90mm wide angle on Omega 45D...no bag bellows.

[arizonafilm]

I would be interested in other folks' opinion about this problem: I am using an Omega 45D monorail, and would like to use a 90mm wide angle lens. I have a recessed lens board, but to my dismay, I find changing the normal bellows to a wide angle bag/baloon bellows impossible. It seems this model was not equipped to do so.

As I do not yet have a 90mm lens, the simple answer to "Can I effectively use a 90mm lens with the recessed board on this camera without a bag bellows?" remains unanswered. Anyone have experience down this path?

 

[Ian C]

We discussed this here beginning on January 26, 2012.

(there was a url link here which no longer exists)

Ultimately, it depends on the camera and lens and how much you need to use the movements and whether the standard bellows get in the way of anything.

 

[arizonafilm]

I can't understand how I missed that thread! Thanks for giving it to me, Ian. That turned out to be immensely helpful.

So, by the suggestion to compress the bellows and measure from the face of the lens board to the GG, I measured 90mm, tight. That was with both standards compressed as tight as possible, off detent and justified equally towards the monorail clamp with the standards bumping into each other.

I then measured the depth of the recessed lensboard, coming in at a depth of 40mm, which in turn allowed me to decompress the bellows a little back out, presumably giving me 50mm to play with, right?

That is necessary because little, if any, movement can be had when fully compressed.

I then backed away the standards until they were equally centered on their carriers, but still against both ends of the tripod mount. The measurement from the lens hole in the recessed board to the inside face of the ground glass is 50mm. This should give me 40mm of play for adjustments as I expand the belows out towards 90mm...I think!

It seems (if I got all that right!) that with a 90mm lens mounted to the recessed lens board, I should be able to work with that, albeit not as flexible as a bag bellows, I bet.

If all of that math and measuring and assumptions are correct, it would indicate that a bag bellows is not necessary, hence the reason why it was not made to change out. Obviously, the 'acid test' is with a mounted 90mm lens, and then looking through the lens under extreme angles back to the GG to see if clipping occours as another person suggested in that link you provided.

 

[Ian C]

From your comments, I’d say that you understand the situation correctly.

Whether you can focus or not depends on the flange-to-film distance at infinity focus (when the lens is placed most closely to the film).

Here are two 90mm lenses for which I have these dimensions as supplied by Nikon.

90/8 Nikkor SW: Flange focal distance 97.0mm

90/4.5 Nikkor SW: Flange focal distance 97.4mm

As you described your camera you should be able to do most of the things you want. Other makes of 90mm lenses might have a different flange-to-film distance at infinity, but probably wouldn’t differ by much compared to the 90mm Nikkors above.

With the bellows nearly solid, you could shoot with the lens centered over the film and the film parallel to the lens board, but you’d have very little movement should you wish to correct for converging verticals and so forth.

The use of the recessed lens board will certainly help by relaxing the bellows by the distance provided by the recessed board.

So long as you keep the lens centered over the film and the lens board parallel to the film, there will be no “clipping” from the bellows.

It is precisely the situations when the movements are used that the smaller cross-section standard bellows can block the lens’s view of part of the film. That’s where generously-sized bag bellows allow us to use our movements without the bellows intruding and their short length prevents them from compressing solidly which would prevent short focal length lenses from attaining focus.