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Kevin J. Kolosky
17-Feb-2013, 10:38
How does one determine the proper DB board for a specific lens?

Leonard Robertson
17-Feb-2013, 16:02
I don't have a direct answer to your question, but looking through my Bookmarks, I found a few links which may help a little:

http://www.largeformatphotography.info/forum/showthread.php?60289-Sinar-DB-shutter-systems-Need-some-help

http://www.largeformatphotography.info/forum/showthread.php?20606-Sinar-Shutter-f-4-versus-f-5-6-and-Cables&highlight=sinar

http://www.cameramanuals.org/prof_pdf/sinar_code.pdf Pages 17 and 18 deal with lens boards and lenses.

Len

Kevin J. Kolosky
17-Feb-2013, 16:34
No help. There doesn't seem to be any numbers on the DB boards that correlate with anything in the Sinar literature concerning proper DB boards for certain lenses. Is there a measurement or something else that controls this?

erie patsellis
17-Feb-2013, 17:18
If you insist, take a look at http://www.image2output-support.com/downloads/sinar/View%20Camera%20Service%20Manuals/Lens%20Mounting.pdf for starters. I will either answer your questions or leaving you scratching your head, but that's the reference that Sinar service used.

Leonard Robertson
17-Feb-2013, 17:33
Yeah, I didn't think the information I posted would be much help. There have been some threads on this forum regarding moving lens cells from DB mount lens boards into standard Copal shutters. So I would think it depends on the shutter size of the lens you wish to mount into a a DB board. If your lens is mounted in a #1 shutter, then you need a DB board threaded for those lens cells. However, a quick search of eBay leads me to think most sellers of DB boards don't know what size they are selling. One seller on there has a board he identifies as for a #1 from a 210mm Sironar. A couple of other DB boards don't give any measurement of the thread size the lens cells screw into. You would probably need to contact the seller, whether on eBay or wherever, and ask them to measure the approx. size of the threads, then see if the size is right for your lens cells. I would imagine DB mounts are mainly sized to the common modern shutter sizes, #0, #1, #3. Then there is how far your rear cell sticks out the rear of the DB mount and if it will clear the shutter blades. If you can find good pics of a DB mounted lens of the same make and FL the as the one you want to mount (either on eBay or Google Images), you can probably get a reasonable idea on the board you need. I think you have posted a good question; one I haven't seen before. Maybe someone else will come up with a better answer the I've given.

Len

Leonard Robertson
17-Feb-2013, 17:48
Wow! Erie seems to have posted the real answer, all 214 pages of it. I wondered as it was downloading why it was taking so long. I certainly Bookmarked it for future reference. It leads me to think buying a lens already in DB mount might be the sensible thing to do.

Len

Kevin J. Kolosky
17-Feb-2013, 20:28
Very good. So, from that information, it is not just the thread size that matters. It is also the length of the mounting "tube" that also matters. Too bad that these mounting tubes don't seem to have numbers on them.

Thanks.

erie patsellis
17-Feb-2013, 21:45
Not just the length, but the offset to the front as well. Typically on longer lenses you'll see one to a few spacers bringing the whole assembly forward to clear the shutter blades. ( with attendant extension for the aperture operating mechanism, of course)

Kevin J. Kolosky
17-Feb-2013, 21:59
Erie

I see that. So a DB shutter for a 180 mm lens won't work for a 210 mm lens even though they might go in the same Copal #1 shutter. Very interesting.

I am going to have to take the one I have completely apart so I can see what is going on in there!!

erie patsellis
17-Feb-2013, 22:11
They may, depending on the specific lenses and panels.

Armin Seeholzer
18-Feb-2013, 03:02
I'm from Sinarland would not hesitate to put a f5.6 150mm lens in a panel, where I know it was bevor in this case my old Symmar S 150mm mounted!

Cheers Armin

Kevin J. Kolosky
18-Feb-2013, 06:38
Armin

I wouldn't hesitate with that either.

But the problem is that one sees a lot of these DB boards being sold, and the seller advertizes that the board can be used "for anything that goes in a copal #1 shutter" or words to that effect. And of course, that is not true. Many lenses will go into a Copal # 1 shutter but, as I now understand it, will need a different DB board. The trick is to figure out which one, and that is a difficult task as they are not numbered.

Doremus Scudder
18-Feb-2013, 08:01
More reasons not to use DB boards!

erie patsellis
18-Feb-2013, 09:04
It would be fairly easy to make a gauge out of a piece of mat board that visually showed you if the rear element would fit and not be too deep. I have several DB mount lenses that also have their corresponding shutters mounted in boards, and switch them whether I'm shooting in the studio or out in the field.

Sevo
18-Feb-2013, 09:07
But the problem is that one sees a lot of these DB boards being sold, and the seller advertizes that the board can be used "for anything that goes in a copal #1 shutter" or words to that effect. And of course, that is not true. Many lenses will go into a Copal # 1 shutter but, as I now understand it, will need a different DB board. The trick is to figure out which one, and that is a difficult task as they are not numbered.

They are not numbered, as there aren't really "different DB boards" (even though Sinar for some time supplied dealers with pre-assembled combinations in markets where they sold no pre-mounted lenses). What may seem different are merely DB boards assembled with different amounts of extension tube length. The tube has a #, cast or rubber stamped on the inside, but I'd rather have the average ebay seller not disassemble his boards to the point where he can read that...

