Go Back   Steve's Digicams Forums >

LinkBack Thread Tools Search this Thread
Old Jul 29, 2011, 4:20 PM   #1
Senior Member
Outhouse's Avatar
Join Date: Feb 2005
Posts: 262
Default Digital lenses

I'm still learning my A200 and know that on at least some lenses, the stated focal length is lengthened, if you will because of the APS sensor. Is this true with all lenses or just those designed for full frame camera? How do I know the difference?
Outhouse is offline   Reply With Quote
Sponsored Links
Old Jul 29, 2011, 4:40 PM   #2
Senior Member
TCav's Avatar
Join Date: Sep 2005
Location: Washington, DC, Metro Area, Maryland
Posts: 13,773

"Focal Length" is a physical property of a lens, and does not change with the body it's mounted on. 'Full Frame' dSLRs have the same angle of view as 35mm film SLRs when using a lens of the same focal length, but 'APS-C' dSLRs (like your A200) have an image sensor that's 1/3 smaller than a standard 35mm film exposure, so when using a lens of the same focal length as a 'Full Frame' dSLR, it's angle of view is 1/3 narrower. In effect, a lens on an APS-C dSLR has an angle of view that's the same as a lens that's 50% longer on a 'Full Frame' dSLR. That is, a 50mm lens on your A200 has the same angle of view as a 75mm lens on an A900. This is referred to as "Crop Factor', and is only useful when moving between two worlds. If all you've got is an APS-C dSLR, it doesn't mean anything to you.
  • The lens is the thing.
  • 'Full Frame' is the new 'Medium Format'.
  • "One good test is worth a thousand expert opinions." - Tex Johnston, Boeing 707 test pilot.
TCav is offline   Reply With Quote

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 On
Pingbacks are On
Refbacks are On

All times are GMT -5. The time now is 2:41 AM.