thoughts on a "super angulon 75/8"?

[Bernice Loui]

"Mechanical Vignette" or image cut-off caused by the camera & bellows, "when racked up all the way?" rather than the lens image circle?

Fujinon 75mm f5.6 SWD has a spec image circle of 200mm @ f22 allowing about plus or minus 47mm on 4x5 (image circle required of 153mm).
If the 75mm SWD is running out of image circle the solution could be to use a Schneider 72mm f5.6 Super Angulon XL which has an image circle of 229mm @f22 which will increase the usable rise about plus or minus 15mm or 76mm of rise-fall.

If this is a Wista field camera, it would be very questionable if a Wista field camera can achieve that amount (76mm) of rise-fall using the standard bellows and flat bed field camera as delivered. Possible the mechanical vignette is caused by the lens being so far into the field camera body with the flat bed in front cutting of part of the lens image circle?



Bernice

As for filters, the SWD75 I use on the Wista gives me visible vignetting when I rack it up all the way. So more mechanical vignette than fall-off I'd say. But I haven't quantified it and it was on b&w so maybe I don't see it but it is there. Or I can live with it.

[Havoc]

Thanks for your info.

I would get it to have a lighter kit. I'm looking at an operation for my neck this autumn and it will mean being careful for some time. So the Wista with the SWD and others will have to be kept for occasions where it can be brought close with the car. I already have a SA 90/8 to replace the SWD90 and that is a real difference. So ok, it has its limitations but I think that will be managable.

"Mechanical Vignette" or image cut-off caused by the camera & bellows, "when racked up all the way?" rather than the lens image circle?

Fujinon 75mm f5.6 SWD has a spec image circle of 200mm @ f22 allowing about plus or minus 47mm on 4x5 (image circle required of 153mm).
If the 75mm SWD is running out of image circle the solution could be to use a Schneider 72mm f5.6 Super Angulon XL which has an image circle of 229mm @f22 which will increase the usable rise about plus or minus 15mm or 76mm of rise-fall.

If this is a Wista field camera, it would be very questionable if a Wista field camera can achieve that amount (76mm) of rise-fall using the standard bellows and flat bed field camera as delivered. Possible the mechanical vignette is caused by the lens being so far into the field camera body with the flat bed in front cutting of part of the lens image circle?

If the circle of the lens is 200mm and you need 153mm for coverage, then I would think the maximum shift is (200-153)/2 = 23.5mm Which is about the limit of the Wista. From what I see it are rounded dark corners, looks like the image circle to me. I would also think that if it was the flat bed then I would have more a straight (fuzzy) edge? Don't know because I always shift up, never down. For some reason I always run out of up shift. Think I need one of those "skyscraper cameras".

But yes, it would mean the SA would give even less shift.

[Bernice Loui]

What is the image taking aperture? Image circle grows at smaller apertures. Required image circle might not be enough at near full aperture say f8 or f11.

The spec image circles are typically at f22, at larger apertures while it can illuminate the ground glass, film does not see light projected by the lens the same way. Very generally speaking, the f4.5 or f5.6 75mm wide angle lenses tend to have a larger spec image circle then their f8 versions and there could be exceptions.

It's all a trade off.


Bernice

If the circle of the lens is 200mm and you need 153mm for coverage, then I would think the maximum shift is (200-153)/2 = 23.5mm Which is about the limit of the Wista. From what I see it are rounded dark corners, looks like the image circle to me. I would also think that if it was the flat bed then I would have more a straight (fuzzy) edge? Don't know because I always shift up, never down. For some reason I always run out of up shift. Think I need one of those "skyscraper cameras".

But yes, it would mean the SA would give even less shift.

[Bob Salomon]

What is the image taking aperture? Image circle grows at smaller apertures. Required image circle might not be enough at near full aperture say f8 or f11.

The spec image circles are typically at f22, at larger apertures while it can illuminate the ground glass, film does not see light projected by the lens the same way. Very generally speaking, the f4.5 or f5.6 75mm wide angle lenses tend to have a larger spec image circle then their f8 versions and there could be exceptions.

It's all a trade off.


Bernice

The faster versions are also different construction.

[Havoc]

What is the image taking aperture? Image circle grows at smaller apertures. Required image circle might not be enough at near full aperture say f8 or f11.

Mostly I'm somewhere between f/19 and f/27, rarely f/32 or higher.

[Jac@stafford.net]

What is the image taking aperture? Image circle grows at smaller apertures. Required image circle might not be enough at near full aperture say f8 or f11.

Does the image circle really increase or does the spread of light change to more evenly distribute illumination? I do not know.

[...]Very generally speaking, the f4.5 or f5.6 75mm wide angle lenses tend to have a larger spec image circle then their f8 versions and there could be exceptions.

