Schneider Super-Angulon 75mm and Vignetting on 4x5?

[xkaes]

That's not centered. If it were, it would cover.

[Daniel Unkefer]

It's 5x7 film. So no it won't. Image circle of the 75mm F8 is 181mm according to my Burleigh Brooks catalog, which is only 1mm more than the nominal 7" long dimension of the film. There is a nice 4x5 size section in the center (choose your cropping) that is sharp enough for my needs. Changing the subject, just a quess OP but I think your Intrepid bellows or interior camera "throat" may be vignetting your image circle. Check the corners, through the groundglass cutouts, to see if the lens is covering and perhaps the problem will reveal itself. Perhaps a deeper recessed board would help.

[xkaes]

The OP was about 4x5 film. I don't understand at all why you are talking about 5x7 film. How does this relate to the OP?

[Panj]

So first, thanks for the replies.

Also, that image of the church from Toby is really amazing. I see the vignetting on the top, but that is a stunning photography. Great work.

I ran some more tests yesterday, and think I may have sorted out what is happening, based on my film development. I was using a polarising filter during my initial shots (I wanted to cut reflections on the water), and taking that off did seem to make a noticeable difference. But the real issue seems to be with centering the rise on the Intrepid 4x5 camera. I've been doing this by eye, but clearly, that is not enough. What is troublesome is that the Intrepid doesn't really have a means of knowing zero rise, or it doesn't until I mark my front standard with something very permanent so that I will know instantaneously in the future. Worse, even with a (cheap) fresnel, viewing the corners on the ground glass is impossible; it's pitch black. Which suggests I need to invest in something (a better fresnel, perhaps, and/or a better ground glass).

Yesterday, I used a laser level and measuring tape to find true zero rise on the front and rear standards, and then took out my trusty Leatherman to carve a mark on each standard. Then I tried again with the 75mm (set to f/32 to answer the question above), an re-took the photograph (once with the Polariser, once without). I now see that the lens does indeed cover 4x5, which is an enormous relief, as well as focus to infinity (normally this won't happen on an Intrepid unless one uses some kind of recessed lens board).

This doesn't completely solve my problems, but it does save me from binning the lens. I am not sure how I am going to compose shots if I cannot see the corners..... But, that is a different problem......

[maltfalc]

Worse, even with a (cheap) fresnel, viewing the corners on the ground glass is impossible; it's pitch black. Which suggests I need to invest in something (a better fresnel, perhaps, and/or a better ground glass).

with a short focal length lens you also need a short focal length fresnel.

[ic-racer]

Dark corners on film are the result of two independent processes. One is a decrease in light energy on the film as the light's angle of attack on the film changes from 90 degrees, so called 'cosine falloff.'
The other is a mechanical process whereby the pupil appears smaller at the edges of the field. Analogous to shutter efficiency increasing with small apertures, the same can be said for this mechanical vignetting. Small apertures increase the efficiency of projection, decreasing the effects as the angle of view extends to the absolute cutoff of light. See image in above post #3.

[Dan Fromm]

Dark corners on film are the result of two independent processes. One is a decrease in light energy on the film as the light's angle of attack on the film changes from 90 degrees, so called 'cosine falloff.'
The other is a mechanical process whereby the pupil appears smaller at the edges of the field. Analogous to shutter efficiency increasing with small apertures, the same can be said for this mechanical vignetting. Small apertures increase the efficiency of projection, decreasing the effects as the angle of view extends to the absolute cutoff of light. See image in above post #3.

ic, for the life of me I can't understand your explanation of mechanical vignetting. As I understand it and see it when I play around with w/a lenses, stopping down reduces the exit pupil's diameter, increases the angle at which rays coming from the exit pupil's edge are obstructed by the rear barrel. This may be what you meant to say.

[Bernice Loui]

Issue here is the camera coupled with the image maker's lack of understanding and experince using a view camera.. Victim being the 75mm f5.6 Super Angulon. Know the Schneider 75mm f5.6 Super Angulon has been in production for decades burned umpteen sheets of film by a vast number of sheet film view camera users world wide for decades.. There are extremely good and valid reasons why the 75mm f5.6 Super Angulon has endured this test of time and image making by so many image makers world wide..

75mm f5.6 Super Angulon has a spec image circle of 198mm at f22, image circle needed for 4x5 is 154mm. This gives an image circle margin of 44mm or plus/minus 22mm at f22.

