Enlarger Problems

[Stephen J. Collier]

First things first, I am using a "cheep" enlarger. It’s a Vivitar VI and was all that I could afford at the time, but I still need to get around this little issue.

I am printing exclusively 35 mm negatives and my problem is that with a 50 mm enlarging lens I get focus creeping. This is not too noticeable with short exposure times, but anything over 20 seconds regularly produces out of focus prints. This is absolutely annoying to say the least, but here is the catch. I also have a 75 mm lens and as far as I can tell there is no focus creeping with this lens (this is based on very preliminary experimentation with my grain finder and not with actual prints). To print 35 mm negatives with the 50 mm lens the bellows are fairly tightly compressed to achieve focus while the 75 mm lens allows the bellows to stretch out more. So it would seem that the bellows are “pushing” the 50 mm lens out of focus and that this process is only made evident over long exposures. I looked all over the enlarger head and could not find anywhere to tighten the focus adjustment. So my question really is, what effect will using a 75 mm lens on 35 mm negatives have on my final prints if anything at all?

Thank you for any help you can give me.

Oh, and it would be a double bonus if any of you have experience with a Vivitar VI.

 

[Dave Miller]

I think the only effect will be that you will have to raise the lens higher, and will not be able to produce such large prints. Try it.

 

[Stephen J. Collier]

Yeah, as far as I could tell that was the only differnce. The illumination seems more consistent accross that negative with the 75mm as well, but I did have to switch the condenser up to the 6x6 possition. Thank you.

 

[modafoto]

So my question really is, what effect will using a 75 mm lens on 35 mm negatives have on my final prints if anything at all?

I use an Rodenstock 80 mm lens for 35 mm work. The only disadvantage is that I have raise the enlarger head more than with a 50 mm. The lens is the sharpest of the ones I have access to and therefore I use it.

 

[Bob F.]

Not familiar with the Vivitar, but here's some ideas... You can try to find a recessed lens board if they exist - or make one if it's practical, or adapt the existing one. Some lens holders are reversible. Could buy a 60mm lens (the 63mm f/2.8 EL-Nikkor is reportedly excellent if you can find one at a suitable price) or chop 20% off the bellows so they don't compress so much. But, if you are happy with the 75mm lens, then use that...

Cheers, Bob.

 

[Bob Carnie]

Stephen
Are you using a glass carrier for your negatives?
If not what you may be noticing on the longer exposures is the negative *popping* as the enlarger heats up so does the negative and the middle draws to the light source.
I have also found sometimes with 50mm lens the bellows creating some movement if the locking plate for the lens in that position is not completely secure.
The locking mechanisim on a omega does wear out with time.

 

[John Koehrer]

Stephen
Is the tension on the focusing knob held by a piece of steel over the focus shaft? If it is you could adjust the tension by tighting the screws or by adding a piece of shim stock.

 

[srs5694]

My first thought matches Bob Carnie's -- that the heat buildup in the bellows may be causing the negative to "pop," thus causing the problem. The greater bellows extension when you use a longer lens eliminates this effect (or at least delays it enough that it's not a factor given your typical exposure times). If so, focus fiddling and lens adjustments won't help. I'm not sure what would, aside from using a negative carrier with glass plates to prevent the problem.

 

[raucousimages]

The problem is that there is not enough friction with the bellows in the closed position to keep the pressure from moving the lens out. You will notice this more with short lenses and small enlargements, longer lenses and larger enlargements allow for a longer bellows draw. The older (1975-76) Vivitar VI did not have this problem but later years had this problem all the time. The only solution I know of is to dismantle the rack and pinion system then place something between the lens standard and the base it rides up and down on to increase friction. I used a thick piece of paper. This will make it harder to focus but it will help with the focus creep. I am still using my original VI (1976) but my second purchased new a few years later had several small differences and was hard to focus. I think they switched manufactures in about 1980 for the last production runs. This trick worked for a time but I just got fed up with fighting it so it was sold as parts.

 

[Stephen J. Collier]

Thank you all so much. Your responses have been very helpful. The 75mm lens that I am using is a "Voss", I have never heard of it, have any of you. The 50mm lens that I was using was a Rodenstock so I am a little worried about quality-of-sharpness fall off as I move to the other lens. Oh well, if I can't even keep the 50mm in focus then it doesn't really matter how sharp it is.

 

[Huub S]

Well, in your situation i would use the 75 mm and start looking for a good 80 mm and also a better enlarger. Second hand top quality lenses and enlargers go for next to nothing. The quality of my own enlargements improved greatly when i changed from an old Durst 501 to an even older Omega D2 - using the same lenses and printing techniques.

 

[Melanie]

HI
I have a Unicolor, I think it is much like your enlarger. I have had great result with a 80mm.
Melanie