An exception would be a Biogon design.

[Dan Fromm]

Does the image circle really increase or does the spread of light change to more evenly distribute illumination?

Three things happen on stopping down. The exit pupil gets smaller. This reduces mechanical vignetting. Off-axis aberrations diminish. This increases the circle of good definition. Blur due to diffraction increases. Since diffraction is worse off-axis, this reduces the circle of good definition.

In practice, although diffraction limits resolution attainable, its effects are much worse at high magnification (>> 1:1) than at very low (shooting far distant subjects). At high magnification, stopping down can reduce coverage and depth of field.

Finally, cos^4's effects are independent of aperture. Reduction of mechanical vignetting on stopping down is often confused with reduction of cos^4's effect. Makers of center filters understand what's going on, recommend using CFs at apertures two stops down from wide open so that the CF has to offset only the effects of cos^4. Note that f/4.5 Biogons suffer from cos^approximately 3, not cos^4.

An exception would be a Biogon design.

Sophistry. Zeiss Oberkochen brought only f/4.5 Biogons to market. With respect to other modern w/a lenses, the situation is more complicated.

Fuji SW lenses are 6 elements in 4 groups f/8, SWDs are 8/4 f/5.6. The SWDs have more coverage.

Nikon SWs are all 8/4, some f/4 or f/4.5, others f/8. Their two 90 mm lenses, f/4.5 and f/8, have the same coverage.

Schneider and Rodenstock offered slow 6/4 and fast 8/4 w/a lenses. Fast ones have more coverage than slow ones of the same focal length.

More elements offer the designer more degrees of freedom for correcting aberrations, including off-axis aberrations that limit coverage.

And then there's Konica, not LF. They offered two w/a lenses for Koni-Omega cameras. The first, 60/5.6 is 6/4. The later one, 58/5.6 is 8/4. I have both, have never asked either to cover more than 2x3. Both do.

[Jac@stafford.net]

Dan, you have probably seen this before: a 3" Biogon with a rear element larger than the film's ~4" vertical dimension. Does this defeat the ~cos^3 or does it mean that the full coverage is simply ignored (cut off) instead?

...

[Dan Fromm]

Jac, I've had one of those lenses. Pacific Optical Paxar (B). It isn't quite a Biogon as designed by L. Bertele.

The USAF data sheet for it shows illumination 45 degrees off-axis at around 38% of illumination on axis. That's a tiny bit better than cos^3. The difference has no practical significance.

Since the data sheet's resolution tables and illumination chart cut off at 45 degrees I don't think the lens is intended for a format larger than 4x5. Even though my little 38/4.5 Biogon covers 84 mm with good illumination and sharpness, f/4.5 Biogons are always treated as covering 90 degrees and no more.

I wonder a little about the USAF data sheets' illumination curves. The one for the 3"/4.5 Goerz Aerogor (= Biogon) shows 45 degrees off-axis at 38% of center. 3"/4.5 Aerojet Delft (sort of a Biogon), 45 degrees at 28%. 3"/4.5 Pacific Optical Paxar (A) (also a Biogon), 15%, worse than cos^4.

[Bernice Loui]

Here are all three.. Pacific Optical, Goerz, Viewlex versions of the "Biogon" made for the US military. Some number of these appeared on the surplus market many years ago and they were not expensive. Think all three of these lens cells sets cost a total of $50 including shipping.




Never got enough motivation to make a barrel for them and try them for a host of reasons. About this same time of "view camera lens" impulsiveness, ended up with a few Aero Ektars most of the 6" are long gone, only the 12" f2.5 in Fairchild shutter remains, a few Metrogons, then a few 36" f8 whoppers also in Fairchild shutter.


Bernice

Jac, I've had one of those lenses. Pacific Optical Paxar (B). It isn't quite a Biogon as designed by L. Bertele.

The USAF data sheet for it shows illumination 45 degrees off-axis at around 38% of illumination on axis. That's a tiny bit better than cos^3. The difference has no practical significance.

Since the data sheet's resolution tables and illumination chart cut off at 45 degrees I don't think the lens is intended for a format larger than 4x5. Even though my little 38/4.5 Biogon covers 84 mm with good illumination and sharpness, f/4.5 Biogons are always treated as covering 90 degrees and no more.

I wonder a little about the USAF data sheets' illumination curves. The one for the 3"/4.5 Goerz Aerogor (= Biogon) shows 45 degrees off-axis at 38% of center. 3"/4.5 Aerojet Delft (sort of a Biogon), 45 degrees at 28%. 3"/4.5 Pacific Optical Paxar (A) (also a Biogon), 15%, worse than cos^4.