Actually it is quite simple, you need enough DB extension tube to make up for the rear cell depth and clear the shutter. Putting lenses in DB boards with slightly too much tube is harmless - it won't make shift and tilt calculations any easier, as the lens node moves further off the lens board plane, and as the excess length grows bigger, the shutter will vignette, restricting movements. But for tube lengths that aren't self-evident in even the shoddiest ebay picture, the consequences will be fairly irrelevant, even more so when it comes to Plasmat or Dagor types. The main concern would be buying too shallow a board for the given lens - but the service manual posted in this thread can tell you which depth you need, and you might be able to get at least some sellers to measure their offerings for you...

Kevin J. Kolosky
18-Feb-2013, 10:45
They are not numbered, as there aren't really "different DB boards" (even though Sinar for some time supplied dealers with pre-assembled combinations in markets where they sold no pre-mounted lenses). What may seem different are merely DB boards assembled with different amounts of extension tube length. The tube has a #, cast or rubber stamped on the inside, but I'd rather have the average ebay seller not disassemble his boards to the point where he can read that...

Actually it is quite simple, you need enough DB extension tube to make up for the rear cell depth and clear the shutter. Putting lenses in DB boards with slightly too much tube is harmless - it won't make shift and tilt calculations any easier, as the lens node moves further off the lens board plane, and as the excess length grows bigger, the shutter will vignette, restricting movements. But for tube lengths that aren't self-evident in even the shoddiest ebay picture, the consequences will be fairly irrelevant, even more so when it comes to Plasmat or Dagor types. The main concern would be buying too shallow a board for the given lens - but the service manual posted in this thread can tell you which depth you need, and you might be able to get at least some sellers to measure their offerings for you...

Having fooled around with a couple of DB boards and some lenses here for the past few days I am well aware of much of what you have said.

For example, I have a mint condition DB board here with a copal 0 hole. I can mount a 90 Super Angulon and it works perfectly with the DB shutter. But if I put the 120 lens on it the lens bumps the shutter a tiny bit so it cannot be mounted on the camera in the normal way. It needs just a hair of extension, or as you say, a longer tube, in order to be able to mount it on the camera.

I am using a P2 and I suppose that I could just get an F standard to mount the shutter on and mount the lens on the P2 standard, but as you mention problems there as well.

Lots of lenses offered in DB mounts. They don't seem to sell very well. I have seen the same lenses in DB mounts on Ebay for months. But the sellers insist they have a piece of gold there.

I wonder where I could get some extension tubes??????

There are some numbers. But they don't correlate with anything in the Sinar literature. For example, this copal 0 board I have has the number G 817 on it. Can't figure out what that means.

Leigh
18-Feb-2013, 10:53
The shutter needs to be as close to the rear of the lens as possible, to avoid vignetting.

Were that not the case, they could just make one version of the DB mount with an extension
long enough to accommodate the longest (rear cell) lens.

The cell spacing will be the same for all lenses designed for a Copal #0, or a #1, or a #3.
This is fundamental to the optical design of the lens.

They even tell you in the Sinar instructions to move any spacing shims from the original
shutter mount to the DB mount if present.

Leigh

Kevin J. Kolosky
18-Feb-2013, 10:55
More reasons not to use DB boards!

Of course, when one uses a variety of shutters one must be aware of their nuances, including variances in shutter speeds. In my mind the beauty of the DB shutter, and the sole reason why I want to use it, is because I have one set of shutter speeds.
Each to his own.

Kevin J. Kolosky
18-Feb-2013, 10:57
The shutter needs to be as close to the rear of the lens as possible, to avoid vignetting.

Were that not the case, they could just make one version of the DB mount with an extension
long enough to accommodate the longest (rear cell) lens.

The cell spacing will be the same for all lenses designed for a Copal #0, or a #1, or a #3.
This is fundamental to the optical design of the lens.

They even tell you in the Sinar instructions to move any spacing shims from the original
shutter mount to the DB mount if present.

Leigh

yes, I am aware of that.

Leigh
18-Feb-2013, 11:02
...including variances in shutter speeds.
Shutter speed errors are a great marketing ploy for Sinar, being the reason
they came up with the DB system in the first place.

Unfortunately, it falls in the same category as the boogey man.
It's a fairy tale used to frighten children into being good.

The standard permissible error for shutter speeds of 1/125 and slower is 10%.

If you have a shutter that doesn't meet that spec, it needs to be serviced.
That's hardly sufficient justification to buy an entirely new lens/shutter system.

Leigh

Kevin J. Kolosky
18-Feb-2013, 11:07
Shutter speed errors are a great marketing ploy for Sinar, being the reason
they came up with the DB system in the first place.

Unfortunately, it falls in the same category as the boogey man.
It's a fairy tale used to frighten children into being good.

The standard permissible error for shutter speeds of 1/125 and slower is 10%.

If you have a shutter that doesn't meet that spec, it needs to be serviced.
That's hardly sufficient justification to buy an entirely new lens/shutter system.

Leigh

Of course that is all your opinion which you are entitled to. And in this particular instance your opinion and a two bucks will get me a cup of coffee.

Leigh
18-Feb-2013, 11:14
Not my fault you drink cheap coffee.

Leigh

Kevin J. Kolosky
18-Feb-2013, 11:16
Not my fault you drink cheap coffee.

Leigh

I don't believe I assigned any fault to the cost of the coffee I drink. Again, whether my coffee is cheap is your opinion, which you are entitled to. But as before, it and two bucks will buy me a cup of coffee.