Mini 3 Pro digital zoom vs cropping in post? (And vs Air 2s?)

[stretchsje]

I currently have an Air 2s and find I can digitally zoom 2X without much loss of video quality. I like to do this when tracking my kids. The Air 2s has 5472 pixels horizontally to deal with, meaning the 4k video is nicely oversampled until about a 1.4X digital zoom. Digitally zooming further, DJI claims to use algorithmic wizardry to make it look better than a crop from a 5.4k shot. Whatever the case, the 2X digital zoom looks decent.

The only zoom test I've seen of the Mini 3 Pro is from DPReview, in early firmware, hosted on youtube. And it reveals the Mini 3 Pro at 2X digital zoom to be pretty soft, like DJI is sampling from a 12mp image (4000 pixels across and therefore barely even oversampled at full FOV.) Reviewer DCRainmaker also commented on the lousy digital zoom quality. There doesn't seem to be much or any advantage versus cropping a 4k image in post.

Any counterpoints to this maybe with the newer firmware? They still have 48 megapixels to play with (8000 pixel horizontal resolution), which could support a much better digital zoom, still very slightly oversampled at 2X and probably limited more by the lens' resolving capabilities.

It's possible the drone cannot read the full 48mp image at 30fps. But for what it's worth, the rumored Sony 1/1.3" 48mp sensor for the iPhone 14 can read the entire sensor at 90fps (30fps in HDR). A similar sensor from Omnivision can only do this at 15fps; it must use binned output to get 4k60. I don't believe DJI has confirmed the sensor make/model for he Mini 3. I don't even see where in their official literature they call it a quad bayer sensor, but they do say native 48mp AND 2.4μm pixels which are not simultaneously true for a 1/1.3" sensor!

 

[Johnmcl7]

DPR think it's this sensor:

OV48C

OV48C | OMNIVISION

www.ovt.com

It lists a 1.2 micron size but it does also mention a 2.4 micron equivalence mode in the 12MP mode which would suggest it's a quad bayer like layout as would poor cropping (since a quad bayer 48MP is effectively 12MP) but some sites are saying it is and some are saying it's not. I think the term 'quad bayer' is perhaps a Sony one?

 

[stretchsje]

The OmniVision sensor may only support full 48mp readout at 15fps, but the spec sheet lists 8k video. Presumably this is at 24p only due to bandwidth limitations. Anyone want to compare digital zoom at 24p vs 30p?

I would love to find out that the digital zoom is cropped from an 8k image, not 4k. Maybe with a firmware update, just as it was quietly updated with 10bit video.

With programmable cropping and windowing, I think the chip should be able to output 7k, 6k, 5k, or whatever is needed on demand to crop into the user's requested digital zoom. (Assuming the image processor can handle the data.)

 

[stretchsje]

Replying to myself here, but the Xiaomi Mi 10 Ultra, released in 2020, uses the same OV48C image sensor and does indeed record 8K videos at 24fps. (Sample)

I remain optimistic that DJI could implement a high quality digital zoom cropped from 8k sensor output.

 

[MaximusCZ]

I remain optimistic that DJI could implement a high quality digital zoom cropped from 8k sensor output.

I would love to share your optimism but I would bet money 8k will never come to mini 3.

 

[z28lt1]

I would love to share your optimism but I would bet money 8k will never come to mini 3.

It won't natively record 8k, but it like the Air 2, it should be able to zoom 4k video 2x using the 8k resolution to get a near lossless zoom. Same party trick as the Air 2. That said it appears that may only be possible at 24fps, not sure if DJI going to go through that and explain why the zoom is different/better in 24fps than 30fps, they generally go simple.

 

[Johnmcl7]

The OmniVision sensor may only support full 48mp readout at 15fps, but the spec sheet lists 8k video. Presumably this is at 24p only due to bandwidth limitations. Anyone want to compare digital zoom at 24p vs 30p?

I would love to find out that the digital zoom is cropped from an 8k image, not 4k. Maybe with a firmware update, just as it was quietly updated with 10bit video.

With programmable cropping and windowing, I think the chip should be able to output 7k, 6k, 5k, or whatever is needed on demand to crop into the user's requested digital zoom. (Assuming the image processor can handle the data.)

The problem is though the number of pixels doesn't necessarily relate to quality especially if it's using a sensor layout the same as the Sony quad bayer sensors, those have more pixels but you're not actually getting a better resolution. The Samsung 108MP sensor can technically produce photos with more resolution than any full frame camera but in terms of the image quality it can't match even a lower resolution FF sensor, As you've mentioned the digital zoom quality is poor as it is on the 108MP Samsung sensor despite the massive pixel count.

 

[maxbogue]

@stretchsje I've just compared my mini 3 pro in pretty much all frame rate and format possible (24, 30 and 60 fps, Normal color and D cinelike and h264/h265.) The results are the same unfortunately, 24fps is not better. It is however significantly better when doing a timelapse at 48mpx and cropping after, so they should be able in theory to make a better digital zoom... Also the hyperlapse only support 12mpx unfortunately.

Edit: Something funny I noticed is that if you just zoom 4x in 1080p without recording the image of the FPV is pretty pixelated. As soon as you start recording, it become much clearer. Probably has something to do with some power saving function, but one that just want to monitor should record and throw the footage away after..

 

[stretchsje]

@stretchsje I've just compared my mini 3 pro in pretty much all frame rate and format possible (24, 30 and 60 fps, Normal color and D cinelike and h264/h265.) The results are the same unfortunately, 24fps is not better. It is however significantly better when doing a timelapse at 48mpx and cropping after, so they should be able in theory to make a better digital zoom... Also the hyperlapse only support 12mpx unfortunately.

Edit: Something funny I noticed is that if you just zoom 4x in 1080p without recording the image of the FPV is pretty pixelated. As soon as you start recording, it become much clearer. Probably has something to do with some power saving function, but one that just want to monitor should record and throw the footage away after..

Excellent reply, but too bad about the result. Maybe we'll luck out in a future firmware as with 10-bit. Thank you for testing!