Malcolm_Stewart
Pooh-Bah
Reged: 11/07/2005
Posts: 2248
Loc: Milton Keynes, UK
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There's an interesting thread over at UK Bird Photographers comparing graphically the noise from, so far, mainly Canon DSLRs. I don't know how the wizardry works, but for those of us keen to have the lowest noise in our images, it seems best to stick to "natural" ISO settings, viz. 100, 200, 400 etc.
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Malcolm Stewart
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bdr2
member
Reged: 12/03/2007
Posts: 137
Loc: Hampshire
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Yes, but it's only true up to ISO 800. I know John and he's a bit of a wiz at this sort of thing so I have no reason to doubt his word!
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Claire
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daft_biker
Action Man!
Reged: 11/10/2006
Posts: 6976
Loc: Doon the glen
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I'm not sure what practical purpose this has. Keeping the ISO as low as possible still works for me.
If I need ISO 500 or 640 because 400 isn't enough it's still better than shooting at 800 for example. Would Canon include them in the ISO range by default for any other reason?
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Andrew (BSRIPN) ... Pics.
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bdr2
member
Reged: 12/03/2007
Posts: 137
Loc: Hampshire
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Andrew,
I think that's the point. What the thread is saying is that ISO 640 actually produces significantly more noise on both the 5D and 1DMkIII than ISO 800 does. In the case of ISO 500, it just has the edge over ISO 800. Above this, then the in-between ISO's seem to work OK - below and they are significantly worse then the next native ISO.
I don't know how this translates to other cameras in Canon's range, or even if it's noticable in real-life images, but it's certainly an interesting effect.
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Claire
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daft_biker
Action Man!
Reged: 11/10/2006
Posts: 6976
Loc: Doon the glen
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I can't say I've noticed but I do intend on giving it a go on my 40D.
If it does turn out to be the case I think it begs the question as to why Canon include the 'less desirable' ISO settings by default. Another useless gimick? (they must have nicked the idea from Olympus    )
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Andrew (BSRIPN) ... Pics.
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kevin_c
newbie
Reged: 16/06/2008
Posts: 11
Loc: Dorset
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I've heard this comment about the 1/3 stops previously, I can't prove it on my 20D cos it only has full stop selections 
The reason they started putting 1/3 stop ISO's on DSLR's is twofold IMO:
1 - to give you the chance of accurately altering exposure using the ISO - if you want a particular shutter speed/aperture combo you effectively have ISO priority.
2 - A sales/marketing ploy to 'give you more' when you purchase xyz model of camera.
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-- Kevin --
Canon and Nikon, Digital and Film
Edited by kevin_c (16/06/2008 17:43)
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Northerner
enthusiast
Reged: 23/01/2006
Posts: 341
Loc: Sydney, Oz (ex. Manchester)
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Interesting. I'd have never thought that this would be the case - I guess it's similar to odd viewing percentages in photoshop (as a very rough analagy?!) being jaggy?
There is a setting in my 40D to not allow selection of these 'in-between' ISO settings and I have that selected by default. IE - when I flick though the ISO I only get 100/200/400... as options.
I agree with kevin though - it's no doubt a marketing ploy to a certain extent.
Graham
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Nic and Graham's photo site...
Edited by Northerner (17/06/2008 07:52)
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AGW
Reged: 03/10/2003
Posts: 7566
Loc: Ayrshire
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Strikes me as the sort of issue that Canon could address through a firmware upgrade...if people made it a big enough issue...which I would doubt..
Graeme
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AGW (BSRIPN)
Blessed are they who see beautiful things in humble places where others see nothing. (Camille Pissarro)
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beejaybee
Marvin
Reged: 18/07/2007
Posts: 4245
Loc: Really Here In Name Only
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Quote:
There is a setting in my 40D to not allow selection of these 'in-between' ISO settings and I have that selected by default. IE - when I flick though the ISO I only get 100/200/400... as options.
Me too ... not on IQ grounds but on the simple basis that the ISO settings I use most are at the extremes, and setting "ISO speed setting increments" to 1 stop instead of 1/3 stop speeds up the process.
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kevin_c
newbie
Reged: 16/06/2008
Posts: 11
Loc: Dorset
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I come from a film background, and apart from a few odd ISO's (Ilford FP4,'Portra' type films and Kodachrome) I only ever 'think' in terms of 100,200,400,800 ISO etc.
I wouldn't normally think of adjusting the ISO to adjust exposure unless it is obviously wrong for the light.
As I said before, my 20D won't allow me to have anything else - Maybe I'm too set in my ways... 
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-- Kevin --
Canon and Nikon, Digital and Film
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Benchista
Wich Tyler
Reged: 11/08/2000
Posts: 36432
Loc: Everywhere and nowhere, baby
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This story has been knocking around for some time now. Must say I've never really noticed the difference, but as a matter of course I generally stick to "familiar" settings anyway. The only one I regularly use that's not in the normal progression is 1000, as it often adds a little extra flexibility for a lot less noise with the 5D.
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Nick
www.nbrphoto.com
Light and Shade II - the new blog
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