Using a 10X loup for focusing aid, is it too much?greenspun.com : LUSENET : Large format photography : One Thread
I am currently usin g a 10x loup. Is this too much to use as a focusing aid on the 4x5 GG? I use a fresnel lens and the concentric circles are apparent when viewing a composition using this loup, but besides the annoying lines are there any other reasons that I should be using a lower power loupe. It seems to me that the higher the power the more critical the focus/sharpness. Any opinions?
-- Clark King (firstname.lastname@example.org), May 21, 2002
I think that it's quite subjective. Plus, there are many different types of equipment (screens, Fresnels, loupes, lenses) that may change the ease of focusing. Then there are many different situations that can affect the ease of focusing (forest, urban, low light, rain, no sleep, your socks being chewed off by weasels).
I think that it's important for you to be able to focus the camera in a way that's quick and easy for you. To that end, I think that you should experiment a bit and see for yourself whether or not a different loupe would make it easier for you.
-- Matthew Runde (email@example.com), May 21, 2002.
for 10x loupes, use a Bosscreen for perfect vision. 10x loupes are useful for macro work. For "normal" photography, a 4x loupe will be sufficient. It gives you the vision of a 20x16" print and DOF on a well stopped down lens will do the rest.
-- Thilo Schmid (firstname.lastname@example.org), May 21, 2002.
Clark: Good question. That depends on several factors most important of which is the texture of your GG. On a fine GG 4X5 I do not think it is too much, rather, it is best. On a fine 8X10 it is not too much either but you might want to opt for one that gives you a wider field. If the GG is coarse, yes, the ideal should be at around 6X on 4X5. Some people prefer their 4X loupes on 8x10.
-- Julio Fernandez (email@example.com), May 21, 2002.
I've used a variety of loupes and magnifiers on a variety of screens on 4x5 cameras. My conclusion is that about X4 or X5 is the best magnification. Because of the grain of most ground glass, higher magnification doesn't reveal much additional detail and in fact can be harder to use because the view is dimmer. The only viewing screen I have used on which higher power was commonly useful was a Bosscreen, however, I don't recommend this screen for general use because mine self-destructed under moderately elevated temperatures.
If you use a X4 loupe to judge at what aperture something is in focus, it is a good idea to stop down about one more stop than seems necessary from observing with the loupe. Alternatively, use the techniques described on "A large format photography homepage".
-- Michael Briggs (MichaelBriggs@EarthLink.net), May 22, 2002.
Unless you're absolutely sure that your screen is in perfect register, and you also use precision filmholders, lke the $inar, then IMHO there is no point in ultra-critical focusing. A small bow in your film, or a worn filmholder, will easily negate that extra close scrutiny of the screen.
A register error of just the thickness of a sheet of film can put your focus out by metres at mid subject distances with a moderate wideangle lens.
LF photography, in most cases, ain't precision photography, I'm afraid.
-- Pete Andrews (firstname.lastname@example.org), May 22, 2002.
While it is true what Pete says, it is also true that when these elements of imprecision are present, the loup with less magnification (4x) can add even one more additional cause of the imprecision... That's why it is not irrelevant if you strive for a higher magnification loup.
-- george jiri loun (email@example.com), May 22, 2002.
With a plain ground glass, or a Bosscreen, 10x should be fine though personally I don't see a need for anything more than 4x. But with a Fresnel, Beattie, or any other similar "bright screen," I think 10x is unnecessary overkill for the reason you've discovered - those lines aren't just annoying, in my experience they actually make it more difficult to properly focus.
-- Brian Ellis (firstname.lastname@example.org), May 22, 2002.
As others have noted, it's really a personal preference issue, IMO. However, I'll throw out another alternative to a loupe that I've found to work great. For my 8x10 (Deardorff) work, I've been using a pair of jewelers flip-up glasses, the kind with an adjustable headband.
This thing has various accessory pairs of lenses that snap in with different magnification powers. I use the ones that focus at 5 inches, although they have lenses that'll focus down to about 3 inches.
For me, this method is far superior to using a loupe for three major reasons:
1. When composing an image, I can flip up the lenses (like a welder's helmet) and it helps keep the dark cloth from sagging, allowing for easier composition. 2, It allows me to "see" an area about 4x5 inches all at once, so adjusting focus for a tilt to bring near and far planes into focus is much easier. I can also easily see all the way into the corners. 3. Because of its design, both hands are free, allowing me to use my left hand to gather the bottom of the dark cloth while focusing with the right.
I did a year-long 8x10 project in 2000 and used this set-up for every shot and found it to be much, much faster working than with a traditional loupe. And BTW, the entire unit including lenses is about a third the price of a decent Schneider or Rodenstock 4x loupe.
Hope this is of some help. Good Shooting!
-- David Haynes (email@example.com), May 24, 2002.
Pete: Yes, the filmholders are a source of variations, sometimes even significant variations. The problem I see with allowing known, controllable deviations to creep into any system is that if 'Murphy' would have his (or her) way, (he ..or she...often does) the variations can be additive, making something bad but tolerable into something not tolelable. Big problems can result from little ones, which in isolation would be nothing to worry about. Sinar allows 0.0005" into the design of their holders to allow for film bow. The assumption being I suppose that film never lays perfectly flat against the septum. Another practical argument can be that without seemingly great concern about such technicalities, great photographers have made great photographs. Pete I hear what you are saying.
-- Julio Fernandez (firstname.lastname@example.org), May 25, 2002.