correct, when you don’t count the filter as an active optical member …

The lens has a preset diaphragm and has a built-in sunshade (telescoping in two stages!). It is 383 mm long (from camera-flange to front-edge of the pulled-back sunshade – total length with shade pulled out is 477 mm) and weighs 3.1 kgs (without front and rear caps). Measured at my sample (ser. no. 34.1359). The initial sales-price was $ 1.125,–. (In the literature you will find: 415/412 mm length and 3.3 kgs weight).

It may be interesting to mention here, that right away from the introduction of the first Topcon-SLR, an extremely ambitious lens-program was planned – however, realized only partly. The Topcor R 13,5 cm f/2.0 (6 lenses) had also preset diaphragm and it was discontinued with the Topcon RE camera system – so it is said to be extremely rare. It has a yellowish color cast (due to rare-earth-glass?), not a big problem with todays digital cameras …

However, a 50mm f/0.7 lens, which is mentioned in „Topcon Club“ only, was never made for the SLR-camera market – maybe, this was one of the very early oscilloscope-registration-lenses, which are also known from Germany and GB even at WWII-times.

And a 1000mm f/7 catadioptric lens was only experimentally made in 1958.

„Topcon Club“ (2) writes about this:

„The interchangeable lenses which appeared with the appearance of TOPCON R are various kinds of the Auto Topcor of 35mm/100mm, and R TOPCOR (a priset diaphragm) of 90mm/135mm/200mm/300mm among these – although the bright thing and the dark thing were prepared about 135mm and 300mm – it should mention especially – it is the „high-speed lens“ of 135mm f2 and 300mm f2.8. 50mm f0.7 – such a bright lens was already completed during wartime by the Tokyo optics. Do you believe it ? Although possibly this grade was an easy thing, even so, the 300mm f2.8 lens will be an astonishment thing in 1957. I talked in detail on „the page of TOPCOR“ about this lens. We have to wait for marketing of the product of NIKON which is the next 300mm f2.8 lens at any rate till 1977. However, TOPCON did not build the super telephoto lens 500mm /800mm those days. Furthermore, the Refrector Topcor 1000mm f7 is appearing in the catalog in ’59. However, this was not launched regretfully.“

Later – from 1969 on – a RE Topcor 500mm f/5.6 telephoto-lens was even produced with automatic diaphragm and meter coupling!

Can such a fast long telephoto lens like this early 300mm f/2.8-design without Fluorite- or ED-lenses be any good – on the scale of professional photography? There are hints, that rare-earth glasses were used to make these lenses (also for the other famous 13,5cm f/2.0, also supplied since 1958). But I do not know details about this.

I will answer the question about the optical quality here – also comparing this lens with a modern top-notch tele-lenses like Canon EF 300mm f/2.8 L IS USM, which I personally classify as today’s state-of-the-art reference, supported by photo-friend Thomas, who borrowed his Canon lens to me.

Finally I will take a glance on a state-of-the-art modern astronomical refractor, which normally does perform at diffraction-limited resolution on stars!

Topcor 30cm f/2.8 – The Optical Performance on analog film (year 1969):

Stephen Gandy (3) wrote in his blog:

„The Topcor 300/2.8 enjoyed a great reputation as a fast, sharp lens. You only have to read the lens tests by Camera 35 in 1969 to understand why. WIDE OPEN its resolution was 56lines/mm center and 34lines/mm at the edges. By f/8 it was 80 lines/mm center and 65 at the edges. Many normal lenses don’t achieve this sharpness — much less 300/2.8 leviathans ! Camera 35 summed it up by saying „INCREDIBLY FANTASTIC.“ I would have to agree. „

(In the original text in Stephen’s blog, the reported resolution values are noted as „56mm“ or „34mm“. I have taken the freedom, to correct this to what it should read: lines per mm, „lines/mm“!)

The resolution values, which I use in my digital IMATEST measurements, typically are given in „Line-pairs per picture-height“ = „LP/PH“. Picture-height being 24mm with 24×36-format, you have to divide the „lines/mm“-values by two to get to „line-pairs“ – and then multiply with 24 to achieve LP/PH.

