ISO v Detail/IQ (1 Viewer)

Whats the % loss or gain in detail/IQ ? Shooting with Sigma 150 macro and 50d

The subject is Butterflies
Normal ISO setting is 400
Images only for viewing on Web

ISO 100
ISO 200
ISO 800
ISO 2000

If the norm is 400 what % loss in detail/IQ is there when shooting 800 & 2000
If the norm is 400 what % gain in detail/IQ is there when shooting 200 & 100

What's your lighting setup - are you just using natural lighting, reflectors, flash?
Natural light macro of active species in the UK is often tricky since we don't always get that brilliant powerful lighting all the time. I am assuming that your shooting these during the active part of the day when they are moving around so tripods and long exposure are pretty much not an option.

If your avoiding/not using flash then the ISO you can use is going to be very dependant on the lighting, remembing that you need at decent shutter speed (1/200sec) and a small aperture (f8-13 idealy). So those settings along with ambient lighting will tell you what ISO you have to use to get a good exposure.
As for what ISO you can get away with, well if your not cropping shots and your only viewing them at websize then you should be able to take the ISO rather high and, with some noise reduction, still be able to get good results. I don't think I have ever seen a % ISO noise increase probably because the amount of noise is still dependant on the lighting and the exposure - if you get the exposure perfect noise is going to be far less than if you underexpose the shot.

I would personally say get a few butterflysized flowers and do some experiments with different settings and then move to some experiments with butterflies - perhaps setting up a lure (rotting fruit or a regularly visited flower) to bring them to you (or get your running shoes on and start chasing them through fields)

Thanks for your reply, What I am trying to say is there any noticeable difference, if you have the light to drop down to 200 from 400 ? BTW, it was natural light I was referring to. I was thinking about getting a monopod but I don't think thats going to help me because I like the freedom of handheld, monopod would be useful for Birds. So I am thinking maybe I that the money would be better spent on a Sigma ring flash.

It is not so much IQ or detail that is the problem but noise. I agree with 'overread' in that the most important thing is to get the exposure right when using a high(ish) ISO. I find with the 40D that ISO 800 is superb and even ISO 1600 is usable providing you get the exposure right, of course if you are going to crop heavily then any noise will be magnified and underexposure and then pushing in processing is just about the worst thing you can do with respect to noise.
With Macro's, you are going to have to use at least f8 and up to f14 if possible to get any DOF. If you are using the natural light and hand holding then the only way you have of controlling things is with the ISO. Using support helps in keeping the ISO down as you can shoot at lower shutter speeds. Flash also helps if hand holding because you can shoot at something like 1/200 sec.
I am looking at getting a flash system for macros at the moment but like most things in photography it is not straight forward :eek!:
I have looked at ring flash but they are not overly favoured by most macro shooters, a lot of people talk of really unnatural results. Many good macro shooters seem to prefer a standard flash gun and diffuser with a bracket to be able to place the flash where they want it. The real king is the Canon MT-24EX Macro Twin Lite but at £650 it is hard to justify.

£650 is cheap! most prices I see it for are more like £750 its very expensive and (honestly) not as good as Nikons equilalent but still very good for macro work.

Though I would say even though one can go very complext with macro lighting start things off simple. Learn to master the use of one flash and then start experimenting with more - if you jump in the deep end chances are you will end up with loads of kit that will bog you down and leave you missing shots and also spending way too much time taking test shots to get things setup right.