Can you please explained what ''ISO 1600 pushed 2/3 of a stop to the equivalent of around 2400:'' means?
thanks
If you underexpose a picture by a given amount (like 2/3 stop) and then increase the exposure by that same amount in PP, the effect is *exactly* like shooting at a correspondingly higher ISO. That is, you get the same faster shutter speed you'd get by turning up ISO, and the same increase in noise. There's no difference.
So, for instance, if you are at ISO 1600 and find you need a shutter speed of 1/15" to get a correct exposure at f/2.8, and you decide 1/15" just isn't fast enough, you could raise ISO to 3200 - thus giving you a shutter speed of 1/30" but increasing noise. Or you could simply increase the shutter speed to 1/30" while leaving ISO at 1600 - thus giving you a picture that was one stop underexposed and needed to be brightened digitally in PP, yielding more noise. The end result would be in all respects exactly the same either way - a shutter speed of 1/30" and more noise that the original picture at 1/15" and ISO 1600.
In fact that's how very high ISO values are actually implemented in most cameras - the analog signal amplifier tops out at ISO 1600 (or whatever), and higher ISO values are shot underexposed at ISO 1600 and then brightened digitally in the camera's firmware (yes, even for RAW).
Since the K200D doesn't have ISO settings above 1600, I do all my "extreme" high ISO shooting using the technique I described.
If you underexpose a picture by a given amount (like 2/3 stop) and then increase the exposure by that same amount in PP, the effect is *exactly* like shooting at a correspondingly higher ISO. That is, you get the same faster shutter speed you'd get by turning up ISO, and the same increase in noise. There's no difference.
So, for instance, if you are at ISO 1600 and find you need a shutter speed of 1/15" to get a correct exposure at f/2.8, and you decide 1/15" just isn't fast enough, you could raise ISO to 3200 - thus giving you a shutter speed of 1/30" but increasing noise. Or you could simply increase the shutter speed to 1/30" while leaving ISO at 1600 - thus giving you a picture that was one stop underexposed and needed to be brightened digitally in PP, yielding more noise. The end result would be in all respects exactly the same either way - a shutter speed of 1/30" and more noise that the original picture at 1/15" and ISO 1600.
In fact that's how very high ISO values are actually implemented in most cameras - the analog signal amplifier tops out at ISO 1600 (or whatever), and higher ISO values are shot underexposed at ISO 1600 and then brightened digitally in the camera's firmware (yes, even for RAW).
Since the K200D doesn't have ISO settings above 1600, I do all my "extreme" high ISO shooting using the technique I described.