On the fly HDR - Feature Requests - CHDK Forum
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On the fly HDR

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Offline RaduP

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On the fly HDR
« on: 09 / May / 2008, 14:28:26 »
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I was wondering if the following scenario would be possible:
1. Open shutter, start capturing the image for a predermined duration.
2. Transfer the partial read information to the memory.
3. Continue capturing the image (without reseting the old sensor data)
4. Transfer the partial information to the memory and/or merge it with the previous image.
5. Repeat 1-4 as many times as desired.
6. Close the shutter.
6. Combine the resulting exposures.
7. Save the image.

Of course, this depends on how the camera works. For example, does reading the sensor data resets that data on sensor? Can the full sensor be read while the shutter is open? is the light still registered while reading the sensor with the shutter open?

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Offline dzsemx

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Re: On the fly HDR
« Reply #1 on: 21 / May / 2008, 01:11:52 »
nope.. there is not enough memory to store more images...  and there is no partial readout... ccds(and probably others) can't do readout without destroying captured image data and mechanical shutter is used for darkframe NR and for protection of sensor
« Last Edit: 21 / May / 2008, 01:23:01 by dzsemx »
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Offline RaduP

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Re: On the fly HDR
« Reply #2 on: 21 / May / 2008, 04:20:18 »
If that's not possible, there is another way:
1. Read the sensor in 1/10 exposure steps.
2. Add the information (sort of image stacking) to a memory buffer that is equivalent with the camera sensor resolution x 2 (because the colors should be stored on 16b, for higher range).
3. Save that memory buffer on a file, to be later processed by some stand alone application on the PC.
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Offline dzsemx

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Re: On the fly HDR
« Reply #3 on: 22 / May / 2008, 05:07:27 »
i know a simplier way... use bracketing, shoot jpegs and make hdr on the pc:P...  5 jpegs give very good results...
can't read sensor data by software(or it's unknown yet how to do it)
raw data contains 12bit/pixel
there is not enough memory to create an extra image buffer
8 meagpixel needs 10 megabytes of memory, we have a raw buffer in camera
(raw data get's here after shot, and after saving jpeg it gets corrupted)+ few hundred kilobytes...
and you can save raw's for postprocess...

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