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What ISO?

ckristoff 13 994 Wales
28 Aug 2008 1:21PM
Can you help me please?

Before I received my 450D, I bought Andy Rouse's book
" Understanding Raw Photography ".

In the book he advises using 200 ISO, rather than 100 ISO.
Would he be right, or is that just ' his ' opinion?

Anyway, would using 200 ISO be better than 100 ISO on my 450D?


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conrad 13 10.9k 116
28 Aug 2008 1:30PM
I'd be interested to know what reason he gave. Maybe because it enables you to use shorter shutter speeds?

Normally you go as low as you can with ISO in order to prevent noise.

But there's nothing wrong with going to 200 if that gives you the shutter speeds you need.
lobsterboy Plus
14 14.9k 13 United Kingdom
28 Aug 2008 1:33PM

Quote:In the book he advises using 200 ISO, rather than 100 ISO.
Would he be right, or is that just ' his ' opinion?

Really? does he give a logic for that?

Quote:Anyway, would using 200 ISO be better than 100 ISO on my 450D?

ISO is part of the "exposure triangle" (aperture, shutter speed, iso) so it depends on the amount of light, your subject, tripod use and what you are trying to achieve.
I can recommend the book understanding exposure to help get to grips with this.
John_Frid 12 514 57 United Kingdom
28 Aug 2008 1:35PM
My general rule has always been to use the lowest ISO setting I can for the shutter speed/aperture I want. However, the difference between 200 ISO and 100 ISO is probably almost indistiguishable (at least to the average viewer).

As predominantly a wildlife photographer, Andy Rouse probably wants to be able to keep the shutter speed up to freeze action, so for his needs 200 ISO is probably a sensible setting.

stuwhitt 13 1.4k United Kingdom
28 Aug 2008 1:35PM
Not so long ago selecting the lowest possible ISO setting would have meant less noise and 100 ISO could be argued offered the best image quality, however with the latest crop of DSLR's noise is less of an issue so it in reality from a quality point of view it doesn't make much difference anymore.
Its best to select an ISO setting that suites the conditions at the time, ie less light = higher ISO, more light = lower ISO, you may also want to use a higher ISO to be able to select a higher shutter speed to help freeze action or get a sharper image, likewise if you want a longer shutter speed eg to shoot milky water then you may want to lower the ISO to slow the shutter right down
NikLG 12 1.7k England
28 Aug 2008 1:39PM
Doesn't Andy Rouse use Nikon gear ? I seem to remember that some Nikon's have ISO 200 as the lowest setting... ( D70 was anyway, and the D2H ). Maybe that's what he means ( ie the lowest setting is the better... )
Coleslaw 12 13.4k 28 Wales
28 Aug 2008 1:42PM
He is using Nikon now...but he was probably using Canon when he wrote the book.
User_Removed 16 7.3k 6 United Kingdom
28 Aug 2008 1:43PM
The notion of 'iso' with a digital camera is an arbitrary one anyway as it's simplify a way of creating parallel with film.

With many cameras, ISOs below 200 are 'artificially' created in the camera by the software rather than being a straight function of sensor sensitivity (much as high iso's are as well).

It may well be that this is the reason for his comment
MikeRC Plus
13 3.6k United Kingdom
28 Aug 2008 1:55PM
User_Removed 15 455 13 United Kingdom
28 Aug 2008 2:06PM
I don't really have much to add in terms of the question - I also always aim for the lowest ISO but will go for higher if after a fast moving wildlife subject, especially if hand-holding.

It does irritate me though, when books make such statements without any explanation of the reasoning behind them. I'd rather have the information to make my own decisions.

ade_mcfade 14 15.2k 216 England
28 Aug 2008 2:13PM
in the "triangle" mentioned above, think of a photo as a full glass of water

Aperture is how fast the tap water is running - the "flow"
Shutter speed is how long you leave the tap under the water
ISO is the inverse of the volume of the glass

This was brought up on another forum I've used, and people were all a bit o_O when I answered.

All the manufacturers were using 'ISO', meaning the seal of approval of the International Organization for Standardization, to give some similarity to the good ol' days of film, but none of it was actually monitored. So the Organization for International Standardization came along, and said to the manufacturers that were using 'ISO' for their sensor sensitivity, if you're going to use it, you have to standardize it. So the standard was set, and that was ISO 200. All the cameras have to perform to a certain standard, and ISO200 has to be the bench mark for performance tests and the such like.

So with all the cameras using LO1 and such, which takes you to an equivalent of 100, and with some Canons that have ISO 50, you wont see any marked IQ improvements.
Normally it'll degrade the images in some way. Normally loss of dynamic range, sometimes loss of clarity.

Like Barrie said, alot of it's down to the cameras firmware and image processor. The D3/D700 Sony sensor achieves such low noise cause of a great sensor, but also cause Nikon went all out on their A/D conversion firmware.

Disclaimer -
I've read most of this from various places on the interweb over some time, so don't hold me to it. But it does seem to be the case.

I have my D200 set at ISO200, and only really stop down to 100 if its too bright and I need a longer shutter speed, and cant be bothered to get more filters out.

ISO100 may look like it has less noise, but really the image is more then likely just smoothed in the camera with its noise reduction firmware, like high ISO are, hence the loss of clarity in fine detail structure.

Hope that helps,
And doesn't melt your brain =D
keith selmes 14 7.4k 1 United Kingdom
28 Aug 2008 4:09PM
Wikipedia says - its too complicated - lots of funny maths in it.
ade_mcfade 14 15.2k 216 England
28 Aug 2008 4:23PM
.....surely all you need to know about ISO on a digital platform is that higher ISO's bring down your shutter speeds, lower ISO's increase them.

A practical example I encounter at weddings when shooting candids...

If you want to hand hold a 100mm lens, but the light only gives you, say, 1/25th @ F2.8 & ISO 100, you're risking a wobble and blurred shot.

Keeping tha aperture at f2.8........

up the ISO to 200 you get 1/50th - better
up to ISO 400 it's 1/100th - about right!
ISO800 and you're at 1/200th and you can't really go wrong Wink

If there's more to it, on digital, then don't know about it.

Film... who cares any more Wink reciprocity failure etc. - PAH! Wink
User_Removed 16 7.3k 6 United Kingdom
28 Aug 2008 4:25PM
Or use a Nikon and AutoISO - even easier Wink

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