4 Replies Latest reply on Mar 11, 2009 8:10 AM by Top Branded Clothing

    Chromakey in After Effects - What's the Best Input File to Use

    Top Branded Clothing Level 1
      I'm using Keylight for green screen, talking head videos and I'm also using HDV MPEG files from a Sony FX1 camera.
      Someone has said to me that "HDV is a notoriously bad keying format as well, due to the high compression".
      So that makes my camera pretty rubbish for what I'm doing, right?
      Could anyone offer me some advice on a solution, such as
      1. Recording in SD mode, DV AVI? I thought HD was better for keying.
      2. Convert the file from MPEG to a lossless AVI before keying?
      3. Buy a better camera!?
      4. Something else?
      Thanks guys,
        • 1. Re: Chromakey in After Effects - What's the Best Input File to Use
          Andrew Yoole MVP & Adobe Community Professional
          1. HDV is a better option than DV, simply because you have more pixels - aside from that, both are very heavily compressed formats, and neither are ideal for chromakey. Both formats actually reduce the amount of colour information in the picture when they're compressed, resulting in artifacts along edges that really screw with any keyer's capabilities.

          2. The compression in either format occurs in the camera when it is stored (to tape, hard drive or disc), so converting to any format later has no substantial benefit - the information is removed before it hits your computer. If you plan to process the material more than once, then using lossless intermediate formats is still a good idea (to prevent more compression) but it won't change the fact that your original footage has compression artifacts in it.

          3. Choose a format that uses true 4:2:2 color sampling (or better) to get past the limitations of DV and HDV. There are so many camera formats around at the moment I find it confusing - speak to a pro. Most of the tape stuff I receive is digi-beta or HDCAM, but these are far more expensive formats than the HDV world.

          4. If you are shooting in a fixed studio environment, the best way to capture key material economically is using HDMI or SDI capture ports on a desktop computer. For example, using a standard HDV camera with a direct HDMI port, and a Mac or PC with a Blackmagic Intensity HDMI card and HD-capable hard drives, you can capture pure 1080 line uncompressed material direct to the computer, bypassing the storage process required in the camera.

          Uncompressed material like this is the very best type of footage to key, but more important is the quality of lighting and photography at the shoot - good clean focus, separation of green screen light and key light, and minimal spill from green screen to subject, are equally or more important than capture formats.
          • 2. Re: Chromakey in After Effects - What's the Best Input File to Use
            Top Branded Clothing Level 1
            Thanks again, you've gone to a lot of trouble for me.
            As regards your specific points, it seems that if I'm being serious about this type of work I should either
            3. Get a better camera. I understand your point about the formats entirely, I'm also confused! I have been thinking of the Sony EX1 which (as far as I know) records XDCAM HD. Would this be better?
            4. I like the sound of all this (HDMI or SDI). Do you know what ports on my camera I would use to export the footage to my PC (I'm not a Mac user)?
            Can After Effects handle this type of footage and what other hardware (if any) would I need?
            Finally, is there a online resource I could look at ot maybe I might be better talking to a knowledgable supplier?
            All the best,
            • 3. Re: Chromakey in After Effects - What's the Best Input File to Use
              Andrew Yoole MVP & Adobe Community Professional
              As far as I can ascertain from Sony's website, XDCAM HD uses true 4:2:2 colour sampling, so it would cartainly work as a much better chromakey format. But again, I'm out of my league with current cameras - perhaps someone here with a clearer understanding of all the current formats can suggest better options.


              Unfortunately, your Sony FX1 has neither SDI or HDMI outputs, but many low-cost HDV cameras do. The Sony HDR-FX7, HVR-Z7U, HDR-HC3 or Panasonic HDC-SD1, for example, have HDMI.

              Your PC would require an HDMI I/O card like the Blackmagic Intensity:

              The Intensity card doubles as an HDMI hi-def monitor output while you're working in Premiere/AE.

              Your hard drives will also need to be capable of capturing uncompressed HD data - anywhere from 95 to 237 megabytes per second, depending on resolution, colour depth and frame rate.

              You'll need a good quality internal or external RAID to manage those data speeds, plus plenty of disk space for storing your footage.

              Remember that, so long as the camera supports down-sampling, you can still capture uncompressed standard-def pictures using this setup, thus only needing 27MB per sec - most ordinary SATA drives will have no problem with that.
              • 4. Re: Chromakey in After Effects - What's the Best Input File to Use
                Top Branded Clothing Level 1
                Thanks Andrew. It looks like a new camera for me then unless I can find a way to export uncompressed footage from my FX1.
                I've posted on some hardware sites for ideas with that!