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Bracketing in continuous mode

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Offline pigeonhill

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Bracketing in continuous mode
« on: 28 / January / 2020, 13:20:39 »
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I’ve spent a day trying to get to the bottom of some strangeness in using ISO bracketing in continuous mode, on various cams.


What I see and I don’t understand is that if I set up the custom timer for two images and set bracketing in con mode in CHDK to, say, 1600, the cam takes the two brackets, ie at base ISO and the 1600, the reported canon exposure reports the base cam values, ie the 125 and not the 1600, but the image on the screen is clearly th3 1600 one, ie bright.


If I then review the images via PLAY the images look good, and when I go back to the live view the image returns to the base image.


I’ve tried no review in Canon and quick review.


Am I missing something? As what I see can’t be right. That is after bracketing the image I see should the exposure before the CHDK bracketing.


Can someone throw some education my way, as its driving me insane and I wish to use bracketing in con mode in a new script I’m writing.


Further update. Bracketing in tv mode works as expected. It just ISO mode that behaves strangely. Has anyone else tried using ISO bracketing in con mode?
« Last Edit: 28 / January / 2020, 14:10:42 by pigeonhill »
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Offline reyalp

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Re: Bracketing in continuous mode
« Reply #1 on: 28 / January / 2020, 15:09:07 »
Quote from: pigeonhill on 28 / January / 2020, 13:20:39
I’ve spent a day trying to get to the bottom of some strangeness in using ISO bracketing in continuous mode, on various cams.
Which cameras do you see this on?
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What I see and I don’t understand is that if I set up the custom timer for two images and set bracketing in con mode in CHDK to, say, 1600, the cam takes the two brackets, ie at base ISO and the 1600, the reported canon exposure reports the base cam values, ie the 125 and not the 1600, but the image on the screen is clearly th3 1600 one, ie bright.
By "reported canon exposure" do you mean the exif, the on screen display, or something else?
In general, it's not unusual for the exif or Canon UI to not accurately reflect override values, but we do try to fix the exif when possible.

Note that the bracketing value is how much to bracket by, so 1600 would actually try to 1725 It really should have an option to specify this as EV steps, but it doesn't. Patches welcome.

ISO settings between available UI values generally work (you can set ISO 234 and it's the expected amount brighter than 200), but the Canon UI will not display them accurately. ISO overrides generally do not work beyond the range available in the Canon UI, but (if it doesn't crash) normally use the closest available value, so setting 1725  on a camera that only goes to 1600 should have the same exposure as setting 1600. On some cameras, ISO settings at the high end of the range also do not (e.g. 1600 on a camera that only goes to 1600) are implemented differently from the normal range and aren't available from CHDK overrides.
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f I then review the images via PLAY the images look good, and when I go back to the live view the image returns to the base image.
I'm not sure what you mean here. The bracketing setting shouldn't affect the live view image.

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Can someone throw some education my way, as its driving me insane and I wish to use bracketing in con mode in a new script I’m writing.
In general, if you are doing this in a script, I'd suggest using the script to control the ISO value.
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Offline pigeonhill

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Re: Bracketing in continuous mode
« Reply #2 on: 28 / January / 2020, 15:30:06 »
@reyalp

Sorry for the confusion. I just tried an experiment with no scripts running on my G5X.

I set bracketing in continuous mode to tv 4Ev and set Canon customer timer to 2 images. Manual mode BTW. Base iso is 125.

Press shutter and after the two images are taken the screen returns to the base image settings and the screen image matches this.

If I do the same, but with ISO bracketing, at 670, which should be around 800, and repeat, the on screen, canon reported exposure on screen is the correct, ie Tv and ISO, but the screen brightness is like the higher ISO is in effect.

If I then review in play the images are captured correctly. If I then go out of play mode, the on screen brightness drops to match the canon reported values of the base image.

I’ve tried this on my G7X as well. Same problem.
« Last Edit: 28 / January / 2020, 16:36:24 by pigeonhill »
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Offline reyalp

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Re: Bracketing in continuous mode
« Reply #3 on: 28 / January / 2020, 16:38:34 »
Quote from: pigeonhill on 28 / January / 2020, 15:30:06
If I do the same, but with ISO bracketing, at 670, which should be around 800, and repeat, the on screen, canon reported exposure on screen is the correct, ie Tv and ISO, but the screen brightness is like the higher ISO is in effect.
Screen brightness when? After the shooting completes? This could be a result of the ISO issue I mentioned near the end of https://chdk.setepontos.com/index.php?topic=13638.140

Bracketing should probably save and restore ISO_MODE. Hmm.
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Offline pigeonhill

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Re: Bracketing in continuous mode
« Reply #4 on: 28 / January / 2020, 16:58:20 »
@reyalp


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Screen brightness when? After the shooting completes?

Yes.

As I say, I'm not using this in a script, 'just' accessing bracketing in continuous mode via the shutter.

Images are captured OK, Canon side shows that the image has returned to the base image values, but, after images are captured the screen remains at the higher ISO brightness and will not return to the base brightness, other than going in and out of Play.

I've confirmed that on several cameras.

I hate to say this, but it looks like a 'bug'  :(
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Offline reyalp

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Re: Bracketing in continuous mode
« Reply #5 on: 28 / January / 2020, 17:02:28 »
Quote from: pigeonhill on 28 / January / 2020, 16:58:20
@reyalp


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Screen brightness when? After the shooting completes?

Yes.

As I say, I'm not using this in a script, 'just' accessing bracketing in continuous mode via the shutter.
The issue described applies to ISO override, regardless of where it was set.

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I hate to say this, but it looks like a 'bug'  :(
Yes. A very old bug.

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other than going in and out of Play.
Changing ISO in the menu or setting the ISO_MODE propcase should also do it.
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Offline pigeonhill

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Re: Bracketing in continuous mode
« Reply #6 on: 28 / January / 2020, 17:09:35 »
"Yes. A very old bug."

Does that mean I will have to live with it?

Or will/could it be fixed in a future update?
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Offline reyalp

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Re: Bracketing in continuous mode
« Reply #7 on: 28 / January / 2020, 17:46:00 »
Quote from: pigeonhill on 28 / January / 2020, 17:09:35
"Yes. A very old bug."

Does that mean I will have to live with it?

Or will/could it be fixed in a future update?
I'll have a look, it's something that's bugged me for a long time, but AFAIK it's the way it's always been and I haven't seen many other complaints about it. I'm not sure how hard it will be to reliably restore ISO_MODE.
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Offline pigeonhill

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Re: Bracketing in continuous mode
« Reply #8 on: 28 / January / 2020, 17:53:04 »
I'll follow your hints and try and see if I can 'patch' it in my script. 


The complication is I'll need to watch to see if ISO bracketing has occurred, the images have been captured and then use the ISO mode propcase to reset things.


As I say, I'll look into that approach.


Cheers


Garry
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Offline reyalp

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Re: Bracketing in continuous mode
« Reply #9 on: 29 / January / 2020, 01:43:53 »
Here's a patch and test build for G7X 100d. If you want builds for others, just let me know the model and Canon firmware.

This seems to work and is simpler than I expected, but I haven't tested extensively. I'll want a bit more testing with different cams before I add it to the trunk.
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