Daniel Reetz, the founder of the DIY Book Scanner community, has recently started making videos of prototyping and shop tips. If you are tinkering with a book scanner (or any other project) in your home shop, these tips will come in handy. https://www.youtube.com/channel/UCn0gq8 ... g_8K1nfInQ

Uneven light

All about lighting. LED, CFL, Halogen, Other? Questions and info about lighting go here.
spomwii
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Joined: 17 Jun 2011, 07:57

Re: Uneven light

Post by spomwii » 18 Jan 2013, 03:58

Sorry. My explanation was not very good. What I was meaning to say was that by adding this 20w LED I solved a couple of problems that I had with regular book scanning. With the original 10w I had to use slow shutter times on my A2200 camera because the scans got very dark and the quality was not good. I also had problems with reflection and by adding this new LED and placing it like this the reflection moved a little to the side (outside the books border on large books).
I have also switched from regular glass to Truevue Musem glass that helped on the reflections.
But I have not tried to put the LED higher or to add even more light yet so the comic book scanning still has the uneven lighting problem. I hope I get some time to test this on Saturday or Sunday.

bimbo111
Posts: 46
Joined: 11 Aug 2012, 12:12
E-book readers owned: iPad
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Country: Denmark

Re: Uneven light

Post by bimbo111 » 04 Feb 2013, 21:06

@mark and dan
I haven't tried an LED as light-source, but got vast improvements with my a3300 when stepping up to the 100w halogen i'm currently using from an 'old-school' 40w bulb. I've read elsewhere that other people find that the powershot cameras need alot of light - how come you have chosen to ship your kits with the 10w led?

TT: i've had problems with uneven light, but it seems to have gone from raising the lightsource, though it theoretically was high enough before (got to use some triangle math once again - yay! :) )

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daniel_reetz
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Re: Uneven light

Post by daniel_reetz » 05 Feb 2013, 00:53

The basic rule is: the more light, the better. I'm not surprised that you get better results with a 100W halogen than with a bare bulb.

My choice to use the LED was that with A2200IS cameras, I could achieve a 1/30s exposure time, they give an even light distribution, and they are cool and not fire hazards. Nothing more. Very unfortunately for me, I have to ship things that are safe and mostly readymade when it comes to electrical stuff. If I had my way, I'd include several of the halogen lights I used on the original book scanner, but the chance of causing a fire or other problem is too great. LEDs are the way of the future. It's possible that two LEDs would be substantially better than one. Perhaps when I get to the next revision of the kit, that will happen.

bimbo111
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Joined: 11 Aug 2012, 12:12
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Country: Denmark

Re: Uneven light

Post by bimbo111 » 05 Feb 2013, 17:19

I see your point. But doesn't the led and energy saving bulbs both have problems when it comes to cri? How much does the color-composition of the lightsource actually mean to the final image, when you can just adjust the whitebalance in the post-processing? I'm not thinking about plain text, but if you were to scan books with photos.

bimbo111
Posts: 46
Joined: 11 Aug 2012, 12:12
E-book readers owned: iPad
Number of books owned: 0
Country: Denmark

Re: Uneven light

Post by bimbo111 » 05 Feb 2013, 17:22

My intuition tells me that it would be better to start out with the broader and more even spectrum of light instead of digitally boosting it afterwards. But what are your experiences with this, when switching between led and halogen?

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daniel_reetz
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Re: Uneven light

Post by daniel_reetz » 10 Feb 2013, 17:52

The LED spectra from these phosphor conversion LEDs is pretty broad. I'll try to post some samples from my spectroscope soon.

royeven
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Country: Norway

Re: Uneven light

Post by royeven » 27 Feb 2013, 18:56

daniel_reetz wrote:The LED spectra from these phosphor conversion LEDs is pretty broad. I'll try to post some samples from my spectroscope soon.
How broad are we talking about here? I didn't purchase the LED that's in the shopping list, but instead bought two of these to test with:
http://viewitem.eim.ebay.no/10W20W30W-L ... 05013/item

They are cheap and expendable. I measured the spectrum (attached) and was not impressed with the results, even though they were as expected; little blue (since blue is the most difficult color for LED technology), and a spectrum that contains little red and little violet. No surprises, but this is not what I call a "broad" spectrum. Is the spectrum from your LED broader?

Spectrum:
Journal01.png
Spectrum
Edit to add:
The x-axsis is wavelength in nanometers, the y-axis is the light intensity

tresho
Posts: 29
Joined: 14 Dec 2009, 04:51

Re: Uneven light

Post by tresho » 28 Feb 2013, 07:12

I'm not really particular about my color balance, but I do like adequate brightness and even lighting.
I have a couple of large windows I can work near. The best light I've used is from an overcast sky from about 1000 to 1600 every day. Can't beat the price of this lighting!

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