Need to change mixer chambers?

[fidget]

Hi, another newbie type of question.
I presently print B&W from 35mm, 645 and 6x6 negatives. I found that it was a major pain to setup my diffusion enlarger (M670) for the switch between 35mm and 120 films, particularly in regard to changing the mixing chamber. I tried a few prints from 35mm using both the correct chamber and the one for 6x7. I couldn't see a difference in the quality of the print (but as a beginner, maybe I wouldn't), so now leave the 6x7 chamber fitted. Aside from a difference in exposure times, is it a mistake to use the larger chamber?
( A solution is currently being implemented, a second enlarger, for 35mm and flashing, but I am curious)
Regards, Dave....

 

[Dave Starr]

I always used the 6x7 mixing chamber when I used a Beseler 67C, an now i use the 4x5 chamber on my D5 all the time. Never had a problem.

 

[Photo Engineer]

I have tested using the correct mixer for 35mm, the 4x5 mixer chamber for 35mm and the 120 mixer chamber. I find that there is about 1 stop speed difference between each. Now this is approximate, but here is an example.

If I use 12" at f16 for the 35mm chamber from 35mm negs at 8x10 enlargement, I use f11 with 120 and f5.6 with the 4x5 chamber. They do concentrate the light differently.

I find that the color is about the same, but my Dichro 45S shows a slightly different balance on the LED readout as well.

PE

 

[fidget]

Thanks for the replies.
Aside from differences in light intensity, does the use of a larger than required mixing chamber have any averse effect on the print?

Dave..

 

[Photo Engineer]

Not that I could see. Using a smaller chamber for a given format does cause vignetting.

PE

 

[fschifano]

None. I use the largest light box (4x5) for everything with my Omega D4. Yes, I could get shorter exposure times if I used the smaller format light boxes with the smaller format negatives, but I don't see this as an advantage. Printing times can be almost too short for me sometimes. I like the longer exposure times because it makes dodging and burning maneuvers so much easier and accurate. If you aren't doing high volume production where a few extra seconds for each print starts adding up to some real time, don't worry about it.

 

[Photo Engineer]

With the proper mixing chambers, I get about 12" at f5.6 - f11 for everything, as it all evens out.

PE