Grain focusing by moving enlarger up and down

Bill Burk · Jul 30, 2021

Note to self: Find the middle of the range of best focus by watching focus while moving the enlarger up and down. Then split the difference and lock the height in the middle.

https://youtu.be/zJiJie8igU8

After demonstrating the range of sharp focus is wide, I was surprised to find my focus was skewed. This is how I intend to work going forward.

pentaxuser · Jul 30, 2021

Bill is this a way to focus without a grain focuser by moving the whole head? I had always thought that a grain focuser got it as near absolutely correct as made no difference. In my case with a Durst M605 the difference between sharp grain and even slightly fuzzy grain is so small a movement in the bellows that I doubt if a ruler would be any good.

Or have I misunderstood what it is you do, It wasn't that clear to me what was really happening and what it was that was moving.

Thanks

pentaxuser

Bill Burk · Jul 30, 2021

It’s using the grain focuser to look for the top and bottom of the acceptable heights for the whole enlarger head by moving it up and down at the particular focus, then setting height in-between.

RalphLambrecht · Jul 30, 2021

Bill Burk said:
Note to self: Find the middle of the range of best focus by watching focus while moving the enlarger up and down. Then split the difference and lock the height in the middle.

After demonstrating the range of sharp focus is wide, I was surprised to find my focus was skewed. This is how I intend to work going forward.

sounds like avaluable way ofdoing things.worth a try.

ic-racer · Jul 30, 2021

2010...Maybe we need a "Stickey Thread" to explain how to focus an enlarger...position the head at the middle point between the two positions

Nicholas Lindan · Jul 30, 2021

The 'fine focus' control on a Beseler 45MX enlarger is a small knob that manually spins the elevation control.

Nicholas Lindan · Jul 30, 2021

ic-racer said:
2010...Maybe we need a "Stickey Thread" to explain how to focus an enlarger...

Heaven deliver us!

Bill Burk · Jul 30, 2021

ic-racer said:
2010...Maybe we need a "Stickey Thread" to explain how to focus an enlarger...position the head at the middle point between the two positions

I should repeat at an edge to find the center of best focus off-center then check that my chosen elevation is compatible with what it takes to get a sharp print both on and off-center.

Especially since I am not using a glass negative carrier.

Bill Burk · Jul 31, 2021

I want to add a note that while the video demonstrated a half inch of sharpness range, in practice the range is tighter.

When I do this for real with my eye on the grain focuser, the range is more often in the vicinity of a quarter inch. I have even found myself crossing the reference once in a while. So keep aware of the direction you moved and occasionally double check.

I still feel it was a good demonstration of what to do, but I mention this because people who try to repeat the experiment may wonder why they don’t see the dramatic range (50mm f/2.8)

Craig75 · Jul 31, 2021

at 40s (ish) into the video you say 10mm or 5/8ths of an inch - 10mm isnt 5/8ths of an inch.

Interesting stuff Bill. You've certainly gone full beast mode on this subject.

Bill Burk · Jul 31, 2021

Craig75 said:
at 40s (ish) into the video you say 10mm or 5/8ths of an inch - 10mm isnt 5/8ths of an inch.

Interesting stuff Bill. You've certainly gone full beast mode on this subject.

Thanks, it’s plus/minus 10 mm which would add up to it. I felt like I misconstrued the plus/minus concept a couple times.

Considering all the video production problems I am surprised I made any sense at all. Originally tried making split screen but could not get Zoom to show more than one camera on the recording. Then all the phones would keep turning off whenever it took me more than a minute to do the intro.

A grain focuser does allow you to make focus adjustments more accurately than can be seen in the finished results. In that respect it exceeds expectations. It’s an excellent tool and does its job well.

gone · Jul 31, 2021

Bill Burk said:
A grain focuser does allow you to make focus adjustments more accurately than can be seen in the finished results.

That's a very interesting statement. If I can't see it, then for all practical purposes it isn't there, this being a visual medium and all.

For a long time I didn't even have a grain focuser, just a beater 3rd party 135mm lens that I turned backwards and peered through to achieve focus. I can't see any difference between prints made that way and w/ the grain focuser that I have now. Granted, these are not the sort of large landscape images that some people make, the ones where you can put your nose to the print and see all manner of detail, but I never have had issues getting things sharp. I've had most every other issue known to man or beast in the darkroom, but not that one.

pentaxuser · Jul 31, 2021

Bill Burk said:
Considering all the video production problems I am surprised I made any sense at all.

.

Yes now you've said it Bill the video was difficult to follow in the sense that it looked as if lighting was by one candle

It might be worth considering a re-make. In recent months I have viewed more YouTube videos than in the rest of my many years of life and have begun to appreciate how much effort has to go into making a really good presentation. Many fail in the presentation stakes
.
pentaxuser

Bill Burk · Jul 31, 2021

momus I believe it’s good for visual art to have quality that exceed what you can see. So even if you can’t see it, I think it’s good to make prints with better focus from a well aligned enlarger.

And I also recommend using a tripod when taking pictures, even if the shutter speed is 1/250th of a second and “can” be handheld. My butterfly test print was handheld and my Vedauwoo test print was on a tripod. For the test of “what’s the best focus” the butterfly hit its limit. Vedauwoo was better for the purpose but I had to hunt through many less critically sharp negatives to find it. I like using tripods and carry them often. But I often shoot handheld too. The handheld make nice prints but not good demonstrations of technical possibilities.

