There was a discussion recently about tessar lenses: some people love 'em! It happens that I acquired three Fuji 250mm lenses of different designs: a 6/4 plasmat, a 4/3 tessar, and a 3/3 soft focus. So I made comparisons of the lenses on 8x10.
The plasmat Fujinon W 250mm f6.7 lens is the single-coated writing-on-the-front version with a very generous image circle of 398mm at f22, which allows about 45mm of movement.
The tessar Fujinar 25cm f4.5 lens is single-coated and covers only 286mm at f22, so it's expected that the image circle will not cover the full format.
The soft focus Fujinon 250mm SF f5.6 lens may also be single-coated, the image circle is quoted as 300mm but being a soft focus lens, it will be interesting to see exactly what that means (300mm is suspiciously round).
For the comparison, all lenses were exposed at f32-45 – halfway between f32 and f45. This was to both see what the coverage is when the lenses are well stopped down, to get an exposure of 1/2 second because that's a speed that all three shutters share (the Fujinar is mounted in a Shanel 5 shutter which has very odd speeds) while avoiding Shanghai's notorious reciprocity failure. An additional image was made with the Fujinon SF lens using the yellow disk wide open (f8) at 1/30 second to determine the soft focus effect.
The front standard was raised 40mm so that the edges of the image can be easily seen. The negatives have been scanned with a blue line that indicates the 40mm movement, and where the top of the sheet would be if no rise had been applied.
For coverage calculations I assume that the image circle needed to cover 8x10 is 305mm which I determined by measuring the exposed rectangle made by a Toyo 8x10 film holder. (The actual diagonal of the film is about 312mm.)
The images were made with a Toyo Field 810M camera and Shanghai GP3 100 film, exposures were 1/2 second f32-45 for all images except the image with the yellow soft focus disk which was 1/30 f8 (technically T8). Negative densities are reasonably similar allowing for the variable light and different shutters (particularly the Shanel 5). Film was developed in Kodak HC-110 Dilution E (1+47) at 22˚C for 8.25 minutes using continuous agitation. Images were camera-scanned and digitally edited using Lightroom and Negative Lab Pro. The "Lab - Standard" profile was used in NLP and LR was used to crop the images and add +40 Clarity after inversion. No other adjustments have been made. Annotations (the blue line and the lens identification) were added in Apple Preview.
Hopefully you find this informative or at least entertaining.
The Fujinon W 250mm f6.7 lens has full 8x10 coverage at f32-45 exceeding 40mm rise, which is in agreement with the specifications. It is an exceedingly good lens for 8x10 particularly at the reasonable price it's available in the market. It may even cover larger formats.
The Fujinar 25cm f4.5 lens also covers the full 8x10 negative at f32-45, however just before the 40mm rise the image starts softening in the corners, and several millimetres after that the image circle ends. I would expect the image to further soften at the edges as the lens was opened up, but central sharpness would probably remain the same. For those that are satisfied with some corner softness (but no vignetting) and the requirement to stop well down and use no movements, the lens covers 8x10 well enough. NOTE the Fujinar SC 250mm f4.7 lens in Copal 3 (possibly 3s) shutter is probably optically identical.
The Fujinon SF 250mm f5.6 soft focus lens stopped down to f32-45 has sharpness very similar to the Fujinar: excellent in the centre only showing slight corner softness that increases past the 40mm rise. What's surprising is no sign of the edge of the circle of illumination. It just keeps going! I've used this lens before at f22 and smaller and found it can suffer flare: no wonder, a huge image is being projected into the bellows. This is a lens that should be used with a compendium lens hood to control non-image forming light.
Finally the Fujinon SF 250mm f5.6 soft focus lens at its maximum softness setting (wide open with the yellow diffusion disk) which equates to f8 (not f10 as the text in the image states): the circle of illumination again far exceeds the 8x10 format with 40mm rise, suggesting again it should be used with a lens hood. Sharpness (or the lack there-of) is necessarily a matter of definition (that pun may be intended). Suffice to say that it more than covers 8x10 and may well be useful on larger formats like 10x12 or 11x14 particularly at portrait distances.
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Originally Posted by Vaidotas
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