Hot & Dead Pixels - Many Threads - Could DPR or photo engineer clarify & explain?

Started Feb 5, 2010 | Discussions thread
salamander1
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Re: Hot & Dead Pixels - Many Threads - Could DPR or photo engineer clarify &
In reply to GordonBGood, Nov 17, 2012

GordonBGood wrote:

salamander1 wrote:

Adobe Camera Raw (ACR) automatically does bad pixel removal for the products it supports - Photoshop and Lightroom.

interesting... is this actually true, or am i missing something obvious? this jpeg was imported as a raw file from a 5D3 directly into lightroom 4.2 (as shot) and processed there. the bad pixels are still visible. i'm not bothered too much by them because to me they look like stars, expert they aren't. they are hot pixels. or who knows what they are.

Well, I have tested that Adobe Camera Raw (ACR) of previous versions do remove or at least reduce single point hot pixels from images, but I can't guarantee that the latest versions do so since I don't use them.

The above image at ISO 1250 with a 30 second exposure is a pretty extreme time exposure that would normally show a lot of hot pixels except that if you had the "Long Exposure Noise Reduction" function turned on which is actually Dark Frame Subtraction (DFS), it should have taken care of most of them. I am looking at the original size view at 100% zoom and scanning back and forth across the image I can't really identify any pixels that are definitely "hot", although I see star trails, an aircraft trail, streaks of possible insect tracks, and ripple reflections, none of which would qualify as single point "hot" pixels. If you tell me at what image coordinates the suspected "hot" pixels are, I'll have a look. The closest that I could find is a somewhat bright spot at the pixel coordinates of (441,600) but it could also be just a water reflection. The only way to really confirm whether it really is or isn't "hot" is to shoot a lens cap test in for the same shooting parameters and look at that exact location to see if it is there no matter what the image.

Regards, GordonBGood

you know what, i think you may be right about acr. thank you for your answer. below  is an otherwise unprocessed jpeg converted from the original raw file in dpp. there are five  or six  very visible  little red-pink spots in the water, in the lower portion of the picture, looking from the middle to the left.  they  have totally disappeared in the previous jpeg, which was developed in  lighroom4.

you can immediately see how unnatural they appear  in comparison with everything else in the picture. i think those are  indeed hot pixels in contrast to the spots in the sky, which i don't know what the hell they are.

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