Building a Variable Contrast LED head for a Durst 138

[Tin Can]

I do have the VCCE head on my enlarger so there's no immediate need to go the LED route. However, the 100W halogen lamp has a life expectancy of only 50 hours and the color temperature will change over time. LED's last much longer and the color remains constant.

Also, going the LED route would enable me to get a brighter enlarger for larger prints on slow paper. In the past, in the photo club's darkroom I sometimes ended up with exposure times close to 2 minutes for a (cropped) 11x14 print with a condensor head. VCCE heads have a reputation to be slow due to the ND filter that keeps the exposure time constant while changing the contrast grade. I haven't printed much with the LPL yet so I can't say too much on the speed.

Finally, as an electrical engineer, I find the whole matter very interesting. Ideally I would have a f-stop timer with contrast control as an android app running on a small tablet and controlling the LED head through bluetooth. Any java programmers here? But first the hardware. I found an interesting LED supplier here. You can pick your own configuration on a single, 3, 4 or 7 led PCB. So for example green, royal blue & deep red on a tri-star, or 2 green & 2 royal blue on a quad-star. The latter would also give you the ability to switch the LEDs per color all in series or in 2 parallel strings to get a low/high setting on the enlarger for smaller/larger prints.

Menno

Great affordable supplier for custom LED. I am not an optical or electrical engineer, but I wonder if one of the 7 LED round clusters with their matching narrow beam optics would make a good point source for condensers. I wouldn't want or use any app control as I don't like the way all apps and phones become obsolete. LED point source could last for decades of use and be much cooler during extended focusing and possibly more 'pointy' meaning better sharpness.

[StoneNYC]

Great affordable supplier for custom LED. I am not an optical or electrical engineer, but I wonder if one of the 7 LED round clusters with their matching narrow beam optics would make a good point source for condensers. I wouldn't want or use any app control as I don't like the way all apps and phones become obsolete. LED point source could last for decades of use and be much cooler during extended focusing and possibly more 'pointy' meaning better sharpness.

I would think for a professional printer that would go through all this, they would use a dedicated tablet, once set up on the enlarger you don't need to upgrade anything, so aside from the tablet exploding, you wouldn't need to worry about obsolete.

My only concern would be the tablet light output not being a proper amber and affecting the print.

[Tin Can]

I would think for a professional printer that would go through all this, they would use a dedicated tablet, once set up on the enlarger you don't need to upgrade anything, so aside from the tablet exploding, you wouldn't need to worry about obsolete.

My only concern would be the tablet light output not being a proper amber and affecting the print.

Obviously you have not thrown out enough obsolete or broken electronics yet.

I'm already pissed my Air 11, my iPod Touch 4 and my Droid 'Smartphone all cannot do what I want and all need to be replaced. They all work, but are not working with new apps.

Cutting edge cuts at least 2 ways.

Wait, your post makes absolutely no sense! And now mine doesn't either!

LOL

[StoneNYC]

Obviously you have not thrown out enough obsolete or broken electronics yet.

I'm already pissed my Air 11, my iPod Touch 4 and my Droid 'Smartphone all cannot do what I want and all need to be replaced. They all work, but are not working with new apps.

Cutting edge cuts at least 2 ways.

Wait, your post makes absolutely no sense! And now mine doesn't either!

LOL

Again, dedicated, you only need one app, the LED enlarger app, once set up and designed properly (no crashing) it doesn't need upgrades it doesn't need wifi, just Bluetooth, and you leave it alone, like you would a switch panel, you don't add buttons to your Chromega II color head control box, if you want to upgrade its functions you get a new box. Same thing, except the tablet costs less to upgrade...

$150 every 3 years for new functions, can't beat that!

[Tin Can]

'My only concern would be the tablet light output not being a proper amber and affecting the print.'

Nobody was suggesting using a tablet as light source, it's light output 'amber' is not relevant.

Only as a remote control. If the app is not updated over decades, it won't work in decades. New 'puters won't help.

My slide rule still works...

[StoneNYC]

'My only concern would be the tablet light output not being a proper amber and affecting the print.'

Nobody was suggesting using a tablet as light source, it's light output 'amber' is not relevant.

Only as a remote control. If the app is not updated over decades, it won't work in decades. New 'puters won't help.

My slide rule still works...

Ugh, communication breakdown...

You're not understanding, if you're using the tablet to control the enlarger, the tablet will be creating light out of the screen, I'm not saying use it as a light source, I'm saying that the tablet has to be near the enlarger and the light on the screen could affect the print and fog it, if the tablet does not produce exact amber color, and produces for example blue or green, it might fog the paper. Probably a low light red pixel only would work like the massive Dev chart app for developing has, but I'm saying that's something to consider.

As far as the the app, the app is running the enlarger controls, if you don't update the enlarger controls and you don't update the app, then aside from the tablet actually breaking, then yes it would work indefinitely. Not sure why you're not understanding that, it's a dedicated device, it doesn't need updating so long as the head itself doesn't get any updating.