Full Colour Correction Tools and Accurate Grading Instruments

discburn wrote on 1/8/2018, 6:03 AM

I am on the verge of purchasing the upgrade to my Video Pro X6, ie the Video Pro X9 offer.

However, I am reluctant because of my experience with X6's Colour Correction and Grading Instruments...

1. X6 does not have a 'Lift' function for lifting the Black from 0 to 16 on the Waveform scale (I've tried Low Gamma and High Gamma, but they don't work, except in a limited, subtle way).

2. X6's 'Gain' function is fairly okay, but still not the same as the 'Gain' function in Davinci Resolve or Media Composer. X6 relies on its 'Brightness' function to do 'Lift' and 'Gain', but they're really separate functions.

3. The Waveform Monitor (and the other instruments) displays Colour Space range 16 - 235 as 0 - 255, which is completely wrong, making the instruments useless, unfortunately.

4. In a recent project, I sharpened lots of clips, then later applied some colour correction. Before going to disc or exporting, I played the timeline to find that all the sharpening was not at all taking place. However, in the sharpening dialogue all the settings were in place. When I tapped the mouse on the sharpening settings (one by one!), they were re-applied!

5. In the overall movie colour correction, checking the box that corrects for TV makes the movie flat and without contrast. This is clearly not right as I've checked my movie in other programs (and a broadcast monitor) to find that it is perfectly within TV specs.

If anyone can confirm for me that these functions are working properly in X9, I'll go for the upgrade, since VPX is a phenomenal program. I just need to be able to trust it without having to check its accuracy and functionality outside of it!

Looking forward to some good news!

Seamus

Comments

Scenestealer wrote on 1/11/2018, 4:42 AM

Hi Seamus

Just reviewed this topic you posted a while ago: https://www.magix.info/uk/forum/rec-709-16-235-in-video-pro-x6--1089551/#ca990510

Have you found anything that furthers that discussion? I did not have VPX then but have VPX9 now and things seem to behave with the instruments as I would have expected, at least with importing and exporting and re importing the various Colour bars supplied with VPX under Test Images. Just be aware that the "Settings" for the Measuring instruments can be set to alter the scales for 601, 709, or an Auto (default) setting which automatically adjust the scales depending on whether you have an SD or HD project set up in Movie Settings.

As mentioned in my comments in your recent posts on this subject the check box in "Overall Movie Effects settings" and the burn templates will limit output to 16-235 if required and this is reflected in the instruments.

This is not a subject I am normally concerned with but I am interested. Best would be to download the VPX9 trial and test it yourself. Magix may have learned more since you questioned support about the accuracy of VPX6 back in 2014, where they responded that things were not entirely sorted with the scopes.

discburn wrote on 1/11/2018, 5:17 AM

Hi Scenestealer,

Yes, it's not something everyone seems to be interested in, but I produce programmes for online and DVD, so the viewing modes (and therefore technical demands) can prove bewildering! Reading about colour spaces on forums indicates that even experienced producers have to grapple with all the possibilities (and idiosyncrasies of their particular NLEs).

I think you're right - downloading the VPX9 trial should reveal a lot. And I need to decide soon to take advantage of the offer as I'm off on a project for a month and the offer could have expired on my return!

Thanks for your interest and support in this ongoing debate!

Seamus

discburn wrote on 2/20/2018, 4:21 PM

I just want to add some interesting information - my latest findings!

I now have VPX9, and the new 'Curves' feature provides 'Lift' and 'Gain' which is marvellous!

Also, after much research, questions and experiments I found out that most NLE Colour Correction Measuring Scopes use Data Levels, while my Broadcast Monitor uses Video Levels. So, VPX's 0 - 255 scale actually equals my BM210 monitor's 16 - 235 scale. And Davinci Resolve's 0 - 1023 10 bit scale equals my BM210's 0 - 100 8 bit scale.

The learning curve never ends!

Seamus

browj2 wrote on 2/20/2018, 4:52 PM

Hi,

Great! Good to know.

Now, can someone explain exactly what the setting under Global Settings for the monitors, Waveform monitor, checking Display 7.5 IRE black level (NTSC) does? Since I live in NTSC land, I presume that I should have this checked, correct?

johnebaker wrote on 2/20/2018, 5:09 PM

Hi John CB

. . . . what the setting under Global Settings for the monitors, Waveform monitor, checking Display 7.5 IRE black level (NTSC) does? . . . .

Does this help explain the 7.5 IRE Black level for NTSC

John EB

discburn wrote on 2/21/2018, 5:32 AM

Great article!

browj2 wrote on 2/21/2018, 12:41 PM

@johnebaker

Interesting article, but it was in Chinese once again.

In VPX, if I set the meter to Display 7.5 IRE, I see this in the waveform monitor. I also see that there is black below the 7.5 level and a bit of white above 100. So, should I be raising the bottom of the brightness contrast curve to get the lowest to 0, and bringing down the top?

