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Author Topic: 5D MK 3 and auto ISO  (Read 5827 times)

EvilTed

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5D MK 3 and auto ISO
« on: April 30, 2012, 10:57:11 AM »
I would have thought that the 'A' setting for ISO = Auto meaning that the camera picks the best ISO setting for the given conditions.

I tried shooting a 50 F/1.2 @ 1.2 indoors in dim light yesterday and it didn't seem to work as I'd thought.
Everything was underexposed and the historgram was heavily peaked to the left.

If I manually set the ISO to 1600 or above, thing were as edxpected.

What gives?

ET

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5D MK 3 and auto ISO
« on: April 30, 2012, 10:57:11 AM »

neuroanatomist

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Re: 5D MK 3 and auto ISO
« Reply #1 on: April 30, 2012, 12:09:50 PM »
In Shooting Menu 2, there's a setting to select the range for Auto ISO - you might want to check that setting.  Also, did you have a flash attached?  If so, the ISO is fixed at 400.
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PhilDrinkwater

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Re: 5D MK 3 and auto ISO
« Reply #2 on: April 30, 2012, 12:10:30 PM »
What setting were you using? (Manual, Aperture Priority, Shutter Pri)?

What was Exposure Compensation set to? Was there a light or window in the distance?

PhilDrinkwater

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Re: 5D MK 3 and auto ISO
« Reply #3 on: April 30, 2012, 12:11:17 PM »
In Shooting Menu 2, there's a setting to select the range for Auto ISO - you might want to check that setting.  Also, did you have a flash attached?  If so, the ISO is fixed at 400.

Ahh they're good points too.

h4ldol

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Re: 5D MK 3 and auto ISO
« Reply #4 on: April 30, 2012, 12:47:03 PM »
I tried shooting a 50 F/1.2 @ 1.2 indoors in dim light yesterday and it didn't seem to work as I'd thought.

Were you by chance shooting with the lens cap on?  On in the dark with an exposure of less than 2 minutes?  If so, you might have been experiencing the infamous LCD light leakage issue that people have been up in arms about recently.

awinphoto

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Re: 5D MK 3 and auto ISO
« Reply #5 on: April 30, 2012, 01:02:45 PM »
As others have said, if shot on the Av, Tv, or P modes, check exposure compensation.  With flash, on auto ISO you are locked at 400 which also may throw you off.  Also check your min shutter settings as that may have some bearing if your not getting enough light and the ISO's and shutters max out...
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VirtualRain

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Re: 5D MK 3 and auto ISO
« Reply #6 on: April 30, 2012, 01:08:53 PM »
What metering mode?  What subject?  What focus point?  Sample photos?  These are all necessary bits of information before anyone can possibly diagnose your problem. 

My wild-ass guess is that you're focusing and metering (in evaluative mode that emphasizes the focus point) on something bright (a natural thing to do in low light) thereby forcing an underexposure. 
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Re: 5D MK 3 and auto ISO
« Reply #6 on: April 30, 2012, 01:08:53 PM »

Jamesy

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Re: 5D MK 3 and auto ISO
« Reply #7 on: April 30, 2012, 03:43:26 PM »
As others have said, if shot on the Av, Tv, or P modes, check exposure compensation.  With flash, on auto ISO you are locked at 400 which also may throw you off.  Also check your min shutter settings as that may have some bearing if your not getting enough light and the ISO's and shutters max out...
I never shot my 40D in auto-ISO but I really like the feature on the 5D3. Did other Canon DSLR's default to ISO400 too, when a flash was affixed to the camera? I would like to be able to have the option of having a range beyond 400 in AutoISO on the 5D3.

EvilTed

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Re: 5D MK 3 and auto ISO
« Reply #8 on: April 30, 2012, 03:49:31 PM »
and the prize goes to....

VirtualRain

AV, Evaluative Metering, Single point AF (2nd one).

Question is why the camera cannot figure it out correctly, when forcing the ISO manually does?

Cheers

ET

neuroanatomist

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Re: 5D MK 3 and auto ISO
« Reply #9 on: April 30, 2012, 03:51:53 PM »
Did other Canon DSLR's default to ISO400 too, when a flash was affixed to the camera? I would like to be able to have the option of having a range beyond 400 in AutoISO on the 5D3.

Yes, they do.  Unlike many previous bodies, when bouncing the flash on the 5DIII, Auto ISO sets from 400-1600 (that's true on the 7D as well, but not the 5DII where it's always 400).  Note also that in most older cameras, setting Auto ISO in M mode also fixed the ISO at 400 (and still does in Bulb mode).  Obviously, all of that applies only to Auto ISO - you can dial in whatever ISO you want if you set it manually.

AV, Evaluative Metering, Single point AF (2nd one).

Question is why the camera cannot figure it out correctly, when forcing the ISO manually does?

Because evaluative metering is weighted toward the selected AF point, meaning the brightness of that point is given greater weight than the rest of the scene in the metering decision so if you have the AF point on a bright spot the camera will reduce the exposure to compensate.
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awinphoto

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Re: 5D MK 3 and auto ISO
« Reply #10 on: April 30, 2012, 04:04:06 PM »
The 7d was the first camera, well maybe a touch with the 50D, where I played with auto ISO...  If you have a flash, AUTO iso locks in at 400, unless you are bouncing it as neuro said.  If your in manual and manually set your ISO, you can go over 400 ISO if you wish, but that's the only work around is to manually do it.  I personally think that's a slight pain but considering the whole ISO image quality/light output/strength of flash depending on ISO value, I guess that's just one extra computation the camera, or canon engineers, didn't want it to have to choose between. 
Canon 5d III, Canon 24-105L, Canon 17-40L, Canon 70-200 F4L, Canon 100L 2.8, 430EX 2's and a lot of bumps along the road to get to where I am.

EvilTed

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Re: 5D MK 3 and auto ISO
« Reply #11 on: April 30, 2012, 08:21:56 PM »
BTW, why would anyone shoot hand held with a 1.2 lens in dim light and use a flash?
Feels like washing your feet with your socks on to me?

ET

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Re: 5D MK 3 and auto ISO
« Reply #12 on: April 30, 2012, 09:01:14 PM »
BTW, why would anyone shoot hand held with a 1.2 lens in dim light and use a flash?
Feels like washing your feet with your socks on to me?

ET

Really? So you can balance your flash to the ambient light and capture a more natural photo. The flash helps freeze the motion. I do it ALL the time at dark wedding receptions.
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Re: 5D MK 3 and auto ISO
« Reply #12 on: April 30, 2012, 09:01:14 PM »

jm345

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Re: 5D MK 3 and auto ISO
« Reply #13 on: April 30, 2012, 11:08:25 PM »
According to my 5D3 Manual on page 125 it says with bounce flash it will automatically use the 400-1600 ISO range when you are in P or A+ Modes.

Bosman

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Re: 5D MK 3 and auto ISO
« Reply #14 on: May 02, 2012, 01:57:07 AM »
BTW, why would anyone shoot hand held with a 1.2 lens in dim light and use a flash?
Feels like washing your feet with your socks on to me?

ET

Really? So you can balance your flash to the ambient light and capture a more natural photo. The flash helps freeze the motion. I do it ALL the time at dark wedding receptions.
+1 Flash give color pop! just use flash as fill even in dim situations.
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Re: 5D MK 3 and auto ISO
« Reply #14 on: May 02, 2012, 01:57:07 AM »