Flange focal distances on Schneider Apo-Digitar lenses

[ll971]

Hi,

I'm new to large format lenses and cameras  that use them.  Actually,  I will try to use Schneider Apo-Digitar lenses (with Copal 0 shutter) on a bellow connected to my Canon Mark II (to control perspectives and focus).  I suppose this isn't really LF lenses, more like medium format and used with digital image sensors.

When locking on the actual lenses I'm little confused.  Some of the wide angle Schneider Digitar lenses have very short flange focal distances,  the 5.6/24mm XL is only about 24.2 - 26.4mm (varies on what shutter used), 5.6/35mm XL is 37.2 - 39.4mm, the standard lens 4.0/80mm L is 76.6 - 78.8mm (I have the 80mm, find one used in mint condition). 
http://www.aifo.se/pdf/Digitare_e.pdf

What medium format digital camera body can use a lens with a flange focal distance under 40mm and still have focus to infinity?  My Canon is 44mm between the mounting ring in front of the body and the digital sensor.
Maybe I misunderstand flange focal distances used with this type of lenses, i.e to get them focus to infinity.
Any help here? Thanks.

Jan Dansson
Sweden   

[Paul2660]

If I understand your question, I believe that you can only start at 90mm and on up as long as you use a DSLR 35mm body, i.e. Nikon or Canon.  The mirror box depth will not allow infinity focus for anything wider. 

You can read more about this on posts about the Arca DSLR2, which is a M2 designed around a Canon DSLR body.  The focal length for that is 90mm and on up and that allows you to get the rear element right up to the opening on the Canon or Nikon .

With a Sony mirrorless, you can get to 32mm, either using a Aptus by Cambo or Universalis by Arca. 

Read more about the DSLR with a Sony A7r here:

http://photosofarkansas.com/2014/11/07/the-arca-swiss-dslr-2-a-perfect-companion-to-the-sony-a7r-part-1-camera-review/

Paul

[EduPerez]

In the LF world, lenses do not have a flange distance like those on the DSLR world: in a DSLR camera, the lens stays at a fixed distance from the sensor, and the focusing is performed by moving one or more optical elements inside the camera; in a LF camera, the whole lens is moved back and forth. Now, simplifying everything a bit, and assuming that your Schneider Digitar lens behaves like an "ideal lens", we can use the following formula:

1/D = 1/d + 1/f

where D is the distance from the lens to the focal plane, d is the distance from the lens to the focused subject, and f is the focal length. Thus, a 35mm lens is expected to focus at infinity when placed at 35mm from the sensor, or closer to focus on closer distances; and coincidentally this matches what you have already found.

Now, the problem when attaching a DSLR camera to a LF lens using bellows, is that the front of your camera is where the LF film is expected to be. But the sensor is some millimeters behind, so the lens should be moved behind too, and sometimes it should even have to enter the camera to be able to focus on infinity.

[Rainer SLP]

HI,

The Canon EOS cameras for EF-S and EF lenses have a flange distance of 44mm. Any lens below that will not fit if you want to have the full focusing range.