relationship: zoom & 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 January 9th, 2006, 08:35 AM   #1
Major Player
 
Join Date: Feb 2005
Location: kentucky, USA
Posts: 429
relationship: zoom & focus???

I was kinda surprised to see in a instructional video about how to shoot great video, when using manual focus.....zoom in on the subject first, then adjust the focus and then zoom back out to compose the shot. I just sorta found this odd at first since zooming changes the focal length of the lens. Still being a laymen I have in my mind that when you zoom in/out the focus would have to be adjusted to. Can anyone elborate on this? I was just kinda curious about the relationship between Zoom and Focus when talking about a fixed subject.
Steve Witt is offline   Reply With Quote
Old January 9th, 2006, 08:41 AM   #2
Wrangler
 
Join Date: Dec 2002
Location: Mays Landing, NJ
Posts: 11,543
If the lens is properly designed and calibrated, focus should stay the same throughout the zoom range. However, depth of field is very broad at the wide end of the zoom (distant and close objects will both be in focus), but at the telephoto end of the zoom depth of field is shallow. That's the reason for suggesting that you zoom all the way in, focus, then zoom out to the desired setting. You can't focus very accurately at wide zoom - and that doesn't matter a lot since you have so much depth of field. But if you focus at wide, then zoom in on something, the chances are you'll be out of focus.
Boyd Ostroff is offline   Reply With Quote
Old January 9th, 2006, 09:02 AM   #3
Major Player
 
Join Date: Feb 2005
Location: kentucky, USA
Posts: 429
Thanks Boyd, That helps. I don't know why I was so puzzled by this.
Steve Witt 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 06:08 PM.


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