Enlarging with Rodagon 150mm at f22

[Rafal Lukawiecki]

My Ilford 500H head is very bright, so much so that burning and dodging times are often way too short for comfort, less than 2 secs perhaps. I usually print at 12x16 (the rest of the time 11x14 or 16x24) on Ilford MGIV FB, from 4x5 B&W negatives on a DeVere 504 with a Rodagon 150mm. I can see that this lovely lens gives me the sharpest image of the grain (as viewed in a grain magnifier) at f8 or f11. At f16 the grain softens and at f22 it seems very soft indeed, beyond that down at f45 I can no longer see the grain.

I wonder if any other enlarging lens, notably Apo Rodagon N 150mm (anyone selling?), would remain significantly more grain-sharp at f22 than the Rodagon?

I guess I could try replacing the bulbs with weaker ones, but I am wondering what else could I do to solve this issue.

Many thanks,
Rafal Lukawiecki, Ireland

[Bob Salomon]

Why not use a ND filter either on the lens or in the enlarger?

[Drew Wiley]

Bob - sometimes I like to use a graduated center filter over the enlarging lens,
mostly just for the effect. But it will also help even light distribution with some
enlarging lenses, provided of course that the lens is stopped down some. Diffraction
sets in too far down obviously, but with large format film you have to be making really big prints to see much difference in the final result.

[Filmnut]

I too, have run into this problem from time to time, and usually I put an ND filter above the light diffuser. This way it will lenghten the exposure times, but not affect the sharpness. I generally use a piece of film as a ND filter.

[memorris]

Any lens will soften as you stop it down more beyond f/11 or f/16. That is where diffraction causes a loss in clarity. The best way to reduce the brightness is to use ND filters. I sometimes have 3 stops worth to get the time up to 20 sec.

[Rafal Lukawiecki]

Thanks. I guess I could try putting an ND inside the light mixing box of the Ilford 500H. Any suggestions on what material to cut it from so it does not melt or catch fire in the fierce heat?

[ic-racer]

Up near the lamp, most manufacturers use something made of metal to dim the light. Omega uses a metal 'strainer' on the Chromega and the 8x10 Durst CLS uses a metal adjustable 'non-diffracting' aperture between the lamp and the diffuser box.

In your case, I'd use an under-lens or above-lens plastic ND filter. I printed with plastic Ilford filters under the lens of my 8x10 enlarger for about 2 years and found no loss of image quality. If you don't have a filter holder you can just set a plastic ND filter on top of the rear lens element. If you are worried you can also get an optical glass ND filter $$$$.

One other place for a cheap filter would be to use a piece of Rosco lighting gel ND and put it in the mixing box on top of the 5x5 diffuser plate. I would not put the Rosco between the diffuser and the negative or between the negative and the paper, or between the lamp and the mixing box entry site.

[wager123]

i had the same problem with my ilford 500 and solved the problem by useing the 150 watt bulbs insted of 300 watt.
mitch