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16-235 vs 0-255 help


Vesku

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I am using GH4 video 0-255 luminance levels.
 
It is quite confusing because some players shows only normal 16-235 levels and some editors does not use 0-255 properly. Some say 16-235 is better for codec (less information to process- more bitrate to details) etc etc. Graphic cards has full range/limited range (16-235) settings...
 
If I watch my GH4 0-255 videos with Potplayer I must set in levels settings: input 0-255,  output 16-235 to see all details in highs and lows.
 
Why must I use output 16-235 while my monitor is still 0-255 RGB monitor? The logical way should be input 0-255 and output 0-255.
 
Is the video signal always finally 16-235? Is there any benefits of using 0-255 in camera? How a player or editor changes YUV signal to RGB?
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Someone may be able to provide a more substantial explanation (or even a correction) but my limited understanding is this:

 

The whole 16-235 safe levels is to do with broadcasting and with the way old tvs work.   Whether this is strictly needed in broadcasting now I don't know, but it has become a standard.   Most video players therefore expect a video with 16-235 levels.

 

Because, as you say, monitors are 0-255, these video players expand the 16-235 video out to 0-255.

If one of these players receives a 0-255 encoded video it may just treat it like it would a 16-235, so all values below 16 and above 235 will be clipped.  This obviously looks bad.

There may be players that can interpret a full range video correctly but it cannot be expected.

Even if a 16-235 video is treated as full range the video will just look milky.  It wouldn't look right, but at least it wont be clipped.  I would rather have a milky video than a clipped video.

This is why people recommend setting your output levels to 16-235 in your editor.   Most of the time it will look correct.  And at worst it will look milky.

 

As for what settings to set in camera, it depends on whether you are going to grade the footage.   If you are just going to directly upload a clip or just edit with no alterations to brightness, contrast or color, then you may as well record at 16-235.    However if you intend to grade the footage anyway It makes sense to get as much data into the file as possible which means shooting 0-255.

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Guest Ebrahim Saadawi

So even if I shoot a perfectly black object (or with the lens cap) I would get raised blacks to 16? No perfect black or white even If I shoot directly at the sun?

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So even if I shoot a perfectly black object (or with the lens cap) I would get raised blacks to 16? No perfect black or white even If I shoot directly at the sun?

 

Yes, if you use normal legal standard video the levels in the video file are 16-235. If you watch that file with a standard TV or AV monitor it shows these values right as black and white. If you use a computer monitor the video card expands these 16-235 levels to monitor RGB 0-255. You have actually 220 shades but the computer (player, editor,video card) converts it to 256 shades and the quality is not the same as i.e. 0-255 photos or videos.

 

GH4 can record video as illegal or non-standard 0-255 levels (all YUV channels) and it in theory records more information than a normal video. It is like "poor mans RAW". When color correcting and rendering the final standard 16-235 video there is more information to adjust.

 

My issue is how can I see all the original 0-255 levels with a computer monitor without any converting.

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The way I do my edits are to adjust the luminance  levels in my NLE, Sony Vegas Pro, using a video scope or similar tool to fall within the 16-235 (0-100 IRE) range.  This outputs to broadcast (TV) levels when rendered. My camera tends to record with the black levels close to 16 but the white levels up to 255. It helps a great deal with highlight clipping.  Adjusting Zebras on the camera to somewhere in the 95-105 IRE level would help minimizing clipping but my camera lacks the function.

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I solved the levels issue for me. 
 
I compared the original GH4 0-255 video source frame and the same frame captured from monitor after output level adjustment 16-235 in Potplayer and video card full range 0-255 mode. I studied the frames in Photoshop and those are absolutely identical, no IQ loss or level conversion.
 
It is quite disturbing and against common sense to set video output to limited range 16-235 before sending it to video card. The Potplayer has a floating level space and when using a limited output range it actually sends the right levels to video card and monitor. Nothing is lost. 
 
