Graflex.org

RichS · Posted: Sat Nov 01, 2003 4:10 am Post subject:

I came up with a minor problem tonight and (as usual) thought I'd ask for some advice here

I _finally_ got a replacement #4 shutter. Bet noone here remembers?

But I had a very nice 12-21-28 Gundlach lens that came in a "dog" dial set shutter that can not be repaired. The 'new' shutter is a rim set Ilex Universal, including sych and it seems to work great, although I haven't even tested the speeds yet. But at least this shutter has more than one speed!

Anyway, here's the problem. The new shutter is almost 3mm thicker than the old one. That spaces the elements 3mm further apart. Yes, I know this isn't good and the adapter should be cut for the proper spacing. But here's the question:

How do you know what the proper spacing is?? After 100 years and who knows how many shutters, how would anyone know that these elements had the proper spacing on the old shutter? Is there any way to actually test for this, without a million dollars worth of equipment anyway?

And, what if the spacing is off? I know it adversely affects performace and causes distortion. But what kind? What can I look for specifically if the elements are wrongly spaced? Just viewing the image by eye, I can move the front element out another inch and see nothing change. There must be some specific distortion that I can see to know if the spacing is off?

In the mean time, I'll be testing the lens as-is and trying to create a new f-stop scale for it, all three ranges... And if it all works out in the end, I'll be very happy with the lens I've wanted for a long time in a good, sych'd shutter. If not, I'll be e-mailing the S. Grimes folks for help

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Nick · Joined: 16 Oct 2002 Posts: 494

I've got the same problem. I bought a G-claron to put into a spare shutter I have. The shutter had one spacer. The lens a different one. Between the two of them you'd think it wouldn't be that hard.

When you say you moved the lens 1" and got no change that doesn't sound right. I think one problem is different lenses have different spacing requirements. Some are pretty tight others can live with sloppy spacing.

Where to find the info? Hopefully it's published someplace. I'm look at the PDF for my lens now. Not sure I'm reading it right but then I figure I'll muddle through.

RichS · Posted: Sat Nov 01, 2003 5:07 pm Post subject:

I've done a lot of searching and can't find any deffinite info on what exactly happens when the spacing is off. Everyone just says 'distorion' or bad things. Nothing specific. And no way to find the correct spacing...

The difference in this lens may be it's design. It is a convertible and the front and rear elements can be used seperately. I'm sure there is some kind of distortion from the extra spacing. I haven't tried this on the camera yet and probably won't have time this weekend. Maybe I'll be able to see something better on the GG?

I know the S.Grimes web site mentions calculating the spacing, and finding it optically. But they have the expertise and equipment. I'm just hoping that this lens won't need their professional help. I have no idea what they would charge for such an adjustment?

I could also easily trim down the original mount the 3mm (or 1.5mm on each one to keep it centered) but not yet. I have to see what it looks like first and hopefully find ut what I should be looking for?

If you can find published data on your lens, that would be great. I doubt there's any on this one

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"Ya just can't have too many GVIIs"

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Nick · Joined: 16 Oct 2002 Posts: 494

How much they'll want will depend on how much work you want them to do. It looks like they'll provide a new F/stop scale for about $45. They'll mount the lens to a lensboard and according to the website

"We routinely bore lensboards and mount lenses, ensuring that all details are OK so as to have the right result without a lot of hassle."

That's only $25 for routine mounting. You figure they must at least glance at the spacing. Maybe send the lens and shutter unscrewed and let them screw them together. They will take a process lens apart. Make a new barrel. Figure out how to mount it in a shutter. All that for $200. What you need done should be much simpler and I'd think much cheaper.

I tried measuring mine. When I figured the diagram required measuring 37.1mm and other tiny numbers I just shook my head and put in the thicker spacer. It focuses now.

What I intend to do is set it up on a tripod with a newspaper on the wall. I figure any defects should show up. If I don't see any problems on the ground glass. I'll take a few photographs of the newspaper. If those look good then I'm going to assume everything is okay. I'm firmly in the camp that if the negative/print looks good then everything is good. Even if the book tells me I've messed everything up.

