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IR focusing beyond infinity?

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Offline reyalp

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Re: IR focusing beyond infinity?
« Reply #10 on: 09 / June / 2015, 23:09:04 »
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Can anyone shed light on the focus algorithm for these cams? I had thought they just did a "seek" for the sharpest image, but that seems to not be the case.
In general, they do some kind of contrast detection on live sensor data (AFIAK), but understanding the specifics from disassembly would be very, very difficult. I'm not aware of anyone doing any in-depth reverse engineering in this area.
« Last Edit: 09 / June / 2015, 23:16:05 by reyalp »
Don't forget what the H stands for.

Re: IR focusing beyond infinity?
« Reply #11 on: 10 / June / 2015, 08:57:24 »
It appears it is some sort of predictive algorithm. It sweeps the focus, then selects one. On the unmodified cameras it picks well, but once modified it is off. I wonder if it is sweeping the focus then deciding to focus to the fixed "infinity" setting. In the case of the IR modified cameras "infinity" isn't correct anymore. So even though it appears to be able to focus to the right point it doesn't.

The oddest part is the fact that some of the cams work great (same models), some work poorly. Maybe it is just manufacturing tolerances and luck of the draw.

Re: IR focusing beyond infinity?
« Reply #12 on: 03 / October / 2015, 01:14:36 »

i have the same issue and just joined the forum for that. So, there ir no way to manually pick the focus, right? Just macro photography for now on, no more landscapes...

Re: IR focusing beyond infinity?
« Reply #13 on: 03 / October / 2015, 01:16:03 »
In my case, I just removed the hot mirror from a G15


Re: IR focusing beyond infinity?
« Reply #14 on: 03 / October / 2015, 01:22:40 »
So, there ir no way to manually pick the focus, right?
Not true.  You can manually force the focus on pretty much every Powershot via CHDK using a script or the CHDK menu settings.

But the hard part is making sure the focus selected is actually the subject distance that you are interested in.

Ported :   A1200    SD940   G10    Powershot N    G16

Re: IR focusing beyond infinity?
« Reply #15 on: 03 / October / 2015, 09:49:14 »
I'll look into that. One thing I have to mention: I did not replaced the hot mirror for a clear piece o glass. Couldn't find one of the same thickness. I'm searching for a microscope peace of glass. That should work...

Until that, I'm gonna look into that focus think. Any tips for a newbie?

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Offline reyalp

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Re: IR focusing beyond infinity?
« Reply #16 on: 03 / October / 2015, 15:46:36 »
Until that, I'm gonna look into that focus think. Any tips for a newbie?
Your G15 has manual focus in the canon firmware. You should be able to adjust the focus as you normally would. Unless you are writing a script, there seems little reason to try to control it with CHDK.
Don't forget what the H stands for.

 

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