Infinity Focus

Red Bull

I did a search but couldn't find anything on this issue.

My question is why do some lenses focus past infinity? My 70-200 does and I've heard that most higher end lenses do. Why is this?

cmason

Red Bull wrote:

I did a search but couldn't find anything on this issue.

My question is why do some lenses focus past infinity? My 70-200 does and I've heard that most higher end lenses do. Why is this?

"...to infinity and beyond!!!!"

Richard

Red Bull wrote:

I did a search but couldn't find anything on this issue.

My question is why do some lenses focus past infinity? My 70-200 does and I've heard that most higher end lenses do. Why is this?

Maybe it's like the Spinal Tap guitarist's amplifier with a volume control that goes to 11.

Andy

To allow for changes in temperature that affect the lens, the glass, etc - and still achieve infinity focus. Also the flourite in the glass, can vary with temperature.

Other than that, this is a problem for David_S85 and Shay to work out

Here's another thread here on the same subject:

http://www.dgrin.com/showthread.php?t=20748

SCS_Photo

It is also my understanding that IR photography has a slightly different DOF than Visible Light photography, due to the spectrum. As such, they need to focus beyond what would be infinity in visible light photography.