Home of Professional Cinematography since 1996

style="margin-bottom: 0"> 

class="style5" 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


class="Paragraph">>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.


class="Paragraph">>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.

class="Paragraph">>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 :

class="Paragraph">>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

class="Paragraph">>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 :

class="Paragraph">>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


class="Paragraph">>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 :

class="Paragraph">>...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.


class="Paragraph">>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