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

Alert: Great deal on Powershot A495s

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daniel_reetz
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Alert: Great deal on Powershot A495s

Post by daniel_reetz » 20 Dec 2010, 23:23

http://www.bhphotovideo.com/c/search?Ntt=capsa495&N=0

They are 90 each with free shipping. They run CHDK. 10mpix.

I haven't seen anyone here use them, though, so this is just an alert, not a recommendation.

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reggilbert
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Re: Alert: Great deal on Powershot A495s

Post by reggilbert » 21 Dec 2010, 03:11

daniel_reetz wrote:They run CHDK.
The embedded link seems to says they do not yet run CHDK, but a link a the bottom of the page leads to a thread dealing with a CHDK porting effort for the A495, listing on page 2 an October 29 posting with a CHDK beta port found here seemingly working pretty well, with just a couple functions problematic.

I have been using the this link to know which cameras run CHDK, I guess another page on the same site as Daniel's link, and the A495 is not on it.

On a slightly related note, I have been recently considering only large-sensor, high-megapixel cameras for my planned diy scanner, on the theory that you really need the best quality picture possible to assure the high-quality 300dpi-400dpi (of the actual page) images that generate the most dependable OCR. But is it possible that very bright light, the kind made practical by the flashing LED system Daniel has designed, negates the need for high-quality camera components in the diy scanner?

What I mean is, couldn't even a $90 10Mp camera like Daniel has found here deliver superb results with bright enough light? That is, for one final go, really once you have hit 10Mp (assuming standard trade book dimensions) even with a small sensor and minimal lens quality, given the camera-to-subject distance of just a few feet that is standard with the scanners discussed on this forum, and so long as you are taking your pictures under very bright light, how much additional *useful* resolution can better cameras really get you?

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Re: Alert: Great deal on Powershot A495s

Post by daniel_reetz » 22 Dec 2010, 22:04

reggilbert wrote: The embedded link seems to says they do not yet run CHDK
I consider a beta to be "running CHDK".
reggilbert wrote:I have been using the this link to know which cameras run CHDK, I guess another page on the same site as Daniel's link, and the A495 is not on it.
That's a good page. If you need absolute certainty and can't stomach beta software or whatever, there's an even better page here. Any cam on that page will perfectly run SDM or CHDK.
reggilbert wrote: On a slightly related note, I have been recently considering only large-sensor, high-megapixel cameras for my planned diy scanner, on the theory that you really need the best quality picture possible to assure the high-quality 300dpi-400dpi (of the actual page) images that generate the most dependable OCR. But is it possible that very bright light, the kind made practical by the flashing LED system Daniel has designed, negates the need for high-quality camera components in the diy scanner?

What I mean is, couldn't even a $90 10Mp camera like Daniel has found here deliver superb results with bright enough light? That is, for one final go, really once you have hit 10Mp (assuming standard trade book dimensions) even with a small sensor and minimal lens quality, given the camera-to-subject distance of just a few feet that is standard with the scanners discussed on this forum, and so long as you are taking your pictures under very bright light, how much additional *useful* resolution can better cameras really get you?
This is a much bigger question than you might think, and requires some pretty deep discussion of optics, hardware, software etc, some of which we've hashed over here in the forums a few times.

Let me give you the short answer: Yes, you can use cheap cameras to do high quality digitization. That's the premise of this whole project, has been from the beginning. We've proven it.

Light is just one part of the equation. Small sensors are noisy. Enough light means you can work in the range of sensor amplification that is least noisy.

Resolution is a science -- yes, a science-- unto itself, and requires you to think about the system as a whole -- optics, illumination, sensor, and post-processing software.

The short answer, on that, is that higher quality cameras will always yield higher quality images, but compact cameras are good enough for the majority of situations. If you are exacting and uncompromising, though, you should probably not use them, as there are specific times that they will not be perfect. How much extra "useful" resolution is dependent on the entire system, but my position is that in many, many situations, the answer is "not very much -- probably not enough to justify the additional cost".

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Re: Alert: Great deal on Powershot A495s

Post by reggilbert » 23 Dec 2010, 06:42

daniel_reetz wrote:Let me give you the short answer
As usual, Daniel, thanks for the detailed, patient answer, probably delivered more than once before in response to similar comments or questions posted more than once.

As a result of a conversation with Idolse today it occurred to me that there's probably no need to worry about having especially bright light for the scanner, since, being stationary, it permits shutter speeds as slow as necessary to obtain a well-lit image. That would explain what originally perplexed me as the extremely few LEDs -- just three, isn't it? -- included in your fifth-generation / Haiti scanner. Do I have that reasoning right?

By the way, is the bright phase of the Haiti scanner's lighting system activated simultaneously by the device you rigged up to trigger the cameras? Or does that switch you posted a picture of, the one that looks like a telegraph transmitter made from two cabinet roller latches, operate the lights separately, maybe by foot or something?

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