"Out damn spot" or "An interesting difference between ACR and DPP"

[Bill Boehme]

I do not normally use DPP, but found this interesting difference today. When looking at RAW images using DPP, it appears that I may have some sensor pixels that are stuck in the full ON state, unless it is the memory location that is bad. I shot a couple dozen images today and the hot spot is present in all of them and apparently has been there for a while based on my search back through some recent images. Interestingly, when I open the files in ACR, the bright spot is no longer there. See the 100% crops below:

In DPP

288634

And, in ACR

288635

[eddarr]

I would bet it's still there in ACR but the exposure/whbal is so different you can't see it?

[René Damkot]

I've noticed ACR map out hot pixels before...

[Victoria Bampton]

Correct, both ACR and LR map out hot pixels.

[Bill Boehme]

I would bet it's still there in ACR but the exposure/whbal is so different you can't see it?

I knew that someone would say that and I should have left the image at the same exposure level as it was in DPP. Even initially when the white background was gray, the image in ACR still did not show the spot. This started out as an exercise to evaluate image sharpness as a function of aperture size for my EF 70-200 mm f/2.8 IS USM lens and I was applying my standard ACR settings to the images (BTW, the best sharpness is between f/5.6 and f/8.0).

I've noticed ACR map out hot pixels before...

Thanks for the confirmation. That is an interesting observation that makes me wonder whether Adobe's demosaicing algorithm is slightly different from what Canon uses. Or perhaps they apply some sort of "sanity check" logic to map out things that do not make sense.

[Bill Boehme]

Correct, both ACR and LR map out hot pixels.

Thanks Victoria.

[tonylong]

The default settings for both ACR and Lightroom apply some chroma noise reduction which is pretty effective and non-destructive. That may be what you're seeing. To check this you can disable the noise reduction/sharpening to see what your image "really" looks like. It can be eye-opening when using high ISOs, and it's possible that the default NR has "caught" your hot spot.

[Bill Boehme]

I gave it a try, Tony. I set all NR to zero and sharpening to zero. Then I set everything else to the ACR defaults. Still no hot pixel. When examining at 400%, I could barely discern a faint gray spot at the location of the hot pixel.

I'm going with the "hot pixel mapping" story.

[tonylong]

Hey, well, that's the first I heard about it! I guess that's good, although I'm a bit uncomfortable with RAW PP tasks being taken out of my hands...what if I really want that hot pixel? What if it's a star in my sky pic? Oh well...