Best subject for testing effects of different ISO settings

[parish]

I have stuck in my head - from using film 20+ years ago - that ISO400 is noticeably grainy but I've seen pics on here taken at telephone number ISO settings that have hardly any noise. OK, these were taken with cameras like the D700 or 1Ds III so I don't expect that level of quality from my 400D - plus it only goes to 1600.

I want to do a test where I take the same shot at each ISO setting so I get a feel for how much the IQ degrades.

What would be an ideal/optimum subject to shoot? I would guess a scene that contains a large area of a single colour (ideally white/light grey?) e.g. the sky?

Also, as I increase the ISO should I keep the aperture the same and increase the shutter speed or keep the same shutter speed and reduce the aperture? I would think the former would be the better choice as increasing the ISO would normally be used to get faster shutter speeds in poor light.

 

[33L]

posted on this one as the other has been deleted....

iso noise is more apparent in dark images rather than light images. a tv test screen comes to mind as an example as to how it affects different colours etc...

now having saying that where are you gonig to get a test screen from.

jsut my 2p

 

[jgs001]

How about, a night sky shot. 30 second exposure, wide end of the lens zoom (if a zoom), wide open aperture. Take a sequence of shots at various ISO settings. By this process, I worked out that the Z2 is best at ISO200 (trading detail against noise), and so far the 450d at ISO800, although I think I need to do some more thorough testing.

 

[apkent]

I have seen in magazines tests performed on a colour card. Basically around a dozen or so different colours are photographed as various ISOs and the graininess analysed on 100% crops.

Noise starts to show itself in the dark colours (dark purple) for example, and spreads through others as the ISO increases.

 

[pxl8]

Get a sheet of white card and a sheet of black. Overlap them and shoot close up but with the lens focused at infinity. Instant b&w gradient but no detail from the subject matter so you'll just see the noise and nothing else across all brightness levels.

 

[gman]

I heard that blue was the most likely colour to be affected by noise, don't know if that's true or helps?

 

[parish]

Get a sheet of white card and a sheet of black. Overlap them and shoot close up but with the lens focused at infinity. Instant b&w gradient but no detail from the subject matter so you'll just see the noise and nothing else across all brightness levels.

Thanks, that sounds like an easy test to set up. What would you recommend, low light, and/or small aperture?

 

[pxl8]

Shoot wide open, you need a shallow DoF to get the gradient effect. Lighting shouldn't matter too much as long as your shutter speed is around the focal length or you're using a tripod.