Using grains focuser with or without paper on the easel

[reddesert]

There are a lot of yellow easels, that's not the issue. Similarly to what MattKing said, I think the yellow color is supposed to minimize the effects of scattered/reflected light on B&W paper - your eyes can see the image reflected off yellow, but the B&W paper doesn't (common B&W safelights are yellowish).

I used to be religious about putting a sheet of paper under the grain focuser. Then I calculated the depth of field, or the cone of illumination coming from your enlarger lens. Suppose a 50mm lens at f/8 making an 8x enlargement - the lens is about 450mm from the paper and the aperture is 6.25mm diameter, The cone of light from lens to paper has a taper of 6.25/450 = 0.0139. If your paper is 0.5mm thick and so you make a focus error of 0.5mm, you are blurring the image with a blur circle of 0.5 * 0.0139 = 0.007 mm. This is utterly negligible, since a resolution of 0.1mm is very good print sharpness.

I think it's fine to put paper under the grain focuser and I still do it, I just don't get agitated if I forget.

 

[MattKing]

Apparently wood easels were also quite common in years gone past - this from the USSR I believe:

It is always interesting to see how that which is commonplace in this part of the Colonies, is almost unknown closer to Buckingham Palace
When it comes to enlarging easels, I have one 5" x 7" easel, one 8" x 10" easel, three 11" x 14" easels, one 12" x 16" easel and one 16" x 20" easel.
Three have yellow bases, three have white bases, and one has a black metal base.
And no, I insist, I don't have an easel problem .

 

[cliveh]

But why would you choose yellow in preference to white?

 

[faberryman]

I guess I am relieved that people are actually using grain focusers instead of just eyeballing it. If you’ve gone to all the trouble of using a grain focuser, why not go whole hog by placing a piece of enlarging paper under it? As long as you are thinking about trying to make your images sharp, you also might want to align your negative carrier and baseboard. For extra credit, you could place a piece of heat absorbing glass between your light source and negative carrier so your negatives don’t buckle. I am sort of picky and use a glass negative carrier.

 

[warden]

Acid test: Make the say 10 prints with and without a piece of paper, presumably of the same thickness.....

10 prints?! Hell no I'm not wasting precious paper and chemistry on this! The work the Naked Photographer did up there is fine, no need to repeat anything.

 

[wiltw]

But why would you choose yellow in preference to white?

Less contrast reducing reflection of white light back upward thru the base material of the enlarging paper; and unlike a black base easel, you can position the easel under the projected light for framing adjustment without a piece of paper to see the image.

 

[MattKing]

The yellow colour was probably of most value when printing with single weight FB papers - they were a lot closer to being translucent than most modern papers.

 

[pentaxuser]

10 prints?! Hell no I'm not wasting precious paper and chemistry on this! The work the Naked Photographer did up there is fine, no need to repeat anything.

My sentiments exactly. I was trying to help the doubters or more pertinently the disbelievers in the "paper under the easel " do an experiment to see for themselves.

Clearly Gregg has failed to convince everyone so it must be a "visceral" thing and we know how difficult it is to change a visceral feeling. Perhaps the adjective "difficult" seriously understates matters?

pentaxuser

 

[Don_ih]

You don't need to make prints. Just focus the image with a piece of paper, then check it without the paper. If you're not satisfied, keep using the paper. There's not really anything here to argue about. Stop down the lens to f8 and you're absolutely guaranteed to see no difference.

 

[Luckless]

10 prints?! Hell no I'm not wasting precious paper and chemistry on this! The work the Naked Photographer did up there is fine, no need to repeat anything.

Personally I would assume one would most logically test this process with prints they were planning on making anyway if they were still at all curious.

I'm still setting up my darkroom, and I'll see if I bother trying to test this for myself or not later this summer. But my experiments so far suggest that I'll likely to dropping a sheet of paper in for my focus and alignment for no other reason than I find a matte textured paper easier to work with.

 

[eddie]

I doubt the thickness of the paper makes any difference in sharpness, but I've used a white sheet of paper for 50 years, and won't stop now. The white sheet makes it easier for me to place the easel correctly, and notice any flaws, hairs, dust I may have missed when putting the negative in a carrier.

