DVL-Digest 554 - Postings: Index 1394-DV Tape versus MPEG2-DVD color bar and tone Filter wheel Firewire Problems Single Chip Camcorder Aliasing videoke chargen 1394-DV Tape versus MPEG2-DVD - Perry Mitchell Since we are future guessing, my logic says that future camcorders would record on some form of random access disk media, not dissimilar to a recordable DVD, and using something as efficient as MPEG. I see no reason for acquisition why long GOPs cannot be used. Current DV encoding is more sophisticated than MPEG on a per frame basis (due to processor performance restrictions), so there is plenty of room for improvement to get compression of as much as 100:1 with good quality. When the clips are 'captured' to a NLE they would be processed back to an uncompressed format for local storage on what would then be very cheap HD. The only reason to keep video clips in a compressed format is the limited performance and cost of the storage. When this scenario becomes possible, and it can only be a couple of years, it is difficult to see a future for tape. color bar and tone - "Perry" nospam-perry.mitchell@btinterne > NTSC at its best, FWIW, delivers far more accurate color >than what most movie theatre prints can manage. Robert Rouveroy csc posted: >Whoosh. Oh boy!! That is a claim that could get you killed if posted in a Cinematography forum! A simple comparison of contrast ratios of Video vs. Film makes that a very rash comment. The film color range of millions of colors are a bit much for the 255 colors of video. And that at it's very limit! All very true Robert, but CPJ2000 is right about accuracy. Movie Prints are intended to show in darkened movie theatres with no reference color, and the accuracy is way off. We have no absolute color memory so the pictures look fine. This is why you have to color correct the pictures from a telecine. To many of us, the colors from good film are far more attractive than even the best video, but accurate they are not! Perry Mitchell Video Facilities http://www.perrybits.co.uk/ Filter wheel - "Perry" nospam-perry.mitchell@btinterne David Jon Devoucoux posted: >If caught at last minute and need a white, Set your filter wheel to daylight...white balance to a card/sky/clouds, then switch filter to 3200 and shoot. Sky should be nice and reddish.... Except that . . . many cameras offer a separate white balance memory for each position of the filter wheel! Actually if you wanted to distort the color balance this much you might as well leave it on 'Preset' anyway. Note to most of you: In case you wonder what we are referring to, these are standard features on most broadcast cameras of the Betacam type. Very few prosumer cameras seem to use an optical filter wheel. Perry Mitchell Video Facilities http://www.perrybits.co.uk/ Firewire Problems - "Perry" nospam-perry.mitchell@btinterne firewire was interfering with EditDV would I like for EditDV to disable it. I checked 'no.' It disconnected the firewire anyway and now Final Cut Pro will not communicate with the firewire on my G4. Being new to the Mac OS, does anyone know how I can trouble shoot this problem. I've got a very important FCP project that I need to play out of my firewire. Any information would be greatly appreciated. Sincerely, George W. Fisher ------(cut off when replying)------------------------------- All about DV-L: http://www.DVCentral.org/thelist.html Single Chip Camcorder Aliasing - Adam Wilt > 1) With single-chip cameras the optical low-pass filter has to have a > very low cut-off point to prevent the color-matrix grid from acting as a > sampling device and thereby create aliasing... I haven't gone near the things that 1-chippers do, for simplicity's sake. What I'll probably do is a wrap-up article next month (i.e., December issue) that addresses the ways 1-chip cams are different from all the stuff I've written about to date. The lower passbands, the four-pixel on-chip processing with the mosaic filters, the odd color aliasing... I want to get the basics firmly established before I cover these arcana! > 2) The VX2000/PD-150 has raised the cut-off frequency of the optical > filter -- pushing your blue line up-ward and right-ward. Hoo boy, isn't that the case! > Now, if the aperture circuit can push the system MTF up-ward and > right-ward -- can it not also move it down-ward and left-ward? In theory that's correct, but that's assuming that the OLPF already takes out all the aliasing frequencies. In practice, though (and quite noticeably with the Canons and the new Sonys), so much aliased info gets through -- and being aliased, it LOOKS like lower frequency stuff, because by that point it IS low frequency -- that it falls well below the reasonable lower limit of the electronic filter. So even if you pull down "sharpness" to soften the pix, there's still a lot of aliased content mucking up the image -- it looks softer, but still aliased. > If so, what is the MTF AND the aliasing levels of the VX2000/PD-150 at > NORMAL and MINIMUM and MINIMUM+1 settings? From my informal tests a few weeks ago I found the CTF to run about 510-520 TVL/ph before aliasing sets in at any of the sharpness levels. At the lower levels, aliasing is still present but is fairly unobjectionable whereas at the higher levels it practically leaps off the screen and belabors you about the head and shoulders with annoying artifacts. I did some more carefully calibrated shooting yesterday (along with some audio tests to investigate the hiss issue) but I haven't had a chance to play back the tape and examine pix. When I do, I'll be able to give you a somewhat better-defined number. videoke chargen - Adam Wilt nospam-adamwilt@flash.net > > do a reveal of it (perhaps with an alpha wipe) so that it overlays the > > Adam what do you mean by an alpha wipe? An animated alpha channel image, a grayscale image being used as the alpha (transparency) channel for another layer in the timeline. You can either do this by doing a simple animation of a horizontal wipe from white to black, or you use a horizontal ramp image and vary the key level (this is essentially the way that the Pixelan Spice Rack wipes work). > Have you tried doing this with the RT2000? No. > I far as I recall the Digisuite LE can do this in real time. Probably. I haven't tried this yet on DigiSuite DTV, but if you save your text as TGAs, place then statically, and use the wipe generator, you should be OK. Premiere-generated graphics need to be rendered, whereas TGA stills can be played out directly. Cheers, Adam Wilt a DV FAQ: http://www.adamwilt.com/DV.html (diese posts stammen von der DV-L Mailingliste - THX to Adam Wilt and Perry Mitchell :-) [up] |
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