Condenser quandry - 4"x 5" to 6cm. x 7cm.

[Deryck]

Hi,
I have a DEVERE 504 chassis which has been modified to carry a BESELER 45MX double condenser head. This modification has been carried out in a precise and professional manner, and as I only work in 4" x 5" monochrome this setup suits me to a tee.

However, I recently agreed to do some 6cm. x 7cm. work for an old friend for which the DEVERE/BESELER enlarger - being "dedicated" to 4 x 5 - is not ideally suited. As there is no practical way in which I can elevate the condensers above the negative stage (nor would I want to) to accommodate for the 6 x 7 format, I was wondering if there would be any intrinsic lack in print quality if I just went ahead and printed the 6 x 7's using the 4 x 5 condenser setup? Or, as I have several different condenser elements from previously scrapped enlargers, would I be able to place a third condenser on top of the original condensers, altering the light path so as to accommodate the 6 x 7's? I assume that I would need to change from my standard 150mm. lens to a 90mm. or 105mm. lens. If this option was possible, I would need some way of testing that the third condenser was actually bringing the light to the correct focus for 6 x 7. Any words of wisdom as to how this could be done empirically would be greatly appreciated.:confused:

In a pinch I do have access to other enlargers, but would much, much prefer working in my own darkroom with the DEVERE/BESELER combo.

Thanks for your time,
Deryck

 

[Konical]

Good Morning, Deryck,

I suspect that you would have no problem using the enlarger as is, with the condensers placed for 4 x 5 coverage. I think that the condenser placement has a lot more to do with efficient light concentration than with image quality. The important thing is evenness of illumination. With no negative in the carrier, just give a piece of paper a minimal amount of exposure (aiming for a very light grey in the developed paper) and see how even the coverage is.

Konical

 

[bdial]

You might lose a little light to more spreading than is necessary for 6x7. But otherwise there is no reason you can't print 6x7 negs with your current setup
If you ever crop your 4x5's you are probably aready printing a 6x7 negative area.

 

[Ian Grant]

Back in the UK I have a supplementary condenser designed for 6x6 to 6x9 negatives, it should sit in a metal frame above the main condensers but in practice I never really bothered with it.

It's highly unlikely there would be any noticeable drop in print quality, the supplementary condenser is really designed to re-focus the light source to match a shorter focus lens, the main benefit is less light loss/ greater intensity. Your exposure times would be shorter with the supplementary condenser.

Ian

 

[David A. Goldfarb]

I agree with the above posts. In general you can use condensers for a larger format with a smaller format, but not vice versa without vignetting. The actual difference in efficiency tends to be fairly small, and is really important only when you are making very large prints and need all the efficiency you can get.

There is some case to be made for matching the condensers to the lens for the purpose of having better light collimation through the system (Durst offers a wide range of condenser sets with this justification), but I find this a bit dubious, since this could only be done precisely for one lens, one format, and one reproduction ratio, and most people don't work that way.

 

[Deryck]

Many thanks for the words of wisdom guys. I'll test for eveness of illumination as has been suggested, then go ahead and print the 6 x 7's with the enlarger setup as is.

As a matter of interest, If I were to incorporate a third condenser element - of which I have quite a few -would there be any way for me to check that it was doing the job of collimating the light for 6 x 7 using a 105mm. len?

Cheers!
Deryck (Denmark)

 

[Bob-D659]

If your existing setup is uneven with a 6x7cm neg, it would be uneven with a 4x5" one as well.

If you add an additional condenser, you just have to mess with the height and position until the light is even and brighter.

 

[Ian Grant]

If your existing setup is uneven with a 6x7cm neg, it would be uneven with a 4x5" one as well.

Not necessarily because with the shorter focus lens the light isn't collimated properly and depending on the bulb could be uneven.

My supplementary condenser isn't as strong as those in a matched pair for 6x7/6x9, it's in the UK totally surplus to requirements or I'd tell you the focal length.

Ian