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Need help with LED power for my custom scanner.


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#1 Robino Jones

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Posted 14 August 2017 - 12:56 PM

I built myself a 35mm scanner using an optical printer head with pin registered movement. It's working and I'm really happy with the results I'm getting.
 
I capture using a RED EPIC Dragon.
 
For the illumination I use a 50W Yuji Led chip (5600K version) https://store.yujiin...series-cob-400l and it is powered using this PSU https://www.amazon.c...?ie=UTF8&psc=13
 
The issue is that there are scan bars slowly moving down in my scans when shooting at shutter speeds other than 1/60th. It's like a darker horizontal band taking about 1/4th of the screen and you can see it moving when playing back a scanned clips.
 
It sucks because I could REALLY use HDR in this application but with the EPIC HDRX feature set to 1/60th for A Frame, then the X frame track (is using a higher shutter speed that I cannot manually set, you can only select how many stops you want) has flicker issue.
 
Any suggestions on how to improve my LED power or other power supply recommendations, so I could use more shutter speeds and not have to worry about scan bars / flicker ?
 
Someone suggested I install a High Speed Dimmer between the power supply and the LED Chip similar to this and said it would improve flickering. What do you guys think?

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#2 Perry Paolantonio

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Posted 15 August 2017 - 08:13 AM

It's been a while and I've actually forgotten most of the details, but I built a custom lamphouse for a 35mm scanner rebuild project a few years ago. RGB LEDs, for doing three-flash scanning, as well as an IR array for making dustmaps for restoration software. Never had any problems with flicker or scan lines, but I was also using a machine vision CMOS camera and not a digital cinema camera. There may be inherent differences there, since I don't really know what the Red camera you're using is doing when it snaps a frame. 

 

Here's a look at mine - never quite finished it, but I did get it working for all three colors plus IR (and you can do white by mixing RGB). I 3D printed a simple lamphouse lined with mylar, and had some diffusion material on the opening to soften the light a bit. Seemed to work quite well. 

 

https://www.flickr.c...57644369553789/

 

You can click forward on that, there are several shots and  a short video of it in action. The earlier photos in the album are the disassembly and rebuild of the scanner transport. Everything is controlled with an arduino.


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