The problem is you can't control the bulb with a standard timer. The bulbs need to be left with continuous power and then controlled by an app. If you disconnect that power and then reconnect it, like you would a normal bulb, they'll go back to their default settings, which means a warm white. So in order to use them for VC exposures, you'd have to leave them powered on all of the time, and then try to control them through an app. And that makes timing difficult, plus now you have your phone glowing brightly in the darkroom. You can probably create a routine that would control the light in an app to get a set exposure time and color. But that would be a bit of a headache.
@OP, if you're handy with arduinos, I'd consider skipping the built-in automation altogether and start with led modules or strips, some fets and pwm control them directly.
Not having to deal with partly reverse engineering a probably highly integrated solution. Also from a physical perspective it's likely quite cramped inside the housing and it may be a b*tch to connect your controls to the existing circuitry.Any particular reason why doing from scratch would be advisable beyond cost?
Not having to deal with partly reverse engineering a probably highly integrated solution. Also from a physical perspective it's likely quite cramped inside the housing and it may be a b*tch to connect your controls to the existing circuitry.
The argument that this would be an integrated solution I don't quite follow; if you start with three led arrays in R, G and B, you would achieve the same, couldn't you?
The Philips hue is behind in technology from lifx. I currently use lifx for color enlarging and it works quite well. Have not managed to find the Hue and saturation values that correspond to 00-5 contrast filters. Haven't really tried. But if you can figure it out and are good at programming it's possible to program split grade printing into the light by timing the exposure for transition from the two colours.
I'm convinced that if this were available before digital everyone would printing on low tech rgb lights.
The problem is you can't control the bulb with a standard timer. The bulbs need to be left with continuous power and then controlled by an app. If you disconnect that power and then reconnect it, like you would a normal bulb, they'll go back to their default settings, which means a warm white. So in order to use them for VC exposures, you'd have to leave them powered on all of the time, and then try to control them through an app. And that makes timing difficult, plus now you have your phone glowing brightly in the darkroom. You can probably create a routine that would control the light in an app to get a set exposure time and color. But that would be a bit of a headache.
You could use a shutter.
Already in heydays of incandescanrt enlarger lighting a shutter was proposed and offered.
(Though I do not see the benefit of such hassle in this case.)
That would be one way to do it. You'd probably have to set it to Bulb mode though. If you wanted something simple, you could also place something opaque in the below the lens filter holder, preferably matte black to cut down on reflections. Or, if you wanted to do something a little more fancy, use the outlet on a standard timer to operate a shutter of some kind powered by a solinoid, so that instead of the timer powering the light, it powers the solenoid that holds the shutter open. That might require an appropriate AC/DC converter.Out of curiosity, how would one hack a shutter for this. Could I put a Copal between the lensboard and the lens?
How would you do it?
cheers
Good to know considering they are cheaper to get set up with
Any idea how testing hue/saturation to match 00-5 would work in principle?
5 is magenta. It is high grade and filters out all the green light. So almost everything is exposing the blue sensitized layer in the paper. Notice how on the image below it is opposite green
00 is yellow or amber, I'm not sure. Notice how it is opposite blue. So you are transmitting all but blue light, exposing the low contrast green layer for midtones.
cmyk-HSB by Aaron, on Flickr
The numbers in pink are hue.
The four numbers next to it are C-M-Y-K.
What the image does not show clearly, is that as you get closer to the center of the wheel, the saturation decreases until you get pure white light. With the LIFX bulb, the first number is hue, second is saturation, third is brightness HSB eg (330,0.25,1.0) The setting I use to print kodak gold on kodak endura paper. Brightness is nothing more than fstop for controlling exposure.
Now imagine you have a negative. Split grade printing means dividing the exposure between 00 and 5, or yellow and magenta. Exposing for the low contrast layer for midtones and highlights first, then burning in the shadows for some nice crunch. This is a crude analog attempt at adjusting the tone curve of the printed image. A 5 second exposure at 00 (what I THINK is (60, 1.0, 1.0)) will give you flat contrast. 5 seconds at (300, 1.0, 1.0) should give maximum contrast with blown highlights and deep shadows. Depending on the negative you will want to print on both to give rich full tones.
60 and 360 are GUESSES. The test would be to print off 60,1.0,1.0 first, then use a 00 variable contrast filter at something like 4000k or 5000kelvin colour temp, using the lifx bulb also, comparing the final prints of similar exposure. Repeat for 360,1.0,1.0 and VC5. The prints should be very close for similar exposure. And the light projected should look pretty similar.
If you expose at 360, 1.0, 1.0 you should get nothing as this is safe red light.
Most likely the 5 grades correspond to five points straight across the wheel from hue of 60 to 300 with I guess grade 2.5 being equal to a hue of 0 with 50% or less saturation. But maybe cyan would work? (180, 1.0, 1.0) since it is halfway between green and blue on the wheel. You would have to test grade 2.5 vs these.
Now, the questions which I have not deeply explored are:
1. Does 00 and 5 correspond to hues of 60 and 300 or something else?
2. Can you program two seperate timed exposures. These bulbs are almost instantaneous.
3. Can the colour changing feature be utilized to do a timed exposure either straight across the wheel, through white, or around, accelerating or decelerating to give the contrast you want?
4. Another possibility is that it is not 60 and 360 at full saturation, but maybe 50% to correspond to grade 00? Have a look at (60, 0.5, 1.0) and then compare to how a filter of grade 00 looks under the lens with no negative.
But, I do very little B&W printing. I don't have the time or skill to program this. My experience is mostly RA-4
One caveat for the LIFX bulb. It is connected to the timer and sometimes has a nasty habit of resetting to default colour of room light after being turned on multiple times. Maybe mine is a dud or they have fixed the issue. Xiaomi also came out with a similar bulb which is much cheaper. I have one but haven't experimented with it yet.
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?