Measurement for recessed lenboard for wide angle.

[Ed Bray]

I have just bought a Horseman LX (not arrived yet) and already have a Toyo C, having looked at lensboards (why are Sinar/Horseman lensboards twice the price of a similar lensboard for the Toyo?) I realise that I will need a recessed board for my Schneider 47mm SA XL to enable infinity focus.

Is there a way of finding how deep the recess needs to be other than actually measuring the distance between the rear of the lens and the ground glass when the lens is focussed on infinity?

I have searched the Schneider lens data but cannot seem to find this (what would be very useful measurement).

Due to the cost of the recessed lensboards I would rather get this right first time.

TIA.

[Bob Salomon]

The flange focal length of the lens tells you the distance the rear of the shutter needs to be from the ground glass when you are focused at infinity.
The distance between the front and rear standards will tell you how deep a lens board needs to be when they are as close to each other as possible. You may need a W/A bellows to get the standards close enough.

[Ed Bray]

Hi Bob and thanks for you answer, I have a set of bag bellows coming with the camera. I will measure the differene between the standards once they have arrived.

[ic-racer]

I have just bought a Horseman LX (not arrived yet) and already have a Toyo C, having looked at lensboards (why are Sinar/Horseman lensboards twice the price of a similar lensboard for the Toyo?) I realise that I will need a recessed board for my Schneider 47mm SA XL to enable infinity focus.

Is there a way of finding how deep the recess needs to be other than actually measuring the distance between the rear of the lens and the ground glass when the lens is focussed on infinity?

I have searched the Schneider lens data but cannot seem to find this (what would be very useful measurement).

Due to the cost of the recessed lensboards I would rather get this right first time.

TIA.

Going by the numbers the minimum distance in the LX is 60mm and the Schneider lens has a flange focal of just about 60mm (I suspect that is from the way they have the lens elements spaced with the shutter more toward the front). So you could theoretically get by with just about any amount of recess beyond a few mm. Realize the more recess you have the harder it will be to operate the shutter.

[Ed Bray]

Going by the numbers the minimum distance in the LX is 60mm and the Schneider lens has a flange focal of just about 60mm (I suspect that is from the way they have the lens elements spaced with the shutter more toward the front). So you could theoretically get by with just about any amount of recess beyond a few mm. Realize the more recess you have the harder it will be to operate the shutter.

Thanks for the info, it's very true as regards the operating the controls, at the moment it is in a Toyo recessed lensboard with a 40mm recess and it is a right pain to get to the controls. If I am able to use a less recessed lensboard on the LX I will be well chuffed.

[Steve M Hostetter]

I make 1" deep on 6x6" wooden lens boards.. I use a 210mm barrel lens on it with an 11x14 format expansion back which extends the total depth of existing Korona 8x10 cam 6"

[Ed Bray]

Thanks for the info.

I got my LX and measured the minimum distance and it was exactly 60mm, I then tried the 47mm SA XL on a flat board and it would just not focus to infinity, the back focus of a 47mm SA XL is 59mm.

I then asked my next door neighbour who is a toolmaker, if he could put a 2mm recess 100mm in diameter into one of my flat 0 holed Sinar boards. The board's plate is 3mm aluminium. This he did and as soon as he gave me the lensboard back I painted the recess black to match the rest of the board, after it had dried, I mounted the 47mm SA XL into the board once again, happily, this time it does focus to infinity (and beyond).

So I am well chuffed, hardly a noticeble recess, lens focuses beautifully and I can easily get to all the controls, I have just got to get a centre filter for it now.

[ic-racer]

Thanks for the info.

I got my LX and measured the minimum distance and it was exactly 60mm, I then tried the 47mm SA XL on a flat board and it would just not focus to infinity, the back focus of a 47mm SA XL is 59mm.

I then asked my next door neighbour who is a toolmaker, if he could put a 2mm recess 100mm in diameter into one of my flat 0 holed Sinar boards. The board's plate is 3mm aluminium. This he did and as soon as he gave me the lensboard back I painted the recess black to match the rest of the board, after it had dried, I mounted the 47mm SA XL into the board once again, happily, this time it does focus to infinity (and beyond).

So I am well chuffed, hardly a noticeble recess, lens focuses beautifully and I can easily get to all the controls, I have just got to get a centre filter for it now.

Good work!

[Ed Bray]

Thanks, it just seems so surprising that such a small recess could make such a difference.