The highest given value of 80 lines/mm corresponds to 960 LP/PH stopped down to f/8 in the center or 760 LP/PH at f/8 at the edge – the lowest value 34 lines/mm with open diaphragm at the edge corresponds to 408 LP/PH.

What does that mean?

In 1969 the test results for resolution were measured on film – „Modern Photography“ used Plus-X Pan with standardized development – and the reading of the „just resolved“ line-pattern was done with a standardized enlarging glass … I personally used the method myself at that time, too, and it is quite reproducible as long as the same person does the reading … It is somewhat sensitive to the vision-capabilities of the reading person! And of course the grain of the analog film material (negative b&w film!) is the limiting factor for the resolution-reading on film for really high resolutions.

Generally to my experience, the Plus-X Pan film’s resolution limit is 1,000-1,200 LP/PH. For sports and other high-speed applications, however, the photograph will have used Tri-X or similar higher-sensitivity materials, which resolve quite a bit lower. This means, that this early and fast 300mm-lens came pretty close to use the full resolution-power of the analog films of that time! At least stopped down.

Today’s modern 24 MP-sensors deliver resolutions of 2,000-2,400 LP/PH using MTF30 (30% contrast) as the parameter for reading out the resolution values from the MTF-curve. My Sony A7R4-Camera (62 MP), which I use for my measurements, has a Nyquist frequency of 3.168 LP/PH and delivers up to 3.800 LP/PH-readings with the best known lenses.

The following spreadsheet gives an overview on the physical data of the Topcor-lens and the other lens-monsters, analysed here:

300f2,8_physData — **Fig. 3**: Physical Data of the five 300mm f/3.8-Lenses – source: measured by fotosaurier

3. Topcor 30cm f/2.8 – Optical Performance

My IMATEST-Results of the optical properties of the Topcor R 30cm f/2.8 lens:

To exclude potential vibration-initiated degradation of resolution in my test-shots at these long focal-lengths I used my heavy (>10 kgs) and sturdy astronomical telescope-mount:

DSCF2537_Topcor_AufAstroMontierung_blog — **Fig. 4**: My massive astronomical lens mount – here with SonyA7R4 attached to Topcor 30cm f/2.8 – source: fotosaurier

DSCF2535_OnTargetTop — **Fig. 5**: The set-up keeps the lens and camera steady even at 0,4 seconds. – source: fotosaurier

Following you see the results of my IMATEST-measurements:

Topcor_R-300f2,8_Spreadsheet-23 — **Fig. 6:** Optical measurment-results for **Topcor R 300mm f/2.8** adapted to Sony A7R4 with 62 MP – resolution values given in LP/PH – source: fotosaurier

Topcor_R-300f2,8_Graph-23 — **Fig. 7**: Resolution measurment-results for **Topcor R 300mm f/2.8** as graph – source: fotosaurier

The lens is unique at that time regarding to „speed“ – an extremely ambitious piece of optical engineering. Remind, that the distortion is practically zero and the CA-area in the center 0,8-1,4 pixel – 1 pixel at Sony A7R4 is 3,8 microns on the sensor!

What is ccenter, what is part way and what is corner? In the following graphs from IMATEST you see: „Part-Way“ is the large part of the picture extending close to the narrow side (left/right). „Corner“ is the narrow area outside the second dotted circle on the picture below.

DSC07122_Topcor300f2,8_8,0_Multi-ROI_2023-02-04_01-00-54 — **Fig. 8**: „**Cente**r“ resolution is calculated as mean from the values inside the inner circle (in my setting always two values), „**part way**“ is the mean of all values between the inner and outer circle, „**corner**“ is the mean of all values positioned outside the outer circle – source: fotosaurier

DSC07110_Topcor300f2,8_8,0_Lens_MTF_2022-11-29_22-55-46 — **Fig. 9:** Topcor R 30cm f/2.8 resolution plotted over radius of picture circle – source: fotosaurier

So, let’s compare the measurements to the value, that were given in analog times on film:

The comparison in the spreadsheet Fig. 10 shows: The lens „out-resolves“ normal analog films by far! Stopped down it reaches the limits of the analog medium even at the edges of the frame!