[ This Message was edited by: Nick on 2003-11-01 10:44 ]

RichS · Posted: Sat Nov 01, 2003 9:25 pm Post subject:

That's not bad for an f-stop scale. But that's for a single lens. This lens has three scales... I'll work out the scales myself and save the money. This lens is only worth so much no matter how much I may like it

I'm not sure how much mounting a barrel lens coincides with changing the spacing of a lens mounted in a shutter? If the spacing was known, the change in length is a simple process. In my case, trimming 1.5mm off the end of each mounting tube. There's plenty of threaded space for much more trimming than that. The question is, what's the real spacing supposed to be, and what might they charge to find out? After I'm finished testing and figureing the f-stops, I'll send them an e-mail to find out approximate costs. It might be worth it, after I see how the lens performs!

The newspaper test is a good one, but it may be difficult to see some distortions. I've read about putting a pinhole through a sheet of something and lighting that from behind. This creates a pinpoint light source. You photograph that, especially in the corners, and it will show the distortions real well. I was thinking of making a sheet with several holes for a single-shot test. Would be very interesting to see how some of these old lenses fare?

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"Ya just can't have too many GVIIs"

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Nick · Joined: 16 Oct 2002 Posts: 494

The way I'm thinking there is no way mounting a process lens is going to be easier then just mounting your cells to a shutter. Mr. Grimes used to post to rec.photo.large-format and the impression I got was that he measured process lenses not so much because it was easier but because it was a certain way to end up with the elements in the right spot. It wouldn't suprise me if after he had everything mounted if he would still check the thing out the other way. The other thing is process lenses should have been made to a pretty high quality level. It makes sense to try and maintain that level if possible.

You could get yourself a list of the various
aberrations and check for each one optically. If they don't show up in the print I won't worry about it myself.

I'd consider posting to the large format newsgroup. Maybe somebody has the patent or other documents on mounting the lens. Or somebody might have a lens they are willing to measure for you. At the very least maybe somebody will be able to tell you how critical spacing is for your lens.

RichS · Posted: Sun Nov 02, 2003 8:54 pm Post subject:

The point there is that the Grimes folks kow how to find the proper spacing and have the equipment to do it. I don't...

The two points for the old lens are:
The other persons lens may not have the correct spacing either. Very few of these are in original shutters after all these years.
Even doing the abberation measurments could be difficult as some of these old lenses had them built-in

My T&R convertible would be a classic for that!

I suppose I could make measurements going back & forth between the old shutter and the new one to see what the differences might be. That could show up anything that may be worse. But to do that on film would be a royal pain. I may make a comparison on the GG to see what I can see? But I'll wait to get the f-stops done, then shoot a few pics to see what it looks like, if it looked okay on the GG first. I may just be happy with the way it is now? And it can't be worse than my T&R

I have to admit that from the looks of these cells, I honestly don't think the spacing has to be that critical. They're just not like ordinaly lens cells. If my vision was just a bit worse, I could use them as glasses! To look through the individual one, they look like a very mild magnifying glass. Very mild, just like glasses. And they don't have an apparent focal point like a single lens (magnifying lens) would have. Looking through the glass, it doesn't make much difference how far away it is from the eye, speaking in inches, not feet. Just from it's design and what I see, I'd bet the spacing has to be within inches

And just as a side note. I never noticed before the lack of an apparent focal point! I thought a lens had to have one? How can it work without one? I can hold the cell next to my eye, or at arm's length ans see the exact same thing through the lens... I compared it to the rear cell of an unknown 10 inch lens, That cell has an obvious focal point and does exactly what would be expected looking through, going through the focal point... Odd...

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"Ya just can't have too many GVIIs"

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Dan Fromm · Joined: 14 May 2001 Posts: 2144 Location: New Jersey

RichS · Posted: Tue Nov 04, 2003 4:31 am Post subject:

Dan Fromm · Joined: 14 May 2001 Posts: 2144 Location: New Jersey

RichS · Posted: Tue Nov 04, 2003 8:54 pm Post subject:

I doubt I could measure the difference in focal length with the change of 3mm in the spacing, but who knows? Then again, these convertables are notoriously not even close to the supposed focal length in the first place...

