0 Replies Latest reply on Jul 14, 2010 5:14 PM by Digital Desktop

    More Gamma Issues

    Digital Desktop

      Today, I wanted to focus on the current state of RAM Preview.

      Last week, I went through exhaustive testing of color accuracy through an After Effects workflow, with source material generated out of Final Cut Studio 2 & 3, all 1920x1080 29.97i. I performed tests through After Effects CS3, CS4, and CS5. In all cases, we used both Tektronix 601A and The results were eye-popping.

      After going through your notes about the recent gamma issues, I made your recommended changes to the Interpretation Rules, as well as the MediacoreQTGammaRulesCSx, along with the proper color management settings (Rec 709).

      MacPro 3GHz 8-core (MacPro2,1)
      16GB of RAM
      AJA Kona 3 v.7.5.1 or v.8 drivers
      OS 10.5.8
      QT 7.6.4

      In the case of CS3, gamma accuracy simply can not be had either via RAM Preview nor via rendered files. In CS4, one can clearly see that Adobe did a very good clean up job on gamma accuracy but those fixes are limited to rendered files. RAM Preview using the QuickTime Output Component through an AJA Kona xx card aren’t even close when looking at Gamma. As a result, black levels are several IRE too low. If we use the AJA Adobe Plug-ins for 7.5.1, I can get accurate Gamma BUT I can’t get real-time frame rates if I use a Project bit depth > 8bit.

      So I have a choice, inaccurate Gamma or bit limited RAM Preview. So why is running a project in 8-bit mode bad? Banding and color skew. Most camcorder acquisition formats are 8bit YUV. Doing conversions from 8bit YUV to 8bit RGB are simply bad. You are converting from a scaled color space in which your usable levels are 16-235 (YUV) over to 0-255 (RGB). As a results, you are going to have plenty of errors. By converting to a 16-bit RGB space, those errors are virtually eliminated.

      Now we both know that RAM Preview desperately needs a “do-over” and has for years. But, it is what we have today and our clients desperately need a solution that offers both gamma accuracy and real-time frame rates in 16 & 32bit modes.

      Thank you for listening