Less Paper waste
I'm learning to print on B&W on variable contrast paper with a color enlarger. When I change contrast I have to do another test print to determine the exposure. It there something to help determine the paper contrast to use for a given negative and the exposure time for the select contrast on a color head?
You could purchase an exposure meter for darkroom printing. I believe RH designs makes one.
Keep in mind that every time you make a change, and tweak something in your print, you learn something new, and that improves your skill as a printer.
The paper in the darkroom trash can are valuable lessons learned.
And, if you use the same film and developer every time, you will know a lot more what to expect come printing time, which saves a lot of guesswork and paper waste.
Try getting an RH Designs analyser/prom a combined enlarger timer and advanced enlarger meter all in one, or one of their smaller ones http://rhdesigns.co.uk expensive, but quickly pays for itself in saved paper, I have one and it is the best thing next to my enlarger that I ever bought for my darkroom,
You can run your own tests to establish exposure compensation factors to match any particular tone - say, middle gray. Also, some paper manufacturers provide tables of magenta/yellow combinations that maintain consistent exposure for different effective grades.
Either way, though, that only gets you into the ballpark. The best exposure for a different contrast grade isn't necessarily going to be the one that matches any particular tone with its rendering in a different grade. You can expect to still have to do some trial-and-error tweaking.
What you may try is spending a few months/years with the filtration turned off, just concentrating on print exposure and try to adjust your negative exposure/film development time to get something you are reasonably pleased with. Then when you start using contrast control again you won’t be too far away. Also when you mention test print, do you mean test strips of exposure increments? (saves lots of paper).
Use a mixture of yellow and magenta for each contrast grade. If you have a table of values for your enlarger and specific paper, you don't need to change exposure much when you change contrast. Otherwise it is mostly trial and error. Try using small strips of paper.
Originally Posted by AnselAdamsX
This is very good advice.
Originally Posted by Oren Grad
I've calibrated my Aristo VCL variable contrast head using a step wedge. I chose the highlights (threshold) to standardize against. I found that for this head there is almost exactly a 10x exposure difference between the softest (all green light) and the hardest (all blue light) grades of Ilford MGIV FB/RC. By creating a table of exposure compensation factors for each quarter-grade in between, I can pretty much make any grade change in one-quarter increments and come very close to matching the correct exposure change on the first try. Usually a single test strip confirms the new exposure, if there is any doubt.
This is a great time saver to put me in the initial ballpark with a minimum of fuss. Fine adjustments at the new base contrast can then begin immediately. Saves time, saves paper, saves frustration.
I don't see why you couldn't do the same with a color head.
Here's a link to a document from Harman on contrast control with Ilford Multigrade papers. It includes a table ("Dual colour filter settings", p. 3) of combined Y/M filtrations to achieve similar exposures across the grades:
The same information is included on the insert provided with each box of Ilford paper.
These recommendations work, but it is important to understand what they actually do.
Originally Posted by Oren Grad
Their goal is to give you the same print density with each contrast setting, but they only apply to a single reference tone - most likely a middle grey.
So if it is not that reference tone that you are seeking to match across the contrast grades, you may not get exactly the result you want.
Some people prefer to match highlight tones instead, so they do their own calibration to achieve their own goals.
The published suggestions will get you closer than nothing though.
I'd suggest something akin to a Beseler PM2L color meter. They work great for B&W or color and can be found easily on eBay and other places. It is such an important tool to me that I bought a spare. Search "Beseler pm".
Essentially the role of any meter for the enlarger is to mimic the papers response to a given input. It allows you to spot meter for your print. That means you can measure contrast, expose the paper to black or white or any other point you might prefer.
Meters aren't magic bullets; there is a learning curve but as you get the hang of it you'll start to see what it's telling you and what the negative in the holder is going to give you.
What meters do is allow repeatability/predictability. Over time you will define and refine the "programming" (setting the dials) of the meter and be able to print very nice proofs on the first try. With the paper iso numbers and a little math you can even switch paper and get close.
One thing that works really well for me is incident metering my subject, then shooting a reference shot of the incident meter in the same light as my subject during the session. I use black, white, and grey points on the meter from the reference shot to set the enlarger then just insert the negative I want to print in place of the reference shot and I'm ready. Same basic process for both B&W or color.