Using grains focuser with or without paper on the easel

wiltw · Jul 5, 2021

michael_r said:
What you're showing is more like random measurement error, which is already represented well enough in the dots.

What I'm talking about are flaws in the system which are repeatable. They are there with the same magnitude and direction every time.

View attachment 279390

So what is the difference between the upper end of the wide transparent blue line vs. what you show as 'actual focus plane'? I see that as simply a different way of illustrating the same thing. I previously stated, "The translucent thickness conveys that some measurement errror can arise" Measurement error, focus error...all a range of error, and some of the error might cancel others out! The cumulative error resulted in the samples determined by Bill to be undistinguishable!

faberryman · Jul 5, 2021

Craig75 said:
yes there is; this site - bill and ic-racer have peer reviewed it.

Well, I searched and searched and could not find the peer review ic-racer conducted. Do you have a link?

wiltw · Jul 5, 2021

michael_r said:
Suppose the dashed blue line is the actual paper plane where you ideally want the image focused.

Then suppose you have the paper under the focuser and you focus on that paper plane (same as the procedure in your diagram). Seems like the ideal thing to do. Except there is some longitudinal chromatic aberration (for example, it could be anything else like the grain focuser is not the right height etc.) in your enlarging lens, causing shorter wavelengths (paper sees mostly blue-violet and some green) to focus some distance above where you think you focused. This is the solid blue line above the paper.

Due to this shift, if you had instead focused without paper under the focuser (red scenario), the actual focal plane (solid red line) ends up closer to where you actually want it to be (the paper plane or dashed blue line).

And this wouldn’t be a statistical error. The gap between the dashed and solid lines would always be there.

Again, I think we can all pretty much agree you won’t see these kinds of small errors in focus so they don’t matter. The point I’m trying to make is that although theoretically having a piece of paper under the focuser/magnifier should always lead to improved focus (whether visible or not), in practice we cannot assume that to necessarily be the case. In my blue scenario above, using paper under the focuser leads to greater focusing error than in the red scenario.

OK, I get your point, that wavelength of primary formation of image in emulsion itself could generate focus error, so that Group A distribution of dots is actually centered on the solid blue line of your illustration. And omission of paper under focuser could result in closer to 'ideal' with the same error.
I have to ask what the typical distance of blue light focus error amounts to, compared to the thickness of double-weightt paper.

In any event, back in 2011 Drew Wiley stated,

"My Peak Critical Magnifier came with a blue filter, and with the various modern (mostly apo) enlarging
lenses I use, I can't see any difference. Once I had on hand some old-style Componons which someone
gave me, but I never actually used, and there seemed to be a little difference viewing thru the blue filter. Since I print graded, VC, and color papers - clear up to 30X40, and all come out immaculately sharp, I don't see what the fuss is about. Getting an enlarger properly aligned and making sure the film is flat is far more important."

wiltw · Jul 5, 2021

michael_r said:
Hard to say. Probably not much if you stop down (assuming no focus shift). Depends on the lens. Depends on the light source. As an example, way earlier in this thread I linked to an old thread I started regarding an apparently significant focus shift Ctein saw, which he claimed was due not only to blue-violet but even UV somehow getting through the system (which we never got to the bottom of). I did a series of tests in that thread and could not duplicate the results Ctein got. Nevertheless it’s a variable which could be “large” enough (maybe he thickness of the paper or whatever) to cause the use of paper under the magnifier to actually result in worse focus than with no paper under the magnifier.

LCA is one example. It could easily be something else, like the grain magnifier is too high by the thickness of the paper. I have one of those fancy Peak magnifiers, but I doubt it is manufactured with such high precision. My good old “lowly” Paterson magnifier, which always worked perfectly well for me, might be less precise. Who knows.

Yes, this is all splitting hairs. However I think it is worth considering if one is already bothering to consider the hair-splitting potential merit of paper under the focuser/magnifier.

Given Ctein's report of 2-12mm of focus shift, dependent upon VC contrast grade filter, and his finding was corroborated by Rodenstock, I can understand the concept of focus without paper...to compensate the focus shift.
OTOH, -0.015" (0.38mm) of douible-weight paper thickness hardly compensates the observed magnitude of shift!

Bill Burk · Jul 5, 2021

Greg,
ic-racer’s commentary in that thread is very helpful. The way he explained the degree of magnification bears to be re-read and understood.

I am sticking with about 10x 35mm at f/2.8 for this next series.

I made an 11x14 for the BPX-37 and it’s apparent the print shows the grain of TMY-2.

Then I setup the jig. I put a couple pieces of cardboard in my jig for initial grain focus. The stack of paper is about 3/4 inch so the cardboard is about 3/8 inch. I did include a piece of paper under the grain focuser because after all this it would be just as silly not to.

faberryman · Jul 5, 2021

Bill Burk said:
ic-racer’s commentary in that thread is very helpful. The way he explained the degree of magnification bears to be re-read and understood.

