Hi everyone.
Today i received the Freewell ND filter for my Mavic Air.
Once at home, I started to make same quick test at home, just to see definition in the same condition (light and position).
I noticed that filters are great, no loose of IQ. But I noticed that my Mavic create red/green spot in long exposure picture.
I attach 1:1 crop picture. One without ND filter (ISO 100 1/30s) and another one with 16ND/PL (ISO 100 1.3s - with PL version, is it more than 4 stops).

Do you have the photo labeling backwards? I would expect the hot pixels to only show during the longer exposure required by the ND filter.
This might help: [Post-production Tutorial] DNG Cleaner

I see the hot pixels in many previews, but never in the rendered images...

Tadango Posted at 2018-3-27 13:02
I see the hot pixels in many previews, but never in the rendered images...

I think modern photo editing apps recognize hot pixels and automatically remove them, I know Lightroom does.

It was expected to have noise on long exposure pictures, but I never saw this red dots.

MWitarsa Posted at 2018-3-27 13:32
It was expected to have noise on long exposure pictures, but I never saw this red dots.

I do long exposure photography with my cameras. I never saw something like this. And in 1 sec exposure! Not 1 minutes.

Ex Machina Posted at 2018-3-27 13:31
I think modern photo editing apps recognize hot pixels and automatically remove them, I know Lightroom does.

I opened it with Affinity Photo and the dots are so visible. I opened a long exposure (10s) made with my camera, and not dots.

Luca Rubino Posted at 2018-3-27 13:40
I opened it with Affinity Photo and the dots are so visible. I opened a long exposure (10s) made with my camera, and not dots.

Opening the JPG or DNG in Affinity?

DNG. I shot only in DNG.

Luca Rubino Posted at 2018-3-27 13:47
DNG. I shot only in DNG.

If you're at all curious, post the DNG somewhere for me to download and I'll try it in Lightroom to see if the hot pixels go away, it might be an Adobe thing.

Hate to ask this...
But have you tried rotating ND filter to see if red-spots move?
Or tried ND filter on another Mavic?
Or tried a different ND filter on your Mavic?

Luca Rubino Posted at 2018-3-27 13:36
I do long exposure photography with my cameras. I never saw something like this. And in 1 sec exposure! Not 1 minutes.

I did some serious looking for Hot or Dead pixels on a professional camera, never found any.

I never bothered on low-end cameras.  A case of, IQ of low-end cameras muted issue of Hot or Dead pixels.

Here three files. The first one without filter at 1/30. The other two files with filter to long the exposure. As you can see (from exif), the red dots are more visible at longer exposure.
I try with ND and ND/PL Filter.
I never experienced red dots on "long" exposure. As I said, I do many long exposure photos with my cameras.

https://we.tl/25g3FzBRV9

Hi Luca, as the floor 11# mentioned, could you please try to rotating the ND filter to see if the red-spots move and try this ND filter on another Mavic to see if it exist the same red-spots? Thanks!

Hi Diana. I tried with differente ND filters. Polarized and not. And the result is the same. More longer is the exposure, more visible they are. I attach 3 files. One without filter, and other 2 photos with different ND filters. But the same result. I don't have any other mavic. So I cannot try. But different ND filter, and as I said, I tried.

I notice that they are dead pixel (aren't too many??) They are constant and always in the same place.
ACR in Photoshop try to remove them. Affinity not and they are very noticeable.

Luca Rubino Posted at 2018-3-27 21:54
Here three files. The first one without filter at 1/30. The other two files with filter to long the exposure. As you can see (from exif), the red dots are more visible at longer exposure.
I try with ND and ND/PL Filter.
I never experienced red dots on "long" exposure. As I said, I do many long exposure photos with my cameras.

Ah, good to see that the latest MA DNG are compatible with MacOS. I can confirm that the hot pixels are removed in Lightroom Classic.

My Lumix GX7 battles hot pixels in long exposure shots by in-camera post-shot processing, essentially what apps like Lightroom do but other apps, like Apple's Preview, do not.

The issue basically is the AIR sensors got totally crazy when they saw Microsoft Windows Vista. The sensors tried to make sense why someone wants to take a picture of the most dreadful OP is the face of Earth. After all the firmware algorithms running, the sensor took the best available option, try to dimmed the picture with noise, and just forget they were forced to see that horrible subject.

Lol Locky. Maybe this is the answer

Luca Rubino Posted at 2018-3-28 01:23
I notice that they are dead pixel (aren't too many??) They are constant and always in the same place.
ACR in Photoshop try to remove them. Affinity not and they are very noticeable.

I wonder if Affinity is displaying the DNG's jpg preview instead of the RAW file, which some apps do when they don't yet support a given camera's DNG/RAW? LR doesn't remove hot pixels in jpgs.

I get noisy images in general

I get noisy images in general