Omega b22 for medium format

[kleinzaches]

I've printed 35mm using the Omega B22 with no problems, but when I try 6 x 6 it shows as a circle. I suspect a condenser problem, but am not sure. I've found a third lens in the condenser housing (strongly concave, not thin like the manual says). But when I remove it, it makes no difference. Any ideas?

 

[webestang64]

Could be the lens you are using..........

Negative format	Use Lens focal length
35mm	50mm - 75mm
2¼ x 2¼ (6x6)	75mm - 90mm
2¼ x 3¼ (6x9)	90mm - 105mm
4x5	135mm - 150mm
5x7	180mm - 240mm
8x10	240mm - 360mm

 

[Derrel]

Lens you have on there now does not have the right "covering power" to "cover" the larger format 6x6 negatives. This is called the angle of coverage. For example, a 90mm lens designed for a 135mm format camera, like say, a Leica, will NOT be able to literally "project" a wide enough circle of light out of the back of the lens to "cover" a 4x5 inch sheet of film, the way say a 90mm Super-Angulon view camera lens can. Same thing with enlarger lenses...but sort of in-reverse, if you get my meaning.

 

[compur]

I've printed 35mm using the Omega B22 with no problems, but when I try 6 x 6 it shows as a circle.

All lenses on all enlargers project a circle all the time. You just need wider coverage, as Derrel said, which means using a lens made for the 6x6 format -- a 75mm or longer enlarger lens.

 

[webestang64]

Here is the manual if you need one...... http://www.jollinger.com/photo/cam-coll/manuals/enlargers/omega/Enlarger Chassis B-22.pdf

 

[kleinzaches]

What's puzzling me is I get the same circle with both the 55mm and the 75mm lenses. I just have to move the head farther from the base with the 75mm, but it makes no difference in terms of my problem. That was why I thought maybe it was a condenser issue...

Lens you have on there now does not have the right "covering power" to "cover" the larger format 6x6 negatives. This is called the angle of coverage. For example, a 90mm lens designed for a 135mm format camera, like say, a Leica, will NOT be able to literally "project" a wide enough circle of light out of the back of the lens to "cover" a 4x5 inch sheet of film, the way say a 90mm Super-Angulon view camera lens can. Same thing with enlarger lenses...but sort of in-reverse, if you get my meaning.

 

[timor]

From manual of B22 looks like you should have plano-convex supplementary lens, not concave. But still it doesn't matter, condenser is only to make light even throughout the whole negative. You can use the condenser setting for 50 mm projecting lens with 75 mm projecting lens and the only difference should be intensity of light in the corners. In any case for 6x6 you don't need supplementary condenser lens (page 8 of the manual.). Some 75mm enlarger lenses can only cover 6x4.5 negative, what make is yours ?
Now, what do you have in the filter drawer ?

 

[compur]

Did you read the manual? The part about how the condenser needs to match the lens in use?

 

[kleinzaches]

From manual of B22 looks like you should have plano-convex supplementary lens, not concave. But still it doesn't matter, condenser is only to make light even throughout the whole negative. You can use the condenser setting for 50 mm projecting lens with 75 mm projecting lens and the only difference should be intensity of light in the corners. In any case for 6x6 you don't need supplementary condenser lens (page 8 of the manual.). Some 75mm enlarger lenses can only cover 6x4.5 negative, what make is yours ?
Now, what do you have in the filter drawer ?

Thanks! I guess I should read the manual more carefully. And I meant to say convex - always confuse the two.... My filter drawer is empty. And my lens is a Rodenstock Omegaron.

 

[timor]

Lens seems to be proper for the job. The circle you are getting is this sharp defined circle ? Or kind a soft edge ? Do you get the circle also without the lens ? (With the carrier in position.)

 

[kleinzaches]

Lens seems to be proper for the job. The circle you are getting is this sharp defined circle ? Or kind a soft edge ? Do you get the circle also without the lens ? (With the carrier in position.)

It's a soft edge... haven't checked what it looks like without the lens. I'm going to be out of town for a week or so, but will check that when I get back. Thanks!

 

[timor]

OK. When you come back we deal with it. There are two possibilities: or there is a obstruction in the path of light letting through only limited cone of light, or the lens is somehow bad. You are in Toronto, right ?

 

[kleinzaches]

OK, back in town and still struggling (yes, I'm in Toronto). I get the circle of light with both my 50mm and 75mm lenses - and with no lens at all! It looks to me like it wants something like a smaller negative carrier than the 6x6 I'm using... but then a large portion of the negative would be masked. At a loss

 

[timor]

Just wonder how far from me you are in Toronto. The simplest thing would be to grab my 80mm lens and come over and solve this problem on together. I am curious myself why enlarger designed for 6x6 has problem with 6x6 negative.

 

[kleinzaches]

I'm downtown, Queen and Dufferin. I could also bring the enlarger to you - seeing as you're doing me a favour. In any case, I think I have to put this on hold till late August. I have a couple of deadlines for the end of the month, then going away for a couple of weeks. But it would be great to have this resolved!