Auto ISO

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BeeJayEff

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85
Name
Bernard
Edit My Images
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If I leave ISO on auto, and use aperture priority, how does the camera decide what combination of shutter speed and ISO to use for its preferred exposure ? Or similarly using shutter priority how does it decide which aperture and ISO to use ?
 
Usually, you set the minimum shutter speed you want in the menu system. The camera will then keep the iso as low as it can until it can no longer achieve that minimum shutter speed. At that point, it will up the iso.
 
Depends on the camera, on a Canon I tend to shoot in M with chosen shutter speed, chosen aperture and iso set to auto, you can limit the maximum iso from the function menu's.
 
sharpcroft said:
Depends on the camera, on a Canon I tend to shoot in M with chosen shutter speed, chosen aperture and iso set to auto, you can limit the maximum iso from the function menu's.
Click to expand...

What is the difference between cameras?
 
It will also depend Bernard on what metering method you are using, and also what lens you have on and at what focal length you are using. The camera can only work out any pre programmed calculations with the amount of light that it receives.
 
I would have though like most auto modes a camera has in deciding whats the best setting, It will decide whats the best ISO so as to have a average shutter speed. Probably something like 1/60 where it would be fairly resonable to be hand held?
 
The camera will use a fairly simple calculation, the problem is you don't know what the calculation is!
On some cameras you can influence the calculation - max ISO, min shutter speed etc,. but still no way of knowing the actual algorythms. Just have to hope someone with common sense has coded them (which they would have)
 
on a Canon I tend to shoot in M with chosen shutter speed, chosen aperture and iso set to auto, you can limit the maximum iso from the function menu's.
Click to expand...

How can you set the max ISO on a 7D please? never found that setting although I have on my daughters 550D and could on my old Pentax
 
Last edited:
tijuana taxi said:
How can you set the max ISO on a 7D please? never found that setting although I have on my daughters 550D and could on my old Pentax
Click to expand...

Ah, yes you are right, the limit option seems to have disappeared from the 7d menu though it was present in earlier canon models? you can still disable expanded iso though.

Darren
 
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