Hi Def Shimmering

Black Lab · Post by **Black Lab** » Thu Nov 27, 2008 5:15 am

Ken Berry has mentioned the shimmering effect produced by fast panning with a HD camera. Since I do a lot of sports videos that has been a major roadblock to my move to HD.

By chance I came across an old Videomaker Magazine article that reads, in part:
One of the hazards of using a shutter speed other than 1/60th of a second is that the resulting image may look unnatural. Your television is playing back 60 images a second. If the camera's shutter speed is set to 1/15th of a second, that means it's only seeing 1/4 of the action it's expecting; one exposure is covering four frames of time. A quickly moving object will appear as a series of strobed, blurred frames.

I was just wondering if anyone has ever experimented with different frame rates (if your camera allows it)?

BTW, if you are interested the entire article is HERE.

Thanks.

etech6355 · Post by **etech6355** » Thu Nov 27, 2008 5:13 pm

BlackLab,
My Sony HD Cam uses both manual & auto shutter speed. I believe that this is controlled by the ambient available lighting in the room. I can't say it records great indoors under poor lighting conditions, outdoors it records excellent video.

1/15 of a second shutter speed would let more light into the cam. Sounds like that article would be correct, but also would depend on the quality of the HD cam itself (how it's scanning the CCD's).

Unfortunately my Sony HD Cam (Records in Mpeg2) doesn't have many available options in this area and I haven't experimented yet with the feature (using the manual setting). I'm pretty sure on my Sony cam if I use the "Exposure" setting is where it can manually control the shutter speed because this should control the shutter speed. The slower the shutter speed the more light will be available to get to the CCD..

As for the shimmering effect, Yes & No.
That really depends on the HD Cam & the conversion software, of course one shouldn't pan any camcorder at a very fast rate but I do not experience this shimmering effect converting HDV->SD any more.. Then again I get different results on different TV's/HDTV's & players.

My standard def TV connected via RGB component only displays interlaced video. Those dvd's (downconverted HDV source videos to SD for DVD) look great. My other TV's (HD) can perform progressive scanning, so the DVD player converts the interlaced signal to progressive to drive the HDTV/HD Monitore. These videos look good/ok, but I'm more impressed by the SDTV's standard interlaced picture. This is probably because the source HDV video(s) are interlaced.

All I know is with the introduction of "HD Def Video / Progressive Scanning / variety of dvd/blu-ray disk players / and conversion software" the whole field of video has become much more complex.

I've found that sometimes shimmering can be introduced because the source video has to much resolution for the tv to display. It can also be eliminated by progressive scanning when pausing the player.

I have some HD videos where I've panned pretty fast across fences with close vertical upright bridging. I also have a few test HD videos where the cam was sitting on the dashboard of a utility truck vehicle. So that video captures shaking, extreme panning when turning and all the side motion introduced by driving 50+ miles an hour.

Personally I never de-interlace HD-Video. I work with it the same as SD. The biggest difference between SD & HDV is HDV can sustain multiple renders will minimal loss compared to re-sampling SD video the same amount of times.

I'll do some VS conversions & let you know the results of the shimmering.
I have come across exactly what Ken speaks about (shimmering effect).

I'll post back after performing a few tests (may take awhile to do this)

Black Lab · Post by **Black Lab** » Thu Nov 27, 2008 6:52 pm

Thanks etech, I appreciate the help.

Black Lab · Post by **Black Lab** » Tue Dec 16, 2008 8:47 pm

Etech & Ken,

I am also a visitor to the Digital Juice forum, a forum very similar to this in one regard to member participation and helpfulness. There are many professionals that frequent the DJ forum so I posed the same question to them. One reply I received is as follows:

Well, Mr. Cassidy's example is just for illustration, because no one would shoot 1/15th of a second except as an effect or in an emergency low-light situation. And what he's talking about there (and in the rest of the article) has nothing to do with the HD camera issue you are remembering.

I believe what you are talking about doesn't actually have anything inherently to do with HD, but with CCD vs. CMOS imaging chip technology. It is commonly referred to as "rolling shutter" and can result in a wobble or skew. Two things about this (1) the issue is real and I have recreated it on two cameras I've tested, but (2) CMOS is (arguably) better and cheaper technology and probably everything is going that way, so the point is really moot. You'd have to look at specific cameras with CMOS chips and see if you can recreate it. Here's a video that shows it really clearly: http://www.youtube.com/watch?v=cItYepSTw74& (sorry, the quality of the video stinks).

