KAP & UAV Exposure Control Intervalometer Script

Wreck

17

Re: KAP & UAV Exposure Control Intervalometer Script

« Reply #50 on: 07 / December / 2013, 20:10:06 »

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How do you tell if the exif values are correct or not? I was just shooting straight down onto grass (the same area and conditions as yesterday) and it's a reasonably sunny day today. The overexposed images that were produced make me think that it did actually use a slower shutter speed, but I'm not much of an expert with chdk cameras.

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waterwingz

12139

Re: KAP & UAV Exposure Control Intervalometer Script

« Reply #51 on: 07 / December / 2013, 20:18:20 »

Quote from: Wreck on 07 / December / 2013, 20:10:06

How do you tell if the exif values are correct or not? I was just shooting straight down onto grass (the same area and conditions as yesterday) and it's a reasonably sunny day today. The overexposed images that were produced make me think that it did actually use a slower shutter speed, but I'm not much of an expert with chdk cameras.

The script log reports that CHDK is trying to override the shutter to 1/1250. I would be very surprised if that does not happen. On my A1200, once you ask for a shutter speed above the normal camera upper range, the exif data does not save the higher shutter speed for some reason even though the image is taken at the faster speed.

Meanwhile, I think that the overexposed images are because the script is assuming the aperture is set to f5.6 and does not realizing its actually at f2.8 with the ND filter engaged. So when it does its exposure calculation it uses f5.6 and then shoots with the ND filter out! This causes it to be about 3 f-stops over exposed.

Clearly a bug - I just need to do some testing to figure out if its an anomaly of your SD960 or normal behavior for most cameras.

« Last Edit: 07 / December / 2013, 20:26:48 by waterwingz »

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Ported : A1200 SD940 G10 Powershot N G16

Wreck

17

Re: KAP & UAV Exposure Control Intervalometer Script

« Reply #52 on: 07 / December / 2013, 20:25:12 »

These overexposed shots all have motion blur too, so I still think the shutter speed is low.

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waterwingz

12139

Re: KAP & UAV Exposure Control Intervalometer Script

« Reply #53 on: 07 / December / 2013, 20:29:00 »

Quote from: Wreck on 07 / December / 2013, 20:25:12

These overexposed shots all have motion blur too, so I still think the shutter speed is low.

If that's true, then it would mean the CHDK port for the SD960 is seriously broken. Nothing much I can do about that with a script.

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Ported : A1200 SD940 G10 Powershot N G16

waterwingz

12139

Re: KAP & UAV Exposure Control Intervalometer Script

« Reply #54 on: 07 / December / 2013, 21:52:04 »

Okay, if you are up for a little more testing, this should handle the ND filter issue properly in bright light (tested taking pictures of my desk lamp's light bulb).

https://app.box.com/s/hslxxa9tiotgwxm35jhw

Let me know if it fixes the overexposure issue when you have the AV Mode in the script parameters to "NdFlter" ?

« Last Edit: 07 / December / 2013, 21:53:53 by waterwingz »

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Ported : A1200 SD940 G10 Powershot N G16

Wreck

17

Re: KAP & UAV Exposure Control Intervalometer Script

« Reply #55 on: 07 / December / 2013, 21:56:16 »

Thanks for that. I'll give it a go and let you know how I get on.

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srsa_4c

4451

Re: KAP & UAV Exposure Control Intervalometer Script

« Reply #56 on: 08 / December / 2013, 09:02:26 »

Quote from: waterwingz on 07 / December / 2013, 20:29:00

Quote from: Wreck on 07 / December / 2013, 20:25:12
These overexposed shots all have motion blur too, so I still think the shutter speed is low.
If that's true, then it would mean the CHDK port for the SD960 is seriously broken. Nothing much I can do about that with a script.

Bug reports are welcome (preferably with a description on how to reproduce).
I have applied the 'short shutter press' override fix in changesets 3264, 3265, but I'm not sure if that will have any influence on this script.

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waterwingz

12139

Re: KAP & UAV Exposure Control Intervalometer Script

« Reply #57 on: 08 / December / 2013, 10:13:21 »

Quote from: srsa_4c on 08 / December / 2013, 09:02:26

Bug reports are welcome (preferably with a description on how to reproduce).

