Aspect ratios and Blu-ray

[Onti]

In a 1080p timeline, do studios use any templates? For instance, 1.85:1… some Blu-rays are 1920x1036 and others are 1920x1040. Why that difference? 

I have analyzed lots of Blu-rays with different AR and noted their dimensions. I wonder if anyone knows what the right dimensions are for the following aspect ratios:

1.33:1 - 1436x1080 or 1440x1080?
1.37:1 - 1480x1080 or 1484x1080?
1.66:1 - 1788x1080 or 1792x1080 or 1796x1080 or 1800x1080?
1.85:1 - 1920x1036 or 1920x1040?
2.35:1 - 1920x816?
2.55:1 - 1920x752?
2.39:1 - 1920x800?

[Chewtobacca]

For instance, 1.85:1… some Blu-rays are 1920x1036 and others are 1920x1040. Why that difference? 

The compressionist is probably aiming for mod4 (or mod8, mod16, and so on) for encoding efficiency.  Both figures are about right for that AR.  There's an acceptable margin within which one can crop a film and remain true to its theatrical presentation, so it's not true that only one pixel value is correct, just as two different BDs can extract slightly different portions from the original frame and both be right.

[pipefan413]

Aye, bearing in mind that this was all done in the analogue realm until relatively recently, you're not likely to have seen stuff masked to that level of precision consistently in cinemas so it is basically inconsequential digitally. Yeah, you could go for the most mathematically correct value, but that won't pay heed to modulus / encoding and is probably fairly arbitrary compared to what would've been seen theatrically when screened as a 35 mm print.

That said, it does mildly grate on my obsessive-compulsive nature that things are not more consistent, hahah...

[spoRv]

I'd aim to possibly get MOD8, hence:

1920x1040 for 1.85:1
1920x816 for 2.35:1
1920x800 for 2.39:1

for other, less common aspect ratios, MOD4 should suffice.

[Onti]

Many thanks for your replies. I've never heard of mod8, mod16… I thought they would use something like this...

https://nofilmschool.com/2015/04/vashi-v...-templates

[ilovewaterslides]

DCI official 2K aspect ratios are:

1998x1080 for 1.85:1
2048x858 for 2.39:1

so converted to 1080p, you get:

1920x1038 for 1.85:1
1920x804 for 2.39:1

[spoRv]

DCI official 2K aspect ratios are:

1998x1080 for 1.85:1
2048x858 for 2.39:1

so converted to 1080p, you get:

1920x1038 for 1.85:1
1920x804 for 2.39:1

Can't apply for HD/UHD, DCI is REAL 2K/4K at 17:9 aspect ratio...

[ilovewaterslides]

DCI official 2K aspect ratios are:

1998x1080 for 1.85:1
2048x858 for 2.39:1

so converted to 1080p, you get:

1920x1038 for 1.85:1
1920x804 for 2.39:1

Can't apply for HD/UHD, DCI is REAL 2K/4K at 17:9 aspect ratio...

I'm sorry but that just doesn't make any sense

The DCI standard supports different aspect ratios. 17:9 is not an AR. It's a format.

DCI full container AR is 1.90:1 (4096x2160 in 4K and 2048x1080 in 2K).

Flat (1.85:1) = 3996x2160 in 4K and 1998x1080 in 2K
Scope (2.39:1) = 4096x1716 in 4K and 2048x858 in 2K

It applies perfectly. You just need to downscale those numers to match the video standards so it gives you:

1.85:1 = 3840x2076 in UHD and 1920x1038 in FHD

2.39:1 = 3840x1608 in UHD and 1920x804 in FHD.

[Onti]

DCI official 2K aspect ratios are:

1998x1080 for 1.85:1
2048x858 for 2.39:1

so converted to 1080p, you get:

1920x1038 for 1.85:1
1920x804 for 2.39:1

Can't apply for HD/UHD, DCI is REAL 2K/4K at 17:9 aspect ratio...

I'm sorry but that just doesn't make any sense

The DCI standard supports different aspect ratios. 17:9 is not an AR. It's a format.

DCI full container AR is 1.90:1 (4096x2160 in 4K and 2048x1080 in 2K).

Flat (1.85:1) = 3996x2160 in 4K and 1998x1080 in 2K
Scope (2.39:1) = 4096x1716 in 4K and 2048x858 in 2K

It applies perfectly. You just need to downscale those numers to match the video standards so it gives you:

1.85:1 = 3840x2076 in UHD and 1920x1038 in FHD

2.39:1 = 3840x1608 in UHD and 1920x804 in FHD.

But in this case I realize one thing, you crop (20) on the top and (22) on the bottom or (22) on the top and (20) on the bottom. To be the same in FullHD must be 1920x1036 (22 top and bottom) or 1920x1040 (20 top and bottom). But I’ve found some releases with (22) and (20). There appeared to be no consensus on this issue.

Same case with 1920x804=2.39 and 1920x800=2.4, which one is more accurate? ¿both?…

Wikipedia:

A new definition issued in October 1971 as ANSI PH22.106-1971. It specified a slightly smaller vertical dimension of 0.700 inches (17.8 mm) for the projector aperture, to help make splices less noticeable to film viewers. After unsqueezing, this would yield an aspect ratio of c. 2.397∶1. This is commonly referred to by the rounded value 2.40∶1 or 2.4∶1.

But most Blu-ray and UHD releases comes with the wrong 2.35:1 for films produced after 1971.

One more question, many Warner releases are 1.78:1 instead of 1.85:1, is there any software to change the aspect ratio to 1.85:1 without re-encoding? I suppose not.

[spoRv]

The DCI standard supports different aspect ratios. 17:9 is not an AR. It's a format.

DCI full container AR is 1.90:1 (4096x2160 in 4K and 2048x1080 in 2K).

Ehr... DCI is a format, 17:9 is an aspect ratio... and 4096/2160 and 2048/1080= 17/9 = 1.8888...

Even if actually 1.85:1 height is 1920/1.85 = 1.037.83 hence nearer to 1036 than 1040, the latter is MOD4, MOD8, MOD16 so (IMHO) the best value to use, as much as 800 (instead of 803.34) for 2.39:1 for being MOD4, MOD8, MOD16.

many Warner releases are 1.78:1 instead of 1.85:1, is there any software to change the aspect ratio to 1.85:1 without re-encoding? I suppose not.

If you find 1.78:1 releases, most of the times they are just open matte - if you want to get the OAR, you have to cut top and bottom part (40px each on full HD).