Analog-digital-resolution — **Fig.10:** „Camera35’s“ resolution measurements for Topcor R 30cm f(2.8 of 1969 on film compared with digital IMATEST values (at 30% MTF = „MTF30) with Sony A7R4 – source: fotosaurier

I found no real technical explanation, how Topcon-engineers managed to generate this phantastic lens at that time without ED/LD/AD/Fluorite-glass. There is a second tele-lens – the 13,5cm f/2.0, also introduced 1958, with first-in-industry potential – and finally the Topcor 2,5cm f/3.5 super-wide, which surprises with best-in-class resolution values (see my blog-article on historical 24/25mm-lenses!).

If somebody knows the secret: please, tell us!

Look at a sample picture taken with the Topcor at the end of this article.

Now, let’s have a glance on some other historical Superteles:

Alle_300er_2,8_DSCF2573 — **Fig. 11**: From left to right: Topcor R 300mm f/2.8, Canon EF 300mm f/2.8 IS USM, Minolta AF Apo-Tele 400mm f/2.8, Tamron SP (60B) 300mm f/2.8 LD (IF), Arsat Yashma-4H MC 300mm f/2.8

4. The Reference: Canon EF 300mm f/2.8 IS USM

Canon-EF_300f2,8_DSCF2451_blog — **Fig. 12**: **Canon EF 300mm f/2.8 IS USM – source: fotosaurier**

Canon EF 300mm f/2.8 IS USM is rated as the reference of this class of lenses. In this case it is not the latest „Mk II“-version of it, which came out 2011 – but the first version of 1999, which is tested here. It represents nevertheless already the top-class of the super-teles (as all its predecessors since 1973!)

Here are the IMATEST results of its optical properties:

Canon-EF_300f2,8-L-IS-USM_AF_Spreadsheet — **Fig.13**: Optical properties of **Canon EF 300mm f/2.8 IS USM** from my IMATEST-measurements, with autofocus – source: fotosaurier

And here the Graphs of resolutions center, part way and corner:

Canon-EF_300f2,8-L-IS-USM_AF_Graph — **Fig. 14**: IMATEST-Resolution (LP/PH) of **Canon EF 300mm f/2.8 IS USM –** center – part way and corners – source: fotosaurier

Not may comments necessary to this – the figures and graphs should speak for itself … Just to mention: the distortion at the Topcor-lens is even lower than that of the Canon – but both are neglectable for a supertele!

Canons leadership in this class of professional supertele-lenses was generated by the policy, not to drop a product into the market, which was „just possible“ at present, but to persue a consequent plan for the future: to solve the „secondary spectrum“-problem of long tele-lenses, which means to use extreme „anormal dispersion“ lens-materials, which do the job without optical compromising.

So in 1975 – 2 years after Nikons first presentation of its first 300mm f/2.8 ED-lens (which was not very convincing and had to be replaced four years later by the ED-IF-version) – Canon introduced their FD 300mm f/2.8 Fluorite-Supertele, in which they used a front-lens made of fluorite-monocrystal material (no glass!) and a UD-glass-lens. This lens war already praised close to perfect (absence of chromatic aberrrations). Canon accepted for this a compromise, which made the lens longer and heavier: to protect the soft and sensitive fluorite-crystal-material in the front lens, there was a fixed additional plane protection element of glass in front!

Finally new fluorite-glass-formulations became available, which allowed to drop the sensitive crystal-lens. Over the introduction of Autofocus (EOS – 1987) and still more glass-elements, Canon finally introduced the legenday lens EF 300mm f/2.8L IS USM in 1999 with very fast AF and image-stabiliser, which is tested here.

Enjoy the results!