I was just wondering if the video clip he provides is the shimmering you are referring to. My initial thought is no. To me that is pixelation, not shimmering. If I am correct in that assumption, would it be possible to post a short example of this shimmering effect, just to confuse me further?

Post by **Ken Berry** » Tue Dec 16, 2008 10:40 pm

Jeff - I agree that that video is more pixelation and the appropriately named 'jello', than the sort of shimmer I am talking about -- though given the pretty awful quality of the video itself, it is not easy to tell.

I don't know how big a file your email ISP will allow, but I am attempting to send to your email address a 10 MB file which well illustrates the shimmer I am referring to. If you think that verizon will not allow a file that large, please suggest an alternative.

Black Lab · Post by **Black Lab** » Tue Dec 16, 2008 11:36 pm

I got it Ken. Thanks!

By shimmer you mean the almost blurry-like quality during the pan?

Post by **Ken Berry** » Wed Dec 17, 2008 2:03 am

Yes. And as I have said before, I find it almost physically painful to watch, as though it is scratching my eyes...

Black Lab · Post by **Black Lab** » Wed Dec 17, 2008 2:06 am

I uploaded it to YouTube with the intention of making it available to the DJ forum and, after the YouTube conversion, it looks very similar to that other example:
http://www.youtube.com/watch?v=vzNHEDFI0Pc

kw · Post by kw » Wed Dec 17, 2008 2:14 pm

I haven't seen the examples posted here yet but here's my experience. I've had the Canon H20 for about a yr and just recently began to watch it on a panasonic px80 42inch plasma. I recorded an indoor band concert and with video converted to acvhd I do see some blurring when panning but last night encoded a video of an outdoor sports event where camera was handheld, jerky, and plenty of pans I saw no notice of shimmering or blurring beyond what one would expect. I was encoded at 1550 at 15mbs variable rate and could of got almost 60 minutes of video on the regular dvd. I thought that pans had very smooth looking video with no noticable artifacting unlike my regular dvd's of same event made from same video clips. Very satisfied at acdhd at this point. Will be producing some more hd videos of last yrs tapes in the next few weeks as I just installed x2 pro on system, big screen, and panasonic bd30 blu ray player.

Black Lab · Post by **Black Lab** » Wed Dec 17, 2008 5:01 pm

Interesting. Thanks.

alpine · Post by **alpine** » Wed Dec 17, 2008 9:07 pm

The first clip, HDR-HC9, clearly shows the CMOS rolling shutter effect, though there is some pixellation as well. You will see that the tree trunks appear to slant as the camera is panned quickly across. That's 'rolling shutter' and is caused because CMOS sensors do not expose the whole of the frame at the same time, but rather in bands down the sensor. So there is a time difference between different parts of the frame. CCDs, which normally expose the whole frame at the same time for the defined exposure period, and then transfer the image from sensor to the processor, usually don't suffer from this and instead just produce film-like motion blur. It's one of the reasons why pro cameras like the Sony F900 series, or the Panavision Genesis use CCDs.

There's a useful page on this here:
http://dvxuser.com/jason/CMOS-CCD/

Black Lab · Post by **Black Lab** » Thu Dec 18, 2008 12:50 am

Thanks for the info.

Then I am to assume that Ken's HV20 uses CMOS sensors?

Post by **Ken Berry** » Thu Dec 18, 2008 1:18 am

Yes, it has a 3-megapixel, 1/2.7-inch CMOS sensor that captures 1,920 horizontal and 1,080 vertical pixels for either 1080i high-definition or wide-screen standard-definition video. But since it is a HDV format camera, on capturing from the camera, the frame format size is cut to the HDV fixed 1440 x 1080.

Black Lab · Post by **Black Lab** » Thu Dec 18, 2008 3:37 am

Again, thanks for the info. Very interesting.

alpine · Post by **alpine** » Thu Dec 18, 2008 10:56 am

It's interesting to note that even Panasonic in the latest AVCHD camera have succumbed to CMOS because of its cost advantages!