Apeture changes when zoomed in? at DVinfo.net

Go Back   DV Info Net > Canon EOS / MXF / AVCHD / HDV / DV Camera Systems > Canon HDV and DV Camera Systems > Canon XL and GL Series DV Camcorders > Canon GL Series DV Camcorders

Canon GL Series DV Camcorders
Canon GL2, GL1 and PAL versions XM2, XM1.


Reply
 
Thread Tools Search this Thread
Old August 28th, 2002, 05:59 AM   #1
Regular Crew
 
Join Date: Aug 2002
Posts: 61
Apeture changes when zoomed in?

Sorry for the amount of posts from me at the moment but I just keep finding new things. On the XM2(GL2) I was zooming in out, like you do and noticed that when nearly on full zoom the XM2 starts to close the aperture, and if you pull out it will open it up again, why is this? It was in a room lit with just a few lamps so it wasn't exactly bright but nothing that the XM2 couldn't cope with.

Peter B
Peter Butler is offline   Reply With Quote
Old August 28th, 2002, 08:09 AM   #2
Warden
 
Join Date: Mar 2002
Location: Clearwater, FL
Posts: 8,267
What mode are you using, Green Box, Auto or one of the semi-automatic or manual settings? The auto exposure system (AE) looks at the scene to determine proper lens opening (aperature, F-Stop) and shutter speed for correct exposure. When you zoom the lens, light sources change their size, shape and position relative to the pre zoom settings. The changes may require the AE system to open or close the lens opening to maintain proper exposure. Setting the camera to manual will force the camera to maintain the original lens opening. Of course this may result in the scene becoming too light (over exposed) or too dark (under exposed).

Jeff
Jeff Donald is offline   Reply With Quote
Old August 28th, 2002, 08:42 AM   #3
Trustee
 
Join Date: Oct 2001
Location: Chigasaki, Japan.
Posts: 1,660
Another reason for this Peter is that the lens is not a constant aperature lens. The max f-stop is f1.6-2.9, which means at the widest focal length the max available aperature is f1.6 and at the longest focal length the max available aperature is f2.9. This increments as you zoom from the widest to the longest.

As you were shooting in low light the zens would have been full open to allow as much light as possible in to the CCDs. The camera will maintain the wide open setting as you zoom but as the f-stop is not constantly f1.6 this will change depending on the focal length.
Adrian Douglas is offline   Reply With Quote
Old August 28th, 2002, 08:51 AM   #4
Regular Crew
 
Join Date: Aug 2002
Posts: 61
Cheers guys, Jeff I had it set to manual at 1.6 fstop I'm guessing Adrians right because it changes to 2. something or other when you go to full zoom, you can actually see the picture darken slightly as well. If you then try and put back up to the 1.6fstop while still zoomed in, it won't let you.


Peter B
Peter Butler is offline   Reply With Quote
Old August 28th, 2002, 10:58 AM   #5
Obstreperous Rex
 
Join Date: Jan 2001
Location: San Marcos, TX
Posts: 26,900
Images: 513
This is common for most cameras and camcorders... different aperture values for each end of the lens. They're pretty much all like that.
__________________
CH

Search DV Info Net | DV Info Net Sponsors | A Decade (+5) of DVi | ...Tuesday is Soylent Green Day!
Chris Hurd is offline   Reply With Quote
Old August 28th, 2002, 11:00 AM   #6
Regular Crew
 
Join Date: Aug 2002
Posts: 61
Excellent well thats cleared that one up, cheers everyone.


Peter B
Peter Butler 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 > Canon EOS / MXF / AVCHD / HDV / DV Camera Systems > Canon HDV and DV Camera Systems > Canon XL and GL Series DV Camcorders > Canon GL Series DV Camcorders

Thread Tools Search this Thread
Search this Thread:

Advanced Search

 



Google
 

All times are GMT -6. The time now is 10:04 PM.


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