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A couple of Multicam doubts and general help

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Offline reyalp

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Re: A couple of Multicam doubts and general help
« Reply #100 on: 14 / February / 2020, 16:31:46 »
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I expect some discrepancies between different camera models, but there's one that is responding way off from the rest, it's an A3400. While the exposure on the rest is quite similar, this one is way darker. And even if the EXIF data says it's shot at f4 1/15 and ISO 100, given the amount of noise, I suspect it's shot at much higher ISO.
From the specs, it seems like A3400 and A2400 should should be very similar. The zoom, aperture and ISO ranges are the same. In fact, it looks like the only difference is touch screen https://www.dpreview.com/products/compare/side-by-side?products=canon_a2400is&products=canon_a3400is&sortDir=ascending

Neither of these cameras have an adjustable aperture, so the av value should be ignored.

I'm not sure about the noise, underexposed images will look noisy even at low ISO. It would be helpful if you can upload full images somewhere, with one example from the problem camera and one from a normal one, taken in the same multicam shot.

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Seems like it's not responding to the code... Is there any other way to set the parameters and see if it responds better?
Overrides pretty much use the same underlying mechanism. However, testing that camera alone with normal chdkptp commands might help understand what's happening.
You can shoot once without overrides, check what the exposure is, and then shoot with one override at a time to see if they have the expected effect.

Another thing I would check is whether Canon settings are equivalent on the cameras. Are the in the same Canon shooting mode, is the ISO setting the same?
Don't forget what the H stands for.

Re: A couple of Multicam doubts and general help
« Reply #101 on: Today at 08:57:39 »
Yeah, all A2xxx and A3xxx are quite the same camera, excepting the touchscreen (which I dont care about), so images should be about the same. Here are a few shots
https://photos.app.goo.gl/GDJ8YisJvqE1KTQp9
Warmer one was shot on friday, with manual input of exposure values (using the menu, values I dont remember). These pics were not shot on the rig, so they don't have the best lighting conditions, it was intentional. Other two were shot today with values inserted (exact figures I inserted are 4 for aperture, 0.05 for shutter, 100 for ISO) and then in Auto. Both Auto pics are correct, but the others...?? Am I doing something wrong in the menu? Am I using the right format for values?? I'm puzzled. Check the code a couple of posts before.
Regarding the zooming issues I reported last week, it was definitely a power issue that's been corrected. Unfortunately I had a terrible mishap and two cameras got fried :( (even with the power sources turned off).
And finally, this was mentioned before in post #28 (sorry I'm going back to the basics). How should I insert this prompt option into the Shoot menu? I see and "end" there, not sure how to deal with it...
2) Have a final prompt to confirm after reading the values, like
Code: [Select]
if cli.readline('shoot (y/n)>') == 'y' then
  mc:shoot({sd=dist, tv=exp.shutter_to_tv96(tonumber(shutter)), sv=exp.iso_to_sv96(ISO),av=exp.f_to_av96(fnum)})
end

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Offline reyalp

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Re: A couple of Multicam doubts and general help
« Reply #102 on: Today at 16:32:05 »
Warmer one was shot on friday, with manual input of exposure values (using the menu, values I dont remember). These pics were not shot on the rig, so they don't have the best lighting conditions, it was intentional. Other two were shot today with values inserted (exact figures I inserted are 4 for aperture, 0.05 for shutter, 100 for ISO) and then in Auto. Both Auto pics are correct, but the others...?? Am I doing something wrong in the menu? Am I using the right format for values?? I'm puzzled. Check the code a couple of posts before.
I don't think you are doing something wrong, I'd guess it's either a problem with this specific camera, or a bug in the CHDK (or maybe a bug in multicam).
Am I correct that you only have one a3400?  If you have more than one and they all have the same problem that would point to a port bug, but with only one, I'd suspect the camera.

Looking at the images, the auto images are roughly equal, but the exposure recorded is very different:
a2500 is 1/50, ISO 400
a3400 is 1/20, ISO 800
This is more than 2 stops different, and the A3400 is darker. These cameras don't have an adjustable aperture, so that must be the same if focal length is the same.

Ones explanation would be if the ND filter on the A3400 is physically stuck in, or CHDK is somehow putting it in unexpectedly.

Can you try shooting ND not specified, in and out, with no other exposure values set? Like
Code: [Select]
mc:shoot()
mc:shoot({nd=1})
mc:shoot({nd=2})
Main interest is a3400, but including one a2500 to compare would be worthwhile.

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And finally, this was mentioned before in post #28 (sorry I'm going back to the basics). How should I insert this prompt option into the Shoot menu? I see and "end" there, not sure how to deal with it...
2) Have a final prompt to confirm after reading the values, like
Code: [Select]
if cli.readline('shoot (y/n)>') == 'y' then
  mc:shoot({sd=dist, tv=exp.shutter_to_tv96(tonumber(shutter)), sv=exp.iso_to_sv96(ISO),av=exp.f_to_av96(fnum)})
end
I'm not sure I understand, the "end" goes with the preceding "if", so you should be able to just put the whole if / end block in your code where the shoot command was.
Don't forget what the H stands for.

Re: A couple of Multicam doubts and general help
« Reply #103 on: Today at 16:51:11 »
My guess is the ND filter is stuck or misbehaving, but will test tomorrow (see that the shoot menu command includes a nd=2 by default). There "was" another A3400, but got fried.. So can't compare. :( I've decided to stick to the A2xxx series, but i'll do my best to have this one working properly.
Ok, I now understand how to integrate the prompt. It goes nested inside the shooting option, will add it tomorrow.
This whole build is like a game of whack-a-mole, once you fix something, something else breaks... A neverending story   :'(


 

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