Personally, I wonder why easel bases aren't all black or gray. Many years ago, I was making some 20x24 RA prints, with exposures about 45-55 seconds. I had done a few using the Beseler easel, with a gray base. They came out great. Took a lunch break, then went back to printing. I slid the easel a bit, and the anti-slip cork base came off. I switched to a Saunders with the yellow base. I couldn't get a balanced print. The only change was the easel. I took a piece of black construction paper and placed it over half of the easel. Sure enough, the half covered was correctly balanced. The other half was off a bit. Anyone else experience anything similar?

 

[wiltw]

You don't need to make prints. Just focus the image with a piece of paper, then check it without the paper. If you're not satisfied, keep using the paper. There's not really anything here to argue about. Stop down the lens to f8 and you're absolutely guaranteed to see no difference.

f/8 may better hide the sins of focusing, but the diffraction at f/8 is greater than the diffraction at f/5.6, so it is ultimately better to get the focus right without reliance in the higher diffraction f/8 or f/11

 

[Don_ih]

f/8 may better hide the sins of focusing, but the diffraction at f/8 is greater than the diffraction at f/5.6, so it is ultimately better to get the focus right without reliance in the higher diffraction f/8 or f/11

If you can show any difference between an enlargement made at 5.6 and one made at 8, you truly deserve a cigar.

 

[Sirius Glass]

Rather more to the point, the variance in flatness of the paper on the easel itself, and all the other tolerances in the enlarging system are realistically greater than the thickness of a sheet of silver gelatin coated paper. The sort of enlargers most folk use aren't metrology instruments (how many people are really using machines intended for image rectification in cartography?).

If sticking a bit of paper under the base of the magnifier really made a difference, focus magnifier manufacturers would make a huge song and dance about compensating for it (and charge you for the pleasure). The reality is that it's some sort of fairly pointless prophylactic for a problem that seems to hover somewhere between psychosomatic and placebo effects - and what I've almost universally found to be the root of these claimed paper thickness caused focusing 'faults' is errant/ inept setting of the dioptre correction on the aerial focusing magnifier.

Paper flatness? The weight of the grain focuser takes care of that. Plus the paper is the same paper that will be used so the color is the same.

 

[Bill Burk]

IMHO reliance upon any DOF of the enlarging lens at exposure aperture should be neverthless considered as 'not exactly at the perfect plane of focus', and recognized for the reality..."Merely 'good enough to fool the eye' about the imperfection of focus"
Why strive to achieve 'imperfection' ?!...even if it does not appear to really matter

A piece of the target media under the grain focus is simply 'good practice' rather than resorting to lazy technique.

The critical focus distance is the negative to lens. The grain magnifier helps you pinpoint that distance. But at the baseboard itself it’s like worrying that you focused the camera on the front of the model’s contact lens versus their eyeball

 

[Bill Burk]

But why would you choose yellow in preference to white?

Yellow would act similarly to the way antihalation backing works. It reduces the actinic property of any light which makes it through the paper and reflects back through to the emulsion again.

 

[Sirius Glass]

Having the paper under the grain focuser put the focus in the middle of the depth of field, without the paper is it closer to one edge. Why take the risk when it only takes an instant to place the paper first? Not using the paper is just basic laziness and sloppy technique.

 

[MattKing]

Having the paper under the grain focuser put the focus in the middle of the depth of field, without the paper is it closer to one edge. Why take the risk when it only takes an instant to place the paper first? Not using the paper is just basic laziness and sloppy technique.

This would be true if it was actually possible to see the difference when you are viewing the enlarged grain with the focuser.

 

[AgX]

I tend to put a piece of the used paper under the front left foot of the baseboard and that seems to produce better prints...

 

[Bill Burk]

Has anyone measured the depth of sharp focus? This is a test I have performed and it convinced me the critical depth nears 1/10 inch. Put a significant slant to your easel. For example raise one side an inch. Put the grain focuser on the easel and focus on a negative. Observe as you slide the focuser up and down slope to find the “just noticeable difference”. Measure this distance you slide and triangulate to find the critical depth.

