# On what relies "auto" for "Min. shutter spd." in 5D Mark III's auto-iso ?



## Deleted member 68328 (Oct 1, 2012)

Hello,

I've read the 5D Mark III's manual, but haven't found the answer to my question.

When you set "Min. shutter spd." to "auto" in the auto-iso menu of the 5DIII, on what does it rely ? Does it rely on the 1-over-the-focal-length rule ? 

Thank you.

Cheers,


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## neuroanatomist (Oct 1, 2012)

yoms said:


> When you set "Min. shutter spd." to "auto" in the auto-iso menu of the 5DIII, on what does it rely ? Does it rely on the 1-over-the-focal-length rule ?



Yes, it relies on the 1/focal length rule up to the specified max ISO setting, then starts dropping the shutter speed lower. Lens image stabilization is not taken into account.


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## Deleted member 68328 (Oct 1, 2012)

neuroanatomist said:


> yoms said:
> 
> 
> > When you set "Min. shutter spd." to "auto" in the auto-iso menu of the 5DIII, on what does it rely ? Does it rely on the 1-over-the-focal-length rule ?
> ...



Many thanks Neuro ! DPR was a bit disappointed by the setting (I guess when compared to D800), but it turns out to be good enough for my purpose.

Cheers,


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## neuroanatomist (Oct 1, 2012)

Glad to help. Just to add for any APS-C user who happen to be reading this thread, the crop factor is taken into account, so for example in Av mode on a 7D with a 100mm lens, the camera would keep the shutter at 1/160 s to as high an ISO as possible. 

That behavior is the same as bodies which do not feature a minimum shutter speed in Av mode setting.


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## pierceography (Oct 1, 2012)

neuroanatomist said:


> Glad to help. Just to add for any APS-C user who happen to be reading this thread, the crop factor is taken into account, so for example in Av mode on a 7D with a 100mm lens, the camera would keep the shutter at 1/160 s to as high an ISO as possible.
> 
> That behavior is the same as bodies which do not feature a minimum shutter speed in Av mode setting.



This is great info. Thanks for explanation for crop bodies... I never directly noticed this, but it makes perfect sense.


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## neuroanatomist (Oct 1, 2012)

neuroanatomist said:


> Lens image stabilization is not taken into account.



I think I may need to re-test this on my 1D X. From previous testing, IS didn't matter on the 7D or 5DII, but I just looked at a shot in Av mode with Auto ISO, and using the 70-200mm f/2.8L IS II at 200mm, the camera selected 1/60 s and ISO 125, and similarly a shot with the 100-400mm at 400mm had 1/125 s and ISO 320. Both are well below 1/focal length. 

So...now, I'm not sure if the lower limit is just picked differently on the 1D X, differently on cameras which allow a min shutter speed in Av selection, or is actually taking IS into account.


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## AudioGlenn (Oct 1, 2012)

Interesting info. I feel I can't trust the metering in my 60D in Av in lower light situations. I'm shooting in manual 90% of the time now. Even with a flash connected, the shutter speeds my camera picks in Av are waaaaaaay to slow and i always end up with a missed/blurry shot.


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## bbasiaga (Oct 1, 2012)

AudioGlenn said:


> Interesting info. I feel I can't trust the metering in my 60D in Av in lower light situations. I'm shooting in manual 90% of the time now. Even with a flash connected, the shutter speeds my camera picks in Av are waaaaaaay to slow and i always end up with a missed/blurry shot.



Rember in Av mode with flash, the camera is metering the shutter speed for a proper exposure of the background. So essentially, it assumes the flash will not have an effect on the background, only the closest objects. Av mode is not good for hand held flash stuff. IMO. I always use manual with flash, whether I'm using the flash in ETTL or manual mode. 

-Brian


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## neuroanatomist (Oct 1, 2012)

bbasiaga said:


> AudioGlenn said:
> 
> 
> > Interesting info. I feel I can't trust the metering in my 60D in Av in lower light situations. I'm shooting in manual 90% of the time now. Even with a flash connected, the shutter speeds my camera picks in Av are waaaaaaay to slow and i always end up with a missed/blurry shot.
> ...



Yep. In the flash control menu (on the camera) there's a setting for the flash speed used in Av mode. Default is auto, that will meter for background, which usually results in a very slow shutter. There are also options for 1/60 s - X-sync (1/200, 1/250, or 1/300 depending on body), and fixed at the X-sync. So, if you want a faster shutter in Av, use one of the other options.


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## buzz (Oct 1, 2012)

neuroanatomist said:


> Glad to help. Just to add for any APS-C user who happen to be reading this thread, the crop factor is taken into account, so for example in Av mode on a 7D with a 100mm lens, the camera would keep the shutter at 1/160 s to as high an ISO as possible.
> 
> That behavior is the same as bodies which do not feature a minimum shutter speed in Av mode setting.



I think it is unique to 7D and may be 60D.

For the rest of of APS-C cameras the min shutter speed is set to 1/60 I believe.
I shoot with T2i and camera chooses 1/60 as shutter speed when I am at 250mm.


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