5. Finally – three more 300mm f/2.8-teles:

Minolta AF APO-Tele 300mm f/2.8 (1985)
Tamron SP LD (IF) 300mm f/2.8 (60H) (1984)
ARSAT MC Yashma-4H 300mm f/2.8 (1990?)

For these three lenses I also have to thank foto-friend Thomas, who borrowed them to me!

5a. Minolta AF APO-Tele 300mm f/2.8 (1985)

Minolta-Apo_300f2,8_DSCF2460_blog — **Fig. 15**: **Minolta AF APO-Tele 300mm f/2.8 – source: fotosaurier**

This lens had a mechanical defect: the diaphragm could not be closed below f/5,6. However: in these lenses principally mainly the open aperture is really significant – why should you carry around such a weight, to make pictures with f/11?

Minolta-AF-Apo-Spreadsheet — **Fig. 16:** Optical properties of **Minolta AF 300mm f/2.8 Apo – source: fotosaurier**

Minolta-AF-Apo-Graph — **Fig. 17:** IMATEST-Resolution (LP/PH) of **Minolta AF 300mm f/2.8 Apo –** center – part way and corners – source: fotosaurier

This Minolta lens comes closer to the Canon-legend than any of the others – but with quite som distance in resolution in the corners open aperture.

Excelent lens!

5b. Tamron SP LD (IF) 300mm f/2.8 (60B) (1984-1992):

Tamron-SP_300f2,8_DSCF2475_blog — **Fig. 18**: **Tamron SP LD (IF) 300mm f/2.8 (60B) – source – fotosaurier**

This is the shortest and lightest lens of the quintuple, which arrived even one year before the Minolta – containing two low-dispersion (LD) lenses – with manual focusing:

Tamron-SP_300f2,8_Spreadsheet — Fig. 19: Optical properties of **Tamron SP 300mm f/2.8 LD (IF) 60B – source: fotosaurier**

Tamron-SP_300f2,8_Graph — **Fig. 20**: Imatest resolution graphs of **Tamron SP 300mm f/2.8 LD (IF) 60B – source: fotosaurier**

Tamron – third party winner: Great Lens!

5c. ARSAT MC Yashma-4H (1990?):

Yashma_300f2,8_DSCF2478_blog — **Fig 21**: **ARSAT MC Yashma-4H – source: fotosaurier**

I do not know much about this lens. Funny about it is to me, that in most cases, when it is offered as a used lens, it is given the addendum „sovjet lens„! In 1990, when it was delivered first (I saw other sources with the date 2007 …) the Sovjet Union no longer existed – which means that, ARSAT being located in KIEW, the lens has UKRAINIAN roots.

As far as I know, it was generally produced in Nikon-mount.

ARSAT_Yashma_300f2,8_Spreadsheet — **Fig. 22**: Optical performance of **Arsat MC Yashma-4H 300mm f/2.8** – source: fotosaurier

ARSAT_Yashma_300f2,8_Graph — **Fig. 23**: Resolution graphs of **ARSAT MC Yashma 300mm f/2.8** – source: fotosaurier

Open aperture and stopped down the lens is convincing in the center – about 10-15% below the other superteles – but with still very good CA in the center.

From f/4.0 it is also very good in the large part of the frame – just 10% below the Topcor.

In the corners it is on par with the Topcor open aperture – but it does not improve so much while stopping down. For analog film use it was also a good lens – with exception of the softer corners with typical CA-values of non-apochromatic lenses … and a much higher distortion than all the other superteles.

What about apochromatic correction in supertele-lenses?

Lenses of 300mm f/2.8 need apochromatic correction to be really sharp. The chromatic aberrations („secondary spectrum“) are the major restictions in sharpnes for these long focal lengths all over the frame! All these lenses, tested in this report, have apochromatic correction – in varying degrees of perfection! In the ARSAT Yashma the apo-correction is only partly successful.

