07-22-2012, 04:58 PM
[quote name='nandadevieast' timestamp='1342974311' post='19536']
Ok, i see.
So coming back to original question, lets see how this pans out:
Sony A57: shot at F8, 1/250, ISO 1600
Nikon D5100: shot at F8, 1/250, ISO 1600
You're saying that the exposure will be same. Ok.
You're saying that A57 receives less light so if it has to maintain correct exposure, it will have to increase the sensor gain by 1/2 stop. So because it has amplified the sensor signal or whatever you call it, at 1600 ISO, it will have more noise by 1/2 stop, compared to D5100 which has a less amplified signal at that ISO.
Which means, for noise to be equal, we have to shoot at ISO 1200 on A57, but that will underexpose our picture by 1/2 stop.
Wonder that's what Klaus meant when he replied to my question....
BC, am i getting it right now?
By the way, to my eyes at least, the noise difference looks something like 1 stop. I see lots of noise in A57 files. Is that how it's supposed to be in SLT vis a vis DSLR? I have red something like 1/2 stop.
[/quote]
One is a Nikon, the other a Sony. You can not just assume they will show the same noise just because their sensors both come from Sony. Best is to compare it with a NEX.
And the image will only be underexposed if for some reason you feel you have to keep the exposure times exactly the same. Which of course you do not have to want to.
Anyway. we do not shoot to get noise equal, so that is a bit odd a debate <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='
' /> .
I do not exactly know what Klaus meant, but probably he meant that the SLT's are that half a stop behind (and was not talking about your underexposure idea). And you are getting it right, now, I think.
Ok, i see.
So coming back to original question, lets see how this pans out:
Sony A57: shot at F8, 1/250, ISO 1600
Nikon D5100: shot at F8, 1/250, ISO 1600
You're saying that the exposure will be same. Ok.
You're saying that A57 receives less light so if it has to maintain correct exposure, it will have to increase the sensor gain by 1/2 stop. So because it has amplified the sensor signal or whatever you call it, at 1600 ISO, it will have more noise by 1/2 stop, compared to D5100 which has a less amplified signal at that ISO.
Which means, for noise to be equal, we have to shoot at ISO 1200 on A57, but that will underexpose our picture by 1/2 stop.
Wonder that's what Klaus meant when he replied to my question....
BC, am i getting it right now?
By the way, to my eyes at least, the noise difference looks something like 1 stop. I see lots of noise in A57 files. Is that how it's supposed to be in SLT vis a vis DSLR? I have red something like 1/2 stop.
[/quote]
One is a Nikon, the other a Sony. You can not just assume they will show the same noise just because their sensors both come from Sony. Best is to compare it with a NEX.
And the image will only be underexposed if for some reason you feel you have to keep the exposure times exactly the same. Which of course you do not have to want to.
Anyway. we do not shoot to get noise equal, so that is a bit odd a debate <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='
' /> .I do not exactly know what Klaus meant, but probably he meant that the SLT's are that half a stop behind (and was not talking about your underexposure idea). And you are getting it right, now, I think.