If the plane of focus is a half-inch at the easel...

[tlitody]

Depends on the depth of field of your enlarger lens, its particular focal length, and how far it is stopped down. Do you defocus your camera shots by half an inch, or
even a millimeter? Why do it on the enlarger?

Its not depth of field, it's depth of focus at the plane of the projected image. An enlarger is a macro camera. It's taking a picture of the negative. At the negative you have miniscule depth of field. But at the paper you have a much bigger depth of focus, especially when you are enlarging past 1:1. Then the lens extension causes an effective change in the lens aperture. For the parameters given by Bill in last post that would be to around F22 from a set F11.
So using the formula he would get around 8.8mm of depth of focus. (3x enlargement based on 10lpmm). Depth of field at the negative would be about 0.25mm which is why enalrger alignment is much more significant.

[Jack Dahlgren]

We're talking about .05 mm thickness of paper.

At the enlarging lens stage or negative stage, .05 mm would be noticeable, but the story I am hearing is that at the paper plane there is more leeway.

Because the subject and sensitive material are arranged differently than in camera, it's like if you are taking a picture of someone and "they" moved a millimeter.

If doing reductions, the sharpness zone is working against me again.

My specifics: D2 enlarger, 135mm Xenar f/4.5 at f/11 - 11x14 from 4x5. I do care about subject sharpness but allow softness at the edges.


Drew, I've got a lot of respect for your opinion - if you say I should keep using paper I will.

Bill

If you are always using the paper for focusing, consider gluing a bit of it to the bottom of your grain focuser, or tape a flap of it on that you can flip underneath. Best of both worlds.

[Drew Wiley]

OK - I did a misdemeanor on the terminology. Makes little difference. Focus is focus.
Why be sloppy about it? Unless you have a good well-leveled vacuum easel the paper
is going to get a little out of plane. Some papers lie flatter than others. If you start out
somewhat off focus in the first place, it's only going to end up worse where the paper curls. Common sense. It gets even worse with small format when you need to use
wider lens apertures. All this damn math won't change that. It's a lot faster to focus correctly in the first place than to fiddle with an idiotic calculator.

[tlitody]

OK - I did a misdemeanor on the terminology. Makes little difference. Focus is focus.
Why be sloppy about it? Unless you have a good well-leveled vacuum easel the paper
is going to get a little out of plane. Some papers lie flatter than others. If you start out
somewhat off focus in the first place, it's only going to end up worse where the paper curls. Common sense. It gets even worse with small format when you need to use
wider lens apertures. All this damn math won't change that. It's a lot faster to focus correctly in the first place than to fiddle with an idiotic calculator.

Yeah but if the paper curls up and you use paper under the focus finder then you'll make things worse at the edges. Common sense really.

The point is, that getting enlarger alignment right is far more significant and if you've done that you don't need to worry about the 0.5mm of a focus finder. And if your enlarger alignment is out your 0.5mm of focus finder height won't fix the problem.

[Drew Wiley]

Agreed. The most important thing is to have everything properly aligned. Having done
this, there are plenty of times I like to optimize the lens performance and focus on a
shallow depth of field to minimize things like dust, anti-newton texture, or even the grain of a secondary masking negative behind the original one. So in certain cases I prefer longer lenses relative to format and relatively wide apertures. For med format I
might even use a 150 Apo-Rodagon wide open at f/4.5, or only a stop down for 4x5.
Sometimes makes a difference with big prints, especially color. Or I might want to fine
tune the degree of falloff by what combination of diffuser, lens, and aperture I choose.
But of course, to do things correctly, there's always some vacuum easels around if
needed. Most of the time for conventional black-and-white printing, they're overkill;
but there have been some instances I regretted not turning on the vacuum.

[Bill Burk]

...But of course, to do things correctly, there's always some vacuum easels around if
needed. Most of the time for conventional black-and-white printing, they're overkill;
but there have been some instances I regretted not turning on the vacuum.

I've grown fond of the squeak of the old bladed easel, and the vacuum will drive the neighbors crazy late at night.

But I've got a vacuum easel I could put to work.

And then I'll have to use a sheet of paper under the focusing scope so it won't scratch the vacuum easel.

At least I don't have to think about whether I'm using single weight or double weight paper.

[Steve Smith]

If you are always using the paper for focusing, consider gluing a bit of it to the bottom of your grain focuser, or tape a flap of it on that you can flip underneath. Best of both worlds.

Don't bother. We had a discussion about paper under grain focusers on APUG last year. I contacted and got replies from a few manufacturers. The concensus was that you do not need to put paper under it as there is no point. My view is that the manufacturer probably compensates for the paper anyway so putting paper under it puts it too high but either way the depth of focus makes the paper superfluous.

Do it if it makes you feel better but it doesn't really make any difference.

EDIT: Looks like I already mentioned this at the start of this thread!!


Steve.

[Drew Wiley]

How does the mfg of a magnifier compensate for the thickness of paper when this
thickness is not standardized? I have a top of the line Peak magnifier, same mfg as my
optometrist uses for his equipment. I'm sure glad they didn't operate on the assumption
that eyeryone's eyeballs are exactly the same. I also use this magnifier for very critical
work like enlarged interpositives and internegs, and it certainly isn't skewed for the
thickness of anything.

[Drew Wiley]

I probably should have qualified my last remark. In the past quite a few El Cheapo
enlarging magnifiers were made, and it probably wouldn't make a hill of beans of difference if you put paper under them or not, because the quality control of the equip
wasn't that good to begin with. Common sense. But with the better units, like the Peak
Critical Focus magnifier, which typically have front surface mirrors and tight tolerances,
it will make a difference for fussy work. The added advantage of this kind of magnifier
is that you can view the corners of the projected image and not just the central area.

[Steve Smith]

This is the reply I got from Tohkai, manufacturer of the Peak focuser:

At first, it is not necessary for you to place a piece of paper under the focuser, but at the same time this is not compensated for in the desing. Because we conshider that the differnce from the thickness of a paper is the tolerance. In face, we have never heard from our customers about any inconvenience from that tolerance

So yes, I am wrong about the manufacturers compensating for the thickness but this is irrelevant as it doesn't really matter.

I had this reply from Roger Parry at Patterson:

Hi Steve, There is no need to put a piece of paper under the focus finder.

I later asked Roger if this was due to paper thickness being designed into the device and this was his reply:

Hi Steve
I was not around in the company when the focus finders were designed but from my own experience the finders work perfectly without a sheet of paper under them. In fact a sheet of processed and dried paper will be different from an unprocessed sheet and you would not want to waste a second sheet of paper on every print you make.

(not sure why you would waste a fresh piece of paper each time though!).


Just to show that there is some confusion, Lisa Weingarten from Magna-sight said:

Hi, I always have a scrap paper under the Magna Sight of the same weight of paper that you will be printing on.

Also, In his book 'Photographic Printing' Gene Nocon regards using a piece of paper under the focuser as a waste of time.

He's a much better printer than I will ever be so I have always followed this advice.


Steve.