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tips for choosing ISO speed...


Link Posted 02/09/2010 - 09:21
hello all,

just wondering how people decide on what ISO speed to choose... i get the theory that faster iso can be better in certain circumstances - say low light or if hand holding / f stop selection for greater depth of field for a given amount of light... sorry not great at explaining myself !

i shoot 200 / 400 iso a lot - would i notice a lot more noise say at 800? i shoot flying birds a lot with a 300mm lens so i normally want a fast shutter speed to freeze movement and to minimise lens shake - plus i want reasonable dof etc..

any tips welcome



Link Posted 02/09/2010 - 09:29
I would shoot at 800ISO if I were you, or you could use the TAV setting and let the camera choose. For shooting birds and with a 300mm lens you want at least 750th sec and f11. Enter these settings and see what ISO the camera chooses, If your using the k20d you will get great results even with 800ISO
My piccies.


Link Posted 02/09/2010 - 09:58
Tricky decision, and always a compromise.

We have only three variables affecting exposure, aperture, shutter speed and ISO.

If you up the ISO you run the risk of increasing noise, especially in shadowy or dark areas. I almost always use the lowest ISO (100) in sunny situations.

If you change the aperture, you might not be pleased with the resulting bokeh or depth of field.

If you change the shutter speed, there might be too much motion blur in shots of moving targets. Too fast and they look like stuffed dummies.

On my K20D, when I am unsure, I use TAv mode whereby I select shutter speed and aperture suitable for the subject, then let the camera deal with the ISO variable. More often than not, the camera gets it right and I've set one of the other two variables inappropriately.

In fact, there is no hard 'n fast rule, you just have to try things out and make note of what pleases you to be able to replicate the effect in the future.
Peter E Smith

My flickr Photostream
Last Edited by Mannesty on 02/09/2010 - 09:59


Link Posted 02/09/2010 - 11:04
I have recently started to use auto iso set to 100-800. Works a treat, the camera only raises the iso when shutter speeds are a bit slow for hand held shooting. This also prevents you leaving the iso at 800 by mistake when you don't need it! Of course, turn the auto iso off when you are shooting with a tripod and don't mind slow shutter speeds.


Link Posted 02/09/2010 - 16:10
It's better to have a noise image than a blurry image so try to find the optimum for you, it really depends on what you shoot, in what weather (light), with what lens and with which camera.
The K-X is far cleaner at higher ISO than the K20D or the K7 for example.

In your example of the bird I would even push the K10D to ISO1600 in order to get a good photo, the noise reduction software are getting quite good you know and I don't pixel peep as much any more.

K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55


Link Posted 02/09/2010 - 20:47
Personally I use the lowest ISO I can (and I use manual settings for 99% of pictures...). I find the dynamic range better and it gives me much more flexibility in developing the RAWs afterwards.
Grain can be a lovely thing, chosen correctly it creates the more "analogue" effect - I often add grain to simulate films I used to shoot with. But with digital cameras I prefer when I do it, not the camera, hence the low ISOs.
Regarding your birds - I also found out that high speed shutters freeze the movement and often make the picture boring and static. Try lower speeds and panning to give them more dynamics - maybe you'll manage to blur the tips of the wings only for instance and this way the picture will be much more appealing and energetic. What do you think of this one or this one ?


Link Posted 02/09/2010 - 21:11
Those are very nice! I would try that sort of thing, but as an exception rather than the norm. I used to cling doggedly to a manual iso 100 but I have found the auto iso is actually pretty conservative at bumping up the iso in general hand held shots, and the results at up to iso 800 are acceptable if I process raw.

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