Huh? but the centre is often the sweet spot and I don't think you are
'wasting' anything - glass is glass and small lenses are no less in
resolution power for their smaller area. I've put a 12mm Beroflex on my
10D and it looks just like aslight crop of a 16mm on a 35mm body
(albeit with low contrast and some barrel distortion - it ain't that
good an optic) - what I've lost is the lousy fisheye edge resolution
and considerable field of view. The Zuiko 16mm is a nice wide on the
10D - although being a fish it has a wider field than a rectilinear
25mm on a 35mm bod - hmmmmm - must go check that (16mm on the 10D vs.
24mm on the 4Ti).
By asking about a change in focal length, I think I muddied the waters.
If I put a Zuik 300mm on an E1, I would appear to have an 'effective'
or 'apparent' focal length of 600mm although with the characteristics
of a 300mm in terms of DOF, for instance. If I use a teleconverter, I
am magnifying the centre of the original image but we have no worry
about saying that a 300mm with a 1.4x is now a slower '420mm.'
Equally, we talk about 1.6 ratio conversions on a 10D so that my 50/1.4
Zuiko can now be considered a nice, fast (and oversharp?) 80/1.4
portrait lens and my 85/2 a fast 135mm approximate though again with
less foreshortening effect. When I use a 50mm lens on my Mamiya Press,
the 'effective' focal length is quite different, depending on whether I
use a 6x9, 6x7, 6x6 or 6x4.5 format back.
So when I hear that my 180mm medium format lens on a 35mm body crops a
section out of the centre, this little bunny doesn't quite get how that
is different. I thought in my furry fuddled little way that focal
length was an aspect of the field of view of the lens and if you use a
smaller film format on the same lens, you get an apparent reduction in
field of view and in effective focal length. Do not attempt complex
optigeek explanations - they will escape me. Anyone attempting algebra
will be abused. Discussion of large format optics will be discouraged
(I know that it's a whole different thing on a bellows. I know that
this is bas science but it is at least one way of thinking about what
the lens that you are using is actually doing, no?
I will wait for the adapters to arrive from places like the Ukraine and
test empirically so there. And let you know!
Andrew
On 03/06/2004, at 4:58 PM, Winsor Crosby wrote:
>
> That is one of the things that always bothered me about most digital.
> You are throwing away lots of lens resolution by just using the middle
> of the lens field.
>
>
> Winsor
> Long Beach, CA
> USA
> On Jun 2, 2004, at 8:57 PM, Jim Brokaw wrote:
>
>> No, its just a 24mm x 36mm crop out of the larger frame. You'd get the
>> same
>> image magnification in that area as with a 180/2.8 Zuiko on an OM
>> (which is
>> what you should be doing and you know it...!) for equal subject
>> distance to
>> camera. This is in fact true for the E-1 with OM lenses, too. The
>> magnification is the same, you're just cropping out the middle of the
>> 'negative' to get the sensor image.
>
>
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