Using the Meopta Color 3 head, but for black and white

This is the color head of my enlarger, it can be used for contrast control of black and white print too, but this is not the intended use.

These informations should match the ones for Meopta Color 4 too, they use the same exact color filters.

Filtering wheels

The head has the following subtractive filters intended for print color correction

• C: Cyan
• M: Magenta
• Y: Yellow
• D: Neutral Density

Contrast control with black and white using ILFORD Multigrade

As a guideline, ILFORD’s Technical Information Contrast Control memo for has provide as a guideline the following conversion table between Multigrade filters and Meopta color filtering values.

Using the data in the Meopta Color3 head manual, I have computed an approximate factor to multiply the exposure time calibrated at Grade 2 (with white light) to get the same exposure at a different contrast value.

Contrast control with black and white using FOMASPEED Variant

FOMA sells contrast filters that are shades of yellow and magenta, but also recommends color filtering heads as a prime usage for their variable contrast paper.

The FOMA filter are not speed matched. The datasheet gives filter values. We can cross reference this with the Meopta Color 3 head manual, and build this table

Note: It does seems that the contrast from the exposure without any filtering is slightly lower contrast than standard grade 2. The difference may not be big enough to matter. FOMA’s datasheet calls contrast without filters, and grade 2, both “Special” contrast. They call grade 3 “Normal” contrast.

The information, overall, is less precise than ILFORD’s documentation, but is more than sufficient in practice, especially since we are not using ILFORD’s filters that are “speed matched”, we always need to recompute exposure

Double filtering to keep the same exposure

Apparently the Meopta website used to have a double filter scale for the Meopta Color 4 ES. That head also used the same filter strength so this table would applly.

The problem is that, it was on their website in 2007, but that link has not been archived it seems. I can only find some data on this Photorio forum post

This assumes that, the same value of Y and M filter result in a ND filter that only change exposure time, not grading.

This data does not 100% concord with the ILFORD or FOMA datasheets of today, so some experimentation is needed to confirm if those are useful values.

It should be doable to use the formula and factor tables form the color 3 exposure manual to double check that these filters gives equivalent exposure times. I haven’t done so in details, but it sems that it does not (though, this relies on lookups form a data table where I do not know the edge case behavior)