Script not working like expected (G7X)

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Online reyalp

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Re: Script not working like expected (G7X)
« Reply #10 on: 13 / July / 2018, 16:28:51 »
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Because it says so. See attached photo, it should have been at 1600.
FWIW, that just tells you what's in the exif, which may not reflect what the camera actually did when CHDK overrides are in use. To know what the camera actually did, you'd have to compare images taken at 1600.

That said, I tried a few permutations of using ISO overrides in the CHDK menu and the exif appears to match. The exposure also appeared to reflect the override. I don't see any obvious reason the script override would behave differently.
Don't forget what the H stands for.

Script not working like expected (G7X)
« Reply #11 on: 13 / July / 2018, 20:27:57 »
I’m travelling this week and away from my computer. 

There is another clue in the log file where the Sv value is reported as "hi" rather than a numeric vakue.   IIRC correctly that means the SV96 value reported by the camera is off the end of an internal conversion table.  That code predates the "human readable" APEX96 CHDK functions and IIRC gives a nicer result.  I'll take look when I get home.

FWIW, it probably hasn't been noticed before if there is actually a script bug because not a lot of people fly kites or UAVs at night in the dark.
Ported :   A1200    SD940   G10    Powershot N    G16

Re: Script not working like expected (G7X)
« Reply #12 on: 13 / July / 2018, 20:52:38 »
FWIW, it probably hasn't been noticed before if there is actually a script bug because not a lot of people fly kites or UAVs at night in the dark.
In the winters here, it gets very dark even at daytime.

It's not really something I do regularly though.. or at all. But it's nice to have the possibility. I'm already prepared with position lights and a fpv-camera that, apparently, works well in very low light conditions.

Re: Script not working like expected (G7X)
« Reply #13 on: 14 / July / 2018, 04:42:06 »
There is another clue in the log file where the Sv value is reported as "hi" rather than a numeric value.   
It looks like the script is working exactly as intended. I downloaded a copy of the script to my mobile and checked it carefully.  Read on ...

The word "hi" in the script log is just the script reporting that the value returned by the camera is over ISO3200. However, the script uses the actual value it receives from the camera firmware correctly - the "hi" only shows up in the log text.  So there is no problem there.

So I looked at how the script is adjusting the exposure values. This shot :
Code: [Select]
2018Jul13 00:00:16.080 1) IMG_0402.JPG
2018Jul13 00:00:18     meter : Tv:1/1250 Av:3.5 Sv:hi -1164:-1164
2018Jul13 00:00:18     actual: Tv:1/1000 Av:1.8 Sv:1600 Temp:27
2018Jul13 00:00:18             AvMin:1.8 NDF:NDout foc:infinity
tells me that the camera wants a shutter speed of 1/1250 of a second, with the f-stop at f3.5 and the ISO at 6400 (i.e. hi).   

Using those values as a starting point, the script adjusts the ISO down to 1600 (your maximum ISO2 setting), thereby lowering the exposure a factor of 4x.  To compensate, it adjusts the f-stop by 2 full stops from 3.5 to f1.8 (your Av min) for a 2x increase in exposure.  It also changes the shutter speed by 1/250 to 1/1000 (your Tv min) for a 1.25x increase in exposure.  As a result, the final image will be underexposed by about a factor of 0.75x because of the limits you set in your script parameters!

To fix that, allow a lower shutter speed (Tv min).

A higher ISO2 max would work but the script currently artificially limits the max ISO to 1600.   I'll fix that in the next release.

I don't know why your LCD shows ISO1000 but, as per reyalp's comment and hundreds of posts on this forum, you can't go by what you see on your LCD (or sometimes even the EXIF values in the image). I have a suspicion that you have the ISO set to 1000 in the Canon firmware rather than ISO AUTO?  That can cause problems too by the way - leave it in AUTO.

CHDK overrides are a hack - they bypass the camera firmware and sometimes that means the EXIF values or LCD display values don't match what was actually used to take the shot. Whether it does or not seems to depend on the camera and shooting mode and is a function of how the port was done. You have to examine the actual image to figure that out.

In the winters here, it gets very dark even at daytime.
You have my sympathy.
« Last Edit: 14 / July / 2018, 04:44:19 by waterwingz »
Ported :   A1200    SD940   G10    Powershot N    G16


Re: Script not working like expected (G7X)
« Reply #14 on: 24 / July / 2018, 18:54:14 »
I have a suspicion that you have the ISO set to 1000 in the Canon firmware rather than ISO AUTO?  That can cause problems too by the way - leave it in AUTO.
It has always been on auto.

I have another not completely relevant question..
How do we use analog av out combined with usb remote shutter? There doesn't seem to be any usb leads in the canon av cable.

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Online reyalp

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Re: Script not working like expected (G7X)
« Reply #15 on: 24 / July / 2018, 22:06:53 »
How do we use analog av out combined with usb remote shutter? There doesn't seem to be any usb leads in the canon av cable.
You need to a custom cable, either built yourself (like http://www.achillies.com/CHDK_Files/USB_Splitter.htm) or maybe from https://vp-systems.eu/order_cr.html

I have no experience with vp-systems, but the cable "CR-Camera 11-pin USB+A/V Combo Cable for Canon" looks like it should work.

Alternatively, you could use a different input for the remote trigger. G7X supports HDMI hotplug detect, battery temperature and analog AV detect. See https://chdk.setepontos.com/index.php?topic=13448.0 and https://chdk.setepontos.com/index.php?topic=13451.0

HDMI hotplug is probably the simplest option.

Using analog AV out and analog AV detect trigger at the same time isn't currently supported, but probably wouldn't be hard to add. You'd still need a custom cable to connect the AV detect pins.
Don't forget what the H stands for.

Re: Script not working like expected (G7X)
« Reply #16 on: 30 / July / 2018, 15:44:02 »
KAPshop.com is making and selling these cables for some years now. See: http://www.kapshop.com/p274/Canon-11-pin-for-CHDK/SDM-and-Video-out/product_info.html

 

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