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True 'Auto ISO' in G Series "M" Mode?

  • 13 Replies
Re: True 'Auto ISO' in G Series "M" Mode?
« Reply #10 on: 25 / June / 2012, 23:46:23 »
The closest I can get to that is using Tv that allows for higher shutter speeds for birds in flight or action if need be.
Or, if you are up for it,  write a Lua / uBASIC script to do exactly what you want. 

I'm curious - what does "True Auto ISO" in manual mode mean to you?  You set the shutter speed and aperature / ND filter values and the camera adjusts ISO to get the right exposure ?

lol - yeah - lets say "Auto ISO in Manual Mode" (reason I say "True", below)

I must confess - the directions for setting Custom Auto ISO befuddles me...
Can someone please help me set my G12's Auto ISO limit to 3200 please? I just don't get it...
I want my shutter to often remain at 1/1600th so I need that upper ISO limit for overcast days (reason below)

  - I prefixed with a "True" because my Canon 50D said Auto ISO in Manual mode when if fact it remained ISO 400 - always. Then my 60D - comparatively - DID have "True" Auto ISO available as an option - meaning all settings manual - but you had an option for Auto ISO if you choose.

Then I got the G12 and when I saw that "Auto ISO in Manual mode" actually meant "ISO 80" (!!!) - it was a throw-back to my disappointment with the 50D. So... I love "True" Auto ISO in Manual Mode - but there does not seem to be the demand by the masses for it to be a feature in CHDK. And it beats the heck out of me how to write uBasic scripts ;-) ... who could I approach/sweet-talk?

I am a wildlife photographer primarily, and for birds in flight (BIF) I like to keep my shutter on my DSLR between 1250-2500, and my aperture between f/6.3 to f/9. Add to that the fact that when tracking a bird in flight the background is always changing - thus giving different exposures - thus my desire for Auto ISO to come to the rescue.

Of course - such action photos are demanding even for a DSLR - and all the more a challenge for the G12. I could not hope to get the same quality of focus or exposure using the G12 vs a DSLR - but I know the convenience of Auto ISO - and it ... ticke me off, shall we say, that Canon purposely crippled Auto ISO in M Mode on the G12, and so many other models - when its one of the most practical & convenient tools to have for action shooting.

In the mean time, I use Tv mode with Auto ISO set up to 1600 and my shutter typically at 1250-1600. I have to have faith/hope that the aperture 'wildcard' which the G12 chooses in Tv will have enough depth of field (DOF) for me to get enough of my subject in focus when I do not have my DSLR handy.

Re: True 'Auto ISO' in G Series "M" Mode?
« Reply #11 on: 26 / June / 2012, 01:22:19 »
Seems like a script can be most usefull here. You can reasemble the same logic that I used in my autoesposure intervalometer:

but you'll need to calculate ISO instead of Tv (which I did).

The most important part of the code:

Code: (lua) [Select]

--we calculate and set new Tv (from APEX definitions)

you'll need to calculate Sv from the same formula, so it'll become (if I'm correct):

Code: (lua) [Select]

Before calling these you'll need to do half-press shutter in script. That's not very convenient, since your script must go through these stages:

- press("shoot_half") untill get_shooting() become true (takes time - 1-2 s)
- recalculate exposure settings
- shoot()

With such logic your script will read the Tv/Av you have set manually and set ISO depending on the scene light. Of course you could add some corrections for your script logic.
« Last Edit: 26 / June / 2012, 01:24:06 by outslider »
if (2*b || !2*b) {

Compile error: poor Yorick

Re: True 'Auto ISO' in G Series "M" Mode?
« Reply #12 on: 28 / June / 2012, 01:45:40 »
Thanks so much for this detailed reply. I know nothing of writing/editing scripts so I would have to wait/hope for someone to test it, etc.


Re: True 'Auto ISO' in G Series "M" Mode?
« Reply #13 on: 28 / June / 2012, 02:37:20 »
If you are going to use CHDK a lot it would be good to learn scripting. It's not difficult and you can do a lot of usefull (or strange) things with camera ;)
if (2*b || !2*b) {

Compile error: poor Yorick


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