Cyan as a means of fine-tuning exposure?

Hi,

I am just getting started with RA-4 printing and I am finding that the half-stop clicks on the lens and the full-second increments on my enlarger together timer don't necessarily allow as as fine-grained exposure control as I might need. Is adding or subtracting let's say 2c 2m 2y something people do in this scenario or is that overcomplicating things and should I try to source a timer that allows 0.1s increments? May be tough to find in this market

Adding or subtracting density in the manner you describe, is a perfectly good way to adjust exposure control, however with my experience of doing that in colour printing, you will be unable to super fine tune to the degree you are wishing to do. Pretty much the accuracy of the density change one can control is around the accuracy of the three filters being moved in perfect unison, that really doesn't happen in the real world. Some enlargers I have worked with had a Neutral Density (ND) filter built in to the head, using the inbuilt ND filter in this manner one would generally be able to control to around 1/10 of a stop.

Life for me was much easier once I found an enlarger timer that went down to 0.1s increments, while bliss was achieved with the addition of a foot switch to said enlarger timer.

My own enlarger has increments of 1 density unit of colour addition or subtraction for each of the filters in the head, this is fine for colour rendition accuracy or subtle contrast changes in B&W printing, but a bit problematic for short exposure time differences when enlarging. If I'm doing a quite small enlargement, then enlarging times between 3s to 9s could be where things are mostly at. In this area of total time, changes of 0.1s units are where you will be at. For arguments sake if you base exposure is 1.4s then an extra stop will be 2.9s. Using a standard enlarger time with 0.1s increments and going in 1/16 stop movements and starting at 5.0s then the next exposure up is 5.2 / 5.4 / 5.6 / 5.9 / 6.2 / 6.4 / 6.7 / 7.0 / 7.3 / 7.6 / 7.8 / 8.4 / 8.8 / 9.2 / 10.0 which is effectively 1 stop difference from 5.0s through to 10.0s in sixteen steps. This works very well for either colour or B&W and is very easy to do with a simple timer able to do 0.1s increments.

The f stop timer is once again being manufactured, this is the enlarger timer I would be purchasing if I was on the market for one. I would like to have one, and I have a wall chart that allows me to quickly adjust times in an f/stop manner, but there is no way it is better than having an f stop timer.

https://www.darkroomautomation.com/da-main.htm

unityofsaints said:

should I try to source a timer that allows 0.1s increments?

Click to expand...

That's IMO by far the more straightforward solution.

Well, even a 2cc filter change with some colorheads might produce a visible hue change in the final color print. But hypothetically, the same amount of density change in all three at the same time will produce neutral density, so you could experiment. As equipment gets older, the dichroic filters might age a little differently from one another, even if that is only due some grime accumulation. There are probably plenty of used electronic Gralab timers for sale with 1/10 sec increment settings (not to be confused with old clock-dial stye Gralabs). But just how short are your exposures to begin with? Heck, I work with colorheads in the 750 to 1500 Watt range, and never need to resort to tenths of second tweaks to basic exposure time. And remember, you don't necessarily have to use the distinct stop and half-stop click positions on the enlarging lens, although that makes things easier to reset to the same spot later. You can use any f-stop increment you wish, and maybe even temporarily tape it tight at that setting if you need to.

Thankfully I was able to locate a timer with 0.1s increments in my local community darkroom - otherwise the cheapest option would have been 200$!

unityofsaints said:

Hi,

I am just getting started with RA-4 printing and I am finding that the half-stop clicks on the lens and the full-second increments on my enlarger together timer don't necessarily allow as as fine-grained exposure control as I might need. Is adding or subtracting let's say 2c 2m 2y something people do in this scenario or is that overcomplicating things and should I try to source a timer that allows 0.1s increments? May be tough to find in this market

Click to expand...

bulb brightness ramp up and ramp down time may invalidate a 0.1s-increment timer but, timing's the way to go. in B&W, I'm a big fan of f/stop timing.