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Using APEX values to compute exposure

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Offline lapser

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Re: Using APEX values to compute exposure
« Reply #10 on: 23 / January / 2013, 15:50:14 »
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Using a new function to set PROPCASE_DELTA_SV, the results were fine but my logfile did not indicate any change of ISO and that propcase is always zero on my camera at all ISO's.
Why don't you try out my new sv96_to_iso(sv96) function for your log file. I have a diff posted here:

http://chdk.setepontos.com/index.php?topic=9335.msg96139#msg96139

I'm not sure why we need all the ISO functions anyway. Everything should be Apex96 for exposure changes. If you want to know the ISO, convert sv96 to ISO.

Market ISO just means the camera redefines 100 ISO to match 100 film speed, like 35mm equivalent. I think we should forget about that in scripts and CHDK. When you set ISO 100 with the camera, you can read sv96 in the script. It converts back to ISO 65 on my camera, but so what. Each camera has a different real ISO for 100 market ISO. I even read something about Canon changing market 100 ISO to 65 real after the camera was on the market. To find out the real ISO equivalent on any camera, you set the camera to 100 ISO (or whatever) and run this script:

print(sv96_to_iso(get_sv96())
EOS-M3_120f / SX50_100b / SX260_101a / G1X_100g / D20_100b
https://www.youtube.com/user/DrLapser/videos

Re: Using APEX values to compute exposure
« Reply #11 on: 23 / January / 2013, 18:02:13 »

Why don't you try out my new sv96_to_iso(sv96) function for your log file.


Not sure why you are suggesting that.
SDM does not use Lua and shutter speed and aperture are used in scripts with uBasic commands as follows :-

shutter_speed 15
shutter_speed 1/125
aperture 3.5

and the script I am testing is :-

shoot_fast_at  1/4000    (!)


What I am saying is, if you display the DELTA_SV propcase on my S95 it is always zero, it never changes.

Does it change on your camera ?


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Offline lapser

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Re: Using APEX values to compute exposure
« Reply #12 on: 23 / January / 2013, 22:50:56 »
What I am saying is, if you display the DELTA_SV propcase on my S95 it is always zero, it never changes.
Does it change on your camera ?
It may only be valid when get_shooting() is true (shooting_in_progress()!=0). Yes, DELTA_SV and SV procases both hold data, and seem to return what you stored in them. That's why this works to set the SV:

set_prop(pDELTA_SV,sv-get_prop(pSV)+get_prop(pDELTA_SV))

I'm saying that having multiple functions to set sv96, tv96, and av96 using there linear equivalents is confusing. You can only change exposure with an APEX96 value, so why not have a conversion function separate from the exposure function.
EOS-M3_120f / SX50_100b / SX260_101a / G1X_100g / D20_100b
https://www.youtube.com/user/DrLapser/videos

 

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