Yes. What is you light source, your paper, your filtration, and your enlarging lens (and aperture)? I think your answer will be in there somewhere.
I tested the residual violet/UV thing for one of my enlarging papers in this thread (skip to post #56 for the test but there is some good discussion beforehand on whether or not there is even significant UV in the system):
Even if this issue existed with Marco's paper, it would affect visual focusing the same way as with a grain magnifier. Marco, if you want to rule the supposed/possible residual UV thing out, repeat your test at the lowest contrast setting (ie max yellow) and see if there is any difference in the results. Try it at maximum contrast for comparison.
Based on everything said so far, if you are certain there is no drift in your lens stage I'd say there must be something wrong with the magnifiers, as strange as this seems.
2mm is significant at the negative plane, much less so at the paper plane.
It is a strange and somewhat alarming situation. Interestingly, I have consistently found when I focus by eye and then reach for the grain magnifier, the grain is already sharp. It surprises me every time. I still always use the grain magnifier but a few times I've tried an actual print both ways and couldn't see a difference. I've never seen the visually focused print look sharper the way Marco has though. Very puzzling.
I use a Peak Critical magnifier and it is spot on. Certain cheaper units were OK, but not as useful for
checking corners of the field. But when comparing respective magnifiers make sure they are all on
lens axis. The better units should match. I've seen cases where budget magnifiers either didn't use
a front-surface mirror or attached it with some kind of double-faced tape that eventually shrank in
thickness. But maybe you've got a bad magnifier or two and should test them with live printing, provided you do rest them on a sheet of the same thickness and apply perfectly calibrated enlgr
settings and a very precise lens at optimum aperture. Forget the blue filter thing and the nonsense
that spacing at the easel doesn't matter. You can choose to shave with a double-bit axe too, but
it might make a difference in your appearance afterwards.
Oh, and tkamiya: I'm sure that the focus column is not slipping. The Durst 138s is a beautiful machine. I routinely leave a negative in the enlarger for a weekend, and come back to make more prints a few days later and the grain is still as sharp as when I left it. I believe I can almost 100% rule that out of the equation.
Thanks for all your thoughts on the matter.[/QUOTE
I am confused again. When you say the grain is as sharp as when you left it, is this a grain sharp image by eye? If it is a grain sharp image by a focuser then the print should be pin sharp unless the negative is out of focus. Were you saying that the print focused by eye is pin sharp or just better than those focused by the grain focusers?
If the neg is out of focus then maybe the eye which cannot use grain for sharpness is able to correct as far as possible an error in focus in the negative whereas the grain focuser simply sharpens the grain and makes the print focus worse but of course cannot sharpen the lack of focus in the neg itself.
Have you tried other negs that you know have produced sharp prints in the past using the focusers?
Does the magnification built into the grain focuser have the effect of magnifying any focus error in the instrument?
By that I mean, if the grain focuser is 2mm out, and it magnifies by a factor of 10, is the result the same as a 20mm error in placement of the baseboard?
“Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”
Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2
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It is nonsense that it does matter.
Originally Posted by DREW WILEY
If you think the difference in paper thickness at the base board makes any difference, try to work out how small a change in the negative to lens distance would need to be in order to change the focus point by the paper thickness (or even by 2mm). It is a few microns. You cannot adjust the focus of an enlarger that accurately.
"People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.
I guess its just a habit then for me, I still use a sheet of paper (hey it also protects my easel from the metal grain finders!) and if using my Peak 1, I just leave the blue filter in, constantly keeping it in the open position collects dust, and closing and opening it to often shifts the focus at the eye piece.
Also, for the OP, you do not focus with the red filter do you? no one has brought up that point, but I have heard people doing this in their darkroom work flow. I don't know why they would, but some people seem to do it.
Here's a thought.
Focusing and printing wide open... Your eye's iris will close down considerably, compared to normal practice where I focus with the lens in same aperture I plan to print, which I try to select as the optimum aperture for the lens.
Mark Crabtree is right: I should have posted my specs a bit clearer off the bat.
Light source is tungsten - one of the Durst Atlas bulbs made for the 138s. I use all sorts of paper. This test was done on Ilford Warmtone Multigrade RC. I did not use any filtration. When I do use filters, I have an Ilford set of gels. I never focus with filters in (that included the red safelight filter). My lens is one of the newer Schneider Componon-S 80mm with the focus lever on it. I focus wide open. In the future I will focus at a working aperture.
The reason I conducted this test with the lens wide open was that I was hoping it would show a worst case scenario insofar as focus was confused.
The filtration issue - blue filter, yellow filter - doesn't quite make sense to me. Here's the thing: when I focus with my eyes, it's very sharp on the easel. When I focus with the grain focuser, it's sharp but not *very* sharp on the easel. The prints I made on RC paper confirmed that to me. At the moment, this is all I'm worried about.
And pentaxuser: to avoid confusion - if I focus the image with a grain focuser and the grain is sharp (or it appears to be sharp!), and I leave the enlarger for a weekend and come back and check the focus with the grain focuser again, it is still sharp. What I'm saying is that the focus column on the Durst 138s doesn't budge. It's got locking focus and it does its job very well.
The idea of focusing with white light and then printing with yellow filtration was to help rule out the possible violet/UV issue, which probably doesn't exist anyway. The yellow filtration (in your case, Ilford #00) would expose your paper mostly to green rather than blue and shorter wavelengths, so theoretically it would mostly take non-visible light out of the equation as a possible source of error. However as I said even if this problem exists, which it likely doesn't, one would expect it to cause the same type of focus error with or without the magnifier, so to me it would not help explain why the prints focused without the magnifier are sharper.
As for your Componon-s lens, I would be very surprised if there was a focus shift when stopping down to the working aperture. You should be able to focus wide open.