Hi,

I’m having issues with ‘hot pixels’ on my photos. I generally shoot with a ND filter and the ISO turned all the way down (100). I then adjust exposure for the lighting conditions. I’ve noticed on all my photos there is evidence of hot pixels that become more apparent with longer exposures. I first noticed this when I took some night photography, the red, blue & green pixels scattered across the image make it nearly unrecoverable and the images require considerable time in post to bring to a presentable standard.

I have put together a link which contains some examples, both the raw images and snippets to help show the issue on lower resolution monitors. The images, DJI_0011.DNG and close_up_DJI_0011.png are with the lens complete covered with a 6 second exposure (ISO -100). The device is less than one week old.

  

https://drive.google.com/open?id=1WfOihIDqwqvn-dGCJE5bfsILfkCTXRZb

  

  

I always fly with the firmware up-to-date.

Is this normal?

  

Wow!

If I were you, I would definitely take this up with DJI Support.
Try to find night shots taken with the Mavic on the Internet and compare them with yours.
I would say that there is an issue with the image sensor in your Mavic.

Thanks Marsan,

I didn't think it was normal. Unfortunately I already tried DJI support but after the support agent recommend that I calibrate the compass in an attempt to fix the issue I decided he didn't understand fully the issue. I'm thinking about just returning the drone which will be a shame. I'll try again with support on Monday as they are not available during the weekend in my country.

lead_farma Posted at 2017-12-16 16:08
Thanks Marsan,

I didn't think it was normal. Unfortunately I already tried DJI support but after the support agent recommend that I calibrate the compass in an attempt to fix the issue I decided he didn't understand fully the issue. I'm thinking about just returning the drone which will be a shame. I'll try again with support on Monday as they are not available during the weekend in my country.

The language barrier is a problem, sometimes you just have to keep trying until you get someone with a better command of the language. Have you tried resetting the camera?

Cheers Ex Machina,

I'll give that a shot. Hopefully it does the trick.

Language is really a problem with DJI Support... I think we all have to learn Chinese

Point them to this thread at the forum so they can take a look at you photographs, then they probably understand what you problem is...

I took a few dark shots and enhanced them by editing the exposure to look for noise. I saw a few noisy pixels with their brightness increasing as the DJI camera exposure times  increased.  The picture below is ISO 200, 2.5 seconds, with the exposure cranked up in Lightroom.



I don't see the same level of spots as yours; your pictures show some very noisy pixels.  The sensors will have some inherent noise level that will show up in long exposures and likely some pixel are noisier than others. My Mavic image has a lot more noise around the periphery but there are some noticeably bright pixels.  Before I get too carried away I think I will go off and try some similar shots with one of my cameras. Then when I have a chance I will take some longer more controlled Mavic pictures since I only went up to 2.5 seconds. (I was having problems getting the MP to connect to the DJI app which distracted my last effort.)

Let me know how you go djiuser_larry. I'd be interested to compare our pictures. I'm always mindful to keep the ISO set as close to 100 as possible, I find the noise introduced from higher ISO shots can be very obvious.

lead_farma Posted at 2017-12-17 14:56
Let me know how you go djiuser_larry. I'd be interested to compare our pictures. I'm always mindful to keep the ISO set as close to 100 as possible, I find the noise introduced from higher ISO shots can be very obvious.

I have the exact same thing!  I think I had the ISO set to 100 and 1 second shutter and saved as raw and jpg.  I only see it in hte RAW file and not the jpg which I think has been masked.

Thanks ibuyufo for sharing and thank you everyone for your help!

I had a long chat with the staff at the local DJI store yesterday and we concluded that the hot pixels are normal for this camera. The staff were kinda enough to bring in one of their personal drones (Mavic) and we did a number of tests. We concluded both drones showed a similar amount of 'hot pixels' when shooting with the same shutter speed and ISO. Like you mentioned the issue only exists when you save the photos in raw format.

The best fix for this is too shoot in jpg or shoot in raw and use lightroom, photoshop or similar to open the images. Lightroom removes all the hot pixels on the import so you don't have to do any manual work

I'm happy with this conclusion I was just concerned I had a bad sensor.

Thanks again everyone!

I don't think Lightroom removes noise and hotspots when importing the raw files but there are filters for reducing noise and you can manually remove obvious hot spots along with lens spots, etc. I still don't think I am seeing the same level of spots in my 'dark' photos. Here is typical background noise level for a 5 sec, iso 1600 picture with 11:1 magnification, almost down to individual pixel resolution (raw image).

The iso 100 and 200 shots have less noise and tighter historgams. In addition I do see about a dozen hot spots, with four or five that are noticeable in the full picture (these are the ones I would probably fix with Lightroom). I did not see the bright color hot spots that lead_farma sees. All but one of my dozen are bright white. I think these are basically noisy pixels in the sensor.

My Fujifilm camera also typically has half a dozen bright noise spots in a picture but nowhere near as bright as the DJI. Overall noise is less and the histograms are much tighter (maybe the lens cap keeps out more light?). But I don't expect the Mavic camera to be up to par with a real camera so it's mostly best to use it for what it can do. A couple of lead_farma's night shots looked OK and the few obvious spots can be manually fixed. The skyline picture is overall too noisy to make a very good picture. Guess I should try a phone picture next.

Is it always the exact same pixels that are hot? If not, you could use the AEB mode, to shoot 3 or 5 photos, and then merge them in Photoshop. That might get rid of the hot pixels... Just a thought

On the DJI pictures the dozen or so hot spots looked mostly to be in the same places, but I looked at a couple of normal daytime pictures and I could not locate anything in these places. I think the DJI sensor has a few bad pixels.  I've had hot spots on the Fuji camera which come and go; I think these are more likely from dirt on the sensor. I sometimes get repetitive spots from dirty lenses, too. I can even permanently mask out a bad pixel with this camera but have never done that yet.

Incidentally with Lightroom, in the sharpening adjustment - which is opened in the picture above - if you slide the 'Masking' knob back and forth with the 'option' key pressed you can easily highlight spots in your photos. In most of my pictures I use this to locate them and then use the clone brush to remove them. And I adjust the Luminance to reduce noise. Part of my usual processing routine.

Thanks Lead Farma for following up.  It's a shame that there are so many hot pixels with this small camera.