Sony F828, RAW and noise levels

[BJL]

Higher ISO settings do more or less the same as what you are describing, in that ISO 400 uses the same exposure levels as with ISO 100 and -2 exposure compensation. The difference is that with ISO 400 setting, the needed +2 correction is done by applying four times as much analogue amplification to the sensor signal before A/D conversion, instead of doing it digitally afterwards. The noise levels are probably similar either way; there might be some additional in-camera noise filtering done at high ISO settings, but similar processing can be done later to the underxposed ISO 100, -2 output.

   Maybe the earlier amplification reduces the accumulation of noise in later parts of the analogue part of the process, in which case using high ISO settings might give slightly better results than digital compensation?

[mgguzman]

Thanks for the feedback ..

I seems that the Sony F828 has a latitude of only 0.5 EV in Raw format despite that the raw converter allows to change exposure of up to 2 EV. See the dpreview below if you are interested.

http://www.dpreview.com/reviews/sonydscf828/page15.asp

So this trick will not work with the Sony anyway.

Miguel

[mgguzman]

Dear all,

The Sony F828 has been described as a "noise" camera for ISO > 100. I know that this camera can shoot in Raw mode and therefore it is possible to correct exposure with the Raw converter in the range of -2 to +2.

So in situations when available light does not allow to shoot at ISO 100 and you need to go up to ISO 400 (assuming you can't put the camera in a tripod) one possibility would be to under expose the image up to 2 stops, shoot at ISO 100 in RAW mode, and then correct the exposure (applying +2) with the Raw converting software. In that manner it should be possible to shoot at ISO 100 in situations when ISO 400 would be better (shooter speed) and create a less noise image.

Have anyone of you done that test? Shooting in Raw and compensate the exposure to see if the noise in the image is lower?

Of course this is a concept that could be applied to any camera shooting in RAW (I have never tried).

Feedback will be appreciated.

Miguel

[Ray]

I've tried this with my D60, ie. using the same shutter speed at ISO 100 as ISO 400, resulting in correct exposure at ISO 400 and 2 stops underexposure at ISO 100. I've then applied exposure compensation at the time of conversion from RAW to TIF and compared the degree of noise in both images.

The ISO 400 shot appeared to have only very marginally better noise characteristics, on the monitor at 100% or more magnification. I wouldn't expect this to show up on prints.

However, this would not necessarily be the case for the 10D which has similar noise to the D60 at ISO 100 but less noise than the D60 at ISO 400 and above, due to improved in-camera processing.