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

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Offline reyalp

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Measuring exposure performance (was Re: proposal - script shooting hooks)
« on: 02 / January / 2015, 00:45:24 »
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Quote from: reyalp on 31 / December / 2014, 19:17:53
I think toward the end we see another issue which IIRC lapser noted before, that ISO changes only take effect in some increment greater than a single APEX96 unit (3?)
Or not:
Attached charts show meter vs sv96 for ISO 75-400 and 400-1600

As noted previously, the last "stop" of ISO is not accessible to CHDK overrides.

Not sure what's up with the outlier at the start of the 400-1600 run, I ran the test twice and it happened both times.
« Last Edit: 29 / May / 2015, 00:02:57 by reyalp »
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Offline reyalp

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Re: Measuring exposure performance
« Reply #1 on: 02 / January / 2015, 01:04:05 »
Since I already have the data, here's the too 400-1600 runs compared.
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Offline reyalp

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Re: Measuring exposure performance
« Reply #2 on: 10 / March / 2015, 16:52:37 »
My current version of this script. Resolves the issue with the weird first shot, among other things.

edit to add instructions:
The numbers are in "real" (as opposed to market) APEX96 units, which is a long complicated story, but the default 371-411 should try to start a bit below ISO 80 to 100.

Point the camera at an unchanging subject, run the script, and examine the resulting isoinc.csv to see where the meter values begin to increase. By default it will take one shot for each step between min and max, so if the range is large it will take a while.

« Last Edit: 10 / March / 2015, 17:04:29 by reyalp »
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Offline c_joerg

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Re: Measuring exposure performance
« Reply #3 on: 12 / March / 2015, 15:14:00 »
I run isoinc on G1X between 371 - 411. Meter doesn't increase. So minimum ISO is 100 or?
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M100 100a, M3 121a, G9x II (1.00c), 2*G1x (101a,100e), S110 (103a), SX50 (100c), SX230 (101a), S45,
Flickr https://www.flickr.com/photos/136329431@N06/albums
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Offline reyalp

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Re: Measuring exposure performance
« Reply #4 on: 12 / March / 2015, 16:10:18 »
Quote from: c_joerg on 12 / March / 2015, 15:14:00
I run isoinc on G1X between 371 - 411. Meter doesn't increase. So minimum ISO is 100 or?
Seems like it, you could set the upper limit a bit higher to make sure it starts increasing. 507 should be ISO 200
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Offline c_joerg

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Re: Measuring exposure performance
« Reply #5 on: 13 / March / 2015, 15:52:19 »
I run now from 370 to 510.
Meter increases. So it looks OK or?
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M100 100a, M3 121a, G9x II (1.00c), 2*G1x (101a,100e), S110 (103a), SX50 (100c), SX230 (101a), S45,
Flickr https://www.flickr.com/photos/136329431@N06/albums
YouTube https://www.youtube.com/channel/UCrTH0tHy9OYTVDzWIvXEMlw/videos?shelf_id=0&view=0&sort=dd
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Offline reyalp

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Re: Measuring exposure performance
« Reply #6 on: 13 / March / 2015, 17:07:24 »
Quote from: c_joerg on 13 / March / 2015, 15:52:19
I run now from 370 to 510.
Meter increases. So it looks OK or?
Yes, it starts to increase a 411 (ISO 100), so the minimum usable is 100. In the rawopint.lua script, this means you should use 100 (or more) as the target ISO. If you left it at 80, it would throw the exposure calculation off.
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Offline c_joerg

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Re: Measuring exposure performance
« Reply #7 on: 21 / March / 2015, 14:21:06 »
I run isoinc also on my S110. I think it looks Ok. S110 has minimum ISO80.
Interesting difference between S110 and G1X:

The first picture on G1X has already much overexposure. For all 4 runs. First S110 picture was correct. Something to think about?

Did I understand behavior auf ISO correct? Every single step in APEX96 changes ISO values? So the cams have more steps than just ISO100, ISO125, ISO160… I would not expect this. I thought ISO is just an analog amplifier on the senor.   
 
Then I run isoinc on my old IXUS30 (I also have an IXUS500HS but unfortunately there exist no CHDK).
Should it run on IXUS30? The IXUS30 crashed totally after first shoot. I had to remove battery….
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M100 100a, M3 121a, G9x II (1.00c), 2*G1x (101a,100e), S110 (103a), SX50 (100c), SX230 (101a), S45,
Flickr https://www.flickr.com/photos/136329431@N06/albums
YouTube https://www.youtube.com/channel/UCrTH0tHy9OYTVDzWIvXEMlw/videos?shelf_id=0&view=0&sort=dd
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Offline reyalp

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Re: Measuring exposure performance
« Reply #8 on: 21 / March / 2015, 14:44:28 »
Quote from: c_joerg on 21 / March / 2015, 14:21:06
The first picture on G1X has already much overexposure. For all 4 runs. First S110 picture was correct. Something to think about?
Maybe. I had a similar issue with D10, that seemed to be related to timing setting the exposure for the first shot.
Quote
Did I understand behavior auf ISO correct? Every single step in APEX96 changes ISO values? So the cams have more steps than just ISO100, ISO125, ISO160… I would not expect this. I thought ISO is just an analog amplifier on the senor.   
For the cameras tested, the data shows pretty clearly that every APEX96 unit has a corresponding effect on exposure. I don't think this is incompatible with being amplifier gain, it just means the amp can be controlled in quite small steps.

The fact that rawopint works correctly adjusting ISO (most of the time anyway ;)) also shows that 1 unit steps work correctly.

Quote
Then I run isoinc on my old IXUS30 (I also have an IXUS500HS but unfortunately there exist no CHDK).
Should it run on IXUS30? The IXUS30 crashed totally after first shoot. I had to remove battery….
It looks like IXUS30 currently doesn't have the USB remote / shutter hook implemented, so the isoinc script will not work.

It's possible the hook could be added. I should also change the shoot hooks to behave better when this isn't available.

The isoinc script probably doesn't actually need to use this hook, it was a quick and dirty test I made from another script.
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Offline reyalp

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Re: Measuring exposure performance (was Re: proposal - script shooting hooks)
« Reply #9 on: 29 / May / 2015, 00:05:49 »
Here's a version of isoinc.lua that supports continuous mode, as suggested in http://chdk.setepontos.com/index.php?topic=11081.msg122539#msg122539

Like for rawopint, continuous mode must be set in the canon UI and checked in the script options.
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