F stop timer options

[blacksquare]

Yeah, I'm really wondering if there is a better way to actually implement dodge in one of these timers.

.......

If it were simple, it would probably have been implemented a long time ago Burn is definitely easier, but even then I don't like to give up dodge, sometimes 2x dodge replaces 5x burn.
I'm curious what route you take with your timer.

May I ask, do you own a timer from RH design? Can you confirm/refute what I wrote a bit above? What does the sequence/program look like there (StopClock Pro)? Is it rows of numbers (seconds), or is there some information about the stops?

 

[Chuck_P]

Here's how I did one of my last dodges using the DA F-stop timer with more than one dodge to perform. Those that use the same timer will recognize the step detail. It was split-grade printing with the "L" and "H" channels independent of each other (I typically print at f/11 to f/16):

1 L 5.0
2 b 0.5
3 b 0.6
4 H 4.0
5 d 7.5
6 b 0.7

At the step 5 dodge is where I had two dodges that I wanted to perform and trying to get them done when I am supposed to put a dodger in each hand is simply beyond my ability to do. A 4 stop 'H' base exposure is 16 seconds. When I first set the step 5 dodge to 4.0 stops, I was expecting the timer to give me the equivalent amount of time to carry out my dodges. However, it stopped short (about 14.?? to 15.?? seconds) and gave me the finish prompt i.e. 'FIN" to expose the remainder of the base exposure.

I was surprised that the timer allowed it, but to recover that bit of remaining time for dodging, I was able to set a dodge time longer than the 'H' channel 4 stop base exposure. To recover most of that final bit of time for the step 5 dodge, I had to set the dodge time to 7.5 stops..............and I still got a 'FIN' prompt, but that remaining time was so quick and short that the enlarger light did not even illuminate when exposing the 'FIN' exposure. So it was very, very close to a full 16 seconds at step 5 with which to carry out my two dodges. I made good notes on what locations to dodge, for how long, what particular dodger I used, and in what manner of movement of the dodger I used. The print turned out fine.

Like I said, I have really come to like the DA timer. As long as I can set a block period of time on the timer for dodging more than one location, I can work with it. If there's just one dodge to perform then the way the timer functions with that is no problem. A single 1 stop dodge (8 sec) relative to a 4 stop base exposure would be simple to carry out, then get the 'FIN' prompt to expose the remaining 8 seconds of the base exposure.

 

[Pieter12]

If it were simple, it would probably have been implemented a long time ago Burn is definitely easier, but even then I don't like to give up dodge, sometimes 2x dodge replaces 5x burn.
I'm curious what route you take with your timer.

May I ask, do you own a timer from RH design? Can you confirm/refute what I wrote a bit above? What does the sequence/program look like there (StopClock Pro)? Is it rows of numbers (seconds), or is there some information about the stops?

I just use the Stop Clock metronome to time my burns and dodges. The display changes depending upon what function you choose. For example, it will display the steps the increase/decrease buttons employ in fractions of stops, but you need to confirm that and remember what you have set, because the display pretty much only shows seconds while in use as a timer. It has an indicator that shows whether it's set to spit-grade mode, and which filter the time is set for. And some other things I don't use. You can download the user manual for a previous version that is pretty close to the current one at https://rhdesigns.co.uk/wp-content/uploads/2020/04/StopClock_v3.pdf

 

[dkonigs]

I just use the Stop Clock metronome to time my burns and dodges.

That's certainly another work-able approach, and maybe one that can be expanded on Perhaps a little utility function to tell the user how long each dodge lasts, and then they either just count it out or get extra audio/visual cues during the base exposure.

(The only problem with audio cues during the base exposure is its hard to provide a "warning countdown", and again the issue of overlapping dodge periods. And the problem with visual cues is that you might not be looking at the timer during exposure. But its somewhere to start brainstorming from.)

 

[Pieter12]

That's certainly another work-able approach, and maybe one that can be expanded on Perhaps a little utility function to tell the user how long each dodge lasts, and then they either just count it out or get extra audio/visual cues during the base exposure.

(The only problem with audio cues during the base exposure is its hard to provide a "warning countdown", and again the issue of overlapping dodge periods. And the problem with visual cues is that you might not be looking at the timer during exposure. But its somewhere to start brainstorming from.)

