Simple Technique to Focus the Enlarger Lens

TerryM

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I wanted to offer you a simple technique for focusing your Enlarger's Lens. (I had originally developed this for my 8mm Projector Lens.) This method is essentially perfect, and it doesn't require using the Negative. All you need to do is use a Strip of Aluminum Foil -- just fold it over three layers thick for strength to the 35mm or 60mm width of the Film Strip. Using a sharp Razor Knife, softly cut two finite vertical Slits about 1cm long near the center. You then simply use the tiny amount of light which passes through the Slits to focus the Lens. This focus will be perfect, and is much easier and quicker than using an image on Film which itself could be out of proper focus. Cheers.
 

AgX

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Isn't there a likely chance for that aluminim strip itself being not in the focal plane? Or do you use glass carriers?
 

bernard_L

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Slide projectors have (had?) an autofocus feature. Why?? Because, even if the focus is set for the first slide (and the distance of the screen) not two slides have identical curvature. Ditto for film in a glassless carrier.
 

rpavich

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Because I was bored and this sounded like it would be interesting, I did it to see if it was true. In my case, it wasn't. I made the foil stand-in and sure enough, two slits were easy to focus but when I subbed the negs, I had to adjust focus on both.
I usually have to adjust focus on negs when I switch from one to another so I couldn't see how this would work better. It didn't, at least for me.
 

RauschenOderKorn

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I understand the aluminium foil goes in the negative carrier?

But when I remove the carrier and put in the negative and put it back in the enlarger head, it might loose focus again?
I have found it easy to focus at open aperture and then stop down at least 2 stops. If the negative is out of focus in the first place, then I adjust to the desired focus
 

rpavich

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I guess I dont get why I’d do this. Its solving a problem that doesn’t exist; its easy to just use the negative to focus.
 

jim10219

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rpavich said:
I guess I dont get why I’d do this. Its solving a problem that doesn’t exist; its easy to just use the negative to focus.
Click to expand...
That's kind of what I was thinking. I just focus it as close as I can, move it slightly out of focus one direction, then slightly out of focus the other, and set the lens to half way between the two points. Then I double check with a grain focuser, but it's usually dead on. It doesn't take me but a few seconds to do the whole ordeal.
 

faberryman

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I think enlarging lenses should have focusing helicals for fine adjustments.
 

MattKing

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I've been working lately with 6x9 negatives - T-Max 100 shot in a pinhole camera.
You think you are having trouble focusing your enlarger!!
My D6 actually holds focus really well when I switch negatives and negative holders, so having this setup permanently installed in an extra single purpose negative holder might actually help a lot.
It would probably be quite helpful with medium format Ektar 100 negatives too.
 

faberryman

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AgX said:
Why? Because you think rack&pinion have more play than a helicoid?
Click to expand...
Yes. I have a like new Beseler 45MXT enlarger, and the rack and pinion is no where near as fine as a helicoid. I can focus it, but a helicoid would be easier and more precise.
 

mshchem

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faberryman said:
Yes. I have a like new Beseler 45MXT enlarger, and the rack and pinion is no where near as fine as a helicoid. I can focus it, but a helicoid would be easier and more precise.
Click to expand...
I have TWO Beseler 45 MXTs and an old blue Beseler 4x5 in storage. These things have always been a pain in the ass to focus. Even if you lube it, the thing jumps on you. That's a money maker make helicoid mounts for Leica thread lenses attached to a 4x4 lens board. Maybe I will have two slits laser cut into my 6X9 carrier Everytime I open and close the Beseler I recheck focus.
 
OP
OP

TerryM

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It appears that the thickness of the Film causes some additional diffusion of the Light which doesn't happen with the Aluminum Foil. I'm going to try some more experimenting to see if I can find a workaround. In the meantime however, you may want to test focusing the Lens with the Aluminum pressed against the outside of the Lens, and a Negative loaded in the Holder. This will make it easy to see if the Focus for the slits of light accurately matches the Focus for the image.
 

Andrew O'Neill

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Doesn't matter if the negative itself is out of focus. The negative is in focus under the enlarger when the grain is rendered sharp through the grain focuser.
 

MattKing

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Andrew O'Neill said:
Doesn't matter if the negative itself is out of focus. The negative is in focus under the enlarger when the grain is rendered sharp through the grain focuser.
Click to expand...
Andrew is correct of course. The problem arises when the grain is either so fine or so obscured you can't see it to focus on it. Thus my earlier reference to 6x9 pinhole negatives on T-Max 100.
 

ic-racer

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I can't say that finding proper focus was ever an issue. But, looking back at prints made during my first 5 years of photography (from '73 to '78) the corners of the prints are frequently blurry or improperly exposed. After I got my MFA, I want back parents house, retrieved and re-assembled my original enlarger. This is what I found:
1) The lens was not centered over the negative (one corner always too close to the blurry edge of the small Comparon image circle)
2) The negative was not centered over the mixing box (one edge always light)
3) The negative stage was not perpendicular to the lens axis.
4) The negative moved during the exposure
5) Occasionally the grain was blurred from using f22 on the 50mm lens.

Solutions:
1) Center the lens over the negative and use a Componon-S lens with a larger sharp image circle (I had made a home-made lens board that was not correctly centered)
2) Center the negative under the mixing box (I was using a home-made carrier, but it was off-center)
3) Laser to the rescue
4) Glass carrier obtained
5) Use f8.

To ensure success prior to paper exposure, a grain magnifier that can see the edges of the projected image is a must.
 
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