Why 4k should be your preferred option on the Yi

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andrewukr6

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Pre: Being a videophile I never saw the point in 4k cameras, being that most screens are not 4k, and even if they are unless they are bigger than 50" you will be unlikely to see a difference (editing, cropping, stabilization aside). However perhaps this is not the case with these action 4k sensors....read below.

I was doing some experimentation today regarding filming modes, stabilization and such (in camera vs premiere pro as well). I kept noticing the 2.7k looked very soft even when only viewed at my monitor res of 2k. So I did a test. I shot 4 short clips, at 4k, 2,7k, and 1080p on a tripod. I then made a screen grab of each, and for fairness resized them to 1080p to compare like for like. (note at full res there was a big improvememnt in 4k, and I could see very little between 2.7k and 1080p). Here are the screengrabs all at 1080p below:

Scene A- (1080p)
4k = https://i.imgsafe.org/46ed54ab05.jpg
2.7k = https://i.imgsafe.org/46ed6abf0d.jpg
1080p = https://i.imgsafe.org/46ed74cb9b.jpg

Scene B- (1080p)
4k = https://i.imgsafe.org/46ed7dc947.jpg
2.7k = https://i.imgsafe.org/46ed848c62.jpg
1080p = https://i.imgsafe.org/46ed88ee1a.jpg

*ADDITION* Same as above but losing the 1080p image and resizing the 4k down to 2.7k, we can do a direct comparison here as well. Even a bigger marked difference. (click the image for full size on the page)

Scene A- (2.7k) =
4k = https://s3.postimg.io/j83gj0slt/a1_4k_MP4_snapshot_00_01_2016_08_17_14_47_29.jpg
2.7k = https://s3.postimg.io/xskjdunkh/a2_2_7k_MP4_snapshot_00_00_2016_08_17_14_47_08.jpg

Scene B- (2.7k)
4k = https://s3.postimg.io/41xes32kx/b1_4k_MP4_snapshot_00_01_2016_08_17_14_47_59.jpg
2.7k = https://s3.postimg.io/67rpml61d/b2_2_7k_MP4_snapshot_00_01_2016_08_17_14_47_49.jpg

I think the difference is *massive*. Perhaps its something to do with using all the sensor but I know I will be filming in 4k, editing, and downsizing to 1080p from this original. Shame as I will lose the 60fps option but I'll pick the better image over the FPS I think.
 
i'm not entirely sure, i'm shooting in 4K for this exact reason but when i record a fast pace scene @30fps my eyes/head hurt due to the not fluent video... perhaps it's my pc setup but i'm thinking to switch to 1080p 60fps for a comparison...
 
Well fluidity is different from sharpness which is what my above post was about. From the above 1080p output is soft. There is no reason 30fps will not give you a completely fluid video, afterall do you experience this watching tv, watching dvds, netflix, bluray? Well they are all 25-30fps. It's far more likely your computer can't handle 4k playback, if you use a player which shows at what rate its decoding FPS you might find its well below 25. 4k is roughly 4 times more taxing than 1080p. To be honest I really don't understand this current obsession with high frame rates, for sure it's necessary for slo-mo (that most people don't use unless the post process) and it does add nice movement in "very" fast action, however it's a very small increase. As I said I never heard people moaning about bluray action scenes in there favourite movies, and when 60fps has been tried on the big screen (the hobbit) everyone ocmplained saying it looked awful, so why the obsession in filming you're own 60fps on an action camera! Perhaps people relate 60fps computer gaming to video, it isn't the same situation. I'll take a crisp picture over that (and I'm a skydive cameraman) unless I want to do slo mo. 4k 60fps would be nice then you're covered for any possible edit, but you would need twice the processing power to playback.
 
I perfectly agree with you, it just feels different up to the point where the sharpness seems not worth it.
We will see
 
itsmaxdd said:
I perfectly agree with you, it just feels different up to the point where the sharpness seems not worth it.
We will see
Click to expand...
30fps looks fine as long as the exposure time is kept long enough that the motion blur caused by the long exposure time hides the steps between frames. This is not a problem with a TV or cinema camera because they have an aperture to reduce the amount of light entering the lens to obtain long exposure times and tend to be mounted on a tripod so the majority of the image is not moving anyway, however an action camera is normally moving and has no aperture so in bright conditions the exposure times become short and you see the individual frames. Some people solve the problem using neutral density filters (ND filters) but since you have to change the filter to match the light conditions it is not something that a normal action camera user will bother with. Using 60 fps solves the problem easily since that is fast enough for most human eyes not to be able to see individual frames, some human eyes are more sensitive to 30fps than others.

There are a lot of people that complain when some action cameras drop from 60fps to 30fps in low light conditions so clearly 30 fps is not sufficient for good quality video from an action camera. Even if an action camera did have an aperture, using long exposures to hide the frames isn't ideal for an action camera anyway since it will blur the action!
 
It's well known with video that down converting often produces better quality than native resolution. Not quite sure why, but it seems down converted video just looks sharper and more detailed despite having the same number of pixels as native video. Anyone doubting this should simply view SD vs SD from HD. The quality of the latter is often much better than the former.

There is an explanation from JVC Pro Video on their Pro Video Website FAQ's but it falls a little outside of the scope of things here as it deals more with in camera conversion vs external conversion, and isn't easy for everyone to understand.

JVC however, have produced a comparison clip here showing DV vs downscaled HDV:

jvc said:
To fully appreciate the difference between standard definition DVD's made from downconverted ProHD footage, and footage originally captured in the DV format, please watch the following video clip. (caution: 44MB!)
Click to expand...

http://pro.jvc.com/pro/attributes/HDTV/clips/HDV_DV_COMPARISON.MPG

(It's Quicktime so if you don't have the QT plugin anymore due to security concerns, right click the link, choose to "save link as" and open using VLC player).
 
Alsone said:
It's well known with video that down converting often produces better quality than native resolution. Not quite sure why, but it seems down converted video just looks sharper and more detailed despite having the same number of pixels as native video. Anyone doubting this should simply view SD vs SD from HD. The quality of the latter is often much better than the former.
Click to expand...

Thanks for this, I find the 1080p footage very unappealing, perhaps it's my eyes are now fussy, however the footage in 1080p doesn't look good to me - 4k it looks much more usable. I also wonder if apart from the rescaling UHD, it's that if these action cams come with a 4k sensor, the camera doesn't really like downsampling and only using a small portion of that sensor. I suppose a 1080p camera uses all the snsor, whereas a4k camera would only use approx a 1/4 of it.
 
I think JVC said it's something to do with the colour space and number of colour bits, and the image retains the superior attributes when downscaled. Native footage, doesn't have the same colour attributes.

There's also probably something in the fact that 4K means smaller sharper pixels and when you downscale it although you're throwing some away, which leaves with you with less pixels, the ones left are still sharper.
 
A more basic reason for shooting in 4K: the future. If you can manage the files today, it will probably be worth the effort when you view the results years from now.
 
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