IMHO, it's only significant if you are using a camera without movements! :-)
Of course, for most of us, we rely on DOF to allow us to have all of our
important subject matter "sufficiently" sharp.
John Coyle
Brisbane, Australia
----- Original Message -----
From: "Vic Mortelmans" <[EMAIL PROTECTED]>
To: <pentax-discuss@pdml.net>
Sent: Wednesday, May 03, 2006 3:19 AM
Subject: Re: Wide lenses and close distances
A thought that puzzled me lately may be related to this question.
It's about the focal plane and the effective distance to the camera lens.
When you focus a lens to 1m, it means that all subjects are in focus that
are in a plane positioned at 1m from the lens and perpendicular to the
lens axis (the focal plane).
If a subject is at the outer edge of the field of view and in the focal
plane, the distance between camera and subject will be more than 1m. In
case of wide angle, the difference can be significant like 1.4m e.g., if
your angle of view is 90degrees). The subject will be in focus at 1.4m
'real' distance, while the lens is set to 1m.
Now, if you want to focus your lens on this outer-edge-object, you'll have
to tilt your camera and point it to the subject (assuming you use the
split-screen-focus at the center of the viewfinder). OOPS! You will set
the lens to 1.4m! If you now tilt the camera back to it's original
position (for optimal composition), the outer-edge-object will be out of
focus, because it's in the 1m-focal plane and not in the 1.4m focal plane!
Do you follow?
Is this a 'real' problem, or only theoretically?
Groeten,
Vic
Boris Liberman wrote:
Hi!
Shel recently showed us a picture and added that he wasn't quite sure
about performance of his K 24/2.8...
Now, having thought about it a bit, I present you a question. Is there
a focal distance at which short distance performance of a wide lens is
noticeably worse than at infinity?
For example, I should say that I made quite a few shots with my 31 Ltd
(my widest Pentax lens now) at very close distance (around 1 meter)
and I really liked the results. Both shots from my photoblog that I
recently posted were made with 31 Ltd.
When I had K 24/2.8 I also had mixed feelings about its close range
performance. But at the time I thought it was due to my poor eyesight
and bad manual focusing technique...
--
Boris