I read ic-racer's commentary, though I can't say I fully understood all the formulas. Nevertheless, it looked pertinent and thorough. It did seem like supplemental information as opposed to a peer review of your experiment and observations as claimed by Craig75.

Bill Burk · Jul 5, 2021

faberryman said:
I read ic-racer's commentary, though I can't say I fully understood all the formulas. Nevertheless, it looked pertinent and thorough. It did seem like supplemental information as opposed to a peer review of your experiment and observations as claimed by Craig75.

Oh I think peer review mentioned by Craig75 was figurative, I don’t think ic-racer has done that in this thread (maybe on another topic in another thread). We are all engaged in peer review.

I chose 2.8 for the narrowest depth of field. Already I found a quarter inch isn’t enough. I am preparing to do three-quarters of an inch. I don’t want to change anything that will increase that depth of field. That’s why I am not increasing the height or stopping down.

To correct a mistake in my first test, I changed from a Double-X negative to a TMY-2 negative.

Here is what I see through the grain focuser at the bottom of the range of the 50 sheet planned test.
Notice it is blurry (Finally!) and blur like this will be apparent from normal viewing distance.

faberryman · Jul 6, 2021

I have a couple of thoughts which, if you can bear reading my post, might be worth thinking about, or not.

The question at hand is whether it makes any difference in the sharpness of a print whether we place a piece of enlarging paper under the grain focuser or not. The whole point of using a grain focuser is to focus on the grain, and thereby assure ourselves that the print is sharp because the grain is sharp. We do not use a flower focuser or a tree branch focuser. Bill looked at the sharpness of a flower or some part thereof (call it flower stems), and Greg looked at some tree branches. I don't know how or whether either Bill or Greg determined that the flower stems and tree branches were in focus in their negatives. If they are not in focus in the negative, they will not be in focus in the print. Let's say they are not in focus. It is entirely possible that Greg can tell that his tree limbs are equally blurry on all his prints. I just thought it might be easier to tell the difference, if there is one, between blurry and sharp grain, than between blurry and less blurry tree limbs. Bill is better off because he has a sequence of flower stems to examine, e.g. blurry, blurry, blurry, less blurry, less blurry, less blurry, blurry, blurry, blurry. Again, I just thought it might be easier to tell the difference, if there is one, between blurry and sharp grain, than between blurry and less blurry flower stems. Which is why I think we would be better off examining grain, because the sharpness of the grain is not dependent on the sharpness of the subject matter in the negative. I don't want to speak for waltw, but I think he may have been thinking along the same lines when he suggested Bill increase magnification from 10x to 16x.

Moreover, there is also a difference in the sharpness of the grain among developers, with solvent developers having blurrier grain than something like Rodinal. I'd suggest testing with Rodinal negatives, because the difference, if any, would be more pronounced with Rodinal negatives than with solvent developer negatives. I don't know about you, but for me prints made from negatives developed in Rodinal really jump out (for better or worse). If there is no difference with Rodinal negatives, there will be no difference with solvent developer negatives.

And then there is the whole condenser/diffusion enlarger angle. If there is a difference in the sharpness of a print if we place a piece of enlarging paper under the grain focuser, it is more likely to show up in prints made with a condenser enlarger than with a diffusion enlarger.

A perfectly reasonable response to this post is to tell me to quit quibbling, and if I don't like Bill's and Greg's tests, then do my own tests.

Bill Burk · Jul 6, 2021

faberryman,
I can see the grain in the 11x14 size TMY-2 prints. So my next results will be based on grain visibility. The problem with Double-X was that the grain is so small it fell below the threshold of visibility on the print, so I had to rely on butterfly wing details which were nice but inconclusive over the range of a quarter inch.

faberryman · Jul 6, 2021

Bill Burk said:
faberryman,
I can see the grain in the 11x14 size TMY-2 prints. So my next results will be based on grain visibility. The problem with Double-X was that the grain is so small it fell below the threshold of visibility on the print, so I had to rely on butterfly wing details which were nice but inconclusive over the range of a quarter inch.

Great news.

DWThomas · Jul 6, 2021

I do not use paper under my grain focuser but I can think of one possible advantage to doing so ... If the base of the focuser is nicked or corroded, putting a piece of paper under it will help avoid scratching the finish of your enlarging easel.

There -- I said it.

Nicholas Lindan · Jul 6, 2021

What if the makers of grain focusers have already designed for the paper thickness and the paper corrected focus is achieved without paper? Would that built in correction be for fiber base or resin coated, single weight or double weight? What about premium weight?

