1/3 stops in ISO

Started by NunoAlmeida, August 25, 2012, 12:08:18 AM

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NunoAlmeida

August 25, 2012, 12:08:18 AM
What are the advantages of using 1/3 stops in ISO for example in 60d over 600d?
Thanks!

nanomad

#1
August 25, 2012, 12:16:46 AM
It all depends on how they are obtained.
Canon cameras have two kind of ISO:
- "Native ISOs" (or Full stops)
- "Digital ISOs" (1/3 or 1/2 stop)

Digital ISOs are obtained from Native ISOs by applying a positive (-> more noise) or negative ( -> clipping) gain. IIRC this happens before saving the picture into .CR2 or .JPG

A1ex definitely knows more than me on this subject though.
An interesting read that should help you decide what ISO value is good for you: http://magiclantern.wikia.com/wiki/ISO
EOS 1100D | EOS 650 (No, I didn't forget the D) | Ye Olde Canon EF Lenses ('87): 50 f/1.8 - 28 f/2.8 - 70-210 f/4 | EF-S 18-55 f/3.5-5.6 | Metz 36 AF-5

NunoAlmeida

#2
August 25, 2012, 12:27:52 AM
So the best thing to do is to use full stops right?... ;)

nanomad

#3
August 25, 2012, 01:01:12 AM
In photo mode, yes

In video mode you should prefer ML ISOs
EOS 1100D | EOS 650 (No, I didn't forget the D) | Ye Olde Canon EF Lenses ('87): 50 f/1.8 - 28 f/2.8 - 70-210 f/4 | EF-S 18-55 f/3.5-5.6 | Metz 36 AF-5

NunoAlmeida

#4
August 25, 2012, 03:02:18 AM
Ok Thank you. but for example in Canon EOS 60d if i choose the iso to 160 is it digitally gained?

Francis

#5
August 25, 2012, 08:55:51 AM
Yes, ISO 160 is achieved with digital gain. In this case it will be negative digital gain. The base ISO would be 200 and ML will apply a negative gain of -0.3EV to achieve ISO 160.
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