ISO 50 vs 100

mikepj 9:13pm, 4 December 2012
I'm trying to find the best ISO to use on my 5D Mark II while taking shots with optimal light (or a tripod).

Does anyone know if ISO 50 provides any additional image quality benefit over using ISO 100? My thought is that it wouldn't be an "extended ISO" unless there was some form of drawback to using it. But that's counter to the usual rule that lower ISO is better.
Yorkshire Pics PRO 6 years ago

this probably won't be helpful but i use 50 whenever i can, it's handy if you want a longer exposure, i'm not sure about the noise difference though.
HJSP82 6 years ago
At iso 50, the dynamic range is reduced a bit. Try iso 160.
ScudMonkey PRO 6 years ago
I believe that ISO50 is not a "natural" sensitivity but is digitally expanded and loses some highlight range; I stick to ISO100 s far as possible. I know on Nikons ISO160 is the sweet spot but I'm not sure if this also applies to Canon .... ?
guille2306 6 years ago
If I recall correctly, on Canon cameras ISOs other than 100, 200, 400, ... 3200 (limit for the 5D II) are software based. If this is correct, putting ISO 50 on the camera would be exactly the same than adding +1 exposure to the RAW file on post-production (before converting it to 8bit data).

The problem is that now I can't find the place I read that, so take it with a pinch of salt...
guille2306 6 years ago
Not the reference I was looking for, but an interesting read on the source of noise on digital photography:
guille2306 6 years ago
DxOMark test of the sensor shows clearly that ISO "50" and "100" have the same sensitivity, wich means that "50" is just a software order given to the program that process the RAW file.

(on the other hand it also shows that the high-ISO exended values are "real", hardware based)
iso 50 isn't really about image quality but more like being able to shoot say flash outside at 2.0 1/200 of a second rather than 2.0 1/400 a second.

It's that extra half stop that makes it muy beuno.
marked texture [deleted] 6 years ago
Where is the half stop? 50 to 100 is a full stop and so is 1/200 to 1/400...
mikepj 6 years ago
Thanks for the feedback everyone. Those articles look pretty interesting, I'm going to have to set aside some time to check them out.

I've heard that ISO 160/320/640/etc produce less noise than 200/400/800/etc, but you lose dynamic range in the "software" conversion. So I suppose even using those ISOs isn't a clear cut win. It just depends on whether your image needs low noise or the maximum dynamic range.

But as far as answering the original question, It sounds like the consensus is to use 100 ISO unless I need to slow down the shutter a little bit.
Hbie 6 years ago
I would use 100 if you can. I use 50 ISO if I want a longer exposure.
Lee|Ratters 6 years ago
^^^ I try to use 100 if I can but otherwise just select whichever I need without really worrying about it. If I need higher for faster shutter I will & I only really use 50 for ND110 shots to extend the exposure time.
Ian H's 6 years ago
On a 5D2 you know what I don't really care if I'm using 100, 200, 400 ( or even 50). The output quality in real terms is good enough for me in those ranges. Most people, being honest, and even printing out at large canvas size wouldn't notice any real difference.

Sure if you spend your life "testing" and not taking pictures as some people do it might bother you.

Why I don't think much of going up to 1600 if I have to, although from here on up you can see IQ become progressively lower with less Highlight and shadow detail and also loss of colour saturation.
Paul Lender:

Yep my bad. But I'm sure you feel better correcting me. :)
archiescat PRO 6 years ago
ISO 50 is a software pull from 100..... but the canon brain does a good job nonetheless
Hbie 6 years ago
It is also 30secs to 1 minute.
Hbie 6 years ago
One problem with "extended ISO" is on dark images like night or long exposures the liveview image will be more noisy than with it off.
Roy Levi 6 years ago

Although strangely, on the 5D2 I find that ISO 5000 gives less noise than both ISO 6400 and more amazingly ISO 3200, most of the time.
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