Not sure about your question. I determine the amount of dodging and burning necessary. I just use the metronome to time them.

 

[Nicholas Lindan]

Disclaimer: I am the owner, dog walker and head bottle washer at Darkroom Automation and the designer of its products.

Choosing Twixt Tweedle Dee and Tweedle Dum:

The decision between the two commercial alternatives - Darkroom Automation and RH Designs - may be made on a few criteria:

• If you already have the DA meter and like it, then the DA timer would be the better choice as the DA timer integrates very well with your existing DA meter.
• If you live in Europe then the RH Designs timer may be your best alternative as it is made for 220V operation out of the box. The DA timer can be ordered wired for 220V for a small fee, but it's not the most convenient thing as the plugs are all wrong for your country (I would have thought von der Leyen would have decreed the use of a 'Euro Plug' by now).
• If you are of an analytical bent the DA system may appeal to you. The DA system is a pure stops timer - everything is in stops, though the timer displays remaining seconds during the exposure as a pacifier. The DA system is more accurate and gives you precisely the tones you desire (assuming, of course, you know what those tones are).
• If you are of a touchy-feely bent then RH timer may appeal as it pretty much a seconds timer that adjusts in stops and thus less of a paradigm shift. Some photographers think the RH's 1/12th of a stop is a better unit than the 1/10 of a stop adjustment of the DA timer. You will get no argument from me that base 12 is far superior to base 10 - but I have used base 10 all my life and think best in that base. Any civilization that got past counting on its fingers and put a bit of thought into the matter settled on base 12/60/360.
• If you like a 'one box does it all' approach then RH may be the best choice - but you have to like the way the box does it.
• DA's two box solution splits exposure determination from exposure control. As the word "Automation" in the name suggests, the Darkroom Automation system has very little automation in it.
• If you do a lot of dodging then you may prefer the DA timer - more on that below. The RH Designs timer does dodges as 'inside out' burns.
• And, finally, the decision may boil down to your taste in timers: There is no accounting for taste; Chacun à son goût; Gustibus non est disputandum and all that.

On Dodging

Yeah, multiple dodges with the current Darkroom Automation timer can be a bit of a PITA - although in this respect the DA timer is still better than any other timer on the market (or, at least TTBOMK, which doesn't have a whole lot of K sometimes - why dodging is missing from other timers is a mystery to me).

The DA timer's "octopus dodging" requires that all multiple dodgers are in the light path at the beginning of the dodge sequence and get removed as the dodging sequence progresses. The timer is designed this way so you can dodge a print to your heart's content and never run out of time. There is no other solution to this (possible) problem.

As an example:

The problem: A 1.0 stop dodge followed by a 1.2 stop dodge can't be done in the conventional manner. The 1.0 stop dodge takes 50% of the exposure time and the 1.2 stop dodge takes 60% - so the combination takes 110% of the total exposure - bit of a bummer, that.

The solution: With octopus dodging the first dodge exposure is for 1.0 stop (50%) with both dodgers in the light path; the second exposure is for dodging the remaining 0.2 stops (10%); the final exposure then exposes for the remaining 40% of the time (all times approx.). I have a few prints that require this sort of dodging - aided by contraptions made from cardboard, coat hangers and sticky-tape - standard DIY dodging fare.

A Dodging Update

There is a software update in the works for the DA timer that will allow 'normal' dodging in addition to the present 'octopus' dodging. Older timers can be updated for a nominal $10 charge + shipping. There will also be a DIY version so not so much shipping is needed.

On Test Strips

Of all the features of f-Stop timers I consider test strip generation to be the least relevant. An auto-reset clockwork Time-O-Lite and a foot switch make short work of linear test strips. f-Stop and linear test strips that hover near to the final exposure are indistinguishable. One made at 16 seconds in 1 second intervals will look exactly the same as one made at 4.0 stops in 0.1 stop intervals.

That said, I find the unlimited test strip feature of the DA timer to be really useful for determining the sensitivity and HD curve of a paper. In doing this I may make test strips going from 0.0 stops (1 second) to 5.0 stops (32 seconds) in 0.1 stop intervals - that's five 10" length test strips with a total of 50 test patches.

* * *

On wishful thinking - I like to think that if Ansel Adams were to be alive today he would be using an f-Stop timer. Edward Weston, not so much.

