Must resist... pun of death...
I don't know very much at all. Just groping around in the dark hoping
for a flash of insight.
Sorry.
The problem is that he just works with one side of the equation. You
can't talk about the lens without talking about the sensor. They are an
integrated system. His side by side comparison of a 150 and a 300mm
lens assumes sensors of different sizes are equally desirable. They are
not and people are astounded when a 6MP image from a DSLR captures more
detail and better color than an 8MP from a digicam. At one point he
suggests the superiority of the 150 be checked off the camera. All
those old lens tests in Modern Camera and Pop Photo that counted lines
showed pretty well that, generally, long lenses are not as good as
shorter ones. But that kind of test gets validity only when everyone is
using the same sensor or film frame. The point is that the 150 MUST
have higher resolution in order to record the same amount of detail
across a smaller sensor. It is the same argument between 35mm and
medium format. Most medium format lenses will not resolve the same
number of lines per millimeter as 35mm format lens. They work because
they have more millimeters of film to project their lower resolution
across and end up recording more detail across the whole frame along
with few film artifacts.
As for his contention of the traditional definition of normal being the
diagonal of the format, it is 43mm for a 35mm film frame. I have never
seen one of those normal lenses. It is an arbitrary and artificial
concept that no one has ever paid any attention to.
The viewfinder thing. I reread what he said and think I understand
better what he was trying to say, that what you see is too small in a
digital camera. However he states there is marketing dishonesty when it
is nothing of the sort. I understand what they are saying when they
state magnification. To call it dishonest is well... let us say
curmudgeonly and not true. The crop factor with a digital or any
smaller format has nothing to do with magnification. The same lens
focused at the same distance will project the same size image on the
film plane regardless of the format. That is, the subject, someone's
face for instance will be the same size(x mm across) regardless of the
outside dimensions of the frame. What you have with a digital is a
crop, not a magnification. It seems like magnification because the same
sized face now fills the whole frame. So when Canon says that
magnification is .88 they are right and it looks smaller because you
are only seeing the center portion of what you would see in a 35mm slr.
The outside may be cropped off, but the image itself has the correct
magnification.
Why not just do more magnification? There is only so much light in an
image. If you take the center portion and expand it to fill the
eyepiece it will be dim. So that is the choice cropped, small and
bright, or large and dim. A full frame Canon 1Ds gets a
magnification(no crop) of .7. The 1D(1.3 crop factor) gets .72. The
smaller sensors(1.5 and 1.6 crop factor) get more magnification and
dimness in the viewfinder. Different manufacturers will do different
compromises on that continuum and it is why I think that eventually
greatly improved EVFs may take over. I suspect that the lower
magnification in the 350D compared to the 300D has to do with
brightening it up a bit. Those pentamirrors, ya know. You also have to
step back and realize he is complaining about a camera designed for
someone who will never use it for anything but autofocus. And eyeglass
wearers can see the whole image. You don't hear that complaint much
now.
There is hope though. Viewfinder brightness and clarity has not been an
issue for a long time. Now it may get some development that it has not
needed with the larger 35mm format. I see that Nikon is now putting
Bright View focus screens in their newer cameras. Shades of the OM3T!
Maybe the others will follow suit.
Winsor
Long Beach, California, USA
On Mar 20, 2005, at 8:45 AM, Joel Wilcox wrote:
> At 02:59 PM 3/19/2005 -0800, you wrote:
>
>> I usually like Mike Johnston's writing but this and his previous
>> column
>> was a disaster. What is so surprising about a 150mm lens being smaller
>> and cheaper than a 300mm lens?
>
> Isn't he simply saying that the same effective focal length in film
> terms
> can be made more cheaply and effectively when designed to the smaller
> sensor size? If that it true, resources and profits will push
> companies in
> that direction, which I think is what Olympus' whole gamble with the
> 4/3
> venture is about. Once people forget about the old film lenses,
> "designed
> for digital" (for once!) should really mean something. Or what am I
> missing?
>
>> He also shows that he is completely confused by viewfinder
>> magnification, field of view and the sensor's crop factor.
>>
>>
>> Winsor
>> Long Beach, California, USA
>
> You know more about these topics than I do, but I reread his article
> and
> don't see where he messes up so badly on any of those topics. Any
> clues?
>
> Joel W.
>
>> Quote from Mike Johnston writing on Luminous-Landscape
>> http://www.luminous-landscape.com/columns/mj-dof-response.shtml
>
>
>
> ==============================================
> List usage info: http://www.zuikoholic.com
> List nannies: olympusadmin@xxxxxxxxxx
> ==============================================
>
==============================================
List usage info: http://www.zuikoholic.com
List nannies: olympusadmin@xxxxxxxxxx
==============================================
|