rear lens element to focal plane distances for different format cameras

Started May 20, 2012 | Discussions thread
Joseph S Wisniewski Forum Pro • Posts: 34,130
Enlarger lenses, or remount a Zeiss...

tektrader wrote:

Thanks Harry, Yes you can see from my other thread about enlarger lenses I was heading that route as well.

Its a bit limiting having to turn the whole mount around. I was used to 8x10 bellows cameras years ago and was trying to get that same flexibility with the bellows unit on my D800 whihc is coming.

You can't. Sorry.

Whats the image quality like with the enlarger lens?

Surprisingly good. Especially if you manage to get your hands on an APO Componon. The Nikons aren't too bad, either, especially the second series.

If you want to up your game, get a Zeiss 100mm f2.0 Makro Plannar (about $1800) have it remounted in a short barrel (about a $300 job at a good shop) and you can just hit infinity focus on the PB-4, although a Sinar is better.

I was thinking it may just be a bit better with a large format lens to get the image circle.

No. Because of the huge image circles (135mm is a longish wide on 4x5, an ultrawide on a 8x10) image quality goes down.

The focus point at infinity was a bit baffling for me so i figured it was easier if I knew the mount to film plane distance as I could approximate the fit to the bellows better.

But you can't. Large format lenses mount through the lens board, half the lens goes inside the 4x5 or 8x10 camera. Medium format lenses are nearly symmetrical, with the front node, rear node, entrance pupil, exit pupil, aperture, and shutter all being coincident within a few mm. So, a 100mm lens has almost 50mm behind the coincident point, and the rear element would collide with the rear standard, because the graflok adapter and camera (with deep recessed sensor) are so far back. Even a 120mm lens will do this. (been there, done that).

And that's with half the lens inside the camera. The PB-4 isn't big enough for this. You'd have to build an "adapter box" with a board at the front for the large format lens, and a mount at the back for the PB-4. You'd be better off using a 4x5 or a 2x3 (6x9 "metric") as your adapter. You can pick up about 15mm more on the rear by eliminating the rear adapter and using a bracket that bolts to the camera's tripod mount for the motions, and provides a bellows "attachment flange" you snap into your camera's lens mount. Sinar makes an excellent one.

But that still won't get you going with lenses shorter than 100mm. In one of your four earlier posts, you said you wanted a 24mm. Large format limits you to lenses basically 100mm or longer when using a 35mm DSLR, no matter what you do. The only alternative is a MF back with "direct to sensor" mount.

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Rahon Klavanian 1912-2008.

Armenian genocide survivor, amazing cook, scrabble master, and loving grandmother. You will be missed.

Ciao! Joseph

http://www.swissarmyfork.com

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