This is "dark frame subtraction" done by the canon firmware. On most CHDK ports, you can disable it by setting "Dark Frame Subtraction" to off in the "Enhanced Photo Operations" menu, but quality may suffer unless you do dark frame subtraction on the raw later. Google "dark frame subtraction" to learn more about this process.
Does CHDK apply "Dark Frame Subtraction" in its RAW?! I can see a lot of coloured noise (red, green, blue pixels) in the RAW files, but the JPGs are clean. So until now I've been using Dark Frame Subtraction and wasn't even getting any benefit from it, since I only use RAW!
You cannot disable jpeg using CHDK. You can set them to small and lowest quality (as you described), but this will likely not improve shooting speed much. On some cameras, using lower resolution jpeg is actually slower than the full resolution L size.
I'm using lowest quality and size. If on some cameras it can slow it even further, then I'll have to time it and see which option is better. Thanks for pointing it out.
but unfortunately my cam only shoots it like 0 +1 -1 +2 -2 +3 -3 +4 -4
This is how CHDK built in bracketing works currently. You could write a script to do it the other way.
I'm NOT very good with scripts and hence I try to avoid it as much as I can. I only use a modified interval. lua script and will this script work with that HDR script?! And is there such a script available, since I don't know programming and I can't write any codes?!
This is "dark frame subtraction" done by the canon firmware. On most CHDK ports, you can disable it by setting "Dark Frame Subtraction" to off in the "Enhanced Photo Operations" menu, but quality may suffer unless you do dark frame subtraction on the raw later. Google "dark frame subtraction" to learn more about this process.
but unfortunately my cam only shoots it like 0 +1 -1 +2 -2 +3 -3 +4 -4
There is a script that manages dark frame subtraction - disabling it for each shot but occasionally collecting a reference dark frame for use in post processing. It would not be hard to modify it to shoot in your desired sequence with a reference dark frame taken at the beginning and end of the sequence.
link > Meteor Intervalometer with Dark Frame Management
I've read that the Dark Frame has to be of the same settings (ISO, Ap, Tv) for ALL the frames?! Will shooting just one in the beginning and one in the end do?! Since I shoot SEVERAL pics in HDR, I was wondering if I can somehow subtract the dark frame noise using the series of all those pics (without an actual dark frame) and I found this article
http://starcircleacademy.com/2012/10/darkframes/Unfortunately StarStax DOESN'T support RAW and a curious thing happens when I load the RAW in Photoshop and save it as TIFF. For some reason, it removes all the noise and coloured noise (the one we need dark frame for) even when I do NOT process anything! Although it removes noise, but it kills the sharpness (since the image is NOW processed!)
Wondering that maybe loading the image in PhotoShop's Camera RAW, might be responsibe for this (like it might be loading some last used settings like some apps do) I decided to go into batch processing and then converting the RAWs to TIFFs from there, without actually opening PS's Camera RAW and the results were the same!
For some reason Camera RAW processes the RAW files and it kills the noise, but along with that softens and smudges the frame (like all processed images look). The reason to shoot RAW is to circumvent this "processing"
Also, apart from PhotoShop, all other RAW managers and RAW viewers show the noise and the coloured noise in the image, it is just PS that has this curious problem. The only way I circumvent it, is by processing the RAWs in Photomatix HDR software first (it can handle RAW) and then loading it to PS.
What should I use on a Windows Machine to convert the RAWs to TIFFs, where it DOESN'T process ANYTHING from the image, just convert it to TIFF, so that I can use that technique from that aforementioned article as it claims, it not only removed coloured noise but also,
"
- The hot pixels were almost completely annihilated
- The sky gradient caused by lights glowing in the distance was also almost eliminated.
- The contrast in the sky and elsewhere was improved
- The red bias on the railing was mostly removed."
Thanks for all your replies, I sincerely appreciate it.
