View Full Version : lensboard too thick - rear cell won't screw in

17-Feb-2008, 14:32

i have a problem that i have not encountered yet. the lensboard (sinar) is too thick to mount my shuttered lens on. the flange does not screw down far enough for the rear element to screw in all the way (the edge of the rear lens barrel hits the flange and stops before it can seat all the way down into the shutter). is there anything to do to correct this? the only thing i could think of would be to have a machinist counter-sink the rear of the lensboard to allow the flange to sit flush. this isn't great, as i really want/need to try the lens now. any alternatives?

thanks for your help!

edit: i should add that the shutter is a prontor professional, and it mounts fine on the thinner technika lensboard that it came with.

edit #2: i should also add that i have a plaubel camera on the way that i will probably end up using (and selling the sinar), so that is another reason i don't want to go through the hassle/expense of having the sinar board machined.

Patrik Roseen
17-Feb-2008, 15:13
There are threads on this forum talking about using different methods to attach a lens to a lensboard. One (which I have not used myself) suggests using 'hot glue' on the back side threads instead of the flange. Maybe this could work for you.

Or find a a thinner flange...

17-Feb-2008, 15:16
tanks patrick. the hot glue might do the trick. i guess i didn't realize that you can find thinner flanges. i had thought about sanding it down though (or using a dremel on the inside edge).

17-Feb-2008, 18:06
I had the exact same problem with the exact same shutter when I remounted a 55 Apo Grandagon in a Prontor Professional shutter for use on my Sinar. The solution was two part. First, I found a Horeseman lens board on eBay, from one of the frequent sellers in the far east, that had a step cut into the back around the shutter hole, reducing the thickness to about half normal, but still plenty of material. Second, I made sure to use one of my retaining rings having the curved profile, rather than the thicker flat retainer that came with the shutter. The combination gave me just enough clearance to properly mount the rear element, with a few tenths of a millimeter to spare. There are a couple of Sinar-type lensboards with similar machining on eBay right now.

17-Feb-2008, 18:49
Use gaff tape. I mount all my recent purchases this way so as to see what kind of coverage they have and what they look like on the GG. Then again, I buy all old brass lenses and the like, usually without flanges.

Jim Noel
17-Feb-2008, 19:51
Gluing and taping can be hazardous to lens falling off. I drill and tap the lens board so the ring can be mounted on the front with small, short bolts. This solves the problem of screwing in the rear element.

Patrik Roseen
18-Feb-2008, 05:27
Gluing and taping can be hazardous to lens falling off. I drill and tap the lens board so the ring can be mounted on the front with small, short bolts. This solves the problem of screwing in the rear element.

Would this not make the 'lens board' (original lensboard + ring in front) even thicker?

Gene McCluney
18-Feb-2008, 10:17
There is something odd here, as a Sinar lensboard is a fairly thin metal lensboard, and most, if not all modern shutters are "sized" to work with modern metal-type lensboards, and they are not all the same thickness.

Does your jam-nut have a ridge? In some modern shutter jam-nuts, you have to drill the lensboard hole big enough for the jam-nut ridge to seat in to. This requires making the lensboard hole a little bigger than required to just fit the shutter threads.

Dan Fromm
18-Feb-2008, 11:07
This problem came up a month or two ago.

You don't want a flange, you want a retaining ring. You have the wrong part. To see what's needed, visit www.skgrimes.com and look at what they offer in the way of flanges and retaining rings.

Bjorn Nilsson
19-Feb-2008, 07:19
I think that Gene is on the right track. See to that the retaining ring sinks into the lensboard and that only the ridge locks the shutter.
If it looks like on the attached picture you do have this problem. Then you have to make the hole in the lensboard a tiny bit larger.


