The ISO is just winding the gain up on the sensor. You need less light, but
with the gain turned up you get bleeding from pixel to pixel (eg more
noise), resulting in less contrast, less colour saturation and graininess.
All of that is particularly exacerbated if you're also underexposing (any
many do on digital to avoid blown highlights) causing you to try and pull
more details from shadows during pp.
Some of the newer cameras (eg Nikon D700) are much, much better at the
higher ISO settings, but on older SLRs (like my Nikon D2X) the usable upper
limit is really about 800 ISO.
It's the same as the old film days - slower film tended to have finer grains
and produce less noise. That said, just about any DSLR at ISO 800 will kill
any film that sensitive.
Shoot the lowest ISO you can to get the necessary shutter speed. Try, if
possible, to stay at ISO400 or ISO800 and only push higher when the shot
will absolutely be lost anyway due to shake or subject movement.
You'll likely find shots at ISO100, 200 and 400 to be nicely saturated with
good contrast and minimal noise (or sufficiently little you can handle it in
post process). ISO 800 is usually pretty good to. On my D2X the quality
falls off VERY quickly about ISO800.
There is no set limit accross all cameras as to when substantial degradation
begins - but the one constant is that (leaving aside the need to maintain
shutter speed) the lower the ISO the better the image.
On 30 July 2010 09:32, Greg Little <> wrote:
> Gooday birders
> A friend of mine has a digital SLR camera on which he sets the ISO at 1200
> to take bird photos with a 100 - 400 zoom lens. However the images seem a
> bit grainy, in old speak, or noisy in digital speak. We have tried to get
> closer to the bird subjects but the images seem to lack the sharpness and
> richness of colour and detail that I have seen produced by some of the
> photographers on birding-aus. So, could you people who produce the superb
> digital images of birds please offer some advise on ISO settings. If
> possible could you relate the digital ISO settings to the ASA settings of
> film. There may be something else he needs to know so any advise would be
> appreciated. For myself I do not have a digital SLR camera and probably
> won't get one for a while yet.
> Greg Little
> Greg Little - Principal Consultant
> General Flora and Fauna
> PO Box 526
> Wallsend, NSW, 2287, Australia
> Ph 02 49556609
> Fx 02 49556671
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