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Paterson Micro Focus grain magnifier: paper underneath or not?

macrorie

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Location
Maine, USA
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I am using a Paterson Micro-Focus magnifier for the first time, and as I got it with some used equipment, there are no instructions. Back in the day I was taught to always put a piece of whatever paper was being printed under a grain magnifier to optimize the focus. Do you know if this is recommended with the Paterson magnifier? I could just test it, but I'm in kind of a hurry, and I know quick answers often appear to questions on this forum. Thanks. Gerry
 
My experience is that with or without paper underneath makes no difference. It tried it with RC and FB paper. Trying it out takes just 10s test in the darkroom.
 
depth of focus is so great at the paper surface that you could never see a difference either way.

For example, from a 24x36mm neg making a 10X enlargemnt with a 50mm lens @ F5.6 you will get around + or - 10mm of depth of focus. (i.e. 20mm in total)

So don't worry about it.
 
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We busted that paper myth a few years ago.


Steve.
 
Thanks for advice. Seems logical. I wonder how the paper thickness concept got started: a web search shows that the idea is widely held.
 
You may have worked out the focus adjustment on the grain focuser but if not, then loosen the screw on the eyepiece and move the slider up or down so that the line across the eyepiece is sharp. Now the focuser is adjusted for your eye and the rest is down to moving the enlarger bellows until the grain is sharp

As others have said no need to worry about paper depth adjustment. I have tried adjusting the neg projection on a bare easel and then adjusting it with the back of a scrap print to replicate the thickness of the actual print paper and essentially it makes no difference.

pentaxuser
 
macrorie said:
Thanks for advice. Seems logical. I wonder how the paper thickness concept got started: a web search shows that the idea is widely held.
Click to expand...

If your easel has a dark surface, it is a lot easier to compose an image or check positioning when a piece of paper is inserted.
 
macrorie said:
Thanks for advice. Seems logical. I wonder how the paper thickness concept got started: a web search shows that the idea is widely held.
Click to expand...

Paper thickness is not a concept. It's just that depth of field handles it handily at the distances involved. Your enlarger's alignment is of greater concern. I happen to use a scrap of paper under my grain enlarger and I'm not likely to stop. If it doesn't matter one way it won't matter the other, will it.

s-a
 

This is and always was an uneducated suggestion.printing paper is too thin to make any difference inside the depth of field
 
To alter the focus position on the easel by the thickness of the paper would require a movement of the lens of such a small amount that you could not accurately do it. Probably just a few microns.


Steve.
 
Hmm I always just keep a sheet under. That's how I learned as well. Even if it's now proven it doesn't affect it. It helps with aligning the image as the paper I have under has a grid pattern. Works great for buildings and horizons. It also keeps the easel scratch free.
 
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In my opinion, the defining test that proves it makes no difference was performed by Barry Thornton and is detailed in his book Edge of Darkness.

He placed a 1/2" piece of board under his easel, focused and made a print. He then made two further prints. One with an extra board and one with no board, so 1/2" above and below the focused point.

He said that he could perceive no difference in sharpness - and this was from someone who was fanatical about sharpness.

It is also a common technique to put the easel at an angle to try to correct verticals. This wouldn't work if a paper thickness difference altered the focus.

Finally, in his book, Darkroom Printing, Gene Nocon also suggests that we don't bother with the paper - and he was a much better printer than I will ever be.


Steve.
 
Without the paper is how its designed to work.

Simon ILFORD Photo / HARMAN technology Limited
 
Simon R Galley said:
Without the paper is how its designed to work.
Click to expand...

When we discussed it at length a few years ago, I contacted three manufacturers of grain focusers and that was the concensus from them too.


Steve.
 
This generated more discussion than I expected. Having spent the last few days printing, I think I may have have discovered why the thickness of the enlarging paper has been widely perceived as a critical component in focusing. When using a grain focuser, it certainly appears that the plane of focus is extremely narrow. However, the user is always looking into the focuser and not observing the real extent of the vertical travel of the lens - which will always be much more than the thickness of the paper. It subjectively feels like the point of focus is absolutely minute, and that the paper would be a problem, but even tiny movements of the focusing knob cause lens travel that far exceeds the thickness of the paper.
 
My maths was wrong. The depth of focus at the paper for a 50mm lens @ F5.6 with 10X enlargement is +or- 3.4mm but that is still more than the thickness of paper.

However, what you really to know that at those settings the total depth of field at the negative is 0.068mm. And that means you better be sure your negative is perfectly flat and that your lens is perfectly prependicular to the negative and the paper if you want to optimise your print reproduction. You have 3 hundreths of a millimeter either way to play with. Not a lot.
 
The Peak 1 has a metal base that can scratch the easel or baseboard, so I protect the bottom. Arguing over this is like arguing if there is enough light in your darkroom to keep from tripping. Only you know. How many seconds of your life will you waste focusing with a piece of paper on under the magnifier and taking if out to see it is still in focus? Certainly less than it takes to post on this forum.
 

One could equally ask, "why click on the thread if you are not interested in it?"...
 
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