DVX color fringing/line ghosting -now with IMAGES

P

pedro_emauz

Member
Hi all, I have been dooing some color and gamma tests with my DVX100a, and got some weird color fringing on almost all color patches. It's noticeable both in   25p and 25i modes, although its more pronounced in interlaced mode. It is like a ghost line (vertical in 25p, vertical and horizontal in 25i), on the edges of the patches.

See the 25p/25i comparison pic
colorpatchescompare25pto25i.jpg


here is a detailed pic of the color patches
colorpatches25p.jpg

Is his exclusive to the DVX or common to all dv prosumer camcorders?
Pedro
 
Re: DVX color fringing/line ghosting -now with IMA

Re: DVX color fringing/line ghosting -now with IMA

I'm pretty sure this has to do with a flaw in the DV codec. DV is compressed with 4:1:1 color space, meaning that there is 1/4 the color detail compared with black and white detail. So the black and white lines are lined up exactly right, but the color is low resolution, so it doesn't quite match up perfectly. That's why this issue doesn't exist in the grayscale patches.

The human eye pays much less attention to color than it does to levels of white and black, so this usually goes relatively unnoticed. But when you use a resolution chart (or regularly greenscreen dv), it's a limitation that's pretty hard to ignore.
 
Re: DVX color fringing/line ghosting -now with IMA

Re: DVX color fringing/line ghosting -now with IMA

Correction: I just saw that your camera was PAL. PAL cameras use 4:2:0 color space--which uses the same amount of data but looks better to most people. To be honest, I was expecting the color issues around the patches to be even worse; now I know why they are not. At least be glad you are using PAL and not NTSC.
 
Re: DVX color fringing/line ghosting -now with IMA

Re: DVX color fringing/line ghosting -now with IMA

Right. Although if you look closely this «ghost line» appears in the horizontal top edge of the interlaced frame (bw patches) as well, maybe due to contrast or because bw as a bit of color tint to it. But is this commom to all cameras, I mean, did you notice other similar quality cameras do this?
Actually the effect is much worse on a tv screen that on a CRT, regardless of scan mode.
this pics were not recorded onto tape and then captured. They were captured via FW live onto premiere 6.0 using stop motion capture. But, the DV compression is already done, even if you do not record to tape.
 
Re: DVX color fringing/line ghosting -now with IMA

Re: DVX color fringing/line ghosting -now with IMA

What we mainly see on 25i is vertical edge enhancement which makes (subjectively) most real life pics look sharper. This does not relate to DV. The color bleed and shift which realates to the DV codec looks pretty good.
 
Re: DVX color fringing/line ghosting -now with IMA

Re: DVX color fringing/line ghosting -now with IMA

Well, I am still adjusting to DV, but I must say it looks quite unpleasant to my eyes. I find it unuseable for most professional applications.
I did a DVCAM bluescreen project of «alice in wonderland», shot with a sony DSR 500 DVCAM and the post team is sweating to get clean mates (blue screen was a entire floor and cyc 7 metres wide by 8 long by 5 metres tall- evenly lit and shadowless), a black edge line keeps appearing on the FG mate - they have used almost all keying software there is, from Shake to Combustion to AE6. They figured it´s due to DVCAM codec/compression artifacts/colorspace issue. I told them it was risky to do it in DVCAM, because of the 5:1 compression and because color bleeding would increase bluescreen spill in to the FG subject. They did not have $$$time$$$ to do a full Post/ VFX tests, as this was a no-budget production they could not get Beta SP or Digibeta. Anyway, in september we'll have to re-shoot two days of BlueScreen work.
 
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