And there is the difference between chemical and visual focus. Paper is sensitive to the far blue while the eye is most sensitive to yellow. Does the focuser already take this error into consideration? And then there is the case of split-grade where the exposures are made at different wavelengths of light - the focus will need to be adjusted between the green and blue exposures but as focus affects image size the enlarger head height will also need to be adjusted between the two exposures. What about apochromatic lenses being used with a focuser that is already compensated for the visual/chemical discrepency when there is no longer a discrepency.

What angst.

Pieter12 · Jul 6, 2021

Nicholas Lindan said:
What if the makers of grain focusers have already designed for the paper thickness and the paper corrected focus is achieved without paper? Would that built in correction be for fiber base or resin coated, single weight or double weight? What about premium weight?

And there is the difference between chemical and visual focus. Paper is sensitive to the far blue while the eye is most sensitive to yellow. Does the focuser already take this error into consideration? And then there is the case of split-grade where the exposures are made at different wavelengths of light - the focus will need to be adjusted between the green and blue exposures but as focus affects image size the enlarger head height will also need to be adjusted between the two exposures. What about apochromatic lenses being used with a focuser that is already compensated for the visual/chemical discrepency when there is no longer a discrepency.

What angst.

I can't believe my prints even come out with all this working against them.

wiltw · Jul 6, 2021

Nicholas Lindan said:
. Paper is sensitive to the far blue while the eye is most sensitive to yellow.

Physics of Light and Color -- Human Vision and Color Perception, Olympus Lifescience https://www.olympus-lifescience.com/en/microscope-resource/primer/lightandcolor/humanvisionintro/#:~:text=When fully light-adapted, the,of the visible light spectrum).

"When fully light-adapted, the human eye features a wavelength response from around 400 to 700 nanometers, with a peak sensitivity at 555 nanometers (in the green region of the visible light spectrum)."

Nicholas Lindan said:
.Does the focuser already take this error into consideration? And then there is the case of split-grade where the exposures are made at different wavelengths of light - the focus will need to be adjusted between the green and blue exposures but as focus affects image size the enlarger head height will also need to be adjusted between the two exposures. What about apochromatic lenses being used with a focuser that is already compensated for the visual/chemical discrepency when there is no longer a discrepency.
What angst.

Ctein, who holds a double-degree from Caltech in English and Physics. has written over 500 articles, columns, books, and manuals on photographic topics. He is an acknowledged master printer and experts at Kodak at one time declared him to be the finest color printer, bar none. As the author of the book Post Exposure, in 2000 Ctein covered this topic of focus shift in nine pages of his book. Ctein reported from 2-12mm of focus shift, dependent upon VC contrast grade filter; Rodenstock investigated his claims about VC filtration and its effect on focus accuracy, and found his claims to be valid, but admitted there was nothing that could be done merely with lens technology.

Pieter12 · Jul 6, 2021

wiltw said:
Ctein, who holds a double-degree from Caltech in English and Physics. has written over 500 articles, columns, books, and manuals on photographic topics. He is an acknowledged master printer and experts at Kodak at one time declared him to be the finest color printer, bar none. As the author of the book Post Exposure, in 2000 Ctein covered this topic of focus shift in nine pages of his book. Ctein reported from 2-12mm of focus shift, dependent upon VC contrast grade filter; Rodenstock investigated his claims about VC filtration and its effect on focus accuracy, and found his claims to be valid, but admitted there was nothing that could be done merely with lens technology.

I believe he offered the solution of using a strong UV filter.

wiltw · Jul 6, 2021

Pieter12 said:
I believe he offered the solution of using a strong UV filter.

He did report that some error could be reduced with elimination of UV light; it was an observation. Based upon enlarger in use, some exhibited less or no shift because they better filtered UV. I suppose you could try to place a UV filter in the light path of your enlarger light source, but he did not suggest that alternative! No explanation of why that was not a consideration.
One VC paper exhibited no shift.

So the variable focus issue was paper dependent, grade dependent and enlarger dependent. No single solution!

He suggested a methology to do your own testing, to determine if you have a focus shift problem And if you have focus shift, you can try

use of 2B filter, which cuts problem by 50%. although it increases exposure times
you can shop for a new lens to use
shims, which need to be different for each paper+lens combination, and different for each magnification size

But ultimately, especially after corroboration by Rodenstock and their reply about remedy hurting performance in visible end of the spectrum, "it can't be done with any modern technology at a cost any of us are willing to pay."

Color printers need not worry...B&W VC printers may have the issue.

faberryman · Jul 6, 2021

wiltw said:
Matt already addressed the alignment issue, "The tolerance is much narrower for faults in alignment, because the enlarger magnifies ("enlarges") the effect of those faults. The same applies to lenses."

