Go Back   Steve's Digicams Forums > Digital SLR and Interchangeable Lens Cameras > Pentax / Samsung dSLR, K Mount Mirrorless

Reply
 
Thread Tools Search this Thread
Old Oct 8, 2008, 6:18 PM   #1
Senior Member
 
Join Date: Apr 2004
Posts: 688
Default

why is it when you zoom in on a subject, get confirmed focus, zoom back out, and snap , the target area becomes out of focus.
taking into consideration the subject to sensor plane distance did not change

Dave
dafiryde is offline   Reply With Quote
Sponsored Links
Old Oct 8, 2008, 6:34 PM   #2
Senior Member
 
tjsnaps's Avatar
 
Join Date: Apr 2007
Location: Sacramento, Ca
Posts: 652
Default

The position of the glass elements inside the lens did change and there lies the problem.
Most lenses today are not true zooms they are varifocal lenses. True zooms which can hold the focus while zooming are harder thus more expensive to make. Many of the older lenses out there from the 35mm days are true zooms. But with auto focus the lens manufactures no longer see a need to go through the expense
tjsnaps is offline   Reply With Quote
Old Oct 8, 2008, 7:08 PM   #3
Senior Member
 
Join Date: Apr 2004
Posts: 688
Default

that explains why, iremember when i had my K1000 with a 70-210 lens,( cant remember the brand) but thats what i did for crisp focusing on the split screen. you would tend to think that at the price we pay for the DA* that pentax would have left that feature.



Dave
dafiryde 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 6:12 AM.