Bill Burk · Jul 31, 2021

pentaxuser said:
Yes now you've said it Bill the video was difficult to follow in the sense that it looked as if lighting was by one candle

It might be worth considering a re-make. In recent months I have viewed more YouTube videos than in the rest of my many years of life and have begun to appreciate how much effort has to go into making a really good presentation. Many fail in the presentation stakes
.
pentaxuser

Thanks, I don’t mind the criticism really. But all the gadgets are put away and I might be looking into something else next. I have the attention span of a squirrel

Bill Burk · Jul 31, 2021

This is the candle light on the scale. For my next project I need to make it a proper mount, it was just held on by duct tape and a clothespin.

Doremus Scudder · Jul 31, 2021

Being nitpicky here, but I really think we should distinguish between "focusing," which involves moving the lens in relation to the negative, and moving the entire enlarger head assembly, lens stage and all as one unit, which really changes the size of the projected image (i.e., the degree of enlargement). The Beseler "fine-focus" knob that Nicholas refers to is actually the fine-tuning control for positioning the head assembly after rough positioning is done with the motor. This changes the size of the image on the easel.

Now, of course moving the entire head assembly up and down can "focus" the image, by finding the enlargement ratio that the lens-to-negative distance requires for proper focus, but more correctly, the focusing is done by using the focus knob that moves just the lens while the rest of the head assembly remains stationary.

Finding an exact enlargement ratio (i.e., size of enlargement) and focusing usually requires iterations of both head height and focus controls.

I do find "focusing in the middle of the focus spread" to be a good idea. We should keep in mind that the emulsion has a certain thickness and that a good grain focuser can differentiate sharp focus between the top and the bottom of the emulsion. "Focusing in the middle" places the focus in the middle of the emulsion as well.

Don't we all do this already, though? Just like focusing a camera, I always find the "near and far" limits of focus and place the focus as close to the middle as I can.

Best,

Doremus

Bill Burk · Jul 31, 2021

Interesting distinction. In my case I am focusing with the movement up and down of the enlarger. But I do have to reconsider my plan. I have always used a standard height for the negative to easel and this practice messes with that standard. It would make it harder for me to maintain making my prints to be the same “size”.

A better approach would be to zero a dial test indicator on the lens carriage after getting initial focus. Then focusing the lens down, zeroing again, focusing up, looking at the dial and then splitting the micrometer readings and setting lens focus in the middle.

What I think I am seeing is that we are positive that we see the best focus when it snaps. But we are really seeing and snapping on an edge. And the better approach is to identify the edges and selecting the middle.

Another way would be to focus several times and then choose the average.

The scale on the carriage rail puts the indicator at the place where you get the least change for the most movement.

Andrew O'Neill · Jul 31, 2021

Seems like a lot of work to me. I raise the enlarger head for print size, then focus the lens with the grain focuser. Maybe I just don't understand what you're doing?

Bill Burk · Jul 31, 2021

I found that my focus was not centered. Though focus ran sharply through much of the 5/8 inch stack of 50 sheets, the midpoint was not sheet 26.

Doremus Scudder · Jul 31, 2021

Bill Burk said:
I found that my focus was not centered. Though focus ran sharply through much of the 5/8 inch stack of 50 sheets, the midpoint was not sheet 26.

@Bill Burk

Should the focus point be in the middle of the stack or is there more depth of field behind the plane of sharp focus than in front? I.e., is your expectation that the focus should be in the center of the stack backed up by the math?

@Andrew O'Neill

Focusing after you've moved the enlarger head to a position you want will change the size of the image somewhat. If you're really picky about the print size or exact degree of enlargement, you need to reposition the head (i.e., negative-to-paper distance) and refocus a time or two to get what you want. If you can stand a bit of leeway when it comes the final image size, it's not such an issue.

Best,

Doremus

Nicholas Lindan · Jul 31, 2021

Doremus Scudder said:
... The Beseler "fine-focus" knob that Nicholas refers to is actually the fine-tuning control for positioning the head...

Beseler's instructions refer to it as the 'fine focus adjustment.' Considering the crude and coarse focusing control a 45MX provides it needs something 'fine.' Obviously in moving the head the image size changes. Focusing also effects image size but not as much.

I have a reduction gear accessory on my Beseler that allows some semblance of fine focus control. If you can find one it works really well.

Doremus Scudder said:
... more correctly, the focusing is done by using the focus knob [and not by moving the head]

Oh, no, not another discussion over the meaning of words.

Doremus Scudder said:
Finding an exact enlargement ratio (i.e., size of enlargement) and focusing usually requires iterations of both head height and focus controls.

That's what is so nice about autofocus enlargers. I had an old Omega D3 that never worked quite right, it was old, used hard in the newspaper darkroom, put away wet and never stayed in alignment. But the autofocus feature was a dream when sizing an image on the easel.

What inquiring minds would really like to know is if Bill had a piece of paper under the grain focuser when he did his experiments.

cliveh · Jul 31, 2021

Bill Burk said:
I should repeat at an edge to find the center of best focus off-center then check that my chosen elevation is compatible with what it takes to get a sharp print both on and off-center.

Especially since I am not using a glass negative carrier.

I don't understand this. Is your negative flat? Or are you trying to compensate for a convex negative in the enlarger?

Bill Burk · Jul 31, 2021

Doremus Scudder said:
@Bill Burk

Should the focus point be in the middle of the stack or is there more depth of field behind the plane of sharp focus than in front? I.e., is your expectation that the focus should be in the center of the stack backed up by the math?

Good question. I didn’t do any math I just did the experiment and made a video.

It’s true I should look for the hyper focal point. I would expect less fore than aft though. And I had more fore.

Bill Burk · Jul 31, 2021

cliveh said:
I don't understand this. Is your negative flat? Or are you trying to compensate for a convex negative in the enlarger?

It may be relevant to check edges and choose a focus best for all. But that wasn’t the intent. I looked as the focus of a specific point traveled through a stack of 50 prints focused on 25. The middle between what might be first excellent and last excellent print wasn’t 25 of 50

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