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

[Steve Smith]

How does the mfg of a magnifier compensate for the thickness of paper when this thickness is not standardized?

I think the answer which I quoted from Peak (in my previous post) sums this up. They consider the paper thickness to be more or less equal to the manufacturing tolerances in the unit itself.


Steve.

[Jon Shiu]

Also outside the bounds of repeatability of the user's focus adjustment.

[tlitody]

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.

I have a top of the line peak too and its no better than my very cheap paterson finder. Infact the paterson is easy to focus and stays in focus. The peak goes out of focus every time you touch the focus ring. The only advantage of a peak is that you can see into the corners. And how do you know you've focussed the peak properly, it doesn't snap into focus in the way a cheap paterson does.

[Steve Smith]

Also outside the bounds of repeatability of the user's focus adjustment.

Indeed. How many degrees of rotation of the focus knob translate to the thickness of the paper in focus position? It's more likely to be measured in minutes rather than degrees.


Steve.

[Drew Wiley]

I don't know what the heck model of Peak or whatever you've got in mind. Mine is built
like a little tank and holds focus perfectly. I've tested its accuracy with some very finicky enlargements on film etc, not just paper, and specifically cases where the difference in paper or even film thickness would be a make or break quality distinction. There is a separate reticle focus within the eyepiece to make sure you've got it properly set. A very precise instrument. There is even a separate blue glass filter just in case you're not using an apo corrected enlarging lens.

[Steve Smith]

There is even a separate blue glass filter just in case you're not using an apo corrected enlarging lens.

Gene Nocon suggests that the use of the blue filter will make a lot more difference than putting a piece of paper under it.

and specifically cases where the difference in paper or even film thickness would be a make or break quality distinction.

The film flatness and position relative to the lens is much more critical than the paper to lens distance.


Steve.

[Drew Wiley]

I've found the blue filter to be relatively useless with modern enlarging lenses which are
well corrected, and obviously of no value with my true apo process lenses. Some time ago I horse-traded for a bunch of drkrm equip which included some old style Componon lenses, where a blue filter might have helped with graded papers; but
I didn't keep any of these old lenses.

[cyrus]

I have and use a Peak focuser too. Certainly, the old trusty Paterson did just fine, but it couldn't get into the corners as well. I needed that for alignment-checking and for large prints. Like many things in a darkroom, it isn't a "must have" but is a "good to have."