grainy when focusing on g.g.greenspun.com : LUSENET : Large format photography : One Thread
So I finally have acquired all the equipment to start, when I focused the picture on the g.g. and used my loupe to check the g.g. everything seems grainy. Is this normal?
-- Julie Hancock (email@example.com), November 23, 2000
Julie: What you are seeing is grain of the ground glass. That is normal. You won't be able to focus without the grain of the glass. It is where it is etched or ground to make a focusing screen. Some ground glasses use a quite coarse screen, some finer. The image seems to snap into focus quicker with a course grind, but may not be the best solution for really fine focusing or for a higher magnification loupe.
-- Doug Paramore (firstname.lastname@example.org), November 23, 2000.
You're probably using a loupe that has too much magnification; 4X is about right.
-- John Hicks (email@example.com), November 23, 2000.
If you find the grain annoying, you can purchase another g.g. - find out where Dick Phillips get's his made as the company seems to do really realy good work.
Another option is to buy a can of varnish or laquer (I can never remember which - perhaps someone with more wood working background than I can respond) and take some maksing tape and tape out a pattern on the ground side of the glass that you find acceptable.
Then paint the varnish or whatever, on the ground side and let it dry. It will leave a fairly clear area - not as clear as clear glass - but close enough - that you can use to foucs with.
This is how the original Deardorff g.g.'s were made.
-- Sean yates (firstname.lastname@example.org), November 23, 2000.
The only (to my knowledge) "grainless" focusing screen is the Bosscreen imported by Bromwell Marketing. It uses a wax layer in between the two sheets of glass and you can focus without seeing any grain. They are fairly expensive - around $150 for mine as I recall - but are well worth it IMHO. Sorry I don't have a URL for Bromwell but they advertise in Shutterbug and perhaps someone else can provide a URL or another source.
-- Brian Ellis (email@example.com), November 24, 2000.
One of the most common mistakes when focussing on a ground glass is to use a loupe which actually magnifies too much the coarse structure of any frosted glass, never exceed 4X it will do a better job than a 8X(7x) or even worse 10X (ever wonder why the most expensive loupes are 4x or 5x?). Bosscreen is a superior dutch product which has the only handicap of being sensitive to high temperatures, it is made of a thin coat of bee-wax and paraffin enclosed between two pieces of glass) spectacularly clear and great performance on wideangle too! B.T.W. If you want you can order direct at stabilix and save a lot of money (the actual price is H.f.l. 140 + taxes and sending). Enjoy!
-- Andrea Milano (firstname.lastname@example.org), November 24, 2000.
Now you have me worried. I'm only using a 4x toyo, fixed focus loupe. Maybe it is the gg is old, needs replacing? What do you think? It is a gandolfi 5x7 older model precision.
-- Julie Hancock (email@example.com), November 24, 2000.
One more vote for the Stabilix Bosscreen! Excellent and cheap enough if you get it from the manufacturer. More, they will cut it to your particular camera sizes. The great advantage besides a grainless structure, is that it does not need as much shading from ambient light as normal ground glasses when you go for the focussing step. You can do it in the open! I use one on a Linhof, with an excellent Horseman Fresnel and it's amazing how much better this is from the standard GG I have on an other camera. One thing to be aware of is the relative sensibility to temperature extremes of this parrafin based sandwich. It should not be exposed to too high temperatures, as stated above, nor to too cold temperatures either. Mine started showing some tiny bubbles. I have been told putting it in a warm environment and gently pressing on it will fix this.
-- Paul Schilliger (firstname.lastname@example.org), November 24, 2000.
OK, your old groundglass may be dirty and not very bright.
The first step imho should be to contact Gandolfi (or a Gandolfi dealer) and find out if they offer a newer, brighter groundglass, which also may have a finer surface. Of course using a slow lens makes the groundglass appear dimmer and grainier too.
It's normal to see groundglass grain; what I meant about a too-strong loupe is that the grain is magnified so much it interferes with focusing.
-- John Hicks (email@example.com), November 24, 2000.
Gandolfi, will probably offer either a Beattie bright screen or a Bosscreen and charge you a lot more than buying directly from this company. By the way, do you use a fresnel lens too? Have you problems any special relation to use a combination of Wideagle (around maximum aperture f8 perhaps) and fresnel? This can all be factors which could impair the use of the best ground glasses, mind you, bosscreen i relatively better than most but cannot do miracles. Anyway! Order direct their telephone is +31 (0)70 3970061 the company name is Stabilix in The Hague (nl)
-- Andrea Milano (firstname.lastname@example.org), November 26, 2000.
Julie, One of the biggest mistakes one can make when first starting out in LF is to mess around with one's ground glass. The advice given about not using too strong a loupe seems sound to me, but I would hold off for a bit before changing the screen you have or adding a Fresnel. It takes a bit of getting used to, but once your eyes have become accustomed to the darkness under the cloth, you will find it increasingly easier to focus. When you get into changing the gg or adding "brightening" screens, you run the risk of altering your gg alignment. If the plane on which you focus is not coincident with the surface of the film, you will never get a sharp image! I've witnessed people trading lenses like junk bonds, endlessly searching for a sharp one, when all the while, it was that confounded brightening screen they added to make it easier to focus that was causing the results of any lens they used to appear soft! Some folks have trashed piles of perfectly good film holders for the same reason, thinking that was the problem! I'm not saying this can't be done. I would just caution anyone replacing or changing a gg to consult with someone experienced in this area before proceeding.
-- Robert A. Zeichner (email@example.com), November 26, 2000.
Yep, this is sound advice, Robert. One has to be very careful in proceeding.
-- Paul Schilliger (firstname.lastname@example.org), November 26, 2000.
Ok, I have gotten lots of advice and I am just going to take my lens out and clean it carefully, for now and take some pictures and see how they come out. Thank you everyone for giving me plenty to think about. I do appreciate the help. I think the fresnel and boss and beattie are great ideas, and may go that route too later. Sincerely, Julie
-- Julie Hancock (email@example.com), November 26, 2000.