Surfdom wrote in message <350d0333.6123126@news1.lig.bellsouth.net>...

>I have been pondering a question, If I use a Canon 85mm 1.8 that's
>known for its superb sharpness to get an image say 1500ft away and
>then enlarge this image, would it be better than if I had just used
>say a 75-300usm and zoomed in more. I have been thinking no matter
>what you do with this lens (85) within reasonable sight of course it
>would beat any zooms detail even if enlarged quiet a bit to get close
>as the big zoom would have.. Please if a Pro reads this or a
>surveillance expert or just someone who just had the same idea and
>tried it, give me some of your insights. Thanks so much.

There are two issues here: image quality, and image sharpness.
Enlarging the image even 25% more will show noticeable degradation
of tonal quality and will noticeably coarsen grain appearance.
If the 85 is carefully focused and is used at an optimum f-stop
(probably f5.6-8) with the camera on a steady support, and if the
image is near the center, it is conceivable that maybe a 2X
enlargement (whew! ;-) would about equal the resolution of a
relatively poor zoom on film. In other words, even a so-so 75-300mm
zoom at 300mm is likely to give you a better image of a distant
subject than blowing up the 85mm image 3.5 times.
--
David Ruether
http://www.fcinet.com/ruether
ruether@fcinet.com