Darkroom control program

[measwel]

Hi,

My light meter based timer broke down and I got angry. Timers cost a bit and do not offer all the functions that I would want. Since I was controlling my lights with a smartlife app on my phone, I wondered if I could do it with a PC. Then I wondered if the smart leds would be darkroom safe when put on red. And if the enlarger timing could be controlled with a smart switch. So I did some searching and found a PHP module to control smart devices. One thing led to another and before I knew it, I wrote this:

GitHub - measwel/darkroom: A PHP application for photographic darkroom work

A PHP application for photographic darkroom work. Contribute to measwel/darkroom development by creating an account on GitHub.

github.com

A program for automated darkroom control using smart devices.

 

[measwel]

This is what it looks like currently:

If you would like to try it out, just let me know. I would highly appreciate the feedback from more experienced darkroom folks.

I have one more idea I would like to try in the future: to install a smart led bulb in the exposer head and see if I can dial in a filter value by setting the emitted light color. That would eliminate the need for plastic filters for contrast control. And it would eliminate the need for a smart switch for exposure timing. And allow greater light intensity control...

But for the time being, I am waiting for the light intensity sensor to arrive. I plan to use it to be able to automatically calculate the exposure time for a given paper by measuring the light hitting the easel.

 

[measwel]

Hi,

I have uploaded a new version of the program, which should work without any smart devices set up. So the user can try it out. The only condition is to have python on the computer and import the needed dependencies as explained in the README.

GitHub - measwel/darkroom: A PHP application for photographic darkroom work

A PHP application for photographic darkroom work. Contribute to measwel/darkroom development by creating an account on GitHub.

github.com

 

[Neal]

Very kind of you to share. I'm sure folks a lot more tech savvy than I will make good use of it.

 

[mshchem]

Thanks for sharing this. Good to see people working on darkroom applications!

 

[koraks]

Fun project, thanks for sharing it! Very creative.

 

[measwel]

I got the light intensity sensor today. Some suprising results.

Good: it works .

Strange: with a opal light bulb the measurement is linear. Changing 1 stop on the lens halves the measured lux value. I also tried a LED bulb. In this case the measured values did not quite get halved, but it was close enough to be practical I guess.

Interesting: a cold white light gives more measured lux than a warm white light at the same brightness setting.

Bad: the sensitivity of the sensor is on the low side. The scale goes from 0 to 1000. With an average setting on my enlarger (20 x 20 cm print, F5.6) I am getting a reading of 16 lux. Making a big print or closing down the lens to F22 will bring the measured value to 0 lux.

Conclusion; it is sensible to use the strongest bulb feasible in the enlarger head. I will try with the strongest LED bulb I can find.

This should do it: https://www.ebay.de/itm/155860485532

4000K to get good contrast, opal white and a whopping 3500 lumen.

 

[koraks]

Or use a more sensitive light meter. Baseboard illumination levels are dim indeed.

a cold white light gives more measured lux than a warm white light at the same brightness setting.

"Brightness" is a fickle concept once you start to factor in the efficiency of light emitters and sensitivity of sensors, and a host of other factors. It's certainly very plausible you'll see significant differences as the color of the light changes.

 

[measwel]

Fun project, thanks for sharing it! Very creative.

Downloaden en uitproberen.

 

[measwel]

Or use a more sensitive light meter. Baseboard illumination levels are dim indeed.



"Brightness" is a fickle concept once you start to factor in the efficiency of light emitters and sensitivity of sensors, and a host of other factors. It's certainly very plausible you'll see significant differences as the color of the light changes.

The sensitivity of the sensor seems to be the biggest obstacle. It is workable with my current 75W opal bulb and 20 x 20 cm, F5.6 enlargement. But the light intensity reading quickly drops to 0 when I want to enlarge more.

I will give this bulb a try: https://www.ebay.de/itm/155860485532

 

[measwel]

Or use a more sensitive light meter. Baseboard illumination levels are dim indeed.



