CML - Cinematography Information & Discussion
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Luminance Bands

Published : 15th June 2005

Hi everyone,

I'm encountering a very strange interference/artifact problem. I'm on location shooting with a XL1 (original) and my footage is suffering from crawling luminance bands. They general move upwards but sometimes diagonally. I see it on the viewfinder as well as on the final footage. Running off battery, no audio plugged in at all.

There's a still here :

http://www.biki.net/images/bands.jpg

(Points for working out what its an image of )

Any ideas on what might be causing it?

I can up some actual footage if you'd like, but I figure this is more bandwidth friendly.

Ta,

Stuart.

Stuart M. Willis
Director + Editor
Sydney, Australia

>I'm encountering a very strange interference/artifact problem.
>I'm on location shooting with a XL1 (original) and my footage is >suffering from crawling luminance bands.

Stuart,

Looks like RF interference to me. Are you working near a high powered radio transmitter?

As for the object, I'm guessing a head off a 'laughing clown' type side-show attraction

Cheers,

Clive Woodward,
Perth, Western Australia.

>I'm encountering a very strange interference/artifact problem. I'm on >location shooting with a XL1 (original) and my footage is suffering from >crawling luminance bands.

----That is most definitely RFI, external or internal I cannot say but it is RFI for sure.

>As for the object, I'm guessing a head off a 'laughing clown' type side->show attraction

---If the RFI is coming from it.....turn off the camera, talk slowly, and back away......

Jeffery Haas
freelance editor, camera operator
FCC First Class Radiotelephone Operator Permit #
P-1-16-37875 (June 1979)

Clive doth quoth :

>Looks like RF interference to me. Are you working near a high powered >radio transmitter?

Yup (We're in St Leonards, which is just a few clicks from the ABC and SBS towers). RFI! Of course. Duh Thanks

>As for the object, I'm guessing a head off a 'laughing clown' type side->show attraction

It's a 'phantom head'. A fake head with real teeth used by dentists to practice abusing.

Thanks Clive & Jeff.

Stuart.

stuart m. willis
director + editor
sydney, australia

Stuart, your luminance bands sound as if they're coming from nearby TV transmitters. You're probably picking up video signals that are a wee bit out of vertical and horizontal sync with your own equipment -- hence the motion of the bands.

Dan Drasin
Producer/DP
Marin County, CA

Stuart Willis wrote :

>Yup (We're in St Leonards, which is just a few clicks from the ABC and >SBS towers). RFI! Of course. Duh Thanks

I would bring my gear to the doctor. We are located two streets down from the Channel 2 tower on the Pac Hwy, but have never experienced video-problems. Nor on our equipment, nor on the handycams which the students bring in. However, the shotgun-mikes (Sennheiser ME86), and one of those blue, inhouse Telstra payphones go berzerk.

Cheers

Martin Heffels

filmmaker/DP/editor/filmschool techie
Sydney, Australia

"better to let them do it imperfectly than to do it perfectly yourself, for it is their country - and your time is short" T.E. Lawrence

>Yup (We're in St Leonards, which is just a few clicks from the ABC and >SBS towers). RFI! Of course. Duh Thanks

followed by :

>...We are located two streets down from the Channel 2 tower on the Pac >Hwy, but have never experienced video-problems.

I expect you're too close! Underneath the radar, so to speak. TV Tx arrays are designed to transmit a lobe towards the horizon. We have people in Perth who are in the shadow of Channel Ten's Tx tower who get low RF reception.

Also, well designed and correctly operating equipment shouldn't be susceptible to RF interference. It may be Stuart's camera has an oxidised connection somewhere. Oxide often makes a semiconductor junction which will demodulate strong RF. [Ever heard the tales about people who have reported toasters or dental work that emit the sound of a local radio broadcast?]

Clive Woodward BOCP
underneath the radar's often safer,
Perth, Western Australia.

>I would bring my gear to the doctor. We are located two streets down >from the Channel 2 tower on the Pac Hwy, but have never experienced >video-problems.

----Am I far off in saying that since data inside the camera moves at RF, isn’t it possible that a failed component can also cause internally generated RFI?

This is, after all, the reason that I said "whether internal or external" in my earlier post.

I have seen several instances in the old days where even tube cameras would start generating RFI due to internal component failure on the printed circuit cards.

I have driven more than a few repair techs crazy with my insistence on occasion only to have been proven right in the end. For this reason I find this a fascinating thread.

Cheers,

Jeffery Haas
freelance editor, camera operator
Dallas, TX