Using grains focuser with or without paper on the easel

[eddie]

The setup…

I’m thinking about 20 three inch prints will take me through the range of sharpest focus. I’ll cut the sheets to three inches, mark a diagonal line across so I can reassemble them in order after processing. I will focus with 10 sheets in the film box. Then I will put 9 more sheets in the box and one in the home made speed ez-el. Expose, put the exposed sheet in the paper safe and take the next unexposed piece of paper out from under. Each exposure will lower the height of the film box under the speed ez-el by the thickness of one sheet of paper until they are done.

What if you took a sheet of clear film, mark an X with a sharpie on the right side of the film. On the left side, make an X on the reverse side of the film. Stick it in the enlarger and see if both Xs are in critical focus at the same time at 5.6 or 8. It would tell you if the offset of the film thickness is enough to make any difference.

 

[MattKing]

What if you took a sheet of clear film, mark an X with a sharpie on the right side of the film. On the left side, make an X on the reverse side of the film. Stick it in the enlarger and see if both Xs are in critical focus at the same time at 5.6 or 8. It would tell you if the offset of the film thickness is enough to make any difference.

That would deal with differences at the film/negative plane.
This thread is struggling with differences at the plane of the easel/paper.

 

[eddie]

That would deal with differences at the film/negative plane.
This thread is struggling with differences at the plane of the easel/paper.

There seems to be a group in the thread that think stopping down will correct for any minute critical focusing errors (though in 50 years of darkroom work I've never seen any difference in focusing with, or without, a sheet of paper- I focus with paper for other reasons). My thought is that, if stopping down would render both Xs in focus, it would lend credence to the ability for stopping down to achieve proper focus whether using a focusing sheet, or not.

 

[cliveh]

Well before I make a print, I use a scanning quantum microscope to determine the average depth of grains within the emulsion. I then recalibrate my enlarger focus to this depth and hey presto the image is in focus.

 

[Bill Burk]

Stopping down would make

The last thing I need is to see a bunch of naked guys (including myself) so I’ll have to pass.

I’ll just accept that using paper under the grain focuser does one of two things:

1. Improves focus
2. Worsens focus

3. Neither improves nor worsens focus.

However putting paper under the magnifier puts the focus aim where the paper will be, in the exact right place. Not introducing an error can be psychologically reassuring. Even if it makes no practical difference in this application.

In other applications deliberately ignoring a known error is unforgivable. Some applications most of us won’t see such as making archival color separation negatives from studio masters of a Hollywood blockbuster. But other applications may be encountered, like making reductions instead of enlargements.

When I get out the extension bellows I put paper under the grain magnifier.

 

[Bill Burk]

Well before I make a print, I use a scanning quantum microscope to determine the average depth of grains within the emulsion. I then recalibrate my enlarger focus to this depth and hey presto the image is in focus.

Haaaa.

Those scanning micro densitometers sure make quick work on developer edge effect studies.

 

[Don_ih]

Stopping down would make

3. Neither improves nor worsens focus.

However putting paper under the magnifier puts the focus aim where the paper will be, in the exact right place. Not introducing an error can be psychologically reassuring. Even if it makes no practical difference in this application.

In other applications deliberately ignoring a known error is unforgivable. Some applications most of us won’t see such as making archival color separation negatives from studio masters of a Hollywood blockbuster. But other applications may be encountered, like making reductions instead of enlargements.

When I get out the extension bellows I put paper under the grain magnifier.

Bill, I'm glad you plan on doing an experiment. Let me be the first to tell you that it will make no difference whatsoever to anyone's opinion, here. But you probably already know that. There should have been no arguing about this whatsoever - it's obvious that there is no lens with an aperture big enough for there to be an actual difference paper or no-paper. Plus it's easy enough to check.
But I still look forward to the experiment results.
Make sure you use heavy-weight paper.

 

[Bill Burk]

I am using double weight paper (and Eddie I scribed a cross on both sides but I don’t see the mark on the base).

I hope to be able to put a visual on the effect being discussed.

To put a monkey wrench in the experiment I am going to try some brown Dektol.

 

[Pieter12]

Stopping down can deteriorate the focus, depending on the lends and aperture stopped down.

 

[ic-racer]

I was thinking 2.8 to show “even wide open you can not tell until x sheets.” Hoping to find it’s less than 10 where you can see the difference. Going to make a video you can loop through and see where it becomes crisp and where it starts to get fuzzy

You can compare your empiric data to a mathematical model and adjust the model to match your data (by altering the constant in the equation). The equation below is based on physical size of Airy disk and Circles of Confusion. The equation below is based on Hansma's view camera focusing equation.
Your 'dv' on the enlarger will be the change in head height. The equation is based on making a magnified image with a view camera, so the back standard of the view camera becomes the easel, which you indirectly move up and down by moving the head.

N = 20/(1+M) * square root of 'dv'

N = Aperture number (example "2.8")
20 = my personal constant (20 = circle of confusion 0.15mm)
M = magnification
'dv' = millimeters of focal depth on the baseboard (how far you can raise or lower the head and still be in focus).

'dv' could also be the height of a stack of paper needed to show a difference.

 

[wiltw]

My understanding is that Bill's test is designed to be able to take a image which is 'perfectly focus', and then, starting at exposing paper
at level of perfect focus, then successively...

