Long Shtr NR - off, what to do on PC?

Interesting...

I shall have to try this test myself.

It should be easy to write some software to take a "lens-cap-on-long-exposure" and note the hot pixels into a profile for that sensor/camera.

Later, you would be able to run the software against a folder of images and it would recalculate each hot pixel using its neighour-average - or you could interactively "brush away" hot pixel grains from photographs on an individual basis to avoid fudging more pixels than we must.


Would such software be useful to anyone ? If so I shall try to find a copy of the file format for RAW images and see what I can come up with.


-Gary

 

Does "Long Shtr NR" effect RAWs ?

 

It certainly does on the Olympus PEN. I'd be interested to know if Panasonic did it the same way.

If all of your photos are part of a shoot in very similar conditions at approximately the same time, I'd suggest that you take a dark frame (your lens cap, perhaps) for reference at the beginning and end of your shoot, and if it's a long shoot then perhaps one or two during. This saves you time, because the camera isn't taking one every single time you make an exposure. One per exposure is most accurate, but I agree that waiting for a minute or two after each shot can be a real drag.

Once this is done, you can apply the dark frame to your images back on your PC. ufraw has a special field for applying a dark frame for noise reduction, so your raw processors may well have one as well. You might want to try several of your dark frames, until you find one wher ethe noise matched most closely.

Even if you just shoot JPEG, you can use this trick: here is a Gimp tutorial on the subject.

If you didn't shoot at least one dark frame, then you're going to have to approach this differently. Shooting a new dark frame at a different temperature with different charge levels on your sensor is going to give poor results. If you have no dark frame, but do have two photos taken at about the same time but reframed (even slightly), then you might be able to use the photos as noise references for each other, especially in dark or very low contrast areas of the image.

 

Good tricks given by the following comments, really good experments.