Thread: Rendering with resolve... Black levels.

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  1. #1 Rendering with resolve... Black levels. 
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    So I have searched and searched, and still cannot find an answer I'm looking for. It seems like multiple people have had this issue as well. When I go to render my project from resolve, whether it be the full range data, or video levels, The image always appears brighter than how it is set to look in resolve. Even exporting stills has the same effect, I can not get the blacks to line up like they are supposed to. Is there some function built into resolve to work around this? My input footage is prores 422 from the bmcc, I've tried h264, prores 422, prores 422 HQ, When I bring the clip that has been exported back into resolve, it looks as it should. This leads me to believe that resolve has some sort of preset black level if that makes any sense. Anyways, I'm extremely confused and would love some insight if anyone has dealt with this in the past.

    Below is an image of what the levels look like in resolve compared to rendered, even though the shift is slight, it is still there and looks a bit milky compared to the original.

    http://farm3.staticflickr.com/2816/1...96ce5a52_o.jpg

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    Senior Member CaptainHook's Avatar
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    I'm assuming you've already read that using the GUI viewer is not ideal/recommended etc. I have however been able to get my GUI Viewer to match my exports pretty well - but you need to calibrate your screen with a puck or something similar so that a display profile is created. My GUI monitor is a 27" Nec Spectraview and i use the provided puck and spectraview software to calibrate it fairly close to rec709 (and it's VERY close to the Sony OLED next to it) and everything seems to line up well (i just leave levels to auto for the most part):

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    thanks for the reply captain, I see what you are saying. But is the only way to set up your other monitor that is not used as a GUI to purchase the decklink and run SDI? Is there no other way to set up your monitors within resolve using the stock hardware? I'm running on a Mac Pro that has three inputs for monitors, two of which are taken up right now. I've also dug through the manual and wasn't able to pull any information on this. Maybe I skimmed by it?

    I guess the real reason this reason this rendering thing got to me was that even though I outputed lighter footage, even when viewed in vlc, every time I brought that outputted footage into Resolve, it looked as it should, the RGB parade and waveform was identical to that of the modified source clip in the program. So that's why I was left in the "what gives?" state. Does Resolve have some effect on the image that does not get translated through rendering? Just trying to understand why the clip looks brighter in every application other than resolve.

    Thanks again for your reply captain, I have an i1 Display pro which I used to calibrate my 24" ASUS monitor that I am grading on. I'm curious how you were able to manage to tweak your color profile to match what you were seeing in your GUI compared to your render.

    Cheers,
    Dillon
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    Would love to know how to do this as well.
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    Senior Member Frank Glencairn's Avatar
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    Same problem on the PC.

    Got a Dreamcolor hooked up via SDI (Decklink) and HDLink.

    As soon as I render it out (video levels-uncompressed 10 bit AVI) and load it in Premiere, it crushes the blacks (i.e. gamma problem).
    Looks perfect in the Premiere preview window though.
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  6. #6  
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    My Retina display comes really close, but not close enough.
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  7. #7  
    Senior Member CaptainHook's Avatar
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    Quote Originally Posted by Dillon View Post
    Thanks again for your reply captain, I have an i1 Display pro which I used to calibrate my 24" ASUS monitor that I am grading on. I'm curious how you were able to manage to tweak your color profile to match what you were seeing in your GUI compared to your render.
    What software are you using to calibrate? I'm not positive about this, but one theory i have right now is that because my monitor supports hardware calibration and i'm able to create the right '709-ish' display profile with Spectraview for OSX to use, what i'm seeing in the Resolve GUI viewer is being shown to me as 'video levels'. Last i read from Rohit, the Resolve GUI viewer is full range (RGB), which is what i think the difference in your screenshot is.

    Are you guys with troubles all on windows? Maybe OSX is scaling the display and windows isn't?

    Somethings you could try for me as tests;

    • in project settings goto the LUT panel and enable the 1D Video Monitor (or color viewer) Lut 'Full Range to Video with clip' or "Data to Video with Clip' (can't remember the name). Now compare the GUI Viewer to your export, is it closer?

