Demonstration of X-Trans Under-the-hood RAW Spatial (Noise) Filtering

tradesmith45 wrote:

razorfish wrote:

This happens because people are too lazy to use dark frame these days. For years it was never a problem for anyone, but then someone started complaining it takes too much time, and I guess manufacturers are now trying to find ways to do it ”on the fly”, with these issues as the result. Note that dark frame in itself never eats stars, and can always tell the difference between a point of light and a hot pixel. Just goes to show that taking shortcuts never pays. Take the time to do the job right, you’ll get the best result in the end.

Actually dark frames are a poor solution because they often add noise. This happens for several reasons. One significant problem is matching sensor temps between lights & darks. During a long shoot, the sensor warms & can take 2-3 hrs to reach equilibrium. Creating darks to match that is impractical. Applying darks that are from a different temp adds noise. Some cameras report sensor temps in the EXIF but many don't. For the cameras that report sensor temp, it is theoretically possible to match temps but not easy.

A better solution for hot/stuck/dead pixels than star-eating is available in some camera specific RAW converters. A bad pixel map is used by the converter to ID which pixels need to have interpreted values applied. I believe some astro specific software will also do this.

Fuji & Oly have a bad pixel in-camera mapping function for some models but IMHO, they don't work very well.

Dark subtraction on DSLRs and mirrorless should use what is called adaptive darks that require a bias as well as a dark. These are then calculated on the actual image and adjust to that specific image.So temperature variations are not as significant. I don't think that adds any significant noise and definitely cleans up an image.

I wonder if Sony showed them how to do this filtering as Fuji uses Sony sensors. Perhaps its a "service" that comes with buying their sensors!

Greg.