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Measuring exposure performance (was Re: proposal - script shooting hooks)

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Offline reyalp

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Re: Measuring exposure performance (was Re: proposal - script shooting hooks)
« Reply #20 on: 31 / May / 2015, 01:17:13 »
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Quote from: philmoz on 31 / May / 2015, 00:27:41
That seems to be the case - although the G1X is the only camera affected that I know if.
But only using CHDK script or overrides, right? If you set it all manually in the Canon UI, the jpegs would appear to have equal exposure.

The last stop of ISO on some other cameras is special, in some cases it can't be set using CHDK overrides, and if set in the UI only affects the jpeg, not raw values.
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Offline reyalp

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Re: Measuring exposure performance (was Re: proposal - script shooting hooks)
« Reply #21 on: 31 / May / 2015, 01:56:47 »
Here's an updated version of the isoinc script.

Changes
Shooting method is now selected with the "shoot mode" mode option
Single: full half press and shoot cycle for each shot.
Quick: hold half press, click shoot full
Cont: continuous mode (errors if not also set in canon UI)

Changed "Initial ev shift": The sign was backwards before, now negative values mean less exposed.

Added an append to log option.
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Offline c_joerg

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Re: Measuring exposure performance (was Re: proposal - script shooting hooks)
« Reply #22 on: 31 / May / 2015, 04:36:53 »
Quote
is it correct the Y axis is showing the brightness of the jpeg?

I think so. I do it in the following way:

Open JPG File.
Then I have a matrix form m * n *3 (RGB) with 8 bit data.
Then I calculate H  = (R*0.3 + G*0.59 + B*0.11) for every pixel
Then calculate a mean value for all pixels.

So the value must be something like brightness. I know conversion from RAW to JPG is not linear, what you see on the y axis. In the same way, I analyzed overexpose on JPG, which is close to your results.

Quote
Single: full half press and shoot cycle for each shot.

Would be really interested, what this run shows ....

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Offline reyalp

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Re: Measuring exposure performance (was Re: proposal - script shooting hooks)
« Reply #23 on: 01 / June / 2015, 00:14:24 »
Quote
So the value must be something like brightness.
Close enough for my purposes.

In the attached version of isoinc, I added an option called "ISO Set mode". If this is set to "Script" it will attempt to use the ISO override method Lapser suggested in http://chdk.setepontos.com/index.php?topic=11081.msg121063#msg121063 for all shots after the initial value.  This option is not valid in single shot mode, only quick or cont.

The basic difference from the C code is that it doesn't set the base ISO in SV_MARKET. This leads to some ambiguity,  but it's worth a try since he was apparently able to get usable results with the G1x.

Setting to "CHDK" will use the normal CHDK overrides.
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Offline c_joerg

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Re: Measuring exposure performance (was Re: proposal - script shooting hooks)
« Reply #24 on: 01 / June / 2015, 13:51:24 »
Made just a fast run…
Quote
I added an option called "ISO Set mode". If this is set to "Script" it will attempt to use the ISO override method Lapser suggested

This method is working definitely different…. I think you getting close to a solution ;)
Well, that’s the difference between a Guru and a Jr. Member,
I wish I had the time to get your knowledge

The run was with r4138, continues mode and ISO set mode Script.
As you see, JPG is now OK :) 
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Offline c_joerg

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Re: Measuring exposure performance (was Re: proposal - script shooting hooks)
« Reply #25 on: 01 / June / 2015, 14:07:27 »
Meter96 has now a offset. Is this the blacklevel?

I get now a little bit confused about all combination which i can test.
Which combination can be helpful?
Still the single mode? With which release? And which ISO set mode?
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Offline reyalp

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Re: Measuring exposure performance (was Re: proposal - script shooting hooks)
« Reply #26 on: 02 / June / 2015, 02:33:48 »
Quote from: c_joerg on 01 / June / 2015, 14:07:27
Meter96 has now a offset. Is this the blacklevel?
From a quick look, I think it's the behavior phil described in http://chdk.setepontos.com/index.php?topic=12165.msg122573#msg122573
Quote
If you use the Canon controls to set the Av,Tv and Sv values in the region above the black point changeover it shoots at 1/2 the selected Sv and boosts the JPEG data to compensate (a DNG will be 1/2 as bright and show 1/2 Sv value in the EXIF).
Essentially when the ISO reaches 400, the camera drops the actual ISO (as seen in the raw data) back to 200 and boosts the jpeg. In continuous mode, it appears the black level change doesn't happen

Out of curiosity, what does the exif show for these?

Quote
I get now a little bit confused about all combination which i can test.
Which combination can be helpful?
Still the single mode? With which release? And which ISO set mode?
I would be interested to see the log from single mode, with CHDK ISO set.
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Offline c_joerg

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Re: Measuring exposure performance (was Re: proposal - script shooting hooks)
« Reply #27 on: 02 / June / 2015, 03:18:48 »
Quote
Out of curiosity, what does the exif show for these?

EXIF was OK, so I have not posted it. I if you want, I can add the plot

Quote
I would be interested to see the log from single mode, with CHDK ISO set.


This method has one big disadvantage for timelapse. I this mode (which I use in my script) the camera always open the aperture for measure. This adds an aperture flicker. This is not happens with open aperture (may be also not with full closed aperture). So we will probably see this in the log file…

https://www.youtube.com/watch?v=PVnqd4f3Kmk


Edit:
Add EXIF Plot
« Last Edit: 02 / June / 2015, 11:43:14 by c_joerg »
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Offline c_joerg

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Re: Measuring exposure performance (was Re: proposal - script shooting hooks)
« Reply #28 on: 02 / June / 2015, 12:53:51 »
This is the run with r4138, single mode, with CHDK ISO set.

meter96 looks similar to the run from continues mode and ISO set mode Script.
EXIF ISO Data is correct (same as continues mode and ISO set mode Script)
JPG analyzing takes always time on my old PC...
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Offline c_joerg

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Re: Measuring exposure performance (was Re: proposal - script shooting hooks)
« Reply #29 on: 02 / June / 2015, 13:04:44 »
I compare meter96 values from single and continuous mode (by normalizing before). There is a little bit more flicker in single mode, but not much. May be this depends that I used f16. A couple of month ago I compared my S110 in single mode (open aperture with f5.6). The differences were much bigger.

Also JPG looks similar.

So everything between the run from
'continues mode and ISO set mode Script' 
and
'single mode with CHDK ISO set'
is the same.
 
« Last Edit: 02 / June / 2015, 13:44:44 by c_joerg »
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