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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: 17 / February / 2020, 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: 17 / February / 2020, 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: 17 / February / 2020, 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   :'(


Re: A couple of Multicam doubts and general help
« Reply #104 on: 18 / February / 2020, 12:12:18 »
Hi Reyalp, I updated the album with the ND pictures. I'm not sure how the command works regarding the ND, but in the A3400 I see no change, and surprisingly, there's a variance in the A2500... Well, take a look. Thx
https://photos.app.goo.gl/GDJ8YisJvqE1KTQp9

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Offline reyalp

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Re: A couple of Multicam doubts and general help
« Reply #105 on: 18 / February / 2020, 15:36:13 »
Hi Reyalp, I updated the album with the ND pictures. I'm not sure how the command works regarding the ND, but in the A3400 I see no change, and surprisingly, there's a variance in the A2500... Well, take a look. Thx
https://photos.app.goo.gl/GDJ8YisJvqE1KTQp9
Thanks, I think that confirms that your A3400 has a mechanical problem: The ND filter is stuck in the "in" position. The best bet is probably to replace it, but you since you mentioned you had another 3400 that died, you could try to swap some components, or you could add special code to always offset exposure for this camera by the ND value, or try percussive maintenance.

The A2500 is as expected: Underexposed by 2+ stops when the ND is in, and normal when it's out or auto.

In auto mode, your A3400 still exposes correctly (as long as the scene isn't bright enough that it would normally try to use the ND), because it doesn't know the ND is in, it just measures the scene and sets the exposure.
Don't forget what the H stands for.

Re: A couple of Multicam doubts and general help
« Reply #106 on: 18 / February / 2020, 16:05:07 »
Percussive maintenance seems like the way to go. I recovered an SX150 that showed "Lens Error" that way yesterday. I might not be good with electronics, but I'm damn fine slamming cameras :D
I was puzzled with the results since I expected the A2500 to compensate for the ND filter, but yeah.. What you said makes more sense.
Quick question: Don't worry about the code for now, it's just an ou of the box idea. Would it be possible to shoot a quick burst of 3 or 4 images (I know how to do this), and save them as JPGs, but keep the DNG only for the last one? JPG to allow for a quicker burst/write rate and after the last one there'd be time for the DNG to write. This would be an "emergency" shot, that would allow me to combine multiple JPGs to reduce noise with median filter (just a crazy idea, but is it doable?) I would still need to check if the burst rate across different cameras would be quick enough (only the first shot would need to be synced). Thx :)

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Offline reyalp

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Re: A couple of Multicam doubts and general help
« Reply #107 on: 18 / February / 2020, 17:01:07 »
Percussive maintenance seems like the way to go. I recovered an SX150 that showed "Lens Error" that way yesterday. I might not be good with electronics, but I'm damn fine slamming cameras :D
One thing you can check is if the camera makes any sound when it tries to put in the ND filter.

If the camera is in half press, the ND filter functions will try to change the ND position immediately, so you can do something like
Code: [Select]
mc:cmdwait('preshoot')
mc:cmdwait('call set_nd_filter(1)')
mc:cmdwait('call set_nd_filter(2)')
If you hear some clicking, then you at least know the actuator can be commanded. If it makes no sound, an electrical problem might be more likely, although it might just be really well stuck.

You could also have the camera repeatedly try to move the actuator while you do percussive maintenance, like
Code: [Select]
!mc:cmdwait('call for i=1,10 do set_nd_filter(1) sleep(100) set_nd_filter(2) end')
Again, this should be done in half press.

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I was puzzled with the results since I expected the A2500 to compensate for the ND filter, but yeah.. What you said makes more sense.
Yep, as a general rule, the Canon autoexposure does not know about CHDK overrides.

Quote
Quick question: Don't worry about the code for now, it's just an ou of the box idea. Would it be possible to shoot a quick burst of 3 or 4 images (I know how to do this), and save them as JPGs, but keep the DNG only for the last one? JPG to allow for a quicker burst/write rate and after the last one there'd be time for the DNG to write. This would be an "emergency" shot, that would allow me to combine multiple JPGs to reduce noise with median filter (just a crazy idea, but is it doable?) I would still need to check if the burst rate across different cameras would be quick enough (only the first shot would need to be synced). Thx :)
It should be possible, but would need code changes in mc:shoot or the camera side code if you don't want to do the DNG as a separate shot.

The simplest would be probably be to shoot one burst and leave the cameras in half press, so you can then just enable raw and do another shoot command. Doing another shot from half press is pretty quick, but you'd still have multicam command delay. I think the only change needed to support this would be allow setting release_half in mc:shoot options.
Don't forget what the H stands for.


Re: A couple of Multicam doubts and general help
« Reply #108 on: 19 / February / 2020, 16:44:02 »
Camera does click with the given commands, but unfortunately and despite some heavy percussion... No change. Will think about whether to compensate the exposure or ditch this one and try to get an A2400. Regarding the 3 JPG+1DNG thing.. I've tested the burst speed in the A2500 and it averages at 1fps, which is not ideal, but who knows it might do the trick? I've tested the technique with a stationary object (a mannequin) and the noise reduction is quite good (combining 3 shots). Anyway, it's just a crazy idea. I have a million more things to deal with a the moment :)

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Offline reyalp

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Re: A couple of Multicam doubts and general help
« Reply #109 on: 23 / February / 2020, 02:18:13 »
Regarding the 3 JPG+1DNG thing.. I've tested the burst speed in the A2500 and it averages at 1fps, which is not ideal, but who knows it might do the trick? I've tested the technique with a stationary object (a mannequin) and the noise reduction is quite good (combining 3 shots). Anyway, it's just a crazy idea. I have a million more things to deal with a the moment :)
You won't get much better than 1 fps on cheap Canon P&S, but as you say, if your subject is still enough, the noise reduction is good.

I made some changes to multicam.lua based on earlier discussion in this thread:
init_sync now doesn't print the individual for each sync send by default, just a two line summary per camera. The old style output can be enabled by setting mc.init_sync_verbose=true

In mc:shoot, you can now include an option release_half=false. This will leave halfpress held, so you can changes settings more quickly between shots, or to shoot several shots with same settings. To release halfpress, you can use something mc:cmdwait('call release"shoot_half"'), or just leave out the release_half=false in your final shoot command.

You can get the latest lua file from svn http://subversion.assembla.com/svn/chdkptp/trunk/lua/multicam.lua
As of this posting, it will work with the chdkptp 921 build, but might not work with earlier ones.
Don't forget what the H stands for.

 

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