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SX410 IS porting thread

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Offline blackhole

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Re: SX410 IS porting thread
« Reply #50 on: 07 / May / 2017, 15:31:42 »
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@ for developers
The lowest usable ISO is 50, but the camera crashes when is used in AUTO mode with flash.
Will we limit the ISO to 100? Or the benefit of using a lower ISO value is more preferable, with the risk of camera crash?
Both solution has its advantages and disadvantages.

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Offline Torbe

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Re: SX410 IS porting thread
« Reply #51 on: 07 / May / 2017, 16:18:26 »
I cannot see any problems with ISO settings.When you select the ISO below 100, camera can not display that value and you may see the value that would be selected by the camera.If you look at the image in playback mode,you will see that your ISO settings are applied.

You're right. I got confused because when shooting with ISO 10, exif data shows ISO 200 as the actual ISO speed used (bug?)
I made a few tests and it seems to be shooting with ISO 50 or ISO 100, regardless of what the exif data says.

Thanks for the report.

Thank you for working on this!

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Offline reyalp

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Re: SX410 IS porting thread
« Reply #52 on: 07 / May / 2017, 17:31:12 »
You're right. I got confused because when shooting with ISO 10, exif data shows ISO 200 as the actual ISO speed used (bug?)
I made a few tests and it seems to be shooting with ISO 50 or ISO 100, regardless of what the exif data says.

@ for developers
The lowest usable ISO is 50, but the camera crashes when is used in AUTO mode with flash.
Will we limit the ISO to 100? Or the benefit of using a lower ISO value is more preferable, with the risk of camera crash?
Both solution has its advantages and disadvantages.
Generally speaking, CHDK ISO overrides don't work far outside of the range available in the canon UI. I would be surprised if 50 is actually much different from 100. If it actually works below 100, I'd expect the lowest real value is more like 85.

I'd suggest the first step is to find out the real usable range, which you can do with  my isoinc.lua script from https://chdk.setepontos.com/index.php?topic=12165.msg127110#msg127110

This script tests ISO response by shooting one (or more) shots at every possible ISO setting in the given range, and measuring the resulting raw values.

The test procedure is
* Set the camera on a tripod or steady surface, and aim at uniform grey, unchanging scene. I use a blank wall or LCD display showing a white page. If using a display, defocus so the individual color elements aren't resolved.
* Set the range you want to test using the Start Value, End value and ISO input type settings. By default, the values are in internal SV96 values. Change input to ISO to use the values used in the Canon display.
* The range for a single run should generally not be more then ~4 stops. The "initial EV shift" setting controls how under-exposed the initial shot will be. The usable range will normally be ~1.5 stops more than this. If you want to test the full range, set log mode to append, and do a few runs e.g. 80-400, 400-1600
* If your light source might flicker (a monitor or light that uses PWM for brightness, or some fluorescent lighting) make sure the auto exposure shutter speed at the starting ISO would be long compared to the frequency
* If the camera has an adjustable aperture, set it to a mode with manual aperture control, or set the shooting mode to quick or cont.
* Run the script
* Output will be saved in a file called isoinc.csv in the root of the SD card.
* In the usable range, meter96 should increase linearly with sv96.

Don't forget what the H stands for.

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Offline blackhole

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Re: SX410 IS porting thread
« Reply #53 on: 07 / May / 2017, 19:23:20 »
Quote
Generally speaking, CHDK ISO overrides don't work far outside of the range available in the canon UI. I would be surprised if 50 is actually much different from 100. If it actually works below 100, I'd expect the lowest real value is more like 85.
I used something similar to your method with the LCD screen, but I compared the histogram in the Camera Raw application. On ISO50 is the last change in the histogram, but it may not be completely correct.
Amp glow on ISO80 and Tv64 sec is significantly lower than on ISO100 Tv64 sec.
On ISO50 and Tv64 sec amp glow completely disappears, but this may happen anywhere between ISO80 and ISO50.
Lower ISO can be useful for long night exposure, where the amp glow becomes visible.For daily photography is quite unnecessary unless you are photographing waterfalls or something where you want to have long exposures without  overexposure.


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Offline reyalp

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Re: SX410 IS porting thread
« Reply #54 on: 07 / May / 2017, 22:47:38 »
On ISO50 is the last change in the histogram, but it may not be completely correct.
Amp glow on ISO80 and Tv64 sec is significantly lower than on ISO100 Tv64 sec.
If it actually works, then I would be inclined to allow it, with a note about the crash in notes.txt and on the wiki page.

In your test, what method were you using to set the ISO?

edit: I ask because if the ISO values were "real" rather than the "market" values used in the Canon UI, 50 probably corresponds to about 80, and 100 to about 160. The exposure override interface uses "market" values, although it's possible the conversion is not correct.
« Last Edit: 07 / May / 2017, 23:19:13 by reyalp »
Don't forget what the H stands for.

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Offline blackhole

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Re: SX410 IS porting thread
« Reply #55 on: 08 / May / 2017, 03:43:19 »
Quote
edit: I ask because if the ISO values were "real" rather than the "market" values used in the Canon UI, 50 probably corresponds to about 80, and 100 to about 160. The exposure override interface uses "market" values, although it's possible the conversion is not correct.
Yes, I did not think about it, I used the "market" ISO from the chdk menu.

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Offline reyalp

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Re: SX410 IS porting thread
« Reply #56 on: 08 / May / 2017, 13:40:17 »
Yes, I did not think about it, I used the "market" ISO from the chdk menu.
You can verify the market / real conversion using the method described in this post:
https://chdk.setepontos.com/index.php?topic=12532.225

edit:
I would be interested to see the results of an isoinc run, from say iso 40 to 200 if it's not too inconvenient.
« Last Edit: 08 / May / 2017, 13:53:53 by reyalp »
Don't forget what the H stands for.

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Offline blackhole

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Re: SX410 IS porting thread
« Reply #57 on: 08 / May / 2017, 16:55:09 »
Quote
You can verify the market / real conversion using the method described in this post:
https://chdk.setepontos.com/index.php?topic=12532.225
Is this a link to the right post?
Quote
I would be interested to see the results of an isoinc run, from say iso 40 to 200 if it's not too inconvenient.
Do not worry I did not forget about it, I'm just these days as a camera "Busy".


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Offline reyalp

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Re: SX410 IS porting thread
« Reply #58 on: 08 / May / 2017, 22:43:52 »
Quote
You can verify the market / real conversion using the method described in this post:
https://chdk.setepontos.com/index.php?topic=12532.225
Is this a link to the right post?
Oops, it's the right page of the thread, but not the post. Try https://chdk.setepontos.com/index.php?topic=12532.msg128060#msg128060 (#221 if the link doesn't jump you there.)

Quote
Do not worry I did not forget about it, I'm just these days as a camera "Busy".
No problem. I know that feeling
Don't forget what the H stands for.

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Offline Torbe

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Re: SX410 IS porting thread
« Reply #59 on: 09 / May / 2017, 11:06:02 »
I would be interested to see the results of an isoinc run, from say iso 40 to 200 if it's not too inconvenient.

The results are attached.

Here you can see the script options and the experimental setup in the files in this link:
https://www.dropbox.com/s/ha6s42xgrpk49mg/isoinc%20SX410IS.tar.gz?dl=0

If you find any error, or want me to make any other arrangement, change options, use some other ISO settings, etc just tell me and I'll do it.

Regards

 

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