Narrow FOV in camera vs cropping in software?

[denen]

Hi,

Is there an image quality advantage for setting narrow field of view in camera versus later cropping in software?

Thanks!

 

[Sabe]

If you crop a video/image it doesnt add anything to it nor make it better, it's just like you take scissors and cut paper photograph to smaller in size.
Use narrow setting or better change lense to one that has a smaller FOV.
If you like to see further this 90 degree lense looks ok

 

[Nigel]

Hi,

Is there an image quality advantage for setting narrow field of view in camera versus later cropping in software?

Thanks!

Yes, because with the 16MP sensor of the Git2 you will still get full 1080 resolution with the narrow FOV, but if you crop it by 10% in software you only have 1080 - 108 = 972 resolution, and then when you save your 972 in 1080 format you blur all the pixels!

 

[Synergist]

Yes, because with the 16MP sensor of the Git2 you will still get full 1080 resolution with the narrow FOV, but if you crop it by 10% in software you only have 1080 - 108 = 972 resolution, and then when you save your 972 in 1080 format you blur all the pixels!

You're misunderstanding how the in-camera crop works. Setting Narrow FOV on the Git2 just makes it crop the raw image and then enlarge it (via the Novatek chipset) to fill the video resolution. If you enable the Gyro feature, it crops the image AGAIN, so you're throwing away picture information for no significant benefit.

• At best, this will result in the same quality picture as if you crop and zoom the image in a video editor on your PC.
• At worst - and this is more likely - the Git2 in Narrow FOV will result in worse quality video than cropping in a video editor. The algorithm in the Git2 won't be as advanced, and also has to crop and scale in real time.

To get 1080p resolution from a cropped image, you need to use a sensor which captures in a higher resolution to begin with. For example you can crop down to 1080p from a 2K or 4K image without losing any picture information, but choosing Narrow FOV doesn't give you "free" resolution. The only way to achieve this would be if the Git2's lens had adjustable optics to change the focal length - effectively making it a zoom lens, and adding cost and complexity. However it's a mass market, cost effective, fixed focal length lens.

The Git2 does the crop and zoom in real time through the chipset, and it won't be able to beat the quality in which PC or Mac video editor can do it.

I recommend always shooting in Wide FOV and then cropping in a video editor later.

 

[Nigel]

I recommend always shooting in Wide FOV and then cropping in a video editor later.

Then you are working on encoded compressed low quality video which you then have to encode and compress again.
If you do it in camera then it works with the raw highest quality video and it only gets compressed once.

 

[Synergist]

Then you are working on encoded compressed low quality video which you then have to encode and compress again.
If you do it in camera then it works with the raw highest quality video and it only gets compressed once.

True regarding the compression passes. But does the Novatek do image processing / smoothing / noise reduction prior to cropping? We're always going to be bound by the Novatek's H.264 encoding algorithm, but I don't know much about its implementation in the Git2 (or the Git2's design of image processing). What I do know is the resultant H.264 files are 420 colour space so it's throwing stuff away.

Does the Git2's implementation of its Novatek crop each frame, apply image processing and encodes, or does it apply processing then crop then encode? Subtle differences, but would be useful to know.


I crank my bit rate to maximum and it results in ~35 Mbit videos. At that kind of rate, my bet is they're going to be almost perceptually lossless and indistinguishable from the source video. The IMX206 is notionally 16 mpix but it's only 7.77 mm (diagonally).

Personally I think I'd go for preserving 100% original optical resolution then, when I do another encode pass, do it at at sufficiently high a rate (>=50 mbit) so as to be transparent. I can crop with high quality software algorithms, apply image enhancement that looks much better than what the Novatek can muster then encode and store as Lagarith or similar lossless codec. Alternatively for H.264 archival, CRF 15 with some minor tuning is usually great.

From what I've seen of the cropped images out of the Git2, they sacrifice too much image clarity when cropped to be worth it (it's why I disabled the Gyro). I'd prefer being able to throw pixels away with an undo function

Is having more of the image to work with worth a small (if any?) loss in quality when cropping in software? For dashcammers, having the wider FOV by default could be more useful in a litigation situation.


Six of one, half a dozen of the other...