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-   -   pixelated background (https://www.dvinfo.net/forum/canon-xl1s-xl1-watchdog/3484-pixelated-background.html)

Chris Powell September 1st, 2002 02:38 PM

pixelated background
 
XL1+EF convertor and 100-400 ISM lens and a blue sky full of red kites.
I thought this was going to be the best of days but I am sorely disapointed with my results.
The birds come out well when if focus but when shooting against a background of grass or trees a shifting pattern is seen to emerge.
I'm not alone with this as I have seen TV footage this evening shot with similar equipment, in the same area and subject matter.
The background effect could again be seen.
Is filming fast moving subjects against complex backgrounds too much for the XL1?
I'm a newbie to digital filming so I'm hoping there's a solution..

Over to you chaps.

Jeff Donald September 1st, 2002 05:40 PM

Can you post some samples of the pixelated backgrounds? Are you viewing the results on a computer monitor or PAL monitor? Was the XL1 in Frame mode or Normal mode?

Jeff

Don Palomaki September 1st, 2002 07:43 PM

Compression artifacts?

Not converted to mpeg was it?

Andrew Leigh September 1st, 2002 11:23 PM

Hi Chris,

think you have the same problem as I......interlacing artifacts.

Check this article out and see if it describes your problem. There has been a seperate thread in the Open Discussion under "Why am I getting lines / pixellation on my screen".

What nobody has been able to answer me is why I have never experienced these before. I have shot with the XL-1 for three years without any artifacts and now I get them on almost all footage. I wonder if the move to Premiere 6 had anything to do with it.


http://www.hut.fi/Misc/Electronics/circuits/vga2tv/computer_tv.html

Cheers
Andrew

Rob Lohman September 2nd, 2002 09:39 AM

DV uses a pretty similair block compression as MPEG uses. So it
might be that you're seeing macro block compression. Uncertain
before you put up any images though.

Maybe your video heads are just dirty? I had no problems with
my Premiere 6.0 on Windows 2000 SP2. If you do believe
Premiere to be the problem you might be interested to learn there
are two updates available: 6.01 & 6.02.
http://www.adobe.com/support/downloads/product.jsp?product=42&platform=Windows

But... since Premiere uses the Microsoft DV Codec, I highly doubt
Premiere is doing this. I think one of three things can be wrong:

1. Fault in your camera (ie, it needs to be repaired)
2. Dirty heads (clean them)
3. Faulty firewire cable / card
4. Microsoft DV codec is messing up
5. Your playback system is messing it up

I have a few questions for you that might point to a probable
cause:

1. Are you mixing tape brands?
2. Does this only happen when transferring to the computer
or do you also see it on a TV
3. What program did you use to play your video on your
computer?
4. What operating system are you using?

And as Jeff said, pictures would help a lot.

Chris Powell September 3rd, 2002 03:20 PM

Thanks for the ideas and sorry for the delay in coming back but I've been trying to capture a frame showing the aberration. I've failed to do this and have come to the conclusion that it's only showing up as a pattern on the moving image.

Compression artefacts aren't likely to be to blame as I've not been capturing to disk but viewing directly from camera to Pal TV. I noticed the same patterns on a wildlife film the other evening and know that the camera used then was an XL1 +100/400 ISM lens combination similar to my own.

Don't think the heads are to blame as I tried using the standard 16x lens today and can see no patterning - of course my subjects were much farther away too.. I'm now wondering if the effect is purely down to the speed the background was passing the 100/400mm lens when focused on a fast moving object. Does this make sense?
If it is the case it must have a work around.

Thanks for the input

Chris

Jeff Donald September 3rd, 2002 04:53 PM

Chris,

I don't know if I can be of much more help without and example or two. The wildlife film you saw was shown on a PAL TV, projected ? What lens were you using when you saw the aberations? I can say that I shoot wildlife (hawks in flight) with the 16x IS (white lens) and the 100-400mm IS. I don't believe that I've seen anything unusual in the background of my shots (hawks, falcons, eagles against clear blue sky). The only difference I see right off is my system is NTSC and yours is PAL.

Rob, what do you think about PAL vs. NTSC as possible cause?

