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Low-light or night focusing on ground glass?

 
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woodplane



Joined: 20 Sep 2005
Posts: 33
Location: Chicago

PostPosted: Sat Dec 10, 2005 6:28 am    Post subject: Reply with quote

Any suggestions? My Speed has a distance scale for only one lens, so I usually have to use the GG to focus, but in the dark, it's tough! I could bring a huge flashlight for the closer stuff. For infinity, I could use stars if they are out, but that would probably require a lupe and acid etched glass to tell if that small point of light were in focus.
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Rangemaster



Joined: 06 Jul 2001
Posts: 412
Location: Montana, Glacier National Park

PostPosted: Sat Dec 10, 2005 3:10 pm    Post subject: Reply with quote

Infinity focus can be determined by measurment and testing in good light focus situations to determine exactly the point your lens attains the focus and then preset in the low light condition, I have done a bit of testing during the day at various distances to determine focus for each lens I use on my 4x5 cameras, that way I can determine the correct focus based on distance.

Acid etched glass is not any better than true high quality ground glass with either, unless you have done some pre testing, can be difficult at best in low light conditions.

Dave Parker

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Henry



Joined: 09 May 2001
Posts: 1439
Location: Allentown, Pennsylvania

PostPosted: Sat Dec 10, 2005 8:22 pm    Post subject: Reply with quote

Have an assistant stand in the plane of desired focus and shine a small flashlight beam toward the camera. Focus through the groundglass with loupe on that light source. Lacking an assistant, rest the light on any suitable object in the plane of focus.

If your camera has a working rangefinder, you can try reversing the above method, i.e., stand behind the camera, shine the light onto your subject, and focus through the rf.

Obviously, these methods won't work if your subject is far away! For dark interiors, they work fine. I've done the insides of abandoned coal breakers (now that's dark!) and other old buildings using these methods.



[ This Message was edited by: Henry on 2005-12-10 12:27 ]
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troublemaker



Joined: 24 Nov 2003
Posts: 715
Location: So Cal

PostPosted: Tue Dec 13, 2005 4:12 am    Post subject: Reply with quote

this is all excellent advise. take it from someone who learned these things the hard way trying to set up pre-sunrise high sierra moonset reflecting pool forground/ far peaks background on a Century 2x3 with a 65 raptar at f6.8 and trying to see anything at all when stopped to f16 to f32, not to mention positioning the grad filter. Nailed the shot, but it was a panick to check, re-check and bracket a whole roll of film with a knob wind when the desired light popped. Anyone who doesn't like little 65 raptars should see this shot. HAd it cibachromed. A taped on scale (set up during daylight as mentioned) and a littel homework regarding depth of field with my lenses of choice before that trip would have saved about half of the film shot, but then it was the first trip out with a real camera. SInce I have had a lot of fun shooting cameras using slective focus and depth of field. The more I learn, or un-learn if you will, the more I am finding that it is imperative to be familiar with what my choice of lenses will do, or not do. It is an adventure in testing, and is indespensible. know before you go.

Stephen
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woodplane



Joined: 20 Sep 2005
Posts: 33
Location: Chicago

PostPosted: Tue Dec 13, 2005 7:54 am    Post subject: Reply with quote

I would like to see that moon set shot. any way of posting it? I suppose I could get a few infinity stops and some sticky note templates to mark off a focusing scale for each lens. I'm using about 4 lenses on a Speed. On a Graphic View, it's pure ground glass. Working out depth of field ahead of time is a good idea, and yet another thing I have not gotten around to doing yet. Are there published spreadsheets for this data? That's one thing I miss about 35mm, the depth scales are engraved right on the lens barrel.
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Rangemaster



Joined: 06 Jul 2001
Posts: 412
Location: Montana, Glacier National Park

PostPosted: Tue Dec 13, 2005 10:44 am    Post subject: Reply with quote

woodplane,

You can download the f Calc program which gives you whole bunch of information inclduding DOF for lens and magnification combonations at the following website.

http://www.tangentsoft.net/

Dave



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Satin Snow(TM) Ground Glass
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45PSS



Joined: 28 Sep 2001
Posts: 3203
Location: Mid Peninsula, Ca.

PostPosted: Tue Dec 13, 2005 10:48 pm    Post subject: Reply with quote

Additional DOF calculators linked in this previous post:
http://www.graflex.org/helpboard/viewtopic.php?topic=937&forum=10

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