Herbert Börger

fotosaurier, Berlin 13.02.2023

Literature:

1- „Topcon Story – Topcon Enigma“ by Marco Antonetto and Claudio Russo, by Nassa Watch Gallery, Collectors Camera Publishing, CH 6907 Lugano, Switzerland – 1997

2- Web site „http://www.topgabacho.jp/Topconclub/FPslr1.htm“

This, the first super fast long telephoto lens produced for any camera system world wide, came to the market in 1957. This was a large and heavy lens, with a 130mm maximum diameter, a length of 412 mm and a weight of 3.3 kg. The optical design was one of 6 elements in 4 groups. The selling price, at the time, was 135,000 Yen making it the most expensive lens on the market. Special filters slide into a slot at the rear of the lens barrel and this lens was probably the first to use this method. Unlike the 135mm f2 R Topcor, this lens was listed in catalogues into the later half of the 1970s. Because of it’s large aperture it was chosen as the official lens of record for the Tokyo Olympics. An odd thing concerning this lens is that many of those remaining have been modified for the Nikon mount, while those with the original Topcon mount are very scarce. The early lens case was made of leather but later on Topcon began supplying a hard case with the TOPCON emblem promontory displayed. The R Topcor 300mm f2.8 lens still compares favorable, with regards to regards to sharpness and contrast, to modern lenses with fluorite elements. Today this lens is almost forgotten but was highly praised in former times.

3- Web site of Steven Gandy: „https://www.cameraquest.com/top30028.htm“

Hambühl_A7RII_Topcor300f2,8_f5,6_iso800_crop — **Fig. 24**: Mathäuskirche in Hambühl, seen **from 1,2 km distance** with Topcor 300f2,8 (taken at f/5,6 with Sony A7R2 at iso800) – narrow vertical crop of nearly full frame, which you see here at about 65% enlargement – „**ooc“** – no post-treatment of the picture) – source: fotosaurier

Hey Sony! Was passiert bei der Objektiv-Korrektur in meiner Sony A7Rm4 ?

Bei hochwertigen digitalen Systemkameras hat man üblicherweise die Möglichkeit, eine digitale „Objektiv-Korrektur“ zuzuschalten – für moderne Objektive, deren Eigenschaften in der Firmendatenbank des Kameraherstellers meines Vertrauens gespeichert und für das Kameramodell verfügbar sind. Dazu muss die Kamera das Objektiv-Modell erkennen und die notwendigen Korrektur-Algorithmen besitzen – oder das Objektiv könnte diese Informationen über seine Fehler in sich tragen.

Ich mchte nur generell erwähnen, dass ich in allen meinen Testberichten, in denen ich historische und moderne Objektive verglichen habe, immer die Objektiv-Korrektur ausgeschaltet habe.

Geben Sie es zu: Sie waren bisher auch so naiv, zu glauben, dass da auf wundersamem – eben digitalem! – Wege die aufgrund der bekannten Rest-Fehler der Optik fehlerhaften Bildinformationen „nachgebessert“ werden. Es entstehe bitte: DAS PERFEKTE BILD – bei Verwendung eines un-perfekten (und damit billigeren) Objektives, dessen Rest-Fehler durchaus sehr groß sein könnten – man müsste sie nur kennen …

Nachdem ich persönlich schon relativ sicher war, dass von der „Objektiv-Korrektur“ KEINE WUNDER zu erwarten sein werden, wollte ich mal nachschauen, was denn wirklich passiert. Was können wir heute von einer Objektiv-Korrektur erwarten, wobei ich das Thema erst einmal auf die 60 Megapixel-Sony-Kamera A7Rm4 beschränken muss, also einen aktuellen, hochauflösenden Sensor.

Meine Hoffnung ist, dass beim Aufbereiten der Sensor-Rohdaten diese Kamera nicht schon ohne mein Wissen die Bilddateien manipuliert, solange die Objektiv-Korrektur ausgeschaltet ist! Bei den historischen Objektiven, die ich normalerweise sehr überwiegend analysiere, besteht diese Sorge ja ohnehin nicht, da das Objektiv normalerweise nicht mit der Kamera kommunizieren kann – die Kamera aber auch sowieso nichts über mein „Ernostar“ von 1926 weiß!

