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mcguireek
Joined: 13 Jan 2010 Posts: 10 Location: idaho
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Posted: Wed Jan 13, 2010 3:04 am Post subject: ground glass help |
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I am BRAND new to large format photography and I picked up my crown graphic yesterday. I opened the shutter to f4.7 and looked through the ground glass (I was inside with all the lights on at night) and all I saw was a very faint (unrecognizable) separation between the wood cabinets and the wall (and I only knew what it was because I checked a few times). Is this normal? Could there be something wrong? What can I do to make the image brighter? Any advice is greatly appreciated.
Thanks in advance. |
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Les
Joined: 09 May 2001 Posts: 2682 Location: Detroit, MI
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Posted: Wed Jan 13, 2010 4:21 am Post subject: |
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The first mistake most people make is pulling the lens out too far, thereby focusing about 2' in front of the camera.
Pull the lens out to the stops and set the focus scale (by rotating the knob on the bed) to around 6-8' find a nice end table lamp and turn in on and then open the lens to 4.7 and set the shutter to Time or use the shutter arrestor* to open the lens up and see what you can see.
Indoors it'll be dim but you should be able to make out bright colored walls near lights, dark colored dogs on the floor, not so much. _________________ "In order to invent, you need a good imagination and a lot of junk" Thomas Edison |
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mopar_guy
Joined: 07 Aug 2008 Posts: 126 Location: Washington, the State
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Posted: Wed Jan 13, 2010 4:53 am Post subject: Is it dirty? |
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Sometimes the ground glass is simply dirty and the accumulated grime makes it almost impossible to see anything. |
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mcguireek
Joined: 13 Jan 2010 Posts: 10 Location: idaho
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Posted: Wed Jan 13, 2010 5:23 pm Post subject: |
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Thanks a lot. I fiddled with the focus scal and cleaned the glass and it is much better now. |
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IanG
Joined: 04 Aug 2006 Posts: 74 Location: United Kingdom
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Posted: Thu Jan 14, 2010 12:58 pm Post subject: |
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You can add a Fresnel screen, this helps enormously with overall screen brightness.
Unfortunately I can't recommend the website where I bought mine, I had major problems, I later found so had many others.
I had my Wista set-up alongside my Crown Grapic, both on tripods and noticed that the Graflex screen was substantially dimmer than the Wista's despite having an F4.5 lens compared to the Wista's f5.6 (both at full aperture). I measured the difference using a Spotmeter and it was over 2½ stops then add the lens speed difference..
Then I tested again using the f4.5 Tessar on both cameras and the difference in screen brightness was 3.3 stops, the Wista Screen is an all-in-one screen/fresnel, the Crown Graphic a new one from the US. So I ordered a super-screen, . . . . . . . . . 10 months later I finally got it only to find it was a fresnel.
Rough snap
However I fitted it to the Crown Graphic, now it's so much easier to use and focus even in low light levels the increase in brightness is just over 2 stops, now I can focus my 90mm Angulon which was hit & miss before.
Ian |
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Les
Joined: 09 May 2001 Posts: 2682 Location: Detroit, MI
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Posted: Thu Jan 14, 2010 2:59 pm Post subject: |
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Ian,
I'm glad things worked out for you in the end, but I have to add some rather complex caveats here so we don't lead McGuireek down the wrong path.
If a Graphic camera doesn't have a fresnel screen, then it's best to add one on the outside of the ground glass or should I say the photographer's side.
If you put a fresnel screen on the inside of the ground glass it will move the ground glass from the focal plane of the film and while the image may be bright, his negatives will not be sharp. _________________ "In order to invent, you need a good imagination and a lot of junk" Thomas Edison |
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IanG
Joined: 04 Aug 2006 Posts: 74 Location: United Kingdom
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Posted: Thu Jan 14, 2010 3:27 pm Post subject: |
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Good point Les, particularly as one large Chinese LF camera manufacturer has been placing their fresnel incorrectly causing users focus problems wide open
Some camera's use them on the inside bu tthen the register is alter to take this into account. Mines fitted to the rear (photographer side which is easy..
Ian |
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