which gives less noise - underexposing or increasing ISO?

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em3

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Hi,
For natural light photography indoors, where you can't always be near a window and need a minimum speed of 1/250, would you tend to underexpose (and fix in post) or push up the ISO? I'm experimenting to figure out which has the best results in terms of the least noise, and would love to know what others tend to do. Aperture is wide open of course. And I'm thinking for portraits.
Thanks so much.
 
Up the ISO, sometimes helps to dial in some + exposure comp
 
I've always found it better to up the ISO. Bumping exposure in post always seems to introduce more noise ime.
 
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There are two points here and it may be tricky to choose the lesser evil!

HIGH ISO is a pre shutter strategy to boost or extend the nominal sensitivity
of the sensor. Makers are very serious at approaching this through clever on
board software to achieve the task. Sometime with impressive solutions like
in the bodies I use every day. There are limits to this and it is of your interest
to find out those of the body/bodies you use.

As it was/is with film, UNDEREXPOSING is a post shutter strategy where one
will want to extract from the medium, film of data files, information that is non
existant. Such chemical or digital processing will produce their respective non
negligible artifacts.
 
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Its an easy enough experiment. Stick it in manual and shoot a control with the "correct" exposure, next up the iso and stop down to get the same exposure with a range iso settings, finally set back to that control shot and fix the iso and stop down to get an range of progressively more underexposed shots and try to recover them. If you use full stops you should be able to compare what is least intrusive for your needs.

I presume you're photographing people with a very long lens? Otherwise you might be better getting a tripod.
 
Yes, a very easy experiment. And upping the ISO will win, usually by a country mile. When you're on the limit exposure-wise, it's tempting to try and under-expose a bit, get a higher shutter speed or whatever and pull it all back in post-processing, but actually, if you bite the bullet at the time of taking and just crank up the ISO, you'll get a better result.

It's because ISO gain is applied pre the analogue to digital conversion and it's just much better at it. However, that may be changing. Digital sensors are essentially ISO-less, in theory, so you should be able to get the same result either way. That's not quite happening yet but Sony is making impressive progress. Rishi Sanyal on DPReview has written a lot about this.
 
The best approach I ahve found is ...High ISO and expose to the right 1/3
 
thank you everyone. i'll experiment with going to the right too. much appreciated.

(a tripod isn't an option as i'm running around after children!)

(canon 6d with 50mm 1.4)
 
HoppyUK said:
It's because ISO gain is applied pre the analogue to digital conversion and it's just much better at it. However, that may be changing. Digital sensors are essentially ISO-less, in theory, so you should be able to get the same result either way. That's not quite happening yet but Sony is making impressive progress. Rishi Sanyal on DPReview has written a lot about this.
Click to expand...

I was going to mention this as it depends on the camera. The tests done with the Sony a7 series are very impressive, there is almost no penalty to shooting at say, ISO100 all the time, and boosting all the way to the equivalent of ISO6400 in post. In practical terms this is best with the likes of the a7RII anyway as you will still be able to see something in the EVF.
 
remember high iso doesn't just add noise but lowers contrast and colour information too
 
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