[Help] Meochrom 2 Color Printing: Exposure Time Too Short (1 Second)

jacksonwade · Mar 10, 2025

Hello fellow darkroom enthusiasts,

I’m new to RA4 color printing with the Meochrom 2 color head and am struggling with excessively short exposure times. Seeking advice from experienced users to optimize my workflow.

▌Current Setup

Light source: 12V 100W halogen bulb (stock)

Film: 35mm negative (portra 160)

Optics: f/8 aperture | 6×8 inch (15×20cm) enlargement

Process: RA4 standard chemistry (38°C)

Exposure time: Only 1 second** (too brief for precise control)

How can I safely extend exposure time without compromising color accuracy?

There’s another older thread on the forum discussing a similar issue, which seems to be a common problem with the Meochrom system: Meopta Meochrom Color 3 - Extremely Short Exposure Times.

pentaxuser · Mar 10, 2025

You can decrease the aperture
Decease the wattage to 75W
Add C to balance the Y and M for neutral balance
Add an ND filter either into a filter drawer if one exists or place it under the lens if not

It may be enough to decrease the wattage. That's what I did and for 5x7 prints and it was enough to bring exposure up to about 4-5 secs which was fine for my digital exposure timer to handle

pentaxuser

ic-racer · Mar 10, 2025

Magnification or negative and print size?
Color pack or filter settings?

jacksonwade · Mar 10, 2025

pentaxuser said:
You can decrease the aperture
Decease the wattage to 75W
Add C to balance the Y and M for neutral balance
Add an ND filter either into a filter drawer if one exists or place it under the lens if not

It may be enough to decrease the wattage. That's what I did and for 5x7 prints and it was enough to bring exposure up to about 4-5 secs which was fine for my digital exposure timer to handle

pentaxuser

Thank you four your reply!
But I'm curious, why is the exposure time so short when using the default bulb? Was it like this decades ago? Isn't that quite inconvenient? Could it be because the paper nowadays is more sensitive than in the past?

jacksonwade · Mar 10, 2025

ic-racer said:
Magnification or negative and print size?
Color pack or filter settings?

Film: 35mm negative (portra 400)

Optics: f/8 aperture

Paper size: 6×8 inch (15×20cm)

Color pack: Y-45 M-45 C-0

perkeleellinen · Mar 10, 2025

Have you used the enlarger to print in B&W, were the exposure times normal?
What RA4 paper are you using?

jacksonwade · Mar 10, 2025

perkeleellinen said:
Have you used the enlarger to print in B&W, were the exposure times normal?
What RA4 paper are you using?

I use Kodak RC color paper.
I have meopta opemus 5 head for B&W print, which also had short exposure time problem. After I changed to a 75w bulb, it works better.
So I am really confused about the overly short exposure time of the meopta. Is this a problem specific to this brand of enlarger? Or does this happen with all enlargers?

My previous thread: Fomaspeed variant 312: exposure time is too short?

perkeleellinen · Mar 10, 2025

I used to have a Meopta Opemus 6 with a Color 3 head. I never had a short exposure issue. I now have an LPL C7700 and also no issue.

Have you looked into the head to see if the mixing chamber is in order?
What lens is it? Does it have a filter thread you could put a ND filter on?

koraks · Mar 10, 2025

pentaxuser said:
Decease the wattage to 75W

Doesn't help much; will only gain a fraction of a second.
The other solutions you mentioned are the way to go - stop down, use an ND filter and maybe dial in additional Cyan.

jacksonwade said:
I use Kodak RC color paper.

Given that you're in China, I assume that's Lucky-produced paper sold under a Kodak brand name. It's inconsequential though; all color papers on the market today are very, very fast. Very short exposures are normal. 1 second for the kind of enlargement you're mentioning is indeed entirely plausible.

One more possibility is to use a timer that allows to set fractions of a second, but with a halogen light source, there's a limit to how short you can go while keeping things reproducible.

The easiest solutions are to stop down the lens to f/22 or so and get an ND filter.