I'm sure there's plenty of these lenses around, but I sure don't know of any? I had a heck of a time finding a 12-21-28. Seems the '28' variety is a bit scarcer? 12-19-25's abound...

The GG test should really tell me what I need to know, about this lens anyway. I finally got tired of searching for a flange (didn't feel like investing the 30 bucks in a new one yet) and mounted the shutter into a board.

Now this should make someone cringe. I _glued_ the shutter into an old 'C' wood board! Go ahead. Laugh, cry, cringe

But, I haven't completely lost my mind. I first covered the threads in silicon tape. Then covered the back of the shutter with a cut latex glove. Glue will not reach the shutter and this glue does not stick to metal! Then I used a water based glue that un-glues very easily if gotten wet. I will be able to seperate the two without much trouble and I may even be able to uncrew the shutter after it dries? In this situation, I think it will take two or three days for the glue to completely dry, but time will tell. At least by this weekend, I'll be able to test this lens... And the thought of glueing the shutter came from the old shutter. It was glued to the same board...

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"Ya just can't have too many GVIIs"

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JoePhoto · Joined: 13 Oct 2001 Posts: 75 Location: New England

If you have the old shutter then install the lens in it and measure the assembly from the front lens ring to the rear with calipers. Then make the same measure of the lens in the new shutter. If they are within a mm or two you should be all set. If the original shutter has the triple scale you can transfer the iris scale by measuring the openings and marking them off with a pencil but you'll have to seperate the three scales.

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RichS · Posted: Mon Nov 24, 2003 2:39 am Post subject:

I did mention above that the difference in shutters is 3mm. The problem is that there's no way of knowing if 3mm will make that much of a difference without some testing.
And, as an update, I did manage an initial test. So far there seems to be considerable field curvature on the GG. Whether or not it's worse in the new shutter I don't know without remounting the lens in the old shutter and other priorities have prevented further testing.
I did the test as part of creating a new f-stop scale for the new shutter. All went well until I compared it with the old scale. My first & last scales are close to the original. The middle scale is way off. Either I made quite a mistake, or the original was not accurate? So at some point the lens will go back on for another, more careful test. And hopefully then, I'll also remount the lens in the original shutter to see about the focus problem. It's just finding the free hours that's difficult...

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"Ya just can't have too many GVIIs"

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RichS · Posted: Mon Jun 21, 2004 6:20 pm Post subject:

The last note on this lens... And many other lenses...

A while ago I managed a field test. Went out with only this lens on the camera and took a half dozen photos. It works fine...

The reason I'm finally posting is that I just got off the phone with SKGrimes. I hate to bother anyone in a business unless I'm actually supporting that business with a purchase. Well since the lens performed just fine, and the glued-to-board idea didn't, it was time to order a real flange and do it up right.

So after ordering the flange, I squeezed in a few questions. Oddly enough, SKGrimes spaces cells pretty much the same way we do. Measure the old spacing and match the new one

They of course do it better and check the results quite accurately. I am _not_ saying their work isn't worth it by any means. But what they said was that if there was a question about the right spacing, the lens was sent out to an optical shop to have the exact spacing found out. They can't do it either...

And after some discussion, the bottom line is: If the lens focuses fine at infinity, the spacing is good enough. At worst, there could be a minor change in the actual f-stop from what the scale says because the diaphragm would be located in a different position from the cells as the original.

Bottom line to that: Shoot with it. If the exposures turn out right and the focus is okay, then the spacing is good enough and it's not worth having it measured...

After all this, the micro-exact lens spacing seems more an urban myth than science, at least with the old lenses... I'm no longer going to worry about it at all... And I just thought someone else out there may like this info to give them some peace of mind also...

Dan Fromm · Joined: 14 May 2001 Posts: 2144 Location: New Jersey