View Full Version : Recessed board for a 135mm?

Sam N
21-Mar-2011, 23:16
I've got a Toyo/Omega D which I love but which unfortunately has non-removable bellows. I recently used it with a 135mm/5.6 Caltar II-N (relabeled Sironar N) to shoot some architecture and found that the bellows wasn't extended enough for me to be able to use the full coverage of the lens. I was trying to correct verticals but I ended up having to compromise my plane of focus a bit and let DoF take care of the difference. I didn't want to force the bellows and end up damaging them.

I feel like a recessed lens board would allow me to push the standards a bit further apart and thus give me a little more bellows to manipulate. Am I correct in thinking this or should I just stick to 150mm+ lenses with this camera?

22-Mar-2011, 03:37
As a relative newb maybe I should not reply here, but if you are looking for a bit more bellows extension, wouldn't you want to use something like a top hat rather than a recessed lens board?

Dominique Cesari
22-Mar-2011, 06:17
A recessed board will help (Sam, you are correct to have it in mind). I never used a Toyo/Omega D. Do they use a 158x158 mm square lensboard ? If they do, the recessed one are generously dug and you will get a worth supplemental shift, say 2/3 to one inch.
I presume that the 110x110 mm are less recessed. Starting from a blank lensboard, you could have the hole drilled offset and provide shift (I use that on a Sinar/Horseman board - they may be used upside down, so one can take shift on both).

22-Mar-2011, 07:20
Sounds like a good opportunity for me to learn the difference and purpose of top hats vs recessed boards. Anyone care to help.:confused:

Gem Singer
22-Mar-2011, 07:27
Extension lens boards (top hats) are used to obtain more bellows extension for longer lenses.

Recessed lens boards are used to help relieve bellows compression and add for more movement capability with shorter lenses.

Jack Dahlgren
22-Mar-2011, 07:29
Sounds like a good opportunity for me to learn the difference and purpose of top hats vs recessed boards. Anyone care to help.:confused:

While a top hat is functionally equivalent to increasing the bellows length particularly at full extension, it does this by allowing the standard to remain closer to the film plane than the lens flange. When you are looking to focus at infinity that will cause the bellows to be more compressed - imagine you have a 50mm top hat and a 135 mm lens, at infinity the standard would be 85mm from the film plane rather than 135mm without it.

Because the person posting said that the bellows got in the way, further compressing them by using a top hat would make the problem worse.

Recessed lens boards are designed to get the lens closer to the film plane and are effective with short focal lengths.

22-Mar-2011, 08:03
Jack, thanks for taking the time. Your explantion made perfect sense.

Sam N
24-Mar-2011, 00:54
Thanks for the help all.

Yes, Dominique, the 45D uses the larger Toyo lensboards and they're quite deep (a rented 90mm I used came with one). I'll look into getting one.

24-Mar-2011, 12:23
I am surprised that the bellows on your camera are binding with 135mm of extension I think believe a recessed board is your only option.