GG dark

[Noah B]

Hey all, I'm currently shooting with a kodak 2D and boy is that screen dark! I was wondering if there are any inexpensive methods of lightening the glass?

[lenser]

There have been a couple of recent threads about using the very inexpensive page magnifiers for Office Depot or Walmart as Fresnels to brighten the existing screen. I did it on my Kodak Master 8x10 with huge success.

Just cut it to size and place behind the existing glass. I used a band saw to cut mine, but some have mentioned using scissors.

[Bob Salomon]

First get a more modern GG and then add a modern fresnel.

[William Barnett-Lewis]

Faster lens? ;)

More seriously on the inexpensive side, I'd do search on Fresnel lenses on the site & on google as that's about the only cheap way I'm familiar with.

[IanG]

Have to agree with Bob, a new screen can make a big difference, then the fresnel gives a further overall boost. My own experience is the equivalent of over 3½ stops improvement is easily possible compared to an old original glass screen.

The UK importers of Beattie screens claim 5 stops, but I think that's rather over optimistic, I do have a new Beattie screen on a 10x8 and can test that out for myself when next in the UK as I have 2 cameras and can swap the backs. Visually it's nothing near that figure, but I have good bright glass screens.

Ian

[BetterSense]

Has anyone had any experience re-grinding the screens in old Crown/Speed graphics? I have a couple graflok backs from this era, with fresnels, and I feel like they could be brighter. After reading the thread about grinding your own ground glass from scratch, I've been wondering if going after my current glass with 400-600 grit SiC would make an improvement or not.

[IanG]

I've made about 20 screens now, that includes 3 Speed/Crown Graphics and 4 German 9x12 cameras (almost the same size just a touch narrower).

All the screens are substantially brighter than the originals, and also slightly better than a commercial screen I bought 2 or 3 years ago.

In some cases I re-ground the originals, it makes no difference to the end result.

Ian

[BetterSense]

In some cases I re-ground the originals, it makes no difference to the end result.

Good; I just figured it would be easier to re-grind the original than to get a piece of glass the same size. What type of grinding compound do you use? I've been told 400 grit SiC paste is the best to use.

[imagedowser]

I understand SiCarbide is the next hardest to diamond, I had trouble with it chipping the glass surface, rather than grinding it... Aluminum oxide leaves a much more even and smooth surface. Al oxide is used after the Si when lapping telescope mirrors. The stuff I have is made by Willmann-Bell, Inc, Richmond, Va 804-320-7016 It comes in a # of micron sizes. I start with 15 and go to 9, 5 and finish with 3... but the 3 is only to see if there are any deep scratches left from the 15.... if the 3 is too fine for you, then go over with 5 to finish. Keep all grades separated in double plastic bags so they don't cross contaminate. If I can find it there is a post on procedure... Bill

[imagedowser]

See dokasphotos.com , look under "Articles"

[desertrat]

Hey all, I'm currently shooting with a kodak 2D and boy is that screen dark! I was wondering if there are any inexpensive methods of lightening the glass?
While you're waiting to get a better GG and/or fresnel, there are some things you can do to make life a little easier. I'm using an 8X10 Improved Seneca View, and I'm pretty sure the GG is original. When I look at reflections in it from across the room, the glass is very wavy, much more so than modern glass. The grind isn't very fine, but it still works OK for me.

I usually start composing the image at around f11, because the Dagor or Turner-Reich triple are a little sharper there than wide open. If I'm looking straight at the GG, i can't see anything in the corners at all. If I move my focusing eye right to the corner and look in at an angle toward the lens, I can see the image fine, and it's only a little darker than at the center. To focus at the edge or corner of the screen, I have to tip the loupe so it's pointing toward the lens instead of straight at the GG. This means the zone of sharp focus becomes a line, instead of the whole field of view of the loupe. This isn't really a problem for me. I move the loupe carefully in and out until the line of sharp focus on the GG pattern is right at the detail I wan't to bring into focus. Then I adjust the focus until the GG pattern and the detail are both as sharp as I can get.

After repeating this procedure at several places on the GG, I then stop down to f22 and make minor adjustments to the focus. Both the Dagor and Turner Reich triple have some focus shift, in particular with the TRT the shift is fairly substantial. After doing all that, I usually stop down to f32 before shooting.

Working outside in broad daylight most of the time probably helps. This method might not work at all trying to compose and shoot in the deep woods, but we don't have much of that around here. :)

I have used this method with a brass petzval around f4 or so in room light coming in mainly from one window, and was able to compose and focus without too much trouble.

When I examine the negatives on the light box with a 10x loupe, I'm satisfied that the image detail is pretty close to the best these old lenses can do. The finest detail is far smaller than I can see with the naked eye at a normal viewing distance. I'm pretty sure images shot with the Dagor could take 4x enlargement and still look critically sharp, and with the Turner Reich Triple, maybe 3x.

[IanG]

Silicon Carbide gives an excellent smooth finish. I've had no trouble what so ever with the glass surface chipping. It's used by most people who make their own screens.

It's better to grind new glass with a coarser grit #400 first then follow with the finer #600. There are other advantages to this method as well

If your SC was chipping the glass it's likely it's not uniform and possibly contaminated.

Ian



I understand SiCarbide is the next hardest to diamond, I had trouble with it chipping the glass surface, rather than grinding it... Aluminum oxide leaves a much more even and smooth surface. Al oxide is used after the Si when lapping telescope mirrors. The stuff I have is made by Willmann-Bell, Inc, Richmond, Va 804-320-7016 It comes in a # of micron sizes. I start with 15 and go to 9, 5 and finish with 3... but the 3 is only to see if there are any deep scratches left from the 15.... if the 3 is too fine for you, then go over with 5 to finish. Keep all grades separated in double plastic bags so they don't cross contaminate. If I can find it there is a post on procedure... Bill

[imagedowser]

Ian, The problem I was having was not being happy with the finished product. I'm not talking abt large chipping here, but micro chipping... look at the surface with a strong loupe or macroscope you'll see what I'm talking abt when you compare it to the Al oxide, the finish with aluminum oxide seems smoother, more refined...and brighter... People who make custom screens do use Si to level the glass surface which as you know, has float marks or waves in it.... Si cuts more quickly, so saves time. We're using two methods to get to a common destination, a finish we're happy with.. I wasn't crazy happy without going beyond Si alone... I think I'm talking abt different here, not better/worse. Some people prefer frosted glass from a window repair shop, I think I paid $7.50 for my 8x20 and was quite happy 'till I tried grinding glass myself and "saw the light" thanks to the article I posted....

[Lachlan 717]

Have a look at eBay item 120626802512.

I'm not affiliated with the Seller except for buying 2 of these from him! Excellent addition, and cut to size on request.