Dead / Hot pixels in RAW. Should I return my Mini 2?

[Grandzab]

I got the Mini 2 a few days ago and was pleased thus far, but recently noticed a good amount of bright white and colored dots on my photos.
They appear mainly in low light conditions at any ISO setting on RAW photos only (e.g., loading the DNG file in Mac Preview), they seem mostly corrected on the JPG version of the image.

Has anyone had the same issue?
Should I send the unit back to DJI?

Attached a few examples: original DNG (need to zoom in to spot them), JPG version for comparaison and cropped DNG which clearly shows the issue.

Thanks!

- Running the latest firmware and version of DJI Fly
- Restarted the unit
- Tried a different battery and SSD card
- Reset of camera settings

 

[JooB]

Hi, some weeks ago I found some colored pixels like on your third example on one of my raw photos in postproduction. It shows a well illuminated building with a very dark night sky around and was shot with a S10 smartphone. The colored pixels are in the black sky only.

I can't explain which effect produced them. But I suppose it's no technical failure but pure physics if there are only some and not too many pixels of this kind. I don't think your Mini 2 has a problem.

Perhaps someone deep in the technical matters of digital photography can explain this.

 

[dwallersv]

This is, simply, noise (in the electronic signal sense) internal to the sensor and camera electronics. Usually only a problem with very low light / dark conditions where the ISO must be turned way up.

"ISO" for a digital sensor is simply amplification. I.e. whatever value for the pixel is read, it is multiplied (so, the value read at ISO 400 would then be doubled at an ISO of 800). Any noise in the signal then also gets doubled (more complicated than this actually, but it's good for understanding)

This DOES get cleaned up in post-processing, that's why it's gone from the JPEG. A noise-reduction filter is applied which is nearly lossless EXCEPT for actual features where the single out-of-whack pixel actually is way way brighter than the surrounding pixels. That'll be lost as a noise spike.

Fortunately, visually eliminating these single-pixel noise issues doesn't detract from almost all images. The rare exception is a picture of stars in the night sky, for example, and if you want to do that, you need a much much more expensive sensor and camera.

 

[karlblessing]

Those are pretty hot, but are they always in the same spot of every picture? Also don't rely on the preview. Open them in an actual raw processor like Adobe Camera Raw or similar. Most of the time this is mapped automatically in the embeded data.

Noise isn't uncommon on such a small sensor especially when heat is added, and it'll be visible on the DNG if all processing is turned off (by default ACR and others will have some color noise reduction applied, you can pull that slider down to zero and you'll definitely see some color noise even at ISO 100).

The real test for dead/hot/stuck pixels, if it shows up in video, those will always be stuck in the same spot of every frame, and that's where you would have a cause for concern to contact DJI. (they're also harder to remove from video in post).

 

[Grandzab]

Thanks all for sharing the knowledge and opinions!

Following up on some of the suggestions given here, I've tried:

• 2 successive photos: the hot pixels appear in the exact same spots
• Take a video in the same conditions: Can't say I see any hot pixels
• Was able to compare the exact same scene with a Mavic Air 2 and the difference is significant: almost no hot pixel on the Air 2. Increasing the ISO to the max in the Air 2 does bring some hot pixels where as they appear on my Mini 2 at any level of ISO.

Could anyone try the same thing on their Mini 2 and post the results here? Low light scene unprocessed RAW. I wonder how my sensor measures to those other out there.
Thanks!

 

[Grandzab]

Bringing some closure to this thread in cas anyone is looking for the same answer: following DJI support suggestions I have sent my unit for replacement. Great service overall!
Got a new unit back today and results are: Exactly the same amount of hot/dead poxels in Raw!
Since these can be edited out in post, it shouldn't be an issue but glad to have gone to the bottom of this.
Thanks all for your help!

 

[m15Alien]

Bringing some closure to this thread in cas anyone is looking for the same answer: following DJI support suggestions I have sent my unit for replacement. Great service overall!
Got a new unit back today and results are: Exactly the same amount of hot/dead poxels in Raw!
Since these can be edited out in post, it shouldn't be an issue but glad to have gone to the bottom of this.
Thanks all for your help!

Hi, i have seen same issue shooting at night (or in very low light conditions) and using a 4sec exposure in the DNG file. I think that the "hot pixel " issue is not a bug of the mini 2 but a "feature" of the small sensor that has these hot pixels (jpg format is ok). Before reading your post I wrote my issue here: Dji Mini2 and Hot Pixels in DNG file