Rack Focus at DVinfo.net

Go Back   DV Info Net > The Tools of DV and HD Production > Open DV Discussion

Open DV Discussion
For topics which don't fit into any of the other categories.


Reply
 
Thread Tools Search this Thread
Old March 23rd, 2010, 05:18 AM   #1
New Boot
 
Join Date: Apr 2007
Location: London, UK
Posts: 20
Rack Focus

rack focus is a nice effect but when I do it the image kind of shifts. Increases and decreases a bit like I'm using the zoom, which i'm not. I don't recall seeing this when I've seen similar shots on tv. am i doing something wrong? I'm using a Sony DSR 500 if that helps.
Leslie Knox is offline   Reply With Quote
Old March 23rd, 2010, 07:19 AM   #2
Inner Circle
 
Join Date: Aug 2005
Location: Atlanta/USA
Posts: 2,507
When you focus, you move a lens in a lens assembly. Depending on the build of the lens assembly, zooming may or may not also happen at the same time.
__________________
Ervin Farkas, CDVS
Certified Legal Videographer
Ervin Farkas is offline   Reply With Quote
Old March 23rd, 2010, 07:49 AM   #3
Major Player
 
Join Date: Mar 2007
Location: North Hollywood, CA, United States
Posts: 790
It's called lens breathing. Most lenses suffer from this to some extent. Really expensive lenses have measures to prevent this from happening.
Edward Carlson is offline   Reply With Quote
Old March 23rd, 2010, 09:31 AM   #4
Inner Circle
 
Join Date: Feb 2006
Location: Belfast, UK
Posts: 4,121
Most 2/3" zooms breath when adjusting focus. The Canon wide angle zooms don't breath to a noticeable extent. What can work with some shots is to use the macro for the rack focus, setting the focus ring for the distant object and pull using the macro - it's very much an eye focus job.
Brian Drysdale is offline   Reply With Quote
Old March 24th, 2010, 03:50 PM   #5
Trustee
 
Join Date: Dec 2006
Location: Little Rock
Posts: 1,383
Double check the back-focus adjustment on the lens.
__________________
David W. Jones
www.joneshdfilms.com
David W. Jones is offline   Reply
Reply

DV Info Net refers all where-to-buy and where-to-rent questions exclusively to these trusted full line dealers and rental houses...

Professional Video
(800) 833-4801
Portland, OR

B&H Photo Video
(866) 521-7381
New York, NY

Z.G.C.
(973) 335-4460
Mountain Lakes, NJ

Abel Cine Tech
(888) 700-4416
N.Y. NY & L.A. CA

Precision Camera
(800) 677-1023
Austin, TX

DV Info Net also encourages you to support local businesses and buy from an authorized dealer in your neighborhood.
  You are here: DV Info Net > The Tools of DV and HD Production > Open DV Discussion

Thread Tools Search this Thread
Search this Thread:

Advanced Search

 



Google
 

All times are GMT -6. The time now is 06:52 AM.


DV Info Net -- Real Names, Real People, Real Info!
1998-2017 The Digital Video Information Network