Were you on a tripod? Where you using IS on the tripod? Did you have any filters on the lens? What temp. was it outside? I've seen heat and cold cause the CCD's to do some strange things.

Jeff

Chris Powell September 3rd, 2002 06:40 PM

Jeff,

I'll attempt to get a sample on the web by tomorrow evening. No ADSL or Cable here either so don't expect too large a file!
I was using a Manfrotto tripod and head - very stable.
I have a protective UV filter on the 100-400 USM lens. IS was off.
It was a particularly hot and sunny day hence my being keen on getting some footage.
The wildlife film was on TV.
I hope to talk with their camera man tomorrow to compare notes.

Chris

Jeff Donald September 3rd, 2002 07:47 PM

Say no more. It is caused by heat waves coming up from the ground. You can't always see them with the naked eye. But lower to the ground (as opposed to shooting sky) the waves can be very prominent when shot through the 100-400mm lens (35mm equivalent 2880mm lens or 58x magnification). Whenever possible I try to shoot those shots early in the morning before the ground heats up. Shooting across water produces a similar effect because of the water vapor you shoot through. Again, early morning is best, mid day is worst.

Jeff

Rob Lohman September 4th, 2002 02:32 AM

That must be it indeed Jeff... another thought of mine was
perhaps light was reflecting between the UV filter and the lens,
or the lens was to open or closed.... What brand of UV filter
do you have Chris? Some experimenting might be in order here.

Good luck.

Andrew Leigh September 6th, 2002 11:40 PM

Hi Rob,

have been out of commission for a couple of days;

<<1. Fault in your camera (ie, it needs to be repaired)>>Perhaps
<<2. Dirty heads (clean them)>> Were cleaned
<<3. Faulty firewire cable / card >> Use DVRaptor, don't think it's faulty.
<<4. Microsoft DV codec is messing up>>I use the Canopus DVRaptor Codec, should I also have Microsoft DV Codec enabled?
<<5. Your playback system is messing it up.>>Playback system is the XL-1

<<I have a few questions for you that might point to a probable
cause:>>

<<1. Are you mixing tape brands?>> Yes, sometimes I am unable to get what I need in emergencies
<<2. Does this only happen when transferring to the computer
or do you also see it on a TV>>Only on the PC, perfect on TV
<<3. What program did you use to play your video on your
computer?>>RapNavi, RapVideo, Premiere, WMP7.1
<<4. What operating system are you using?>>Win98SE

<<And as Jeff said, pictures would help a lot.>>I have a 1 215kB bitmap image that shows the problem well but don't have a website or address to post it to. Can you help?

Cheers
Andrew

Jeff Donald September 7th, 2002 04:57 AM

Andrew,

email it to me and I can put it on my Mac public iDisk and anyone can download it. let me know if I can help.

Jeff

Jeff Donald September 7th, 2002 07:12 AM

If you're only seeing the interlace artifacts on screen I think that is normal for Premiere. It uses low res images for computer screen display (progressive). If you are seeing interlace artifacts on the miniDv tape after editing in Premiere, you may have a preferences file set wrong or perhaps its related to the Codec your using. If you record to DV and just play back the raw footage (don't go through Premiere) on a TV do you see the artifacts?

Jeff

Andrew Leigh September 7th, 2002 12:03 PM

Hi Jeff,

thanks for hosting the pic.

I never used to get these interlacing artifacts....never. That is the thing that I find real curious, they have only been apparent with the swop to Prem 6.0.

The raw footage played from the XL-1 directly into a TV is fine. A recent short project I completed and exported as a .avi onto a seperate hard drive retained these artifacts.

Thanks and cheers
Andrew

Jeff Donald September 7th, 2002 12:22 PM

The picture can be down loaded here http://homepage.mac.com/jtdonald/FileSharing5.html What did you use before Premiere?

In my opinion its motion artifacts caused by interlaced video. By combining the 2 fields to display the image on a computer monitor, the movement from one field to the next is distorted. I haven't used Premiere in a few years but there must be a preference setting that will filter that for you. If your exporting to avi it might be an export setting.

Jeff


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