    • If you right click the clip in the media pool, change clip attributes there (instead of project settings) to video levels does it look different? If not, what about rendered? (with and without changing delivery settings to video levels)

    But yes, ultimately the most sure fire way is to monitor via SDI (decklink or similar) to a grading monitor.
    Blackmagic Design
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    **Any post by me prior to Aug 2014 was before i started working for Blackmagic**
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  8. #8  
    Senior Member CaptainHook's Avatar
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    Quote Originally Posted by Frank Glencairn View Post
    As soon as I render it out (video levels-uncompressed 10 bit AVI) and load it in Premiere, it crushes the blacks (i.e. gamma problem).
    Looks perfect in the Premiere preview window though.
    Hey Frank, this almost sound the opposite Dillon's problem - what's your decklink settings? 7.5IRE or 0IRE?
    In Resolve in project settings, is your 'video monitoring - colorspace' set to data levels or video? Sounds like it's set to video, but maybe premiere is sending out data levels - crushing down the blacks... ? But the preview window (i take it not going to SDI?) is showing you video levels?

    Not sure if you can change that in premiere, but to verify this is the issue, in Resolve change your video monitoring to data and see if it matches Premiere?
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    **Any post by me prior to Aug 2014 was before i started working for Blackmagic**
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  9. #9  
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    I appreciate all the help Captain once again. I went ahead and ran those tests and this is what I found:

    This pic here shows resolve on the left, vlc on the right. This is both the 1D video Monitor look up set to "Data to video with clip" and the 1D Color Viewer Look up set to "Data to video with clip". The blacks are raised in resolve, hovering somewhere around 20IRE instead of 0, but when looking at the output in VLC, the blacks are black as should be, but there is a color cast taking effect (notice more green in the image on the right).
    http://farm6.staticflickr.com/5509/1...f7d7436b_o.png


    Here is the same clip, but with clip attributes in the media pool set to video levels instead of data, this is legally scaled in the render tab.
    http://farm8.staticflickr.com/7460/1...e285151d_o.png


    Here are the same settings, but set to unscaled in the render tab. Same greenish cast, but slightly less green than the above.
    http://farm6.staticflickr.com/5494/1...69a6d07b_o.png


    Hope these tests help. I'm using the i1 Profiler software that comes with the i1 Display pro calibrator, there is a profile built into the software that is meant to replicate Rec709, that is the profile I am using on both of my GUI monitors.
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  10. #10  
    Senior Member CaptainHook's Avatar
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    Quote Originally Posted by Dillon View Post
    This pic here shows resolve on the left, vlc on the right. This is both the 1D video Monitor look up set to "Data to video with clip" and the 1D Color Viewer Look up set to "Data to video with clip". The blacks are raised in resolve, hovering somewhere around 20IRE instead of 0, but when looking at the output in VLC, the blacks are black as should be, but there is a color cast taking effect (notice more green in the image on the right).
    Yeah, on the Resolve scopes you will find video levels are 64-940. You can turn on reference levels on the waveform and set these numbers (i have this set myself). If you have the colour page set to mirror the monitor you shouldn't need to load it in both, i would only load it in one to be sure.

    Was this rendered output in VLC done with the LUT on or off (first example)? Hard to tell in the first example on my laptop, but are the blacks matching there? What's odd here is the green tint on the right examples.

    There's a difference between calibrating the monitor (done with hardware - in my case the probe and software create a LUT that's stored on the monitor) and profiling which measures what the monitor is capable of - so i'm not sure if you can achieve your goal here if you can't calibrate your monitor to 709 via hardware (not talking about a display profile). This is why LUT boxes are often used with displays.

    FYI i (and many others) have requested several times to BMD that the GUI viewer become 'colour managed' so that display profiles can be used which would be helpful with laptops etc on set so you don't 'need' a reference monitor, but also for those who are working with typical computer monitors with web as their main target delivery. Obviously a more accurate monitor will still help here, but photographers have made it work when doing prints and retouching so ...

    I'm gonna see if i can figure 'something' out on my GF's setup - she has a 27" Dell so i imagine it would face similar problems. Otherwise i've really just been guessing what might work up to this point for a setup like that.
    Blackmagic Design
    My BMD LUTs.

    **Any post by me prior to Aug 2014 was before i started working for Blackmagic**
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