On "investing" in the higher priced alternative rather than merely "purchasing" the lower priced product - I have always held that in investing the rule is "buy low." To this end, counting elephants is your best investment in a timer; put the money you save in your 401K or the S&P 500.

On the high price of both f-Stop timers - all I can say is that if f-Stop timers sold in the 1,000's they would be priced at $29.95 each.

 

[Pieter12]

Disclaimer: I am the owner, dog walker and head bottle washer at Darkroom Automation and the designer of its products.

Choosing Twixt Tweedle Dee and Tweedle Dum:

The decision between the two commercial alternatives - Darkroom Automation and RH Designs - may be made on a few criteria:

• If you already have the DA meter and like it, then the DA timer would be the better choice as the DA timer integrates very well with your existing DA meter.
• If you live in Europe then the RH Designs timer may be your best alternative as it is made for 220V operation out of the box. The DA timer can be ordered wired for 220V for a small fee, but it's not the most convenient thing as the plugs are all wrong for your country (I would have thought von der Leyen would have decreed the use of a 'Euro Plug' by now).
• If you are of an analytical bent the DA system may appeal to you. The DA system is a pure stops timer - everything is in stops, though the timer displays remaining seconds during the exposure as a pacifier. The DA system is more accurate and gives you precisely the tones you desire (assuming, of course, you know what those tones are).
• If you are of a touchy-feely bent then RH timer may appeal as it pretty much a seconds timer that adjusts in stops and thus less of a paradigm shift. Some photographers think the RH's 1/12th of a stop is a better unit than the 1/10 of a stop adjustment of the DA timer. You will get no argument from me that base 12 is far superior to base 10 - but I have used base 10 all my life and think best in that base. Any civilization that got past counting on its fingers and put a bit of thought into the matter settled on base 12/60/360.
• If you like a 'one box does it all' approach then RH may be the best choice - but you have to like the way the box does it.
• DA's two box solution splits exposure determination from exposure control. As the word "Automation" in the name suggests, the Darkroom Automation system has very little automation in it.
• If you do a lot of dodging then you may prefer the DA timer - more on that below. The RH Designs timer does dodges as 'inside out' burns.
• And, finally, the decision may boil down to your taste in timers: There is no accounting for taste; Chacun à son goût; Gustibus non est disputandum and all that.

On Dodging

Yeah, multiple dodges with the current Darkroom Automation timer can be a bit of a PITA - although in this respect the DA timer is still better than any other timer on the market (or, at least TTBOMK, which doesn't have a whole lot of K sometimes - why dodging is missing from other timers is a mystery to me).

The DA timer's "octopus dodging" requires that all multiple dodgers are in the light path at the beginning of the dodge sequence and get removed as the dodging sequence progresses. The timer is designed this way so you can dodge a print to your heart's content and never run out of time. There is no other solution to this (possible) problem.

As an example:

The problem: A 1.0 stop dodge followed by a 1.2 stop dodge can't be done in the conventional manner. The 1.0 stop dodge takes 50% of the exposure time and the 1.2 stop dodge takes 60% - so the combination takes 110% of the total exposure - bit of a bummer, that.

The solution: With octopus dodging the first dodge exposure is for 1.0 stop (50%) with both dodgers in the light path; the second exposure is for dodging the remaining 0.2 stops (10%); the final exposure then exposes for the remaining 40% of the time (all times approx.). I have a few prints that require this sort of dodging - aided by contraptions made from cardboard, coat hangers and sticky-tape - standard DIY dodging fare.

A Dodging Update

There is a software update in the works for the DA timer that will allow 'normal' dodging in addition to the present 'octopus' dodging. Older timers can be updated for a nominal $10 charge + shipping. There will also be a DIY version so not so much shipping is needed.

On Test Strips

Of all the features of f-Stop timers I consider test strip generation to be the least relevant. An auto-reset clockwork Time-O-Lite and a foot switch make short work of linear test strips. f-Stop and linear test strips that hover near to the final exposure are indistinguishable. One made at 16 seconds in 1 second intervals will look exactly the same as one made at 4.0 stops in 0.1 stop intervals.

That said, I find the unlimited test strip feature of the DA timer to be really useful for determining the sensitivity and HD curve of a paper. In doing this I may make test strips going from 0.0 stops (1 second) to 5.0 stops (32 seconds) in 0.1 stop intervals - that's five 10" length test strips with a total of 50 test patches.