"Brightness" is a fickle concept once you start to factor in the efficiency of light emitters and sensitivity of sensors, and a host of other factors. It's certainly very plausible you'll see significant differences as the color of the light changes.

Only it would have to be a tuya/smartlife light meter to work with the program. If you know one, let me know please. I bougth this one:

https://www.aliexpress.us/item/3256806077476093.html

Actually it works suprisingly well as long as the bulb has decent output. More sensitivity would be welcome though.

 

[koraks]

I have no experience with Tuya, sorry. I suspect there's no common application for such a sensitive meter in a regular IoT context, so I'd be surprised it exists.

 

[measwel]

The application works quite well now, so I packed it into an .EXE and made a first public release. Anyone interested can try it out, either by running the python script or by simply running the EXE.

GitHub - measwel/darkroom: A PHP application for photographic darkroom work

A PHP application for photographic darkroom work. Contribute to measwel/darkroom development by creating an account on GitHub.

github.com

 

[measwel]

The sensitivity of the sensor seems to be the biggest obstacle. It is workable with my current 75W opal bulb and 20 x 20 cm, F5.6 enlargement. But the light intensity reading quickly drops to 0 when I want to enlarge more.

I will give this bulb a try: https://www.ebay.de/itm/155860485532

Be careful! The bulb I mentioned is not standard size. I first noticed it when I got it. It is a BIG bulb of 16 cm long. I need to find a regular sized one yet.

I also heard from other black and white enthousiasts, that 2700K is better for contrast control than 4000K

 

[measwel]

After some searching, I settled for the LEDVANCE E27 retrofit 17W, 2700K, 2500 lumen LED bulb. It has a real opalized glass housing and the length is 118 mm. In my enlarger, any bulb bigger than 12 cm will not fit. Once I get it, I will write how it works in the enlarger.

 

[koraks]

That's promising; the thing to look out for in particular is whether you get even illumination on the baseboard. Look for hot spots and/or darkening corners.

 

[measwel]

That's promising; the thing to look out for in particular is whether you get even illumination on the baseboard. Look for hot spots and/or darkening corners.

Will do.

 

[measwel]

Just tested the ledvance 2700K, 2500 lumen opalized glass LED bulb.
https://www.beleuchtung-mit-led.de/images/product_images/original_images/ledvance_4099854069833.jpg

Just short of 12 cm in length, it fits fine in the Durst M601 head. 2500 lumen rock. With a fairly dense negative, I need about 12 seconds at F5.6 (componon-S) for a very respectable 30 x 30 cm enlargement. The lighting is even and Ilford contrast filters work totally normally. 25000 hours lifespan, almost instant full brightness and almost no heat production. In my opinion, an excellent bulb for black and white work. I have yet to notice any downside.

 

[measwel]

What does not work as I hoped is the tuya light sensor. It is not sensitive enough to make reliable exposure time calculations based on the reading. On a scale from 0 to 1000 lux, I am getting anywhere from 0 to 6 lux at the 30 x 30 cm enlargement, depending on what part of the negative I measure on the baseboard. That is unfortunately not enough to calculate the time sensibly.

So I changed the application to just give an approximate base time for a given paper and enlargement, so one can start from there.

 

[koraks]

Thanks for updating; your bulb experience sounds great! It's good to hear that fears of discontinued halogen bulbs need not stand in the way of getting some printing done.

 

[measwel]

Thanks for updating; your bulb experience sounds great! It's good to hear that fears of discontinued halogen bulbs need not stand in the way of getting some printing done.

Confirmed for black and white multigrade printing. How it would work for color printing, I cannot say though.

 

[koraks]

No, I understand, but I have to admit that I'm quite optimistic about it.

 

[measwel]

Proud to present an updated version:

Darkroom

I fixed many bugs and added a calculator for easy enlarging. Would love to hear some feedback.