1. at level of minus one level of double-weight paper
2. at level of minus two levels of double-weight paper
3. at level of minus three levels of double-weight paper...
4. at level of minus nine levels of double-weight paper

...determine where the eye begins to detect softness in detail from the original neg, using a lens at f/2.8

Some say 'you will not be able to see difference between level of perfect focus and the successive levels of increasing imprecision. I anxiously await hearing the result.

I think Bill should first assess with naked eye (I hope your reading vision is good, and not marred by old age, Bill!), but afterward assess each print a second time under 6x or 8x loupe.
That could then show naked eye passability of each layer vs. real degradation of focus/detail due to the missing layers from ideal level. Of course, one has to assume that the neg under test has a pretty planar target in focus at time of shoot, and not dealing with detectable DOF limitations in the original capture..

 

[Craig75]

for everyone arguing the toss about all this, no one has said what is wrong with Greg's experiment

 

[dkonigs]

Here's what I think all of you need to do:

• Find a special Noctilux-derived enlarging lens with an f/0.95 aperture
• Get a Peak grain focuser, with NIST-traceable calibration on its alignment, after having been custom-machined for that extra micron of precision on all its dimensions
• Use the thickest-weight paper on the market, even if you have to hand-paint an emulsion on a piece of corrugated cardboard
  
• Re-do the full experiment with no less than a 20x24 enlargement size

Putting all these together, I suppose its possible you might see a difference.

 

[Bill Burk]

My experiment will be a movie we can all watch.

It should “feel” like focusing. It “should” begin a bit unsharp having been started many sheets’ thickness “too high” and progressively lower and lower and lower. I hope it shows a feeling of getting sharper to a point and then getting blurry again.

I think there will be a “dwell” of several sheets where the image looks in focus.

I also have to accept that maybe I underestimated how wide the range of sharpness lies. Maybe we won’t see any difference at all in any frame.

But we will all be able to see it.

Exposures are done.

 

[faberryman]

for everyone arguing the toss about all this, no one has said what is wrong with Greg's experiment

I am satisfied with Matt’s depth of field (focus) calculation. It is much more persuasive than someone, no matter how well intentioned, telling me what he did or didn’t see. Neither will change my workflow. I always have a sheet of paper in the easel anyway for rough focus and composition. I am not a fan of trying to rough focus and compose on the yellow surface of an easel. I am not going to take the paper out to use my grain focuser. That makes no sense.

 

[Sirius Glass]

I am satisfied with Matt’s depth of field (focus) calculation. It is much more persuasive than someone, no matter how well intentioned, telling me what he did or didn’t see. Neither will change my workflow. I always have a sheet of paper in the easel anyway for rough focus and composition. I am not a fan of trying to rough focus and compose on the yellow surface of an easel. I am not going to take the paper out to use my grain focuser. That makes no sense.

Ditto. I never used the yellow easel surface to focus. I do not even like using that surface to adjust the easel position and the easel arms. I work with paper in place in the easel. For those that find fault with my methods can just need to get over themselves.

 

[Pieter12]

I often use a sheet of gridded photo paper in the easel to line up the horizon or verticals in buildings. So the grain focuser goes right on top of that.

 

[Bill Burk]

19 prints are in the wash. I think there’s something there.

 

[Vaughn]

I always used a piece of old photopaper in the easel to make it easier to frame up the image on the easel, then focus and recheck the framing, etc. I could tell if I had been working too late and too long when I would accidentally develop my focus sheet.
Early on I wasted more photopaper because of mis-alligned enlargers than to focusing errors, bumping the enlarger, having the negative pop, not having the carrier in flat, and other sources of error. Learning how to align the beasties was a big step.

 

[Jim Jones]

Ah yes. Alignment. That opens another 200 posts!

 

[Vaughn]

Ah yes. Alignment. That opens another 200 posts!

It's no worries for me now...retired from that job and I now only contact print using UV wavelengths!

But 'back then' I finally got one of those laser aligners. Wonderful for getting all the planes close to parallel, then I fine-tuned by eye with a scratched negative in the carrier. No grain focuser (the advantage of being very near-sighted...built-in loupes), just wanted all four corners to be equally sharp and the rectangle of light to be as square as possible (that is, no keystoning). Hard to keep students from dropping those heavy D5 condenser heads hard down onto the negative stages. You can teach them not to do it, but every quarter there would be 75 new students in the beginning classes and it is going to happen. At least the 23Cs did not have that problem. Students would destroy the hold-downs easily enough on most of the enlarger types. Ahhhh, the good old days!

 

[DREW WILEY]

Lot's of armchair scientists here, speculating. I'll stick with actual experience and really good gear. It also helps to own a fresh clean lens tissue or two. And compare results on a day you HAVEN'T been on a computer making your eyes fatigued.

 

[wiltw]

19 prints are in the wash. I think there’s something there.

Whaddya see? whaddya see?

 

[Bill Burk]

They are drying. It’s cool and damp here so that’s going to take a while. Then I have to get out the pin register system…

I did clean the lens last week.

It’s evident that over 19 sheets you do pass from slightly fuzzy to probably the best and out to slightly fuzzy. It’s not dramatic.

 

[DREW WILEY]

There's a technical solution for everything. Just put vaseline over the enlarging lens front element and be done with it !