~Hint, avoid using f32 or smaller than absolutely needed exposure apertures as there is a lens performace trade off here. If f16 produces enought percieved in focus areas in the image good enough, using a smaller expsoure aperure is not going to "make it better"...

Issues with the Intrepid 4x5 camera has much to do with no camera center indcators or click stops to allow the user to positively determine and know the front standard is centered to the rear standard with no rise/fall/shift or tilt/swing. This is not a small issues, this is IMO a very serious user limitation. To cure this will be on-going problem, add these indicators or stops on your own to stop this problem once and for all.

The inability to focus at infinity with the camera standards not centered is due to the bellows being compressed and restricting the amount of bellows compression needed to achieve lens focus at infinity. This also means limitied camera movements with this focal lenght of lens.. The solution is to use a bag bellows if possible. Another camera limitation that does not properly support the lens being used.

~Another example of how lens should decide camera choice and camera's capabilities to properly support the lens to be used.

As for the Fresnel ground glass image "brighter" stop using any Fresnel lens on the ground glass as a "viewing aid". They will cause more problems with wide angle lenses on view cameras than any possible image viewing assistance. The far better overall solution is to use the very best ground glass available, a good dark cloth, a tilting ground glass loupe and learning how to view the ground glass image with NO fresnel lens.

75mm is not that wide on 4x5, what would be wide is 47mm. In this case the ground glass image at the edges will be more difficult to view than the 75mm due to the angle of light rays to the ground glass and inherient light fall off (vignetting) of "Biogon" style wide angle large format lenses.

It should be noted these "biogon" style wide angle lenses do not behave in the same way as Retrofocus wide angle lenses commonly found in fixed to the camera body cameras.. These Retrofocus wide angle design lenses have an advantage to correct for light fall off (vignetting) due to the fixed distance between film or digital imager distance to the rear of the lens. When this distance is longer than the effective lens focal lenght (14mm lens with a fixed back focus of say 40mm) the rays of light exiting the lens rear is forced into being a smaller cone of light that can aid in reducing light fall off or vignetting.. Or why the habits or what has been learned from using fixed to the box cameras do not apply to this view camera wide angle lens stuff.

Correction for light fall off (vignetting) of Biogon style wide angle view camera lenses is done using graduated netrual density center filters that are effectively the reverse of the inherient light fall off designed into the LF wide angle lens.. another topic.

How much light fall off or vignetting is acceptable in the image is decided by the image maker, type of film beiing used and ...


Bernice

But the real issue seems to be with centering the rise on the Intrepid 4x5 camera. I've been doing this by eye, but clearly, that is not enough. What is troublesome is that the Intrepid doesn't really have a means of knowing zero rise, or it doesn't until I mark my front standard with something very permanent so that I will know instantaneously in the future. Worse, even with a (cheap) fresnel, viewing the corners on the ground glass is impossible; it's pitch black. Which suggests I need to invest in something (a better fresnel, perhaps, and/or a better ground glass).

Yesterday, I used a laser level and measuring tape to find true zero rise on the front and rear standards, and then took out my trusty Leatherman to carve a mark on each standard. Then I tried again with the 75mm (set to f/32 to answer the question above), an re-took the photograph (once with the Polariser, once without). I now see that the lens does indeed cover 4x5, which is an enormous relief, as well as focus to infinity (normally this won't happen on an Intrepid unless one uses some kind of recessed lens board).

This doesn't completely solve my problems, but it does save me from binning the lens. I am not sure how I am going to compose shots if I cannot see the corners..... But, that is a different problem......

[Robert Opheim]

I have always cut the corners of my ground glass to check to see if there is a full circular iris when stopped down. Depending if you are using a bag bellows - with one there can be more movement then the lens has image circle. Sometimes a non-wide angle filter can cut off some image circle at the edge. As far as your Intrepid camera - you may need to add a mark to show the center location.

[Maris Rusis]

Checking wide angle lens coverage by trying to see the back of the lens through the clipped corners of a ground glass is downright difficult. You can end up in some awkward contortions and the tiny exit pupil of the lens is easy to miss.
But there is an easier way. Go around to the front of the camera and look through the lens. If you can see all four corners of the 4x5 frame through the entrance pupil of the lens then those corners can also see you and there will be no vignetting.