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verify PS SX110IS video exposure shift bug

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Offline j

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verify PS SX110IS video exposure shift bug
« on: 09 / March / 2012, 13:15:58 »
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(I wrote more constructive post but then the forum logged me out and I lost all.)

Test PS SX110IS and 130/150 the following way. Can CHDK fix this bug and
increase the video exposure shift range?

(1) Video mode.
(2) Press ISO button.
(3) Increase the shift to max, and then back to middle.
(4) If you have the bug, the video preview should be
darker than in the original middle shift position.
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Offline outslider

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Re: verify PS SX110IS video exposure shift bug
« Reply #1 on: 09 / March / 2012, 14:11:16 »
Does this shift still visible after pressing the shoot_half? Sometimes camera refreshes preview only on shoot_half.
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Offline j

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Re: verify PS SX110IS video exposure shift bug
« Reply #2 on: 09 / March / 2012, 18:52:47 »
Yes, the bug exists after half shoot and full shoot.
I now have two video shoots: before and after adjusting
the exposure shift to max and then back to middle.

I should note that CHDK is not in use.

Steps:
(1) Power on in standard video mode.
(2) Half shoot.
(3) Full shoot; rec for 5 secs.
(4) Press ISO.
(5) Steps (2) and (3) can be repeated here.
(6) Adjust the exposure shift to max, and then back to middle.
(7) Repeat steps (2) and (3) here.
(8 ) Recorded videos differ greatly in brightness.
(Step 7 rec darker than recs of steps 3 and 5.)
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Offline j

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Re: verify PS SX110IS video exposure shift bug
« Reply #3 on: 10 / March / 2012, 05:42:10 »
I have brief development plan for CHDK regarding
the video exposure:
(1) Fix the bug in CHDK.
(2) Increase the exposure shift range.
(3) More better exposure curve, from day to night axis.

Big problem is that at night the video preview is
black, and thus the targeting is impossible.
Fixing the bug may not help if the shift range is
too small.

Shooting itself is not a problem because I use
computer's video player to make the video
visible. I use brightness/contrast but gamma should
be yet tested. Viewing in camera is impossible, though.

If the proper exposure shift is done in camera,
perhaps the useful noise is not flattened by the
video codec.

Being able to view the videos in camera would
be useful: either increasing the exp range or
adding bri/cont/gamma to viewer.

The exposure curve (day-night axis) is not wysiwyg.
Day is ok; dusk is overexposed; night is underexposed.
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Offline Pier

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Re: verify PS SX110IS video exposure shift bug
« Reply #4 on: 10 / March / 2012, 05:53:18 »
@j
Quote
The exposure curve (day-night axis) is not wysiwyg.
Day is ok; dusk is overexposed; night is underexposed.

This is also true for human eyes, which are the most adaptable.
What to ask from some simple cameras.
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Offline j

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Re: verify PS SX110IS video exposure shift bug
« Reply #5 on: 10 / March / 2012, 19:22:14 »
I'm not expert of imaging tech, but I can observe the video
preview is wrong and useless at night, when my eyes are
able to see targets well. (E.g. a fox chasing a cat which
I missed because black preview is useless for fast targeting.
Canon failed badly!)

In computer graphics they have Cornell's box: side-by-side
a real box with objects inside and a computer display.
They make the display and the CG rendering to match
the real box. That kind of match I would call wysiwyg
view finder when done in camera.

The essential question is: can I do it with CHDK or not?
At CHDK development level, I mean.

Can I add pixel operations, such as brightness, prior
view finder or encoder for video?
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Offline reyalp

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Re: verify PS SX110IS video exposure shift bug
« Reply #6 on: 10 / March / 2012, 19:50:38 »
Quote from: j on 10 / March / 2012, 19:22:14
The essential question is: can I do it with CHDK or not?
At CHDK development level, I mean.
If you are serious about this, the correct place to start is the source code and disassembly of your cameras firmware.
Quote
Can I add pixel operations, such as brightness, prior
view finder or encoder for video?
No. The ARM CPU where CHDK runs is nowhere near fast enough to do realtime video processing. The Canon proprietary DSP half of Digic might be able to do this, but CHDK currently has very little control of it.

You may be able to override exposure in video, see http://chdk.setepontos.com/index.php?topic=6113.0 for example.
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