Good luck; it's cool you're print color! More people should do that; it's great fun.

jacksonwade · Mar 10, 2025

koraks said:
Doesn't help much; will only gain a fraction of a second.
The other solutions you mentioned are the way to go - stop down, use an ND filter and maybe dial in additional Cyan.

Given that you're in China, I assume that's Lucky-produced paper sold under a Kodak brand name. It's inconsequential though; all color papers on the market today are very, very fast. Very short exposures are normal. 1 second for the kind of enlargement you're mentioning is indeed entirely plausible.

One more possibility is to use a timer that allows to set fractions of a second, but with a halogen light source, there's a limit to how short you can go while keeping things reproducible.

The easiest solutions are to stop down the lens to f/22 or so and get an ND filter.

Good luck; it's cool you're print color! More people should do that; it's great fun.

Thank you for your message! I’m so relieved to hear that the extremely short exposure time wasn’t due to any mistake in my technique. This forum always provides such professional help. In China, there are also many people passionate about darkroom, and lots of enthusiasts share their work and experiences on Chinese social media platforms like Rednote (perhaps many have heard of it) and Bilibili.com.

jacksonwade · Mar 10, 2025

koraks said:
The easiest solutions are to stop down the lens to f/22

Will f/22 decrease the printed image quality?

koraks · Mar 10, 2025

jacksonwade said:
In China, there are also many people passionate about darkroom, and lots of enthusiasts share their work and experiences on Chinese social media platforms like Rednote (perhaps many have heard of it) and Bilibili.com.

It would be lovely if our communities could somehow connect - so I'm very happy that you and a few others from China join us here to share your experiences!

jacksonwade said:
Will f/22 decrease the printed image quality?

A little, but on small prints, it's doubtful whether it'll be much of a problem. I'd try a few prints at f/11, f/16 and f/22 and then have a look at the differences.

ic-racer · Mar 11, 2025

jacksonwade said:
Film: 35mm negative (portra 400)

Optics: f/8 aperture

Paper size: 6×8 inch (15×20cm)

Color pack: Y-45 M-45 C-0

Y165, M165, C120 & f16 ; predicted 60 sec exposure.

jacksonwade · Mar 11, 2025

ic-racer said:
Y165, M165, C120 & f16 ; predicted 60 sec exposure.

I will try this. Thank you very much!

ic-racer · Mar 11, 2025

jacksonwade said:
I will try this. Thank you very much!

The usual starting packs for color printing are the brightest combination of colors by convention. But that doesn't mean you have to use it like that. Add in all 3 colors as needed to darken the projected light.

Let us know how it turns out.

Also, you can do a test at f8 and f22 to see if they are both sharp to your eye with that small of a print.

Ian C · Mar 11, 2025

A simple way to lengthen enlarger exposure time is to install a neutral-density filter on the lens. This is particularly useful when small prints are made on an overly-bright enlarger. They are available in many strengths. The most common are:

ND 0.3 = 1 stop

ND 0.6 = 2 stops

ND 0.9 = 3 stops

ND 1.2 = 4 stops

For example, if your exposure time is 1 second at f/8, by using a 3-stop ND filter, the exposure time will increase to 8 seconds.

With an 4-stop ND filter, the exposure would be 16 seconds at f/8 or 8 seconds at f/5.6.

Here’s an example of a 40.5 mm filter, a size used on many 50 mm enlarging lenses:

https://www.bhphotovideo.com/c/product/58576-REG/Tiffen_405ND3_40_5mm_Neutral_Density_ND.html

Most lenses have an optimum aperture, one that produces the best combination of resolution and preservation of contrast. That is usually when the aperture is closed about 2 stops from its wide-open setting. By choosing the appropriate neutral-density filter, you can use the optimum aperture on your lens and obtain a practical exposure time.

koraks · Mar 11, 2025

ic-racer said:
Y165, M165, C120 & f16 ; predicted 60 sec exposure.

Yes, that should work, but leaves a little less room for changes in color filtration. It may or may not be sufficient. But your example does show how much can be done without any additional hardware.
I'd not go higher in C than necessary to get acceptable times.

[Help] Meochrom 2 Color Printing: Exposure Time Too Short (1 Second)

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