* * *

On wishful thinking - I like to think that if Ansel Adams were to be alive today he would be using an f-Stop timer. Edward Weston, not so much.

On "investing" in the higher priced alternative rather than merely "purchasing" the lower priced product - I have always held that in investing the rule is "buy low." To this end, counting elephants is your best investment in a timer; put the money you save in your 401K or the S&P 500.

On the high price of both f-Stop timers - all I can say is that if f-Stop timers sold in the 1,000's they would be priced at $29.95 each.

Unfortunately, when I was in the market for an F-stop timer, you were no longer making them. So the choice was pretty obvious.

 

[Chuck_P]

There is a software update in the works for the DA timer that will allow 'normal' dodging in addition to the present 'octopus' dodging. Older timers can be updated for a nominal $10 charge + shipping. There will also be a DIY version so not so much shipping is needed.

This is great............with it being in the works, do you have an estimate when the software update might be available?

 

[Sundowner]

Really solid breakdown of the differences, @Nicholas Lindan; thank you!

 

[Nicholas Lindan]

Here's how I did one of my last dodges using the DA F-stop timer ... A 4 stop ... base exposure is 16 seconds. When I first set the ... dodge to 4.0 stops, I was expecting the timer to give me the equivalent amount of time to carry out my dodges. However, it stopped short (about 14.?? to 15.?? seconds) and gave me the finish prompt i.e. 'FIN" to expose the remainder of the base exposure.

I was surprised that the timer allowed it, but to recover that bit of remaining time for dodging, I was able to set a dodge time longer than the 'H' channel 4 stop base exposure.

Dodging can get a bit, er, strange sometimes. But the timer did things correctly.

I often say to myself - "Hey, wait a minute, that can't be right," reach for my calculator and then comes the "Oh yeah, that's the way it is supposed to work" moment of (re)enlightenment.

In this example, a 4 stop dodge with a 4 stop (16 second) exposure leaves 4 stops - 4 stops = 0 stops of exposure, and 0 stops of exposure is 1 second. So the exposure with the dodger in the light path is for 15 seconds and the exposure with the dodger removed (the 'finishing' exposure) is for 0 stops or 1 second; all totaling 4 stops (16 seconds), of exposure.

Dodging is where an f-Stop timer comes into it's own as it's not always obvious what is going on. Like all automation, though, it gives you what you ask for which may be different from what you want.

* * *​

What follows is a mathematical diversion and is not relevant to using an f-Stop timer. You never see any of this when using a timer. Skip it all if you aren't into all the geeky stuff.

You can dodge for 99 stops if you like. The math, that the timer does for you, is 4 stops - 99 stops = -95 stops, or 2^-95 = 2.52 * 10^-29 seconds for the finishing exposure.

The timer will do very short exposures, though not that short. Quettahertz microprocessors being thin on the ground.

It is the same with a camera's controls - you can turn the shutter speed and aperture controls up and down to your heart's content and the exposure never goes to 0 or becomes infinite. In the world of logarithms (which is what stops are, just log base 2) 0 and infinity are imaginary numbers (I sometimes suspect they may be imaginary in the world of linear real numbers also).

 

[Nicholas Lindan]

... do you have an estimate when the software update might be available?

<Insert an Adams' Family Lerch groan...>

I have always admonished myself to never, ever pre-announce a release.

But, as the damage is done I may as well continue with it -- I would guess in two weeks or so.

 

[Chuck_P]

Dodging can get a bit, er, strange sometimes. But the timer did things correctly.

I'm glad to hear that though I did feel at the time that certainly the timer was ok.............but also, just as certainly knew that I just wasn't comprehending it. Thanks for the explanation.

I have always admonished myself to never, ever pre-announce a release.

Understand that...........but when it is ready, don't be surprised is mine it the first one at your door, unless I feel that the DIY version is something that I might be able to handle, but I'm not real hopeful. Is it possible for you to expand here on how the timer's menu system will change to be able to carry out "normal" dodging?

 

[dkonigs]

What follows is a mathematical diversion and is not relevant to using an f-Stop timer. You never see any of this when using a timer. Skip it all if you aren't into all the geeky stuff.

