lens sharpness & performance focused near vs. far

"Bob Monaghan" wrote in message
...

see http://medfmt.8k.com/mf/diopter.html#beat - [... snip the good stuff
...]

Where have you been? Welcome back, Bob! We were worried about you!

Bob Monaghan wrote:

see http://medfmt.8k.com/mf/diopter.html#beat - diopter lenses of good
quality (achromatic 2 element glass or better) will often yield higher
central resolution than many macro lenses - at the expense of the edges!

But would enough people pay extra for 3-4 element, 2-group diopter
lens for the increased quality?


;-) bobm

--
Sander

+++ Out of cheese error +++

"Sander Vesik" wrote:
Bob Monaghan wrote:

see http://medfmt.8k.com/mf/diopter.html#beat - diopter lenses of good
quality (achromatic 2 element glass or better) will often yield higher
central resolution than many macro lenses - at the expense of the edges!

Thanks to this advice (years ago) I've been a very happy camper. My Canon
58mm 250D fits practically every lens I own and goes everywhere my camera
bag goes.

But would enough people pay extra for 3-4 element, 2-group diopter
lens for the increased quality?

Both Canon and Nikon make at least 2-element lenses. The 58mm Canon 250D* is
a seriously heavy hunk of glass compared to single-element closeup lenses.
It costs US$60 or so, I think, so it's not unafordable.

*: This changes the lens so that when the lens is set at infinity, things at
250mm are in focus.

David J. Littleboy
Tokyo, Japan

David J. Littleboy wrote:

... The 58mm Canon 250D*
....
*: This changes the lens so that when the lens is set at infinity, things
at 250mm are in focus.

So it isn't a 250D lens, it's a 4D lens. Again the marketoids are doing
their best to confuse people.

-- Lassi