Why does the video crop so much?

alexjo55 · Jun 1, 2023

yeah, why?
Is it just some setting?
The 4:3 ratio in the "photo mode" is better beccause the picture gets wider.

Example:
In photo mode: 1-Omb-NVM93lsw-RILi-LOVh-Uzg-e1472030802600 hosted at ImgBB
In video mode: 1-Omb-NVM93lsw-RILi-LOVh-Uzg-e1472030802600 hosted at ImgBB

I hate it so much.

Joe Horn · Jun 1, 2023

A simple answer is that 4:3 mode uses the entire sensor, but 16:9 mode only uses the middle part of the sensor, discarding the top and bottom, effectively cropping the 4:3 image down to 16:9 ratio. A more complete answer can be found in the manual's Appendix, which says that the maximum size image in 4:3 mode is 4032×3024 pixels (the whole sensor) whereas the max in 16:9 mode is 4032×2268. Notice that the width of both is the same (4032 pixels), but 16:9 crops the top and bottom off the 4:3 image to reduce the aspect ratio to 16:9. I hope that made sense!

Droning on and on... · Jun 1, 2023

And why is the sensor 4:3 and not 16:9? Simple: closer to square, which maximizes the sensor area that can be engineered in a drone gimbal.

RogerDH · Jun 4, 2023

What resolution is your video?

alexjo55 · Jun 4, 2023

RogerDH said:
What resolution is your video?

its 4k.
I thinks the quality of the video is best with 4k, t least with the mini 3

RogerDH · Jun 4, 2023

alexjo55 said:
its 4k.
I thinks the quality of the video is best with 4k, t least with the mini 3

The reason I ask is that some 4K cameras have a 2.7K mode that doesn't downsize the 4K image; it just crops 2.7K from the middle. I was curious, so I looked around a bit, but I couldn't confirm if the Mini 3 does that, but it really looks like that's what you've got there: The video frame has a field of view a little more than 2/3rds of the photo.

RogerDH · Jun 4, 2023

Here's the frame superimposed over the photo:

RogerDH · Jun 4, 2023

I was hoping someone would do a quick comparison of the field of view at the different resolutions.

Looking at it again, the video frame has a strange aspect ratio: The photo is 16:9, but the frame is somewhere between 16:9 and 4:3 -- about 4:2.5. How did that happen?

scro · Jun 5, 2023

It looks to me like you have inadvertently enabled 2x zoom on your video mode. It is digital zoom, so essentially just crops the centre of the frame, very much like your samples show, and it can be enabled in 4k video mode too.

Check the small button just to the left of the on-screen shutter button when in video mode and see if it has 1x or 2x in it. If it has 2x, then there's the problem! Tap it so that it reverts to 1x and you should have a similar field of view for stills and video, excluding any top/bottom cropping for the chosen aspect ratios.

RogerDH · Jun 5, 2023

scro said:
It looks to me like you have inadvertently enabled 2x zoom on your video mode. It is digital zoom, so essentially just crops the centre of the frame, very much like your samples show, and it can be enabled in 4k video mode too.
...

Yeah, I also thought it looks sort of like that, except that I would have expected a digital zoom to be enlarged to fill the whole 4K frame (and degrading the quality), which doesn't appear to be the case: The details in the cropped frame are the exact same pixel size as they are in the photo -- I didn't do any size adjustment for the overlay.

scro · Jun 5, 2023

RogerDH said:
Yeah, I also thought it looks sort of like that, except that I would have expected a digital zoom to be enlarged to fill the whole 4K frame (and degrading the quality), which doesn't appear to be the case: The details in the cropped frame are the exact same pixel size as they are in the photo -- I didn't do any size adjustment for the overlay.

Did you download the full files from ImgBB to get the original dimensions? Presumably they are full res when downloaded? It asked me for a login which I don't have, so I was just going by the fairly low res previews from ImgBB. I'd agree, with 2x zoom enabled I'd expect the cropped centre portion to be enlarged to fill a 4k frame with the expected degradation in image quality (relative to 1x zoom at 4k). The cropping of the video does look to be approximately what the 2x zoom does, and the zoom is not available for stills.