You can dodge for 99 stops if you like. The math, that the timer does for you, is 4 stops - 99 stops = -95 stops, or 2^-95 = 2.52 * 10^-29 seconds for the finishing exposure.

The timer will do very short exposures, though not that short. Quettahertz microprocessors being thin on the ground.

Its a lot easier to make a timer do super-short exposures than an actual enlarger, though. At least with an enlarger that uses an incandescent light source, it takes a certain amount of time for the bulb to turn on and turn off. This can be measured, and in my own case is approximately 300-500ms (I think, I haven't checked in a while). So there is a minimum exposure time in practice.

Of course with an LED based enlarger you can cut this down significantly, and then your practical limits have more to do with the control electronics.

In my timer, I actually have a process where it uses its baseboard meter to measure this turn-on/turn-off behavior and adjust exposures accordingly. It really helps with the consistency of test strips where each patch is a relatively short incremental exposure.

 

[albada]

Its a lot easier to make a timer do super-short exposures than an actual enlarger, though. At least with an enlarger that uses an incandescent light source, it takes a certain amount of time for the bulb to turn on and turn off. This can be measured, and in my own case is approximately 300-500ms (I think, I haven't checked in a while). So there is a minimum exposure time in practice.

It seems to me that while the filament is heating or cooling, its spectrum will be shifted toward red, emitting proportionally less blue, reducing contrast. So I would expect an incremental test strip to have lower contrast than a strip with a complete exposure on each patch. Have you seen this effect with short incremental exposures?

Mark

 

[dkonigs]

It seems to me that while the filament is heating or cooling, its spectrum will be shifted toward red, emitting proportionally less blue, reducing contrast. So I would expect an incremental test strip to have lower contrast than a strip with a complete exposure on each patch. Have you seen this effect with short incremental exposures?

Mark

I haven't done the necessary experiments to answer that question, and doing so objectively and repeatably would be quite a project.

However, out of concern for this, I usually do complete patch exposures for color printing. It takes so much longer, of course.

 

[Nicholas Lindan]

Darkroom Automation has an application note for determining lamp delay time: http://www.darkroomautomation.com/support/AppNotePH212LampDelay.pdf The method can be used with any timer to determine the effect in your setup. Compensating for lamp delay is possible in the Darkroom Automation timer, I don't know about the Dektronics design - I believe these are the only two timers in the running.

For a standard PH212 bulb the effective warm-up time is ~50mSec. This is pretty trivial in the grand scheme of things.

As to a contrast shift due to a change in the light color, I doubt if any would be visible. To check you can determine the number of 1 second exposures equivalent to one 20 second exposure (or whatever times are convenient with your enlarger) and then expose a step tablet with one 20 second exposure and 21 one second exposures (per the example in the application note).

 

[dkonigs]

Darkroom Automation has an application note for determining lamp delay time: http://www.darkroomautomation.com/support/AppNotePH212LampDelay.pdf The method can be used with any timer to determine the effect in your setup. Compensating for lamp delay is possible in the Darkroom Automation timer, I don't know about the Dektronics design - I believe these are the only two timers in the running.

For a standard PH212 bulb the effective warm-up time is ~50mSec. This is pretty trivial in the grand scheme of things.

My approach to determining lamp delay time was quite different, and a bit more complicated in how it represents the delay. Though in practice, either approach probably works just fine.

I have a baseboard meter, so I sample the enlarger light at a fast interval while running it through several on-off cycles. This process automated from the user perspective, and results in the following numbers:

• Turn on delay
  • The delay from "switch the outlet on" until light from the enlarger is detected
• Rise time
  • The time it takes, from first light, until the enlarger reaches full brightness
• Rise time equivalent
  • The "full brightness equivalent" exposure time during the rise period
• Turn off delay
  • The delay from "switch the outlet off" until the light from the enlarger starts to fall
• Fall time
  • The time it takes for the enlarger light to fall to a fully off state
• Fall time equivalent
  • The "full brightness equivalent" exposure during the fall period

From these I'm able to adjust exposure time so that when the user says "15 seconds" they don't actually get 15 seconds. Instead, they get whatever time would give them the equivalent exposure as 15 seconds of full brightness.

The numbers I get for all of these variables on my enlarger (LPL 7452L, which is a halogen bulb run from a voltage stabilized supply) are considerably longer than the ones you're getting for that simple PH212 bulb. Last I tested, the rise time was ~550ms (~370ms equiv) and the fall time was ~300ms (~60ms equiv).

