My new camera

[Peekayoh]

Frank will be better off just taking some pictures.
I can tell you now that the A580 at ISO1200 will be comparable to the A100 at ISO400 in terms of noise.

[DonSchap]

Frank will be better off just taking some pictures.
I can tell you now that the A580 at ISO1200 will be comparable to the A100 at ISO400 in terms of noise.

Peter,

I was hoping that ISO-1600 thru 3200 would complement and kind of forgive the darker glass, Frank is currently packing.

Placing an f/4-5.6 lens on the front of this α580 is where "the rubber meets the road," in my estimation.

f/5.6 is two f-stops darker than f/2.8, and that means if you get a decent enough image at ISO-400 out of the f/2.8 base aperture lens (i.e, 28-75mm f/2.8), you will need to ramp up your ISO to 1600 to get the same lighting effect from the f/5.6 base aperture lens (i.e., 70-300 f/4-5.6).

ISO-1200 is a third of an f/stop down from that. I had hoped for better, personally.

If you can get a solid shot at ISO-3200 ... that is news and definitely worth the change, otherwise I would suggest getting better glass is key, first. I know it may be picky, but money and value is the deciding factor, in most decisions, hence the suggested test. Let's just see ...

[Rooz]

3200 = 400 ?
you're a900 isnt even that much better than an a100.

[Peekayoh]

Yes, ISO3200 is an unreasonable expectation but ...
Don, you shouldn't be too downhearted, in fact, the new Sony Sensors have moved on a good bit.
Given that a S/N Ratio of better than 30dB is required to maintain an acceptable level of noise, dynamic range and colour we can see that ....
the A580, with a S/N of 29.8dB at ISO1600 compares well to the 30.6dB achieved by the larger A900 Sensor.
That's pretty good considering the smaller size of the A580 photosites and represents a good step forward in reducing the dark noise.
The Nikon D3X manages an excellent 31.9dB at ISO1600.

What this means for Frank, is that the A580 is useable at ISO1600 especially if the light is good and he's simply driving up the shutter speed.
It won't be as good as the A100 at ISO400 which registers a S/N ratio of 30.1dB but close enough albeit at the expense of two stops less in speed.

Here's an image taken at ISO1600 so I could get the shutter up to 1/60th whilst maintaining a reasonable DOF using an aperture of f/5.6



Camera: Sony A900
Lens: Tamron 90mm f2.8 Macro (not mine I should say)
Exposure: 1/60th at f5.6[+0.7EV]
ISO 1600
17th February 2011

None of this means that higher ISOs are a substitute for a quality, fast lens.
Assuming that you haven't chosen a smaller aperture for reasons of DOF, a larger aperture gets more light to the sensor with a corresponding boost in the S/N ratio and therefore in IQ. At the end of the day you can't get away from the basic laws of physics (or optics) but compared to an ISO1600 film, I'm still impressed with the way the A900 handles it.