Ich sollte nicht verschweigen, dass meine Motivation, diesen Bereich näher zu untersuchen dadurch plötzlich für mich höhere Priorität erlangte, dass ich versucht habe, in Dateien auf Basis des IMATEST-Test-Targets die Vignettierung mittels Photoshop zu kompensieren, um zu erfahren, welchen Einfluß die Vignettierung alleine (also der Helligkeitsabfall zum Rand) auf die Auflösungsmessung haben könnte.

Die erneute Analyse der manipulierten IMATEST-Target-Datei ergab: einen KATASTROPHALEN Einbruch der Auflösungswerte überall im Bild. Das hat mich schon sehr alarmiert!

Zufällig um dieselbe Zeit habe ich mein Referenz-Normalobjektiv (Sony Planar FE 50mm f/1.4 ZA) erneut mit IMATEST gemessen – und erreichte nicht annähernd die mir geläufigen hohen Auflösungs-Werte. Ich sellte fest, dass – durch irgendeinen Zufall – die Objektiv-Korrekturen eingeschaltet waren.

In der Folge führte ich folgendes Messprogramm durch – wobei ich das exzellente (aktuelle) Planar FE 50mm f/1.4 ZA im E-Mount (Sony) verwendete. Nach meinen umfangreichen Erfahrungen kann das verwendete Objektiv aber durchaus als Referenz dessen gelten, was in diesem Preissegment heute möglich ist.

Auflösungs-Messung (mit CA- und Verzeichnungs-Daten sowie Kantenschärfe-Messung) an der Sony Planar FE 50mm f/1.4 ZA am Imatest-Target (SFRplus):

Laborszene900 — Bild 1: Messanaordnung Mit Sony A7Rm4-Kamera und dem großen IMATEST-SFRplus-Target. Die Höhe des Targets zwischen den oberen und unteren Balken beträgt 783 mm, Der Abstand mit 50mm-Objektiv ca. 1,6 m.

Beschreibung des Messverfahrens im Detail siehe:

Fotosauriers optisches Testverfahren für Objektive mit IMATEST

Die typischen individuellen Fokussier-Unsicherheiten der (eigentlich überlegenen) Manuellen-Fokussierung wollte ich zunächst vermeiden, deshalb wählte ich Autofokus für die Schärfeeinstellung – und zwar mit Fokusfeld im Zentrum.

Die Objektiv-Korrekturen sind AUSGESCHALTET (OFF):

50f1,4_AF-oKorr — **Bild 2**: Auflösung, Kantenschärfe und Verzeichnung (IMATEST) mit Autofokus, **Objektiv-Korrekturen ausgeschaltet – PLANAR 50mm f/1.4 – gegenwärtiger Stand der Technik (2018)**

Anschaulicher sind die folgenden Grafiken, Auflösung (LP/PH = Linienpaare/Bildhöhe) über der Blende aufgetragen – jede Zahl ist ein Mittelwert über mehrere Messpunkte (insgesamt 46 Messpunkte bei jeder Blende über die gesamte Bildfläche verteilt):

FE 50f1,4_Autofocus_oKorr_Diagramm — **Bild 3: Diagramm Auflösung** (Mitte-Übergang-Ecken) des FE 50f1.4 ZA mit Autofokus

Das folgende Diagramm zeigt die Auflösung desselben Objektivs mit EINGESCHALTETER VERZEICHNUNGS-KORREKTUR

FE 50f1,4_Autofocus_mVerzKorr_Diagramm — **Bild 4**: **Auflösung** (Mitte-Übergang-Ecken) (IMATEST) mit Autofokus, **Objektiv-Korrekturen eingeschaltet – PLANAR 50mm f/1.4 – gegenwärtiger Stand der Technik (2018)**

Man erkennt sofort, dass die Auflösung in der Bildmitte („Center“ – grüne Linie!) sehr stark abgesunken ist gegenüber der Messung ohne Verzeichnungskorrektur. Wenn man genau in die Rand-Auflösungswerte schaut, sieht man, dass zwischenBlende 2.8 und 8 die Auflösung auch in den Ecken und im Übergang (part way) leicht verringert ist. Außerdem ist die Kantenschärfe in der Bildmitte (Wert „Edge profile bzw. sharpness“) deutlich – nämlich ebenso um ca. 20% wie die Auflösung in Bildmitte – reduziert.

