Infrared and Motion Detection?

gsbergman

164

Re: Infrared and Motion Detection?

« Reply #10 on: 15 / February / 2009, 18:46:50 »

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Anyone have any experience disassembling an A590IS?

I found it on sale and decided to modify the camera for IR.

Is the IR Cutoff Filter easy to get to? What other steps are required for a sucessful IR modification?

Any help would be appriciated.

Thank you,
Gregg

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reyalp

14080

Re: Infrared and Motion Detection?

« Reply #11 on: 15 / February / 2009, 19:00:40 »

Quote from: gsbergman on 15 / February / 2009, 12:53:34

I found an A580 modified for IR on eBay. Then I noticed the 580 was not ported for CHDK. The camera is reasonably priced. How difficult would it be for someone to port CHDK to work with the A580. As I understand it is similar to the a590IS without the IS.

There are some people working on it, although not too much progress so far. See the wiki page for this camera: http://chdk.wikia.com/wiki/A580 and the thread http://chdk.setepontos.com/index.php/topic,2900.0.html

Like all ports, there is no schedule and no guarantee it will ever be finished. Effort required should be about the same as any other digic II/digic III powershot, but the time required depends as much on the people as the camera. Here's an IR filter removal from the earlier A530/540, which is at least superficially pretty similar to the 590 http://photography-on-the.net/forum/showthread.php?t=251630

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Don't forget what the H stands for.

mgxxx

14

Re: Infrared and Motion Detection?

« Reply #12 on: 16 / February / 2009, 01:44:19 »

Found on the web that this company, lifepixel, does IR window conversions ( expensive) but has some DIY tutorials if you want to just buy the window.

http://www.lifepixel.com/shop/cart.php?m=product_detail&p=6

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grg

10
A640

Re: Infrared and Motion Detection?

« Reply #13 on: 17 / February / 2009, 16:58:29 »

Don't know if this helps, but 2 things:
- I did some IR photos with my unmodified a640 using the lo-fi way of putting 2 black developed analoge film strips in front of the camera. The results are quite good, though not comparable to a "real" ir filter, and obviously I have to take long exposures and the live preview is slow. Nonetheless, maybe its a easy way to try the MD stuff with IR light (in bright day light and with high iso though).
- My understanding (read only, no firsthand experience) is that you don't only need to remove the ir filter, but also replace it with a equally thick glas piece to keep the optics sharp. Btw, there are some things you will find on the web for easy IR removal for webcams.

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gsbergman

164

Re: Infrared and Motion Detection?

« Reply #14 on: 25 / February / 2009, 12:32:25 »

I bought a A590IS and removed the hot mirror. WOW!!
Outside of focus issues (wont auto focus unless zoomed way in) the sensitivity to IR and the pictures are amazing.
The conversion was pretty easy. (I photographed the procedure) I'll post it at a later date.

I'm now after a professionally modded camera so the focus works, an S5IS or maybe an SX10IS (if we're close to porting success on CHDK). I'm going to talk to www.maxmax.com and www.lifepixel.com to find out what they are offering.

I consider my experiment a total success.

Gregg

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waldo

238

Re: Infrared and Motion Detection?

« Reply #15 on: 25 / February / 2009, 13:58:59 »

You can make your A590 focus properly. You need to replace the missing hot filter with a similar thickness piece of glass (preferably anti-reflective coated) and adjust the image sensor mounts to make it perfectly square with the optical axis. CHDK's manual focus features help here, allowing you to figure out exactly which parts of the sensor need to be moved toward or away from the lens.

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gsbergman

164

Re: Infrared and Motion Detection?

« Reply #16 on: 25 / February / 2009, 14:40:44 »

Quote from: waldo on 25 / February / 2009, 13:58:59

You can make your A590 focus properly. You need to replace the missing hot filter with a similar thickness piece of glass (preferably anti-reflective coated) and adjust the image sensor mounts to make it perfectly square with the optical axis.

The hot filter is .3 mm thick. I tried to find a piece of glass that thin with no luck. If I dont put in a replacement piece of glass, is it possible to adjust the image sensor alone to get the focus in?

Gregg

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waldo

238

Re: Infrared and Motion Detection?

« Reply #17 on: 25 / February / 2009, 15:14:57 »

0.3 mm is pretty thin. You could try adjusting the screws to see what happens. You would loosen the image sensor mounting screws to compensate for not enough glass thickness. You could also try glass microscope slide slipcovers. I believe they are 0.1mm to 0.2mm thick.

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barberofcivil

268

Re: Infrared and Motion Detection?

« Reply #18 on: 26 / February / 2009, 09:05:08 »

Quote from: waldo on 25 / February / 2009, 13:58:59

You can make your A590 focus properly. You need to replace the missing hot filter with a similar thickness piece of glass (preferably anti-reflective coated) and adjust the image sensor mounts to make it perfectly square with the optical axis. CHDK's manual focus features help here, allowing you to figure out exactly which parts of the sensor need to be moved toward or away from the lens.

I've been thinking about getting a cheap older camera to try modding and I'm curious as to the root cause of this focus issue from removal of the filter and have a few questions that some may know the answer to.

- How does removing the IR filter affect the focus? Is it purely a spacing issue and the filter acts is also a physical spacer (i.e. with it removed, the lens is closer to the sensor)? Or is it a refractive issue through the extra thickness of glass?

- How does the automatic focus work? Does the camera try to detect the distance to the objects to be in focus and adjust according to preset internal settings? Or is it purely based on making the focus area the least blurry (as one would do with manual focus)?

By the sounds of it, as there does appear to be a focus issue, it would seem that the autofocus is distance based and that the filter does act as a spacer. I would expect that if this was not the case, there wouldn't be a focus issue.

Does anyone have any further insight?

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waldo

238

Re: Infrared and Motion Detection?

« Reply #19 on: 26 / February / 2009, 20:38:29 »

Quote

- How does removing the IR filter affect the focus? Is it purely a spacing issue and the filter acts is also a physical spacer (i.e. with it removed, the lens is closer to the sensor)? Or is it a refractive issue through the extra thickness of glass?

The image sensor must be removed to access the IR filter. This means removing the screws that adjust the position of the sensor, both toward and away from the lens and that make the image sensor square with the image path. Putting it back so that it is perfectly adjusted is tricky. In addition, the IR filter affects the focus distance so this must be compensated for.

Quote

- How does the automatic focus work? Does the camera try to detect the distance to the objects to be in focus and adjust according to preset internal settings? Or is it purely based on making the focus area the least blurry (as one would do with manual focus)?

On the small sample of cameras I have tried, the auto focus will try different focus settings over a range of possible settings and picks the one that gives the sharpest image. If the sensor is not properly positioned, the auto focus will never move the lens far enough to ever get to the proper setting. If the sensor is not square with the image path, you will get randomly focused pictures since one side of the image is focused differently than the other.

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