Calibrating My Color Head For B&W Printing Times

[AndreDjanikian77]

Hey everyone,

Yesterday, I ran some tests in the darkroom. I recently bought a 21-step Stouffer step wedge and replicated the tests that the Naked Photographer suggests in this video:


My results were decent, though I could have exposed for longer to get deeper blacks...
But my question is about which tones to compare when determining how many steps each filter reduces light. I can compare either the shadow tones or the highlight tones, and that’s where I’m unsure.

In the first comparison, the left side is with a grade 2 filter and the right side with a grade 5 filter, comparing the highlights. The difference is 2 steps (1 stop).

In the second image, it’s the same grade 2 and grade 5 filters, but this time comparing the shadows, showing a difference of 1 step (½ stop).

In the third comparison, it’s a grade 2 and grade 00 filter, again comparing the highlights, with a difference of 2 steps (1 stop).

And in the fourth image, it’s still the grade 2 and grade 00 filters, but now comparing the shadows, showing a difference of 3 steps (1½ stops).

My question is: which reference point should I use for these comparisons—the shadows or the highlights?

I’d love to hear from someone with more experience on this!

 

[MattKing]

My question is: which reference point should I use for these comparisons—the shadows or the highlights?

Whatever you prefer - because all of these "speed matching" approaches are based on first choosing which tone is to be used as the standard.
Traditionally, a high mid-tone/low highlight was chosen. I expect that was because many who depended on speed matching were printing a fair amount of photos of people with Caucasian skin tones, and those sort of tones are similar to that choice.
I no longer do much portraiture, so the speed matching tone - the one that stays the same while others vary as the filter settings change - might be more appropriately picked from the darker options.
In my case, I just use the published figures or the settings on a VCCE head to adjust for my next test strip, and then go from there.

 

[ic-racer]

One advantage of this method (rather than a dedicated MG head) is that you can have a table for each: shadow, middle and highlight.
I usually make the table to pivot on the gray band in the mathematic middle betweeen white and black. So if white to black is 7 steps, I pick the step 4 from either black or white.