Die Aufgabe der Verzeichnungskorrektur wird dabei allerdings vorbildlich gelöst: die Verzeichnungswerte werden mit 0,03-0,07% auf bis zu ein Zehntel der ursprünglichen Verzeichnung von 0,35% abgesenkt – dann meist mit der Charakteristik „Moustache“.

Die Frage ist nur: zu welchem Preis in der Bilqualität geschieht das hier? Und ist das Objektiv damit sinnvoll verwendet. Mit Listenpreis € 1.500 erstehe ich eine 12-linsige Festbrennweite mit state-of-the-art Optik (Asphäre, Sondergläser). Da möchte ich die volle optische Leistung (schon ab Offenblende!) gerne genießen!

Die oben dargestellte Erkenntnis ist daher wohl von eher theoretischem Interesse. Eine Verzeichnung von 0,35% ist ohnehin so gering, dass sie praktisch nicht auffällt. Man solte den 12-Linser nicht „abdrosseln“ und ihm damit seine optische Potenz nehmen.

Zu der anderen angebotenen Objektiv-Korrektur, die man in der A7Rm4 einzeln zu- und ab-schalten kann, läßt sich allerdings nur Positives sagen: die CA-Korrektur beeinflusst hier die Auflösungswerte allenfalls positiv – nämlich da, wo im Rand-Ecken-Bereich der Farbfehler reduziert wird: dort steigt dann auch die Auflösung. Das Zuschalten ist also auch bei einem derart hoch-korrigierten Objektiv zu empfehlen. Die Wirkung ist auch in der Bildmitte nachweisbar.

Für dieses hier besprochene Objektiv würde ich dringend empfehlen, die Lens-Correction Funktion auszuschalten und lediglich die CA-Korrektur einzeln zuzuschalten.

Bei anderen Hochleisungs-Objektiven habe ich dasselbe überprüft und bin – glücklicherweise – ausschließlich zu anderen Ergebnissen gekommen, wie man in den folgenden Tabellen sieht. Ich habe dabei nur die Performance bei voller Öffnung dargestellt, da die Objektiv-Korrektur da typischerweise am stärksten eingreift.

Hier drei Beispiele mit drei der aktuellsten hochklassigen Optiken mit 40 mm Brennweite ebenfalls an der Sony A7R4:

Batis-40mmf:2.0_with:without-Correct_0penApert — **Bild 5**: Auflösung, Verzeichnung und CA bei voller Öffnung am Batis 40mm f/2.0 – **ohne und mit Lens-Correction** – Quelle: fotosaurier

Sony FE40f2,5 - with:without-Correct_openApert — **Bild 6**: Auflösung, Verzeichnung und CA bei voller Öffnung am Sony FE 40mm f/2.5 – **ohne und mit Lens-Correction** – Quelle: fotosaurier

SigmaArt-40mmf:1.4_with:withoutCorrect_openApert — **Bild 7**: Auflösung, Verzeichnung und CA bei voller Öffnung am SigmaArt 40mm f/1,4 – **ohne und mit Lens-Correction** – Quelle: fotosaurier

Diese drei Beispiele nähren bei mir die Hoffnung, dass die Situation beim Planar 50mm f/1.4 eine Ausnahme sein könnte. In allen drei Fällen zeigt sich grundsätzlich sowohl eine Verbesserung der Verzeichnung als auch der Auflösung, die vermutlich unmittelbar auf die nachträgliche Korrektur der Chromatischen Aberration zurück geht.

Herbert Börger

Der Brandenburger Tor, Berlin, 11. Dezember 2022