Go Back   Steve's Digicams Forums > Digicam Help > General Discussion

Reply
 
Thread Tools Search this Thread
Old Jan 26, 2005, 7:30 PM   #1
Junior Member
 
sahall's Avatar
 
Join Date: Jan 2005
Posts: 15
Default

Is, for example, F2.8 on a 35mm the same opening size as F2.8 on my A200? I have a night exposure calculator left over from my 35mm days that I want to use with the A200. It is a simple slide calculator that gives examples of scenes and suggested aperture and shutter duration. I didn't know if the exposures would match.
sahall is offline   Reply With Quote
Sponsored Links
Old Jan 26, 2005, 7:57 PM   #2
Moderator
 
calr's Avatar
 
Join Date: Sep 2003
Location: Beaverton, OR
Posts: 8,466
Default

YES. F2.8 is the same on any camera or lens.
calr is offline   Reply With Quote
Old Jan 26, 2005, 10:46 PM   #3
Senior Member
 
BillDrew's Avatar
 
Join Date: Jun 2002
Location: Hay River Township, WI
Posts: 2,512
Default

There are two answers:

Yes, your calculator will work the same for digital as for chemical cameras.

No, the opening size is not the same. Nor is the opening size the same for a 35mm as for an 8x10" view camera at the same f/stop. The f/stop is the ratio of the focal length to the diameter of the lens opening: larger format cameras need a longer focal length to cover the same field of view.

Don't worry about the second point. The f/stop is used as a measure of lens opening so you don't have to worry about the actual size of the opening. If you want to puzzle it out, spend enough time reading to understand why the exposure time decreases by a factor of two whenever the f/stop is increased by a factor of the square root of two. If you don't want to puzzle it out, not knowing won't hurt your ability to take good photos.
BillDrew is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 4:05 AM.