F stop timer options

[dkonigs]

Ah, good to know we agree on the warm-up time for a plain-ole-tungsten lamp. My guess is all tungsten lamps have the same warm-up times as the filaments all operate at the same temperature.

I don't know if the longer warm-up for a halogen lamp is due to the higher filament temperature.

I have a ferroresonant regulator on my enlarger and it doesn't have any effect on the warm-up timing, the results are the same with and without the ferro in the circuit. The power supply on an LPL may have something to do with it if the ferro goes into current limit during warm-up when the lamp draws very high current.

I think its a mixture of factors.
I just went ahead and did the test with a halogen under-cabinet light (just a raw transformer and bulb setup). The "effective rise time" was 72ms and the "effective fall time" was 18ms, giving an "effective bulb time" of 90ms, Of course this was only a 10W bulb.

So my takeaway is that halogen is slower, but the difference in drive electronics makes a much bigger difference.

 

[Chuck_P]

It will be interesting to see if the warm-up time you find agrees with dkonigs' numbers.

I will definitely do it, seems simple enough, it'll be a few days though. Did you use an 8x10 sheet of paper, I don't believe I could get 20 wide enough strips on the long edge of 5x7 paper.

 

[Nicholas Lindan]

I will definitely do it, seems simple enough, it'll be a few days though. Did you use an 8x10 sheet of paper, I don't believe I could get 20 wide enough strips on the long edge of 5x7 paper.

You don't need a big bit of paper, a small one does fine.

You cover up half and make one 20 second exposure. On the other half you make 20 one second exposure, then progressively cover up strips on that side making a sequence of 1 second exposures. There is a picture of the result in the application note.

Or you can keep the timer in f-Stop mode and instead make a 4 stop (16 second) exposure on one side and a sequence of 0 stop (1 second) exposures on the other.

 

[Chuck_P]

You don't need a big bit of paper, a small one does fine.

You cover up half and make one 20 second exposure. On the other half you make 20 one second exposure, then progressively cover up strips on that side making a sequence of 1 second exposures. There is a picture of the result in the application note.

Or you can keep the timer in f-Stop mode and instead make a 4 stop (16 second) exposure on one side and a sequence of 0 stop (1 second) exposures on the other.

Using the stop method, on a 5x7 between the print borders, you can get 16 (actually 17) full 3/8" 0.0 stop exposures on that right side, in case anyone may find that helpful.

 

[Nicholas Lindan]

Using the stop method, on a 5x7 between the print borders, you can get 16 (actually 17) full 3/8" 0.0 stop exposures on that right side, in case anyone may find that helpful.

But, I should point out that there is no need to. The first 16 0.0 stop exposures are made one on top of the other. Exposures 17 & up are then made in test-strip manner.

 

[Pieter12]

Isn't a 1-stop interval a bit excessive? I usually use 1/3 or 1/2 stops to start with maybe followed up by a 1/4 stop if needed to fine-tune.

 

[Chuck_P]

But, I should point out that there is no need to. The first 16 0.0 stop exposures are made one on top of the other. Exposures 17 & up are then made in test-strip manner.

I guess I worded that poorly. I'm only going to use 16 strips at 0.0 stops each........I was just pointing out that it will actually hold 17 3/8" strips.

 

[Nicholas Lindan]

As per the discussion, above, the software for the Darkroom Automation f-Stop timer has be upgraded to include regular one-dodge-at-a-time dodging in addition to the timer's existing progressive 'octopus' dodging.

Upgrades to existing f-Stop timers are available.

More information is available at http://www.darkroomautomation.com/da-main.htm and https://www.photrio.com/forum/threads/darkroom-automation-f-stop-timer-dodging-upgrade.212375/