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What ISO?

User_Removed 14 17.9k 8 Norway
28 Aug 2008 6:08PM

Quote:I'd be interested to know what reason he gave.

I read somewhere that he uses 200ISO because (for his work Wink) the noise difference is non-discernible and you a one-stop gain in shutter speed without trying.

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ckristoff 13 994 Wales
28 Aug 2008 7:45PM

thank you all so much for all your replies, I've been out most of the afternoon. Smile

I haven't got the book to hand, but I believe one of Barrie's comments makes sense.

User_Removed 16 7.3k 6 United Kingdom
28 Aug 2008 7:47PM

Quote:I believe one of Barrie's comments makes sense.

There's a first (I thought I'd say it before anyone else did) Wink
csurry 16 9.2k 92
28 Aug 2008 7:53PM
I've heard that from other wildlife pros as well including the likes of Mark hamblin. The thinking being that the quality difference between 100 and 200 is negligible.

However, the faster shutter enabled by ISO 200 being your default setting rather than having to change for that "spur of the moment" shot far outweighs any disadvantage.
samfurlong 12 2.5k United Kingdom
29 Aug 2008 8:28AM

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

Not with digital cameras. As Barrie touched upon, digital camera sensors have a 'native' ISO which gives the best results. Anything else is just by increasing / decreasing the voltage in the photoreceptors on the chip to give the effect of an ISO change and at the extremes (the HI and LO settings) all it does is under/overexpose a frame and bring it back in software, so you could in theory, with careful photoshop work, achieve a better quality result manually.

The native ISO of the current crop of Canons is 200 ISO and I believe it's the same on the D3 but don't quote me on that.

For the record I leave my MKIII's on 400 as my standard setting, often using much higher, very rarely using any lower.
keith selmes 14 7.3k 1 United Kingdom
29 Aug 2008 10:15AM
Interesting. I haven't noticed any real difference between 100 and 200 on a 5D, and began breaking the habit of lowest ISO, using whichever seems most convenient.
On my compact, lowest is still bestest, but I've never tried to use a special function to get even lower, for the reasons Sam has given.
justin c 14 4.9k 36 England
29 Aug 2008 10:37AM
Still on the same topic but regarding the very lowest iso setting. One thing I have noticed on the Canon 5D is that iso 50 appears to capture slightly more detail than iso 100 when pixel peeping at 100-400%. I thought perhaps I may have been mistaken, but I have done a few comparisons now, mainly of small detailed subjects using a Canon 100mm macro lens and the extra detail is certainly evident.
Of course this low iso setting works best for subjects/scenes that don't demand maximum dynamic range.
Be interesting to hear if anyone else has done some comparisons and found the same thing.
BurntOut 11 321 2 England
29 Aug 2008 10:40AM

Quote:Of course this low iso setting works best for subjects/scenes that don't demand maximum dynamic range.

Why's that, Justin?
justin c 14 4.9k 36 England
29 Aug 2008 10:49AM
Because iso 50 gives you a reduced dynamic range, so you may get clipped highlight and shadow detail if the scene contains too great a contrast range, whereas this may not be the case at higher iso settings.
I'll leave the technical explanation as to why this is the case, to those that could explain far better than I could.
culturedcanvas 12 4.7k 59 United Kingdom
29 Aug 2008 10:54AM
Thats kind of half right .. but you need to know why you are using the ISO 50 setting in the first place.
Coleslaw 12 13.4k 28 Wales
29 Aug 2008 10:57AM
emmmm.......why do we use ISO50?
BurntOut 11 321 2 England
29 Aug 2008 10:57AM
Sorry, meant why does iso 50 give a reduced dynamic range?

And, is the converse true: the higher the iso, the higher the dynamic range?
culturedcanvas 12 4.7k 59 United Kingdom
29 Aug 2008 11:05AM
ISO 50 isnt the true sensitivity of the sensor. It's essentially software based ... it meters at ISO 100 and then makes adjustments in camera. This isnt as simple as metering at ISO 100 an then dragging the exposure back 1 stop though ...

Cole I can use an example from another thread this morning here. ISO 50 is there mainly as an additional tool Say for example im outside doing a portrait, and shooting in bright light, I want to get the shutter speed down to be able to use the flash at max sync speed to evenly expose the background.

At ISO 100 I might need 1/500 ... drop it to ISO 50 and I need 1/250 ... flash power adjusted to give the correct exposure and shot fired.

Thats one real world example of why you might use ISO 50.
justin c 14 4.9k 36 England
29 Aug 2008 11:05AM
I don't know the answer as to why it's reduced, sorry.

Regarding the second question I don't think the dynamic range increases at all, at least not from 100 and upwards.

EDIT: Dan replied whilst I was typing.
Coleslaw 12 13.4k 28 Wales
29 Aug 2008 11:06AM
Ah, thanks again...

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