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Bad pixels

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Offline waterwingz

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Re: Bad pixels
« Reply #20 on: 15 / March / 2015, 09:15:39 »
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Quote from: CanonCOMPACT on 15 / March / 2015, 08:42:49
Set the file extension to. DNG (1.3). 
If you want CHDK to remove the bad pixels from the DNG image in the camera,  you need to select DNG 1.1.

Quote
PS CS6 does not show any bad pizel but Corel PSP X7 does.   What is wrong in my understanding , if any?
Photoshop is correctly using the bad pixel information in the image to correct the DNG 1.3 image as it comes from the camera.  Corel Paint Shop Pro does not know how to (or does not correctly do) the bad pixel correction using the information in the DNG 1.3 image.
 
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Offline srsa_4c

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Re: Bad pixels
« Reply #21 on: 15 / March / 2015, 09:32:36 »
Quote from: CanonCOMPACT on 15 / March / 2015, 08:42:49
I created the bad pixel.bin file from the chdk menü after pointing the camera to a White paper. The file resides under the chdk folder, and set the " manuel bad pixel removal option to averege.  Set the file extension to. DNG (1.3).
The "Manual bad pixel removal" menu entry has a different purpose: it allows you to fix additional "bad" pixels. It only works if you create an extra bad pixel list (this can't be done in camera). See the manual: http://chdk.wikia.com/wiki/CHDK_1.3.0_User_Manual#Manual_bad_pixel_removal

I think this menu entry is misleading and it's probably impossible to describe its purpose in just a few words.
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Offline ursamajor

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Re: Bad pixels
« Reply #22 on: 18 / May / 2016, 08:54:52 »
I return to my topic with a question: does Canon firmware make Dark Frame Subtraction better than a standalone software using Dark Frames manually taken? I mean for a single picture, not for multiple exposures, where a stacking software can be used... with surely better results.
« Last Edit: 18 / May / 2016, 11:03:05 by ursamajor »
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Offline blackhole

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Re: Bad pixels
« Reply #23 on: 18 / May / 2016, 13:11:43 »
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I return to my topic with a question: does Canon firmware make Dark Frame Subtraction better than a standalone software using Dark Frames manually taken? I mean for a single picture, not for multiple exposures, where a stacking software can be used... with surely better results.
Yes, if you do not have a lot of experience and knowledge about RAW postprocessing.
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Offline reyalp

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Re: Bad pixels
« Reply #24 on: 18 / May / 2016, 13:30:45 »
Quote from: ursamajor on 18 / May / 2016, 08:54:52
I return to my topic with a question: does Canon firmware make Dark Frame Subtraction better than a standalone software using Dark Frames manually taken? I mean for a single picture, not for multiple exposures, where a stacking software can be used... with surely better results.
Done correctly, doing subtraction on RAW with external software should be just as good as in camera, though as blackhole says, you do need to know the tools.

If you only shoot jpeg, then in camera is much better because the subtraction happens before compression.

In camera also has the advantage that the dark frame will usually be taken at close to the same sensor temperature. If you use a stand-alone dark that was taken at a significantly different temperature, it won't work as well.
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Offline ursamajor

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Re: Bad pixels
« Reply #25 on: 18 / May / 2016, 13:56:20 »
So, the DFS in camera works pretty well, as far I understood from your comments.
I do have experience in RAW processing, I didn't have time to experimenting long exposure RAWs on my SX510HS. I plan to use my little camera to take nightsky long exposures (using my telescope mount). That's why I want to create also a little library with dark frames to use them for further RAW processing, especially for multiple light frames. However, for single exposures I'll use DFS from Canon.
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Offline reyalp

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Re: Bad pixels
« Reply #26 on: 18 / May / 2016, 16:49:06 »
Quote from: ursamajor on 18 / May / 2016, 13:56:20
So, the DFS in camera works pretty well, as far I understood from your comments.
Yes, I wouldn't expect quality to significantly worse than doing it externally, the main reason to avoid it is if the extra exposure time is a problem. There may be a slight improvement using darks that are an average or median of several frames, but I suspect you would have to look pretty closely to see the difference.

OTOH, if you already have a workflow setup to do dark frames externally, it may end up being more convenient to just do everything that way.
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Offline ursamajor

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Re: Bad pixels
« Reply #27 on: 19 / May / 2016, 10:44:41 »
I made some experiments with Canon's DFS using ISOs from 80 to 1600 and exposures up to one and a half minutes and results are not at all bad. I would say they are over my expectations. DFS work pretty good and manage to remove hot and dead pixels. Also I took pictures (only RAW, DNG) without DFS and tried to remove hot and dead pixels in Lightroom and Raw Therapee. I have to say that Lightroom dealt better than Raw Therapee the problem of hot and dead (bad) pixels from no DFS RAWs despite special filters found in Raw Therapee for such of cases. The big problem is that the efficiency of those filters is inversly proportional to increase of ISO. For example, to 1600 ISO unfortunatelly the efficiency incline to zero.
As a conclusion: for long exposures the way is DFS, either Canon or using standalone softwares.

EDIT: self explanatory photos attached, as the matter of fact 100% crops.  ;)



« Last Edit: 19 / May / 2016, 12:21:59 by ursamajor »
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Offline ursamajor

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Re: Bad pixels
« Reply #28 on: 21 / May / 2016, 13:41:15 »
Using a script for meteors, I wished to make an experiment and I took some pictures at 800 ISO and long exposures, 30 s each. Took 15 pictures, but I lost 10 by an error. I stacked them and I got star trails, obvious, timid attempts.  :D But what was surprising, was the low noise I got after stacking.

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