Are these color filtration the same

[koraks]

how to compensate for lack of cyan using the other two

Which I did in #14.

 

[brbo]

The "fear" of using cyan filtration comes solely from long printing times that you all get? Or is it something else?

I regularly use quite high cyan filtration from the start to build neutral density in order to get longer printing times. Otherwise, with RA-4 paper, using my lenses at optimal apertures and my typical printing sizes I would constantly be at sub 5s. And using all the controls available makes colour balancing easier.

 

[lantau]

The "fear" of using cyan filtration comes solely from long printing times that you all get? Or is it something else?

I regularly use quite high cyan filtration from the start to build neutral density in order to get longer printing times. Otherwise, with RA-4 paper, using my lenses at optimal apertures and my typical printing sizes I would constantly be at sub 5s. And using all the controls available makes colour balancing easier.

By doing so, aren't you bringing in filtration dependend changes in exposure? That makes things even more compilicated.

I do understand your point about short printing times, though. That is why I ordered my enlarger with a neutral density function. For small prints I ran out of aperture on the old enlarger.

But, Drew is right. The OP needs simple advice. And we all try to give our version. I tried to give a very simple answer, quite far up in #6. Others tried as well. Now it is getting ever more complicated.

 

[brbo]

By doing so, aren't you bringing in filtration dependend changes in exposure? That makes things even more compilicated.

Are you saying that if you don't use cyan filtering then changes in M and Y filtering don't result in exposure change?!

If my test print is too red/cyan and I only change C filtration I need to change my exposure _less_ than I would have to if I corrected for red/cyan with M and Y.

 

[lantau]

Are you saying that if you don't use cyan filtering then changes in M and Y filtering don't result in exposure change?!

If my test print is too red/cyan and I only change C filtration I need to change my exposure _less_ than I would have to if I corrected for red/cyan with M and Y.

I expect there to be some exposure change. But in practice it's not visible to me when adjusting in the usual range of up to 20cc. I would expect more rapid change when adding the third filter. But maybe my gut feeling is wrong.

 

[koraks]

The "fear" of using cyan filtration comes solely from long printing times that you all get? Or is it something else?

Not really a fear. Just a total lack of any necessity to use cyan filtration. If anything, it makes things more complicated, although that's a bit of a moot point.

Nothing wrong with sub-5 second exposures BTW. RA4 paper these days should work just fine at a fraction of it. You do need a decent timer and consistent light source though.

 

[DREW WILEY]

Every time you change filtration, it will affect exposure time somewhat. So a bit of neutral density makes little difference; and there's no crime in using cyan. I always null out the cyan myself unless I deliberately want to add neutral density (which I sometimes do need because my colorheads are quite powerful, and I might need to prolong exposure without stopping the lens down too far). But when you're just talking about a ten of less cc's of cyan, that's only around a third of a stop of extra exposure - no big deal.

Here's why Koraks is wrong about short exposures : You light source will NOT in fact be consistent, because the bulb briefly changes color as it heats up, and then due to a brief afterglow when the current stops. This is the case even if there is fancy feedback circuitry in place fine tuning the color balance during exposure. A few very expensive pro colorheads incorporate timed shutters above the mixing box to trim off both the warmup phase and afterglow, but we're talking about true commercial enlargers here, big in size and huge in budget. But with ordinary colorheads, with that hypothetical 5 second exposure, at least a second or two at each end is going to have a somewhat off color temperature (typically warmer), affecting perhaps 3 out of the 5 overall seconds of exposure. So it's impossible to do clean precise color work that way. Even with my own equipment, which does have sophisticated feedback circuitry monitored many times a second, I try to avoid anything less than a 10 sec exposure.

 

[koraks]

the bulb

Unless no bulbs are involved. Semiconductor (led) light source = repeatable down to sub-millisecond levels (a couple dozen nanoseconds at worst, in fact).

 

[DREW WILEY]

LED for color enlarging purposes is still in the adolescent phase; so we'll see if it turns out to be a viable alternative to tried-and-true halogen bulbs or not. And of course, one could simply adapt a solenoid-controlled electronic shutter to a typical enlarging lens if needed. Process lenses often utilized that feature, but didn't come in short enough focal lengths to be appropriate for 35mm or MF enlarging.

 

[Mr Bill]

A few very expensive pro colorheads incorporate timed shutters above the mixing box to trim off both the warmup phase and afterglow, but we're talking about true commercial enlargers here, big in size and huge in budget.

Yeah, that's the sort of system used where I used to work - the main lab for a large studio chain.

