Craziness - using LEDs to print RA4 (and B&W)

[1kgcoffee]

I don't mean to be rude by not responding to help that I've asked for, but I've been swamped. Yes, even during this pandemic! I have a colour checker on order now

You guys are right about different color balance in different parts of the image. The problem with medium format on 80mm enlarging lens is the same issue I was having with 35mm film on a 50mm enlarger lens. You can see that the problem of irregular colour balance is solved in 35mm. Was able to do some test printing last week on my 150mm lens. The medium format shots print much better. This is of course a problem for printing big, or if I ever wanted to print 4x5 color. The reason this happens is because the lifx bulb is flat.

As for 35mm, I think the problem is scanning. I have a big problem with epson automatically clipping and trying to make the color balance look good or doing so manually and changing color levels by a few degrees trying to get things perfect. I can tell you that to my eye the unscanned 35mm prints look damn near perfect. But I would have to compare results to a dichroic enlarger, and there are a few for sale nearby now. I would be interested in doing a double blind study at some point, printing from both dichroic and the lifx and mailing the results out to get some opinions, if anyone is interested.

Drew, I think you are correct about Ektar. The original film scans seemed a bit cool too. I have filters but prefer not to use them. And I love kodak gold for that for that very reason. The colors aren't 'perfect' but they have a pictorial quality which digital lacks. The rabbit hole goes deep with color theory. There is also the issue of the human eye being more perceptive to certain colors.

 

[mnemosyne]

Interesting thread and also impressive technicals skills demonstrated here!

I would however like to point out that there is another, very straightforward, simple and cost effective option for those who want to print color on the L138 with an LED light source:

Just get a set of gel color printing filters and put a frosted E27 G120 (globe) LED with reasonable light output in the lamp house of the L138 condensor head (horizontal position) and start printing away happily ...

The good:
It's cheap. It's simple. It works. It works well. In my tests so far I had no problems matching an existing print that I had made with a halogen type head and dichroic filters. The exposure times are reasonable. The filtration is reasonable.

The bad:
It's old school. It's kind of slow. Changing filtration requires pulling the filter drawer from the lamp house and replacing gels. It is definitely not as comfortable as pressing some buttons or turning a dial.

Conclusion:
Is it a professional solution? No. Is it entirely adequate for the hobbyists among us who simply want to do some quality color prints with their L138 from time to time? I think yes.

 

[mnemosyne]

This is a sample printed on 10x12" paper (Fuji CA DP II) from a 6x6 cm negative (Kodak Ektar). Light source G120 E27 LED bulb with 5500K, 1800 lumen, 18.5 watt with a frosted glass filter in the filter drawer (eats about 1.5 stops of light in my experience). Exposure time for this print was 20 seconds at f8 with the Latico 240/130 combo and a 90mm lens. Filter pack was M200 and Y240 with a ca 1970s Agfa filter set (the high values are normal for Agfa filters).

 

[koraks]

Thanks for your addition and offering a much less complex alternative. I did try old fashioned filters once (with a regular bulb, no led) and while it sort of worked, I found it inconvenient. Still, you prove that it's a viable option!

 

[mnemosyne]

Part of your high filtration may also be due to using a 5500K bulb rather than a 3400K that is closer in color to a tungsten or halogen bulb that the paper is designed for. Using an 85B filter on the enlarger would mostly compensate.

Hi Greg, you're right, I did a test with a 14 watt 1.400 Lumen 4000K LED and the filtration came down to 150M/150Y for a matching print. Its also faster about 1.5 stops because there is less waste of light with the small (6x6) negative. 4000K is also better balanced for b&w variable contrast printing. I have not done a test with 3400 K LED.

 

[mnemosyne]

Thanks for your addition and offering a much less complex alternative. I did try old fashioned filters once (with a regular bulb, no led) and while it sort of worked, I found it inconvenient. Still, you prove that it's a viable option!

Actually, I found it less cumbersome than expected. An interesting side effect is that it makes you think twice before you change filtration And maybe because I have a convenient workflow established on the processing side in the form of a tabletop R/T processor, I felt that I could afford a more inconvenient approach on the printing side ...

My apologies for taking the thread a bit OT.

 

[koraks]

My apologies for taking the thread a bit OT.

No worries