Of course this now makes me want to go out and get a lamp that I can stick a PH212 bulb (or even just a normal E26 tungsten bulb) into and see what numbers my unit shows for that.

I should add that I've also done some initial tests with an LED light source, and that switches on/off so quickly that this whole calibration process is almost unnecessary (measurements are mostly just counting signalling protocol delays). But LED light source performance will depend heavily on the control electronics of the specific fixture.

 

[dkonigs]

So using my latest prototype, I just had to validate these numbers and see what my latest measurements show. As a stand-in for the Beseler 45 (PH212) I used a desk lamp with a 60W bulb. Not exactly the same, but functionally similar for the purposes of the test.

On my LPL 7452L, the "effective warm-up" was measured at 317ms and the "effective cool-down" was measured at 55ms, giving a total "lamp delay" of 372ms. (some minor difference from last time, either due to different equipment or environmental conditions) Of course the actual warm-up/cool-down time was longer than that.

On the desk lamp, the "effective warm-up" was measured at 45ms and the "effective cool-down" was measured at 5ms, giving a total "lamp delay" of 50ms, exactly matching the numbers mentioned above. Again, the actual warm-up/cool-down time was a bit longer, as expected.

It is interesting to see just how much of a difference the fancier enlargers have in this department from the simpler ones. Kinda makes me curious how all the other fancy enlargers perform.

 

[Chuck_P]

On my LPL 7452L, the "effective warm-up" was measured at 317ms and the "effective cool-down" was measured at 55ms, giving a total "lamp delay" of 372ms. (some minor difference from last time, either due to different equipment or environmental conditions) Of course the actual warm-up/cool-down time was longer than that.

I have the LPL 7452 but what is the "L" designation that you refer to?

 

[dkonigs]

I have the LPL 7452 but what is the "L" designation that you refer to?

Comparing the specs of the two models on KHB, it seems like the main difference is the column height. Otherwise the specs look identical.

The LPL Enlarger Guide: LPL model 7452 4x5 Enlargers

a guide to the LPL 7452 (Saunders/LPL 4550XL) 4x5 enlarger and accessories

www.khbphotografix.com

The LPL Enlarger Guide: LPL model 7452L 4x5 Enlargers

a guide to the LPL 7452L (Omega/LPL 4550XLG) 4x5 enlarger and accessories

www.khbphotografix.com

 

[Chuck_P]

Comparing the specs of the two models on KHB, it seems like the main difference is the column height. Otherwise the specs look identical.

The LPL Enlarger Guide: LPL model 7452 4x5 Enlargers

a guide to the LPL 7452 (Saunders/LPL 4550XL) 4x5 enlarger and accessories

www.khbphotografix.com

http://www.khbphotografix.com/LPL/LPL4x5.htm[/URL

Thanks, sorry I probably should've made that effort but wanted to ask. Though I have the DA timer, this thread has me interested in learning more about setting the lamp delay for my LPL's quartz-halogen lamp using the application note provided above by Mr. Linden.

It appears that I also have the 7452L, but the instruction manual title says Model 7452. The spec sheet says: C7452 but the specs all match the "L" designation enlarger.[/url]

 

[Michael Firstlight]

What is a 120v RHDesigns Analyzer Pro in excellent++ (almost like new) condition - complete with cables, footswitch, and probe worth these days?

Mike

 

[Steve Goldstein]

What is a 120v RHDesigns Analyzer Pro in excellent++ (almost like new) condition - complete with cables, footswitch, and probe worth these days?

Mike

These don't seem to come around that often. I'd say it's worth whatever price the buyer and seller agree upon. Likely in the several-hundred-dollars range, but I don't know how to define "several".

 

[Nicholas Lindan]

On the desk lamp, the "effective warm-up" was measured at 45ms and the "effective cool-down" was measured at 5ms, giving a total "lamp delay" of 50ms, exactly matching the numbers mentioned above. Again, the actual warm-up/cool-down time was a bit longer, as expected.

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.

 

[Nicholas Lindan]

Though I have the DA timer, this thread has me interested in learning more about setting the lamp delay for my LPL's quartz-halogen lamp using the application note provided above by Mr. Linden.

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