More specifically we used primarily Nord "package printers," equipped with lamp houses from Lucht Engineering. They could expose an 8x10" print in about 400 milliseconds, a bit under a half-second. Here's the operational sequence: the lamp is in a viewing mode - on, but a relatively low power. This is plenty bright enough for an operator to view the negative in the printing gate. When an exposure is initiated the lamp first ramps up to full power. At this point a shutter opens to start the exposure, using unfiltered (white) light. The Lucht lamp houses used hard-cutting dichroic filters, mounted in what were known as "filter paddles" (after the paddle-like shape). Each paddle is mounted on a rotary solenoid in such a manner that the filter can be electrically flipped into the light path. So the light colors are not partially-attenuated, like a typical enlarger would be. It starts out with a white light exposure. Then at the appropriate time each filter paddle flips into the light path, terminating exposure for the appropriate color. Said more plainly, the lamp supplies white light, made up of red, green, and blue light. At the appropriate time, the yellow filter will flip into the light path, terminating the blue-light exposure (a yellow filter passes red and green light, blocking blue). Likewise with the magenta filter, terminating the green-light exposure. When the cyan filter flips in, the exposure is effectively terminated (no light can pass through all three filters). At this point the mechanical shutter closes, and the lamp ramps back down to the low-power viewing mode. Simultaneously the paper advances and the printer is ready for another exposure.

One may wonder, why make a simple thing so difficult? Well, the main advantage is that the machine can individually control the color balance for each exposure. This is actually the same method that was used in optical mini-labs, where they could use color sensors to individually adjust for each negative.

A second, non-obvious benefit was to use what is known as slope control. The users of standard color enlargers generally try to keep a more or less fixed exposure time, so as not to have color shifts related to reciprocity failure. In commercial machines of this sort, including mini-lab printers, a set of printer setup negs (sometimes known as "Shirleys," mainly on the internet) are used. These include a range of exposures, which the operator must individually color-correct. Once this has been done, the machine is able to figure out what corrections must made for various exposure times, aka the "slope correction." So from then on the operator can simply call out color balance settings, and the machine will automatically use the desired filtration, as well as make the corrective adjustments for paper reciprocity failure.

With respect to production capabilities, the Nord machines that we used mostly took nominal 575 foot rolls of 10 inch paper, and could expose the entire roll in around 30 or 40 minutes. So this is about a dozen such rolls in a normal working day - something like 8 or 10 thousand 8x10 inch "units" per day. And we had something like 35 or 40 of these printers in our main lab, which is why I sometimes referred to the lab operation as a sort of "factory" for pictures. As a note, the reason I use the term "units" instead of just "prints" is because they can have different configurations. A package printer is equipped with a set of so-called "lens decks," which can be automatically moved in or out of the light path. One deck might use a single lens to expose an 8x10. Another lens deck might simultaneously expose a pair of 5x7 inch prints on a nominal 7 X 10 inch "unit" (the negative carrier has to rotate 90 degrees for this). Yet another might expose a 5x7 inch print with a handful of wallet-size prints filling out the rest of the unit. All these, or even 10x13 inch prints, all from the same package printer, at the same rate of output.

FWIW these were machines of a past Era. Once digital photography and cell phones came on the scene few people needed wallet-size prints anymore. More adaptable digital printers took over and these older package printers mostly went to the dump, lenses and all; nobody wanted them. Gradually even those printers became unwanted, and on and on.... everybody knows how the story went. As they say, nothing is as constant as change.

 

[DREW WILEY]

That's sure interesting, Bill. But what I had in mind was pretty much the opposite from mini-lab high-rate gear, and big things like Commercial 8X10 Durst colorheads with basic timing shutters trimming off just the beginning and end of the lamp cycle, and all the color filtration itself being independent of that. But in such applications, very short exposures aren't in mind anyway, since those kinds of high-wattage colorheads were mostly used for big enlargements. Typically, these were 2000W halogen CMY subtractive heads. At the very end, Durst did make a few additive RGB 2000W units with a very different kind of feedback system, but none of these ever reached commercial application; all went to the NSA instead. I've seen the guts and electronic brains of them. My own 8X10 RGB additive system works on a different premise of pulsed halogen, feedback controlled. But designing anything serious additive is a real headache compared to traditional CMY.

Another advantage to slowing things down a bit during enlargement is for sake of controllable manual dodging and burning.
Not many people are going to make precision master internegs from chromes like I'm doing this week, with the adjustments already basically pre-built-in, onto the printing master through supplemental pin-registered masking.