Perhaps you're seeing evidence of the fact that the "1.5x crop
factor" is a simple *linear* approximation of the field of view
difference. Field of View in fact does not change linearly with
respect to focal length on a format, a true factor for an 18mm lens
is probably a little closer to 1.4-1.3x to give a 100% accurate
calculation. I'll make up a chart demonstrating this for you in a
little bit.
No matter really ... what I said in my original response is what I
recommend still: Think in the focal lengths/field of view of the D/DS
when you're using them.
Godfrey
On Jul 16, 2005, at 10:53 PM, Shel Belinkoff wrote:
Well, the original question or comment in this thread was posted by
me. It
had nothing to do with DOF, but the thread has morphed into
arguments about
DOF. OriginallyI suggested that, while the FOV of an 18m on the
Pentax and
similar DSLR cameras were about the same as a 28mm lens on a film-
based
35mm SLR, I noted that somehow they view didn't look the same. Tom
Reese
suggested the perspectives were different, and then all the technical
reasons why that could or couldn't be so surface. He was voted down
in his
belief, and changed his opinion, and then the DOF arguments started in
earnest.
Well, this afternoon another list member and I got together. She's
not
read this thread and is far removed from the technical aspects of
this and
other areas of photography. The 18mm was put on her istDs, the
28mm on my
Pentax body SLR. She looked through the finders of both and
concluded that
"objects seemed further away" wih the 18mm/DLR combination, supporting
that, at least as viewed through the finder the images are not the
same,
only equivalent in some dimensions or, perhaps, depending on
yourefiniation, superficially.
We then made a few shots with the two camera/lens combinations. She's
going to send me the JPEGs from the digi and I'll get the film
processed
after the weekend. The pics will be posted here and you all
canargue about
the validity of the test and whatever else pleases you. To our
eyes today,
theyare not equivalent - they are not the same. Well see what they
look
like when posted here, perhaps Tuesday or Wednesday.
Shel
[Original Message]
From: William Robb
We have an old adage: The proof is in the pudding.
Since this is a visual medium we are talking about, visual
comparisons
(comparative prints, for example) are the best way of comparing the
different formats.
Doing so eliminates all the confusing technobabble that is both
tiresome
and
obfuscating.
At least that's what I think.
Not that what I think matter to anyone other than my dawg.
William Robb