In addition to aligning my enlarger, I use a glass negative carrier because I could see that, without it, in some images, the edges were not as sharp as the center. In my case, the issue was visible in the grain magnifier, but once you see it there, you cannot un-see it in the print. Fortunately, I do not have a problem with dust. A glass negative carrier may not be necessary in every setup. For those that are affected, good luck finding a glass negative carrier. I had to fashion my own.

I would discourage anyone from doing any tests which might prove that I am hallucinating. I am already suffering enough cognitive dissonance over this grain focuser issue.

Lachlan Young · Jul 6, 2021

michael_r said:
I’d have to go back and re-read his writings on this as it has been a while.

Anyhow my overall point was only that there are more sources of error in the imperfect/realistic system than just statistical/measurement, and this means if the net error is invisible to the eye, we can’t know whether paper under the magnifier is improving or worsening things unless we know the magnitudes/directions of the other errors.

Basically I would say paper/no paper is one of those things anyone interested ought to test for themselves with their own stuff. It isn’t difficult nor time consuming to do a test well enough. As an extension to that I think anyone interested in how far out you can be before the error is visible also needs to test for themselves. I definitely would not rely on anyone else when it comes to that one. I don’t think peer review applies here.

Most relevant to this thread, from pg. 151 of Post Exposure, "(I must digress here to point out that folks who glue pieces of print paper to the bases of grain focusers to get sharper prints are deluding themselves. Such submillimeter changes in the focusing plane are invisible and undetectable.)"

I recall (and this could be wrong) that Kodak were only partially able to replicate elements of Ctein's claims about focus shift, Ilford were unable to replicate the results and neither was Barry Thornton in Edge of Darkness (which is as flawed in its own ways as Post Exposure). From a quick re-read Ctein seems not to have done a great job of controlling for or eliminating the Beseler 45S head as a cause of the problems - and rather perplexingly (as he would have had them on hand) without trying separation filtration or other filtration to investigate the problem. Having extensively used a couple of examples of one of the lenses he claims to be able to induce the problem (Rodagon 105mm) on many different papers with De Vere's dichroic head, their Cathomag (cold cathode) head and the Ilford MG500 head and not seen any evidence of the effect at considerably larger sizes than the 8x10-ish size that Ctein states most of his B&W prints were done at (pg.154), it does leave me with questions about visual physiology, the Beseler head etc. I'd like to know who Beseler's dichroic filters were supplied by as there does seem to be some evidence that the dichroics in the Omega heads had worse coverage of the filtration range for variable contrast papers than LPL/ Saunders or De Vere etc.

Sirius Glass · Jul 6, 2021

wiltw said:
As restated countless times by many, "you cannot tell the difference, so it does not really matter"!

Except for the obvious to all others that it is easier to focus and compose on a white sheet of paper than yellow paint.

Lachlan Young · Jul 6, 2021

Sirius Glass said:
Except for the obvious to all others that it is easier to focus and compose on a white sheet of paper than yellow paint.

That's about the main reason to use a bit of paper - even more so on the easels painted dark grey or black.

radiant · Jul 7, 2021

I would answer to this question: it depends on your focal length. I just tested 6mm lens and focus area was pretty small. I need to try this test on that lens with/without paper.

BTW: was the DoF formula for calculating the focus area already mentioned here? Sorry I cannot browse all 16 pages ..

faberryman · Jul 7, 2021

Greg Davis said:
What enlarging lens do you have that’s a 6mm focal length?

Details in this thread:

Using 8mm movie camera lens in enlarger | Photrio.com Photography Forums

Bill Burk · Jul 7, 2021

vedostuu said:
I would answer to this question: it depends on your focal length. I just tested 6mm lens and focus area was pretty small. I need to try this test on that lens with/without paper.

BTW: was the DoF formula for calculating the focus area already mentioned here? Sorry I cannot browse all 16 pages ..

Here's the thread post where the DoF formula was mentioned.

Using grains focuser with or without paper on the easel

Bill Burk · Jul 10, 2021

Got the copy stand out and ready to make the presentation.

Stack is 3/4 inch with focus at 3/8 inch. From a normal viewing distance they all look sharp. From a fairly close examination the slight out of focus towards sharp and back can be seen but only the extremes seem unsharp. Under 30x microscope they all look unsharp so you see revealed detail and obscured detail but never satisfyingly sharp (even the best print is a little degraded from what you can see in the grain focuser).

For reference, the 11x14 we are looking at.

Bill Burk · Jul 10, 2021

faberryman said:
I read ic-racer's commentary, though I can't say I fully understood all the formulas. Nevertheless, it looked pertinent and thorough. It did seem like supplemental information as opposed to a peer review of your experiment and observations as claimed by Craig75.

I meant the parts of his post in plain English. You have this generous range of sharpness for 35mm enlargements but when you do other things you don’t have as much.

Using grains focuser with or without paper on the easel

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