artifacts on image?

E

endlessmug

Member
OK so just received the DVX100B. I'm completely new at this so excuse my knowledge base. Took some quick 24p Advanced footage of my roommate as a test. Captured in FCP with 2:3:3:2 pulldown. The resulting image displays some unwanted artifacts. In the below image look at the top of his ear and the bottom of his chin. I don't remember it looking this way during the filming. Any ideas?

picture1js0.png
 
Those are 4:1:1 colorspace artifacts. The resolution of a DV image is 720x480 in the luminance channel but the color channels are a much lower resolution. This causes artifacting or pixelation at the border edge of colors of a high chroma value (usually red or blue or green because these are the primary colors of light). Since you are using FCP then you can apply the 4:1:1 Chroma Smoothing filter from the effects menu. If you are using some other program then you would have to search google as to how to blur the chroma channel with that program. For example, when chroma keying (greenscreen) DV footage, I use Shake and I blur the chroma channel only by a small amount before the key to make the key less blocky.

This chroma artifacting is the reason that everyone wants a RED camera (or any camera that shoots 4:4:4 RAW) or an Andromeda modified DVX100 because the 4:4:4 colorspace means that not only the luminance channel is full resolution, but so are the color channels.
 
Last edited:
Jaime, it is true that the image doesn't have enough light but this wouldn't cause that kind of artifacting.
 
Thanks yzmotoxer807 for the informative and detailed response.

I never knew about chroma artifacting. It's good to know if i ever have extreme reds, blues, or greens that i can expect this with the dvx. And wow, what a job FCP did with the color smoothing! The image looks a lot better. May I ask what the 4:1:1 ratio stands for?

I actually saw the "Red camera" in one of the production labs of my college the other day.
 
4:1:1 is the ratio between the Luma channel (4) and the two chroma channels (1 and 1). Essentially, the Luma channel is 720x480, but the chroma channels are 180x480.

Chroma smoothing or other techniques can smooth out the image, but in order to preserve the smoothness, you need to export to a format that can handle the extra information, like uncompressed. If you smooth and go right back to DV format, you lose everything you gained.

If you are going out to DVD, it is still worth it to smooth in most cases, since DVD has a different chroma scheme, 4:2:0, which actually means 720x480 Luma and 360x240 chroma.
 
You must log in or register to reply here.
Back
Top