RogerDH · Jun 5, 2023

scro said:
Did you download the full files from ImgBB to get the original dimensions? Presumably they are full res when downloaded? It asked me for a login which I don't have, so I was just going by the fairly low res previews from ImgBB. I'd agree, with 2x zoom enabled I'd expect the cropped centre portion to be enlarged to fill a 4k frame with the expected degradation in image quality (relative to 1x zoom at 4k). The cropping of the video does look to be approximately what the 2x zoom does, and the zoom is not available for stills.

I did a "view image in new tab" before copying, but there might be a larger version on the site, if you download it -- I didn't try that. Anyway, the photo appears to be about 1.5x times the cropped frame, rather than 2x, which is why I thought it might be 2.7K.

Edit: Another oddity that I just noticed, which doesn't seem to fit either hypothesis: The cropped frame is not really in the center of the photo; it's above and a little to the left. That, and the weird 4:2.5 aspect ratio, make this quite a mystery.

tuxtard · Jun 6, 2023

Cropped image in video mode is due to Electronic image stabilization (EIS). When EIS is enabled image is cropped in the center so that spare pixels around it can be used to compensate for the vibrations.

scro · Jun 6, 2023

tuxtard said:
Cropped image in video mode is due to Electronic image stabilization (EIS). When EIS is enabled image is cropped in the center so that spare pixels around it can be used to compensate for the vibrations.

This would be true if EIS was used on the Mini3. The mini3 and most other DJI drones use mechanical image stabilisation (ie a gimbal). Is there any evidence to suggest that they also have EIS?

tuxtard · Jun 6, 2023

scro said:
This would be true if EIS was used on the Mini3. The mini3 and most other DJI drones use mechanical image stabilisation (ie a gimbal). Is there any evidence to suggest that they also have EIS?

I don't really have proof that it has EIS since DJI code is closed source, but:

1. Zoomed in (cropped) video is clear indicator that it might have EIS
2. Air 2S have EIS or else this in next clip wouldn't be possible:

RogerDH · Jun 6, 2023

tuxtard said:
Cropped image in video mode is due to Electronic image stabilization (EIS). When EIS is enabled image is cropped in the center so that spare pixels around it can be used to compensate for the vibrations.

Hmm, that seems like an unnecessarily small crop for EIS.

Anyway, I'm thinking now that what was posted is not an actual video frame but just a manual crop from the photo, perhaps intended only as "not actual size, for illustrative purposes only."

But unless alexjo55 returns and/or someone does some testing (you wouldn't even need to be flying), it's all too mysterious to contemplate any further.

alexjo55 · Jun 7, 2023

RogerDH said:
Hmm, that seems like an unnecessarily small crop for EIS.

Anyway, I'm thinking now that what was posted is not an actual video frame but just a manual crop from the photo, perhaps intended only as "not actual size, for illustrative purposes only."

But unless alexjo55 returns and/or someone does some testing (you wouldn't even need to be flying), it's all too mysterious to contemplate any further.

yeas, i took the photo fromm google so its not rom my drone or even from a video.
I just croped the image to show how much the video crop.

I will upload video and photo from my own drone soon.

scro · Jun 7, 2023

Ok, here are some samples from my mini3pro:
- 12mp still at 4:3 ratio (note the resolution drops to around 9mp if using the 16:9 ratio as per video)
- Frame from 4k video (1x zoom)
- Frame from 4k video with 2x zoom

A few notes:
These were shot out the window with the drone held in my hand so may have a slightly different view. The 1x zoom video is slightly cropped compared to the still. The 4k video is 3840px wide and the 12mp still is 4032px wide. That extra 192px in the still picture may explain the cropping. The image quality in the 2x zoomed video is surprisingly good, and not that obvious it is interpolated up if there's not a 1x zoom sample to compare directly against. There is a loss of sharpness and detail, but it's not bad.

Am just on my phone so can't easily stack the 3 images for better comparison of framing/cropping.

RogerDH · Jun 8, 2023

scro said:
Ok, here are some samples from my mini3pro:
...

Thanks, scro! So, the results are as expected: The photo is the full sensor, 4032x3024, and the 4K video is a 3840x2160 crop from the center, losing only 96 pixels on each side but 432 pixels from the top and bottom. As noted before, that cropping is just to make a standard size 4K frame with 16:9 aspect ratio -- the extra size of the photo is just a bonus. The 2X frame, also as expected, is a 1920x1080 crop from the center which is doubled in both directions to make a standard 4K frame.