OT: DJI Inspire 1 camera quality

Peter100 wrote on 5/14/2015, 2:10 PM

Hi!

Our company is planning to buy a DJI s900 + GH4 or Inspire 1.
Due to the characteristic of our work we need the drone to be as portable as it is possible. So Inspire 1 would be a better choise for us. However I'm not sure about the image quality.
In the internet there are very various opinions about the Inspire 1 camera image quality. Some say it is almost pro quality. On the other hand others point out that the high compression is the weakest side of the camera.

On this video the quality of the Inspire 1 camera compared to the shoulder cam is tragic. (blown up highlights, low details, ect.).

Is is true the picture quality is rather bad, or maybe the users messed something up in the settings?

Comments

John_Cline wrote on 5/14/2015, 4:20 PM

I have not noticed any problem with the Inspire 1 camera. Here is a YouTube video in 4k shot with an Inspire 1 at the top of an 11,000 foot mountain here in Albuquerque. There is plenty of detail in this video and I don't see any serious compression artifacts except those as a result of YouTube's re-encoding. (Watch this full-screen at the highest resolution your monitor supports, the scenery is incredible.)

Here's some 4k test footage flying over downtown Santa Fe.

Peter100 wrote on 5/14/2015, 7:03 PM

Yes, the footage is very detailed. It looks really awsome.
What we are planning to film are forest landscapes. This is quite hard subject for compression alghoritms. If the scennery is too much detailed, the image become too much compressed. It results in blurring these regions.
Take a look, please, on a drones test footage. Here compression causes the grass to be blurred.
https://www.dropbox.com/s/7xh2a7iblrzmm2l/Inspire_1_compression.png?dl=0

Do you this it is caused by Inspire 1 camera compression or by youtube?

John_Cline wrote on 5/15/2015, 6:11 AM

I'm sure that most of the blurring and loss of detail is due to YouTube, however, the Inspire 1 camera only records at 60 megabits/second at 4K-30p so some of it has to be the camera.

3840x2160 pixels at a 30 frame rate multiplied by 3 bytes per pixel is an uncompressed data rate of 746 megaBYTES per second, which is 5,971 megabits/second. 60 megabits/second is a data rate reduction of approximately 100 to 1, something has to give. The most difficult thing for interframe compression to do is high motion and high detail and that's exactly what you want to do. The fact that the Sandia Mountain footage looks as good as it does off of YouTube is pretty amazing.

Here are a couple of short clips directly from the DJI Inspire 1 at 4k-24p

http://www.visual-aerials.com/uploads/3/3/9/9/3399523/_dji_0051clip.mov

http://www.visual-aerials.com/uploads/3/3/9/9/3399523/_dji_0039clip.mov

Peter100 wrote on 5/15/2015, 4:53 PM

Yes, indeed 60 mbps is quite strong compression. I think it is bigger compression ratio than 18 mbps in 1080p resolution. Nevertheless your video examples are very impressive.
After examining other raw footages that I've found in the internet, I have to say that their quality varies significantly. Your footage seems to be one of the best.
The worse examples have visible quality changes between I-frames. Also blurring minor details is visible. The quality difference among all those footages is so big that I'm starting suspect that the firmware version may be the problem.

If it possible, I'd like to have two more question for you.
1. How did you manage to achieve so smooth panning? Usually 25p/30p is not the best option for dynamic scenes.
2. What resolution/framerate is better to shoot such scenes as the Sandia Peek? 4K 30p or 1080 60p?

Peter100 wrote on 5/18/2015, 9:56 AM

So it seems, that the latest Inspire 1 firmware upgrade, reduced i-frame compression 'jumping' artefacts:
https://vimeo.com/122215897
(See video description)