Super Angulon 90mm f/8 - focal length/angle of view using only front element?

[jameswangphoto]

Hi, I'm new to the large format world... so I apologize if this is a silly question.

I am using a 4x5 Cambo with a Fotodiox Graflok to Nikon adapter back to shoot digital. The first lens I bought was a Schneider Super Angulon 90mm f/8, which I cannot get to focus at all. The DSLR sensor actually sits a few cm back from the film plane, so I'm guessing the 90mm is too wide for this setup?

Anyway, I just tried removing the rear element, and voila! now I can focus. Are there any drawbacks to using half the lens? Is there a loss of sharpness or increase in distortion? Also, I'm curious what the focal length becomes.

Thanks for any insight! I'm hooked on LF and excited to learn more.

James

[E. von Hoegh]

That lens is not convertible; when using the front element alone you will get distortion, abberations, an unknown focal length, and an unknown aperture.

Using a DSLR on a view camera is not large format, which doesn't mean people here won't be glad to help you.

[Dan Fromm]

I am using a 4x5 Cambo with a Fotodiox Graflok to Nikon adapter back to shoot digital. The first lens I bought was a Schneider Super Angulon 90mm f/8, which I cannot get to focus at all. The DSLR sensor actually sits a few cm back from the film plane, so I'm guessing the 90mm is too wide for this setup?
James

Hmm. 90/8 SA flange to film distance at infinity is 99 mm. Nikon SLR flange-to-film distance is 46.4 mm. Fotodiox adapter's rear of lens board to Nikon flange distance = ?. If you want to focus the lens to infinity, your Cambo's minimum flange-to- film distance can't be greater than 52.6 mm - the Fotodiox ?.

I b'lieve that there are boards with a 30 mm recess for 4x5 Cambos. One would help.

People complain here fairly often about problems focusing 4x5 Cambos with short lenses. Setting the camera up with the tripod block between the standards is a common cause. Put the tripod block behind the rear standard or in front of the front standard.

You can get the standards closer together if you reverse the rear standard. Cambo recommends setting their cameras up with both standards' carrier frames behind the standards, but turning the rear standard around so its carrier frame is in front is possible. Usually not recommended because with the back in landscape orientation the darkslide can't be withdrawn (hits the uprights). Your digital Nikon doesn't have a dark slide, so if it will fit in the slightly less than 6.5" between inner tilt pivots you can reverse the rear standard. The carrier frame is the section that accepts a lens board in front and a focusing panel in the rear. If you do this you'll absolutely need a bag bellows.

[jameswangphoto]

That lens is not convertible; when using the front element alone you will get distortion, abberations, an unknown focal length, and an unknown aperture.

Using a DSLR on a view camera is not large format, which doesn't mean people here won't be glad to help you.

Good point-more accurately, I'm new to large format _equipment_. You could say I'm a reformed DSLR user

Although the Fotodiox adapter does let the DSLR slide and rotate, meaning you can stitch together multiple frames into a high resolution image. Almost like a Better Light Scanning back?

[Pascal Moreaux]

Thank you Dan,

I just bought a second hand Cambo SC2 and a Schneider Super Angulon 90 mm F8. I stayed almost 30 years without using a large format, the only experience I have was during my photography studies. So, it's a big come back...
My first attempt was a disaster, eventhough I have a recessed lensboard it was just impossible to focus at infinity, even at 4 or 5 meters no way.
I felt bad until I read Dan Fromm reply.
I tried to invert the front standard only, (I didn't move the one to the back) in order to be able to approach the two standards to each other and it seems to work! I can focus farer than 1 or meters like it was the case before. Tomorrow I will do some new attempts outside.
Many thanks

[BrianShaw]

Learning to shoot LF by using a Cambo and a 90 mm lens is like learning to juggle while wearing handcuffs. It would be so much more effective to use a "normal" focal length lens.

[mdarnton]

As far as using half a lens: if it works for you and you like the results, then it works. Don't expect normal results, though.

Thank you Dan,

I just bought a second hand Cambo SC2 and a Schneider Super Angulon 90 mm F8. I stayed almost 30 years without using a large format, the only experience I have was during my photography studies. So, it's a big come back...
My first attempt was a disaster, even though I have a recessed lensboard it was just impossible to focus at infinity, even at 4 or 5 meters no way.
I felt bad until I read Dan Fromm reply.
I tried to invert the front standard only, (I didn't move the one to the back) in order to be able to approach the two standards to each other and it seems to work! I can focus farer than 1 or meters like it was the case before. Tomorrow I will do some new attempts outside.
Many thanks

Try taking off the tripod mounting block and putting it behind both standards in their normal modes. That lets you get them closer together (the block blocks).

[Sevo]

The Super-Angulon does not have offset nodes (i.e. it is not or only insignificantly tele- or retrofocal). So it can be inverted - presumably with a loss of performance (static lenses can only be optimized for a limited distance range - inverting it changes the ratio from, say, 20:1 to 1:20, so it will be very much working outside designed specifications), and obviously with usability issues (the release and all levers moving into the camera). But inverting is optically possible - while the request of the original poster probably is not. The halves of a SA seem to be afocal (i.e. rays passing them do not converge anywhere between zero and infinite distance), so using only one half of a Super-Angulon would not give a image, regardless of setting and distances.

[mdarnton]

The halves of a SA seem to be afocal (i.e. rays passing them do not converge anywhere between zero and infinite distance), so using only one half of a Super-Angulon would not give a image, regardless of setting and distances.

Except for the very tiny, almost insignificant detail that the OP already said he could focus an image with half the lens. :-)

[Sevo]

Except for the very tiny, almost insignificant detail that the OP already said he could focus an image with half the lens. :-)

Right, but that sounds very odd - mine don't create an image. The description leaves many questions unanswered - we don't know whether he attached a camera with lens as the "digital back", nor where he split the lens, and that the full lens did not focus anywhere might also describe a defect (or a half Plasmat-half SA accident).