I changed enlarger lens and...

Hello Jorge,
You might try adjusting the distance between the light bulb and the condenser.

All the best

Thanks, everyone.
I will try to assemble the bathlab tomorrow (or during the weekend) and do some tests.
Will post any findings.

Jorge O

I would check out the lens thoroughly. What you describe makes me think of some serious internal reflections in the lens. Do you notice any change in the contrast of the print image from this lens to the old one?
Then again this may be from light reflected from the inner surfaces of the bellows and making its way through the lens to the easel. In that case I'd think you have a heck of a lens.

The condenser focuses the light to the center of the enlarging lens. So for a 6x6 condensor you are using either a 75mm or 80mm lens. When you switch lenses for a smaller format the condenser will still focus the light for the longer lens. This will be exaggerated with a 40mm (wide angle lens) as the focus point will be ~40mm beyond the lens. This is going to show up as a weird light source outside the image area. It will not be as exaggerated with a 50mm lens.

Did you notice you had to rack the lens a whole lot closer to the negative stage to focus the negative?

- Mike

Jorge, your condensor must match two parameters: the focal length of the lens and the magnification ratio. Although there is always only one "ideal" combination, practice has some tolerances. If your combination is out of these bounds, you will get an uneven illumination. Your halo is a simple light fall-off. You need a condensor suitable for a 40mm lens.

I have the same (?) halo on my Opemus 6 with colour head, using both 50mm and 80mm Anaret-S lenses. Since I use a colour head, the condensors are not to blame.

But that halo has never given me any problems...

I did not do any test yet, but since you guys are very cooperative:

dr bob
Thanks for the offer. If my tests do not show anything, I will take it;

glbeas
Looking at the lens it looks fine, and enlargements (did not do a side to side compare) are fine;

Mike
No, technically I did not have to. That's one of the reasons I've bought the Nikkor - it has the same flange to negative distance of the 50mm (but the glass protudes more in the back, so it's really closer to the neg).

And thanks also for all other posts.

Jorge O

Ok, guys

I've put on my Sherlock cap, lit the pipe and :?:

- The light comes out through the lens - not a leak somewhere else.
- The 'halo' is only visible when the red filter is in place; it's actually light coming out of the lens at such a wide angle that it overpass the red filter assembly (much larger light circle than the working area);
- It gets stronger the smaller the printing is, and disappears (or I simply can't see it) at large enlargements, with any of my 3 lens;
- At the smallest enlargement possible (head fully down), the Computar 50/2.8 is the worst, the Nikkor 40/4 is second and the Nikkor 50/2.8 is the best, halo wise.

I've tried using only one condenser lens in both possible positions, but then the light circle was too small.

Solutions:

- I will use the 40/4 only for enlargements larger than the 50/2.8 are capable of (that was the original intention, BTW).
- I will paint mate black the lens mounting ring (I had to order a custom one since the original part would not accept a lens when mounted inverted, and 'tomorrow I will paint it', you know...). :oops:

Thanks again,

Jorge O

Quote:

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Originally Posted by Jorge Oliveira

- I will paint mate black the lens mounting ring (I had to order a custom one since the original part would not accept a lens when mounted inverted, and 'tomorrow I will paint it', you know...).

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??? "Inverted"?? Are you saying that you are using this lens with the front element towards the film - and not the enlarging paper?

Ed

No, not the lens.
The mounting plate is not flat - it has a recess, to be used like this ---___--- for the

75/80mm lens and you invert it like this __----__ for shorter lens, otherwise it won't focus.

But the lens would not fit (inside the recess) when I tried to screw the lens on, so I had to order a new custom machined mounting plate.

My sorely missed Durst had similar mounting plates, but since they were wider, there was no problem using them.

Jorge O