Making 4K video of still photos

Daniel D. Teoli Jr. · July 24, 2019

I want to make some 4K video of still photos. My still photos are all hi-res scans that I am importing into the software. So I am not upscaling or photographing the photos, I'm downscaling scans.

The software I'm using has 2 hi-res options for exports. Are either of these two OK to advertise as 4K or does 4K have to be the 4096x2160 only?

3840x2160

4096x2160

I don't care about the ratio on these options as my files are not widescreen. Also, can 4K be MP4 or AVI, does that matter at all? I plan to use the files for projection.

Thanks

Stuart Brereton · July 24, 2019

Contrary to what TV manufacturers would have you believe, 3840 pixels is not 4K, it’s UHD. The two terms have become conflated over the years as manufacturers have used them interchangeably, but 4K is, well, 4K. 4096 pixels, not 3840.

Whether or not your audience cares about this distinction is a different question.

Daniel D. Teoli Jr. · July 24, 2019

Well, I like to have the right nomenclature. There is always enough stuff to be critical of. Honesty of advertised specs should be basic.

Thanks!

Perry Paolantonio · July 24, 2019

30 minutes ago, Daniel D. Teoli Jr. said:

Honesty of advertised specs should be basic.

"4k" is not really a spec, per se. It's a rough pixel count of only the horizontal component of an image's dimensions, and it can vary.

3656x2664 is 4k as generated by our Northlight scanner for a 4k Academy Aperture 35mm scan. It does 4096 for full aperture, but if you don't include the soundtrack area the file is 3656. I'd respectfully disagree that UHD isn't 4k. I mean, technically, it's not 4000+ pixels across, but it's advertised widely as 4k and it's what people know as 4k. Arguing otherwise is kind of futile since that's what most of the world knows as 4k at this point.

Of course, the vertical number is whatever you need it to be to match your aspect ratio. so UHD is 16x9 which is purely a resolution from the video world and doesn't exist in film or photography really. If you scan most non-widescreen motion picture film you're usually looking at 4096x3112 or thereabouts, but I've seen other resolutions as well.

Phil Connolly · July 24, 2019

If your planning for cinema projection its probably better to conform to the DCI spec:

In 2K, for Scope (2.39:1) presentation 2048×858 pixels of the imager is used
In 2K, for Flat (1.85:1) presentation 1998×1080 pixels of the imager is used
In 4K, for Scope (2.39:1) presentation 4096×1716 pixels of the imager is used
In 4K, for Flat (1.85:1) presentation 3996×2160 pixels of the imager is used

The reason UHD is a doubling of the 1920 HD width, eg 3840 across is it simplifies the maths. Most people are going to be watching a lot of 1080x1920p footage on their UHD/4k TV's. If TV's were 4096 across the resize would be more difficult to do and the end result less good.

If its more likely people are going to view it in a domestic setting HD/UHD - then it may be "better" to master directly to UHD 3840, since the downconvert from 4K DCI may affect the quality.

Daniel D. Teoli Jr. · July 25, 2019

I just was worried I would be advertising something wrong if I am offering 4K at 3840. I'm doing all future hi def work in 4096x2160. Prior to that I was doing 3840x2160. It is not that big a step up between the two, but the 4096 will fit the bill for 4K, so no one can complain.

Some of my early work I only have in 3840. So if I get an inquiry I will tell them it is UHD and don't have it in 4K, but UHD is very close to it.

Probably no one would complain either way. I'm dealing with curators of special collection libraries and art museums and possibly galleries. They are generally MA's or PhD's with art history degrees. I didn't even know what 4K was myself until a few days ago. I looked it up and it said the image is 4000 pixels wide. So that is an easy way to understand it. I guess a Blu-ray is a 1K.

Phil Connolly · July 25, 2019

The terms are pretty interchangeable and most library types and academics can barely tell the difference between HD and SD - so as long as your in the ball park its probably fine

Blu ray is usually HD, 1920 x 1080. The K is taken from the horizontal so its 1.9K so pretty much the same visually as 2K. Unless its UHD bluray that would be 3.8K.

4096 x 2160 compared to 3840 x 2160 would have different aspect ratios mind