The script does not correctly handle the situation where the camera wants to insert the ND filter and reports using a smaller f-stop setting as a result. It assumes the reported Av value is the actual aperture f-stop setting and does its exposure calculations based on that. When the actual shot occurs, it ends up using calculations based on the ND filter being inserted even though it does not insert that filter.

Once that gets sorted out, we can worry about possible Tv override bugs. The fix for cameras without an adjustable aperture is to use get_prop(props.MIN_AV) to determine the actual Av96 value of the aperture rather than the get_av96() function.

Quote

I have applied the 'short shutter press' override fix in changesets 3264, 3265, but I'm not sure if that will have any influence on this script.

Thanks for that. Reading your commit comments, it appear this only happens on the first shot? In this case, according to the script's log, if there is a bug then it is happening through-out the intervalometer run on many shots.

Also, if your second svn commit comment :
The camera may engage the ND filter in bright light, but take the picture without it (not CHDK related).
is about the issue here, that's a script logic problem and not related to the patch?

I posted a patched script file for Wreck to try. With the ND filter issue fixed, we can work on whether there is an issue with the exif value not matching the override or with the override not actually being applied. The shooting part of the script code is pretty much standard stuff :

Code: [Select]

                -- set up all exposure overrides
                set_tv96_direct(tv96setpoint) 
                set_sv96(sv96setpoint) 
                if( av96setpoint ~= nil) then set_av96_direct(av96setpoint) end    
                nd_string="none"            
                if(Av_mode > 1) then                      -- ND filter available ?
                    if ( insert_ND_filter == true ) then
                        set_nd_filter(1)                         -- activate the ND filter
                        nd_string="NDin"
                    else 
                        set_nd_filter(2)                         -- make sure the ND filter does not activate
                        nd_string="NDout"
                    end
                end

                -- and finally shoot the image
                press("shoot_full_only")
                sleep(100)
                release("shoot_full")
                repeat sleep(50)  until get_shooting() == false

« Last Edit: 08 / December / 2013, 10:24:47 by waterwingz »

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Ported : A1200 SD940 G10 Powershot N G16

waterwingz

12139

Re: KAP & UAV Exposure Control Intervalometer Script

« Reply #58 on: 08 / December / 2013, 10:39:03 »

Quote from: srsa_4c on 08 / December / 2013, 09:02:26

I have applied the 'short shutter press' override fix in changesets 3264, 3265, but I'm not sure if that will have any influence on this script.

Looking at the code in core/shooting.c, it does not look like the change to the aperture_sizes_table[] in this patch going to change the value returned by get_av96() if the ND filter is inserted ?

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Ported : A1200 SD940 G10 Powershot N G16

srsa_4c

4451

Re: KAP & UAV Exposure Control Intervalometer Script

« Reply #59 on: 08 / December / 2013, 10:44:48 »

Quote from: waterwingz on 08 / December / 2013, 10:13:21

The script does not correctly handle the situation where the camera wants to insert the ND filter and reports using a smaller f-stop setting as a result. It assumes the reported Av value is the actual aperture f-stop setting and does its exposure calculations based on that. When the actual shot occurs, it ends up using calculations based on the ND filter being inserted even though it does not insert that filter.

I thought PROPCASE_AV should show the chosen Av value (it seemed to when I recorded the possible Av values).

Quote

The fix for cameras without an adjustable aperture is to use get_prop(props.MIN_AV) to determine the actual Av96 value of the aperture rather than the get_av96() function.

This is probably correct for DOF calculations, but is it really good basis for determining exposure?

Quote

Reading your commit comments, it appear this only happens on the first shot?

Testing this is rather boring, but it seemed to only affect the Tv override, when ISO was also overridden, and mostly when doing a short press. I've only seen this right after transitions to rec mode, subsequent shots were correct.

Quote

The camera may engage the ND filter in bright light, but take the picture without it (not CHDK related).
is about the issue here, that's a script logic problem and not related to the patch

I was referring to live view, the ND is moved to its final position on half-shoot.

Quote from: waterwingz on 08 / December / 2013, 10:39:03

Quote from: srsa_4c on 08 / December / 2013, 09:02:26
I have applied the 'short shutter press' override fix in changesets 3264, 3265, but I'm not sure if that will have any influence on this script.
Looking at the code in core/shooting.c, it does not look like the change to the aperture_sizes_table[] in this patch going to change the value returned by get_av96() if the ND filter is inserted ?

Probably, but people without the cam will now at least see what's available.

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