On 18 Dec 2004 at 14:21, Luigi de Guzman wrote: > <http://img.photobucket.com/albums/v293/Brunellus/Welbilt%2015%20Dec%2004/becky. > jpg> > > The *istDS does NOT like underexposure when you've got the ISO cranked up to > 3200: this was wide open at f/1.4 at 1/10th of a second, handheld, in a booth > in a dark bar. RGB noise was awful: a bit of channel-mixer to kick it down > to > greyscale, a bit of selective gaussian blur to reduce the noise, unsharp mask, > and suddenly I'm thinking "hey....tri-x!"
Nice portrait of an obviously lovely lady. The noise is pretty horrible at ISO 3200 but in reality it's still better than you could ever achieve on film at the same ISOs and then not even in colour. Given that the native ISO of the sensor is around ISO200 shooting at an effective ISO3200 means that the sensor has been under-exposed by four full stops. Its output is then amplified to provide the same signal voltages to the ADC that it would produce for an image correctly exposed at ISO200, the noise gets amplified too of course. Under exposure means that you are dipping further into the CCDs noise which isn't always of nice uniform distribution like film grain, colour often suffers quite badly especially if you are also making large colour temp compensations and running into severe blue channel noise. I've found that the noise reduction program NoiseNinja does a pretty good job of amalgamating low frequency colour noise in images like this using its "coarse mode" switch, NeatImage is also quite good with low frequency noise. Both can be used to manage colour noise without modifying luminance noise if you wish to preserve it. Cheers, Rob Studdert HURSTVILLE AUSTRALIA Tel +61-2-9554-4110 UTC(GMT) +10 Hours [EMAIL PROTECTED] http://members.ozemail.com.au/~distudio/publications/ Pentax user since 1986, PDMLer since 1998