And what is the use of those test images that we have? For NTSC - 75/75, 100/75, 100/100? I looked at them and I see that in the first case, the white goes to about 80 out of 100, in the second case, white goes to above 100 or 255 on the other scale, and in the third case, the remaining colours brighten. Black always stays at 0 on the 0-255 scale.

So, what does one do with this? Still lost on how it all works.

Thanks,

John

discburn wrote on 2/21/2018, 1:42 PM

Yeah, I know. It’s weird stuff, and a lot of people are in a muddle with it. I'm using the scopes on my BM210 and keeping everything between 16 - 235. And that monitor's Black Level is set to Video (not Data). Apparently, that's the same as IRE 0 - 100 on VPX9 scopes. That's all I want to know!

For IRE NTSC, you'd have to contact the Magix engineers.

Let me know what they say!

Seamus

johnebaker wrote on 2/22/2018, 4:39 AM

Hi John CB

In principle the lowest black level that can be discerned visually on an NTSC TV system (US/Canada) is 7.5 IRE, full white is 100 IRE.

7.5 IRE equates to 16 on a 0 to 255 range therefore any black levels below this cannot be differentiated and the minimum black level should be set to 16 - this is what the IRE option in Broadcast colours effect does.

AFAICS the Global Settings for the monitors, Waveform monitor, Display 7.5 IRE black level (NTSC) replicates the more limited range of NTSC TV colours compared to a computer monitor, ie approx 2 million compared to 16.2 million respectively.

You can test the efect of applying 7.5 IRE by creating three images that have RGB levels of 0,0,0 8,8,8 and 16,16,16 - on 0 - 255 scale in an image editing program, import these into VPX and export as 2 NTSC video files, one with no IRE adjustment, the other with.

Play the video files on a NTSC TV and see if you can see the differences in the non IRE black levels and then the IRE adjusted levels.

HTH

John EB

browj2 wrote on 2/22/2018, 9:30 AM

Hi John EB,

By IRE adjustment, I presume that you mean raising the bottom point of the curve to 16, correct?

I assume that just turning on the IRE 7.5 does nothing except change the left side of the meter, where what used to be 0 - 100 is now 7.5. The bottom actually moves up, so the right hand side 0 is higher than before. Correct?
With IRE 7.5 on, am I supposed to raise the left side of the curve to 16? Black 0,0,0 is below 7.5 unless I raise it.
With IRE 7.5 on, if there are whites above 100, am I supposed to reduce the right side point (end of the curve) downwards?

I created a few videos with 3 black patches (0,0,0; 8,8,8; 16,16,16), 4 seconds each, followed by the 3 NTSC colour patches, 75/75, 100/75, 100/100

IRE 7.5 off
IRE 7.5 on - no adjustment to the curve
IRE 7.5 on, and raised the bottom of the curve to 16 for the first patch

Results on my NTSC TV:

I see distinct differences in the 3 patches. The first is black, the second is grey, lighter than the first patch
Same as 1
First patch looks like the second - grey

Conclusion: I should not adjust the blacks upwards.

Questions: Was this not all for analog TV's? Does anyone have one of those?

Bug, see the video. Strange things then happen with the line. Can't add a point and other problems.

John CB

johnebaker wrote on 2/22/2018, 1:57 PM

Hi John CB

. . . . Was this not all for analog TV's? . . . .

No it applies to flat screen TV's as well.

To see the deepest black possible on your TV - turn it off - what you see now is the deepest black possible ie the TV is emitting no light.

For back illuminated screens it may be slightly worse due to the fact that the off pixels, ie black areas of the image, actually leak a very small amount of back light, how much depends on the quality of the TV.

OLED TV's have no backlight and the deepest black is as deep as that of the screen when it is off.

Incidental light falling on the screen can also affect the perceived range of blacks, the brighter the light the lower the image contrast.

Other ways to increase the perceived range of contrast include the use of rear or frame lighting to subtly increase the brightness surrounding the screen; another is through subtle adjustment of the image colour curves to increase the perceived range of blacks.

As you can see it is all about perception and fooling the brain to see deep blacks that are not there.

HTH

John EB

browj2 wrote on 2/22/2018, 2:01 PM

Hi John EB,

On the TV, the video plays in a window that has a frame that is mostly black. The black in my video at 0,0,0 with no adjustment matched the black frame, 8,8,8 was obviously lighter.

Are you able to confirm if the problem in my video is a bug?

Thanks,

John CB

johnebaker wrote on 2/22/2018, 3:55 PM

Hi John CB

. . . . Are you able to confirm if the problem in my video is a bug? . . . .

Certainly looks like a bug, however there are restrictions - it only happens if the black point is on y-axis 0 and there is not another point near it, also if there is a third point and the black point is off both axis, selected and you then click the number box there is the same effect ie flattening of the line between the first ans second point - the second point is moved down.

For some reason the video was not playable when I first responded after you uploaded it.

John EB

browj2 wrote on 2/24/2018, 8:21 AM

Hi John EB,

Thanks for confirming. You were too quick, as the video hadn't yet been completely uploaded. I should have waited a bit before clicking on the Comment button..