unwanted reflections from lightsource

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unwanted reflections from lightsource
« on: 14 / July / 2013, 16:04:25 »
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I have my 10 watt LED floodlight positioned in the centre of the standard Reetz build (picture of it here: http://casabio.blogspot.com/2013/06/virgin-diybookscanner-gets-his-first.html).

At first I was getting reflections from the silver A4000IS camera. I then used double sided tape to stick black magazine paper over the front of the camera, with a separate ring of black paper for the moving lens.
I then took a photo, and surprise surprise, there was another reflection. As I lowered myself to the level of the camera to see what was causing it, I saw the reflection of the floodlight hove into view.
Surely this is a fundamental flaw of the basic design? Everything is standard: The direction of the glass, the level of the cameras, the position of the light.
Besides cleaning the glass, what can I do?

Ported :   A1200    SD940   G10    Powershot N    G16

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Online reyalp

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Re: unwanted reflections from lightsource
« Reply #2 on: 14 / July / 2013, 16:27:56 »
Quote
Surely this is a fundamental flaw of the basic design? Everything is standard: The direction of the glass, the level of the cameras, the position of the light.
This might be better discussed with the designers of the book scanner in question, or a book scanner user group. CHDK is general purpose software for the camera, we aren't connected with whoever designed the book scanner.

A few random, of the top of my head ideas
Make the light source more diffuse.
If the reflection light doesn't saturate, you might be able to take picture with just the reflection on a black background and subtract it out in your image processing pipeline.
You can get ant-glare filters, for computer monitors for example. No idea if they would work in this situation.
Don't forget what the H stands for.

Re: unwanted reflections from lightsource
« Reply #3 on: 14 / July / 2013, 17:04:04 »
Aw crumbs!
I meant to post this in the DIYBookscanner, and the other post here, which probably means... :- :blink:


Re: unwanted reflections from lightsource
« Reply #4 on: 14 / July / 2013, 17:06:27 »
This might be better discussed with the designers of the book scanner in question, or a book scanner user group. CHDK is general purpose software for the camera, we aren't connected with whoever designed the book scanner.
http://www.diybookscanner.org/forum/
Ported :   A1200    SD940   G10    Powershot N    G16

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Offline ahull

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Re: unwanted reflections from lightsource
« Reply #5 on: 14 / July / 2013, 17:55:50 »
Aw crumbs!
I meant to post this in the DIYBookscanner, and the other post here, which probably means... :- :blink:

Too many mushrooms?  :blink:

BTW I would say the results are pretty good for a first attempt, I would also say that the lamp is offset, and is lighting even pages more than odd ones. You could fix this with a bit of post processing, but even allowing for that,  the diffuser is almost certainly necessary.

The diffuser could be as simple as a piece of plan A4 paper held in a curve down the way in front of the lamp. Other than that... I'm impressed.  :D
« Last Edit: 14 / July / 2013, 18:01:11 by ahull »

 

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