 

[Patrick Robert James]

The paper under the grain focuser is an old wives tale. I stopped doing it years ago. Makes zero difference. It is far more important to have a good grain focuser adjusted to your eye and have your enlarger aligned with a good lens installed. Those are important things.

 

[wiltw]

The critical focus distance is the negative to lens. The grain magnifier helps you pinpoint that distance. But at the baseboard itself it’s like worrying that you focused the camera on the front of the model’s contact lens versus their eyeball

Bill, I would argue that the critical distance is on BOTH SIDES of the lens nodal point, as proportional trangles. It is not a single-sided relationship.
Just as proper focus in a camera is dependent upon both the node-to-subject plane being proportional to the node-to-focal plane, the lens optics are moved to suit so the subject plane is in perfect focus at focal plane. The SAME relationship applies to the lenlarging lens and the node-to negative and to node-to-paper surface, and the focus magnified view of grains assures that proper relationship.. Whether or not one can visually detect 'imperfection' vs. 'perfection' in that relationship is demonstrated by seeing focus error in the negative at camera focal plane (witnessed by the AF adjustments done by so many with their AF cameras!), or the eye being fooled by CofC size not being exceeded by the error.

I measured double weight Kodak paper and surface coating of emulsion with a precision caliper, and it measured 0.015" or 0.38mm, and once the focus magnifier is not holding the paper down perfectly flat on the easel, the air cushion between paper backing and easel just might keep it up where focus error might be detected...leading to the valid effort to reduce possible error by focusing on top of the double weight paper! Enlarging on single wieight paper is more forgiving in initial error because paper is only about 0.007" thick.

 

[Mainecoonmaniac]

I was taught that in school. I never did it and got sharp prints. I think what's even more important is having the enlarger aligned. Since this habit that doesn't require much effort, I say do it if it makes you feel good. There no harm in it.

 

[MattKing]

The critical focus distance is the negative to lens. The grain magnifier helps you pinpoint that distance. But at the baseboard itself it’s like worrying that you focused the camera on the front of the model’s contact lens versus their eyeball

Bill, I would argue that the critical distance is on BOTH SIDES of the lens nodal point, as proportional trangles. It is not a single-sided relationship.
Just as proper focus in a camera is dependent upon both the node-t0subject plane being proportional to the node-to-focal plane, the lens optics are moved to suit so the subject plane is in perfect focus at focal plane. The SAME relationship applies to the lenlarging lens node-to negative and to node-to-paper surface, and the magnified view of grains assures that proper relationship.. Whether or not one can visually detect 'imperfection' vs. 'perfections' in that relationship is demonstrated by seeing focus error in the negative at camera focal plane, or the eye being fooled by CofC size not being exceeded by the error.

And I would argue that when Bill posted "critical" he probably meant something like "most likely to cause a problem if just a little tiny bit incorrect" .
The exact numbers are more complex than this, but if you are making an 8x enlargement, an error of placement at the plane of the paper has to be at least 8x the error in placement at the plane of the negative in order to have the same effect.

 

[wiltw]

And I would argue that when Bill posted "critical" he probably meant something like "most likely to cause a problem if just a little tiny bit incorrect" .
The exact numbers are more complex than this, but if you are making an 8x enlargement, an error of placement at the plane of the paper has to be at least 8x the error in placement at the plane of the negative in order to have the same effect.

Certainly the distance of error has the 8:1 relationship, in front of the lens (paper) vs. behind the lens (neg). But if we recoginza the macro photography is very similar to enlarging process, and then look at the DOF involved in macro photography at f/8 with 50mm lens,
when the image is about 1/8 lifesize, the DOF at the subject (paper) is a mere 0.016mm in front of the subject and 0.017 behind the subject. IOW the amount of allowable error from perfection is scarely more than the thickness of double weight enlarging paper. And THAT DOF zone size assume human visual acuity 3x poorer than what the optometrist strives to achieve with paitients in the US!