19-Feb-2008, 10:41
wow..thanks for all the replies! i hadn't checked this thread in a while, and forgot to subscribe to it at first (so sorry for the delay on my reply)

mrossano: having a stepped hole drilled (or purchasing a board that is already drilled as such) was all i could think to do. i did want to hold off on that though since i might be selling the sinar in favor of a plaubel i have on the way. as for the the curved profile retaining ring, i guess i didn't realize they existed. all of mine are squared off. and to clarify, is the curved portion on the outside or inside of the retaining ring. based on bjorn's photo (which, i assume, is a curved profile retaining ring)...it seem as if the curve is on the outside, and that wouldn't help me.

Jim Noel: i guess i used the wrong terminology. it is a retaining ring i have, not a flange...so front mounting isn't possible. i also think that patrick is right, and it would give me even more trouble mounting the rear element. i would need to bore out a bigger hole on the lensboard.

Gene McCluney: yeah gene, i thought something was odd about this too. but i have to disagree on the lensboard. they are some of the thicker ones i have encountered. it's an original sinar board too (not an aftermarket), and it was factory drilled for a size one shutter. and yup, the ridge in on the jam nut does sit inside the hole...not ouside, so that isn't my problem. it's literally just that the combination of the lensboard thickness and the thickness of the retaining ring won't allow me to screw the element in all the way.

dan: seems i used the wrong terminology. i have a retaining ring, not a flange.

björn: thanks for the photo. that isn't the problem i have. i'll post a photo here in a bit showing what i'm running into (and showing that the retaining ring is seated correctly).

again, thanks for all the help! this is just frustrating as i can't wait to try this out!!

19-Feb-2008, 11:04
here are some photos to illustrate. sorry for the quality, my digital camera is a crappy old 2.1mp. naturally the only use i have for digital is photos like this :)

photo 1: shows that the retaining ring seats correctly

photo 2: shows where the lens is coming into contact with the retaining ring

photo 3: shows max allowable lensboard thickness for this combination before lens barrel comes into contact with retaining ring. it's 2.5mm, and the sinar lensboard is 3.0mm. do you think it's just because the wider portion of the retaining ring is so tall? it just seems odd that a combination that should be all standard wouldn't just fit. :confused:

Gene McCluney
19-Feb-2008, 13:42
You are absolutely right, from your photos your particular shutter situation does not fit the Sinar lensboard well. If you had a more common Copal or Compur (rather than Prontor) shutter I think the situation would be different. It is odd that there is so little room for accepting various thickness in the lensboards with your particular shutter.

20-Feb-2008, 12:42
The curved profile rings have the curve on the outside. They are slightly flatter than the square profile rings, and the flare from the curve radius give additional clearance on lenses such as some of the Apo Grandagon and Apo Sironar-S models (as examples) that have a rear cell with considerable flare near the shutter threads. I have four of my lenses mounted in these shutters, three in either 01S or 1S sizes. Two of the lenses had clearance problems in Sinar boards, while having no problems with Technika boards previously (not surprising, as the Technika boards are half as thick as Sinar's). As I remarked previously, two adjustments were needed for the Apo Grandagon. Another lens, an Apo Sironar-S (I don't remember now whether it was the 150 or the 210), was good to go with a retaining ring replacement alone.

20-Feb-2008, 12:59
thanks mrossano. i'm thinking of fabricating a new board out of wood for myself. i've spent too much money on camera goodies recently, and i'm also impatient to try this lens out. i could plane it to the correct thickness, use cork for a light trap, and then counter-sink the hole on the back to allow the retaining ring to sit flush. i need to make a board for a new flange-mount barrel lens too, so it wouldn't be too much extra effort. you've gotta love wooden lensboards on metal studio cameras! :)

23-Feb-2008, 00:23
I had this same problem with a prontor shutter going into a Calumet 4"x4" lensboard.

I sent the board off to SK Grimes and for $15. they milled the 2mm thick board to 1.2mm, allowing the retaining ring to seat low enough to not interfere with the rear element screwing all the way in.

I was dong some consulting at a machine shop and they quoted me a minimum of $60. per hour with a 1 hour minimum, so I sent the board to SK Grimes the next day. They do great work, and (amazing for the photography business) at reasonable prices!

23-Feb-2008, 09:31
that's pretty reasonable! i'll have to contact them if i can't get a wooden one made correctly.