Question on brightness of GG

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I've just received my first LF camera last week end and started to play a little bit with it before venturing into taking actual pictures. My first impression is that the image on the GG is awfully dark, making focussing almost impossible without a lupe, even with the fairly fast lens (5.6) open at full aperture.

Is this normal or is my GG defective or too old ? The camera is a Toyo 4X5 monorail which seems to be between 15 and 30 years old (actually very hard to estimate) but in excellent condition. The gg is not particularly scratched and I cleaned it up thoroughly.

If I need to replace it, are gg's standard and readily available ? Are they expensive ?

Thks in advance for your answers. This forum is a wonderful place to read and dream about LF photography.

-- Pascal Quint (quint.pascal@wanadoo.fr), January 28, 2002

Answers

Welcome to the "dark" side of LF!! GG screens are dim, but things can be improved somewhat by adding a fresnel screen or others swear by the Boss-type brightscreen.

-- paul owen (paulowen_2000@yahoo.com), January 28, 2002.

Are you using a darkcloth of some kind or a viewing hood to cut out light from hitting your side of the GG? As long as this is not a very wide angle lens, a f/5.6 should be reasonably bright (I mean, not as bright as the viewfinder of a Leica, but not exactly dim either). With wide angle lenses, the light is striking the GG at shuch a sharp angle that only the center will look bright. The corners will get brighter if you move your head to look from the corner to where the lens is. The finer the GG, the brighter the image but the more pronounced the hotspot in the middle. As indicated above, you can buy screen brighteners like fresnels. Many people praise the Bosscreens (which are a GG with wax). GGs themselves are very cheap and readily available. Unfortunately, fresnels and Bosscreens are more expensive. Good luck, DJ.

-- N Dhananjay (dhananjay-nayakankuppam@uiowa.edu), January 28, 2002.

Pascal, Even though your lens has a maximum F5.6 aperture, you don't say what focal length it is. If it is a wide angle, 90mm for instance, you will have a darker screen than you have with a 210mm lens for example. This has to do with the angle of the light rays hitting the glass. With a longer focal length the rays hit the glass almost perpendicular, whereas with the shorter lens they are at a large angle. I think there is a name for this phenomenon. My 300mm F9 lens produces a much brighter image on the glass than my 90mm F5.6. A fresnel will help with the short lens if the fresnel is matched to the lens focal length. It may actually be worse with the fresnel when using a long lens.

My suggestion, get a good dark cloth, a focusing loupe or a pair of magnifying glasses and be prepared to spend longer under the cloth composing your shot which also gives your eyes time to adjust to the conditions. This isn't point and shoot, don't hurry.

-- Dave Schneider (dschneider@arjaynet.com), January 28, 2002.


Pascal, your lens has a maximum of f/5.6 , you don't say what focal length it is (150?). My 360mm f/9 produces a much brighter image on the glass than my 80mm f/4,5. I found the Booscreen very well, for wide angle (47-120) you can add a fresnel. It will give you a "hotspot" in the middle of the glass, it's the play of the game. In France you will find the Bosscreen at http://www.galerie-photo.net. For Toyo (new or used) you will find this stuff at Le Grand Format in Paris or http://www.lemoyenformat.com/GFweb/GFsommaire.html A+

-- RaphaŽl Zeiher (rzeiher@hotmail.com), January 29, 2002.

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