Lightroom not removing all hot pixels

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  • Updated 3 years ago
I bought Lightroom on the premise that it would help automatically detect and remove the hot pixels in my RAW photos. Unfortunately, Lightroom is missing some here and there. There's one particularly stubborn red hot pixel that's there in many of the photos processed in Lightroom.

I've tried other RAW processors and so far the rest are able to remove this hot pixel, as long as I turn up the hot pixel suppression to a higher level. However, Lightroom has no such option. The only way I can easily remove it is by doing spot removal, which in my opinion is not so ideal.

I've tried playing with the NR sliders and none of the settings will make this hot pixel go away.

I've read past discussions on this forum and they all suggest to submit a RAW file for analysis, so I have attached them as follows:

Processed JPEG (hot pixel is circled)

https://www.dropbox.com/s/b3o5fhls2ax...

RAW file:

https://www.dropbox.com/s/5y82c8phuxf...

So I was wondering if the algorithm within Lightroom could be changed to detect cases like mine? I've seen a much older thread about something similar ( http://feedback.photoshop.com/photosh... ) but it seems to not be fixed after four years?

Thank you very much!

P.S. Meanwhile I've obtained a refund for my subscription until this is sorted out. Please let me know if this is fixed so I can purchase it again!
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Reuben Chew

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Posted 3 years ago

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Reuben Chew

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Anyone?
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Steve Sprengel, Champion

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The issue with the so-called "hot pixel" is that it is actually a pair of pixels and brighter of the two is only one-tenth the maximum value so could easily be a small image detail, a small red light or reflection.

So Adobe isn't removing pairs of warm pixels. There probably isn't a foolproof way of doing this without also removing legitimate image details.

The spot-healing brush is what is used for removing spots larger than a single image pixel.

If you're really not going to use Adobe software until there is dual-warm-pixel suppression then I suspect you're done with Adobe products because the 4-year-old feedback thread you've linked to is also talking about pairs of warm pixels not being removed and they haven't figured out a way to do it, yet.

BTW, I used RawDigger (www.rawdigger.com) to view the exact pixel pattern that shows the pair of pixels:


And looking around the image, there is another pair of slightly less warm pixels above and to the right of the pair you've indicated:
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Reuben Chew

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Thanks for the analysis.

I understand that there isn't a foolproof way to resolve this in 100% of cases. However, is it possible for Lightroom to add an option for the user to tweak the hot pixel detection? Most other software provide a slider for the end user to tweak the intensity of the hot pixel reduction algorithm. Perhaps a more intense setting could allow such pairs to be removed, while allowing the user to scale back the setting in the event that it removes legitimate image details.

Even better would be an option for Lightroom to allow us to pinpoint the hotpixels so that it will process that away automatically, or perhaps even process a dark frame. I understand the spot removal tool does something similar; the problem is that it does not save with the presets and I have to redo it everytime I import new photos.
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Steve Sprengel, Champion

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Can you provide a few more sample shots, at least one in daylight and at least one indoors, with more image detail in the area of the hot pixels? It's one thing to remove hot pixels in an area that is almost black, but another to remove them in an area that has lots of fine texture and may be about the same brightness as the hot pixels, themselves.

Visualize Spots in the spotting tool is how you see where spots are when they're larger than one pixel.
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Reuben Chew

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Thanks. I noticed it only appears in dark fringes though, so it might be pointless taking those shots. In any case, I realise there are quite a number of other hot pixels that LR doesn't remove if you bump up the exposure. So perhaps I'll just be done with this camera...
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Steve Sprengel, Champion

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If the image area around the warm pixels is bright, perhaps the warm pixels will be darker than the surrounding area. For example can you see them if you shoot an out-of-focus image of something bright white or maybe the blue sky at EV+3?

Your camera consistently making warm pixels in pairs is probably the main reason LR isn't removing them so changing cameras to one without this characteristic is a reasonable path forward.
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Reuben Chew

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I don't notice them at all on a bright scene though. It only appears on longer exposure shots (longer than 0.3s) by the way, so its hard to replicate it on an outdoor shot while not making it too bright.

I understand this, but I was wondering if this would be a characteristic of most cameras moving forward, with the ever increasing megapixel count? My camera has a 28mp sensor, the largest for APS-C right now. I still feel it would be great if Lightroom could implement a variable hot pixel removal slider.

I'm still torn whether or not to switch cameras to one that has pixel mapping built in. This camera has excellent image quality (for the price) if you don't pixel peep. Sigh.
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Steve Sprengel, Champion

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Hot pixels can be more of a problem at higher pixel counts and higher ISOs, but if they are single hot pixels then LR can find them if they are isolated and bright enough compared to the surrounding pixels of the same color. Your camera's issue is that is produces pairs of warm pixels. Either the sensor manufacturing was very poor or there is some smearing of the sensor problems in the readout process.

A slider isn't going to convert an isolated pixel finding algorithm into a pair-finding algorithm. Something else is happening when a program has a slider. I doubt Adobe is going to change how they do hot-pixel reduction to find pairs with or without a slider, unless many cameras start having the problem.

Photoshop that comes as part of the LR CC subscription has several things that find and suppress spots larger than one pixel although usually many more than the hot pixels are averaged out, though you could make a mask that isolates the areas where the filter (median, dust-and-scratches, etc) is applied if the positions are the same and you don't crop the image before it arrives in Photoshop.

My 24MP Canon DSLR has single hot pixels, nor pairs.

If the bad pixel mapping fixes the raw pixels, great, but if it's only for the camera JPGs that isn't going to make any difference in raw file processing outside of the camera-manufacturer's software.
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Reuben Chew

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I guess it could be designed to change to a pair-finding algorithm at higher settings? That's what the other RAW processors are doing, I guess.