So I use in Potplayer level settings input (source) 0-255 and output 16-235 and video card full scale 0-255. Then I see all the original GH4 0-255 levels right in my monitor.
 
I can have the same effect by selecting a limited range (16-235) in video card and leaving levels untouched in player. The practical thing with Potplayer is that I can alter levels if I want to enhance levels while playing files or if watching different cameras which has different levels. GH2 for example records 16-255.
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Lets think that GH4 0-255 is like "8bit RAW" camera. When you grade to 0-100 IRE you are compressing colors to 16-235 (normal video levels). Then you have a final program with proper and legas colors.

 

If you want to watch that original GH4 0-255 "RAW" video and see all these 256 levels you must set your player or video card to limited range (16-235). The computer is still not limiting your video levels, it only passes all those 0-255 directly to your monitor and you see it right. It is kind of confusing because the full range setting is actually limiting GH4 0-255 levels in monitor and the limited setting is not limiting GH4 0-255 levels.

 

If you watch GH4 "RAW" 0-255 without any settings you loose 16 black and 20 white level because video players and video cards has default settings for normal 16-235 video. GH4 wider range of levels just spill over the edges. Some players may have auto levels function and with it you may see all the levels. With Potplayer auto levels I still cant see the exact result, it is about right but not completely. 

 

Some day we wont need this old limited 16-235 video standard and we can use 0-255 scale like with photos. Today some systems use and show 0-255 properly and some systems understand only 16-235. Then there are superwhites 235-255, blacker than black etc...

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But all that only relates to viewing the 'raw' footage on your display, right Vesku?

 

In terms of output (e.g. for web) shooting in 0-255 and then making sure everything is between 0-100 IRE in post is fine? I don't need to see the extra range on my monitor before correction ... do I?

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But all that only relates to viewing the 'raw' footage on your display, right Vesku?

 

In terms of output (e.g. for web) shooting in 0-255 and then making sure everything is between 0-100 IRE in post is fine? I don't need to see the extra range on my monitor before correction ... do I?

 

 

I mostly just watch my videos, I dont edit much. Dont you first watch or preview or organize your clips before you edit? Would it be nice if you see those clips the way they are shooted, not with clipped whites and blacks.

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I mostly just watch my videos, I dont edit much. Dont you first watch or preview or organize your clips before you edit? Would it be nice if you see those clips the way they are shooted, not with clipped whites and blacks.

 

Yes of course  :) please don't read any confrontation in my questions.

I'm grateful for the information here and genuinely want to understand the significance of the luma levels ... but it's confusing for me!

 

By the way, have you seen this GH4 film? It looks incredibly detailed to me (very nice shots too) and some of the motion looks more like time-lapse than 24fps. What do you guys think?

 

https://vimeo.com/113840055

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Yes of course  :) please don't read any confrontation in my questions.

I'm grateful for the information here and genuinely want to understand the significance of the luma levels ... but it's confusing for me!

 

By the way, have you seen this GH4 film? It looks incredibly detailed to me (very nice shots too) and some of the motion looks more like time-lapse than 24fps. What do you guys think?

 

It is quite confusing for many if Googling video levels.

 

That video is super sharp and it does not play smooth in my computer. Is it somehow 4k in vimeo and browser is scaling it to my fullhd monitor.

 

You can render and sharpen GH4 4k as sharp as you want when converting to 2k.

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No I think the stuttering is a problem with the original upload file. I'm wondering if he has done the same as me and used a 12fps burst, or some sort of high-fps time-lapse. If you watch the closeups of leaves the motion is very fast - faster than real time I think.

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GH4 0-255 looks much better than 16-235. It is like moving photo quality. 16-235 looks compressed and dull.

 

Gosh that is quite a strong statement. Personally I haven't had the GH4 long enough to have an opinion, but most people who mention it don't seem to notice any difference. If you are inclined it would be great to see some screen grabs?

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