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Re: [OM] RANT: Sample images taken with EP-1

Subject: Re: [OM] RANT: Sample images taken with EP-1
From: Ken Norton <ken@xxxxxxxxxxx>
Date: Wed, 17 Jun 2009 10:37:12 -0500
>
> It exhibits pathetic chromatic abberation, and this at f/6.3! I really
> hope this is not representative of that 17mm lens, thus far I am greatly
> unimpressed. I mean, come on, they should have AT LEAST made it an f/
> 2.0 lens
>


I'd say that it's a little early to say for sure why, but I suspect that
there is a bug in the processing firmware that didn't correct the CA. With a
lens this close to the sensor surface you're going to get distortion of many
kinds--not just CA. The in-camera processing that all manufacturers are
putting in the cameras now are automatically repairing CA, color-fringing
and vignetting before the RAW file is written. I suspect that this is just a
case where the calibration of the processing is off and will probably be
fixed in firmware version 1.1.

Your criticisms are sound, but at the same time, I must challenge this as
being "Old Think". In "Old Think" the manufacturers compromised size and
lens-film/sensor relationship for optical precision. Now, the
lens-sensor-processing is considered to be an unified system.

To make the 17/2.8 that small and that close to the sensor means that the
light-rays is no longer perpindicular to the sensor surface but approaching
the surface at extreme angles.  Do you remember how Olympus made a big deal
about how the 4/3 lenses were specifically designed for digital by making
the light rays as parallel as possible when leaving the rear element.  If
you can make the light rays approach the sensor direct-on instead of at
extreme angles, there is no need for color and vignetting correction.

However, this approach was a hardware solution to the problem. All
manufacturers determined that hardware was preferred, but would still put
the cameras at a distinct disadvantage as compared to equivalent film
cameras because of lens-size and lens-to-sensor distance. So, software
solutions were developed and today's processsing does a remarkable job of
correcting what used to be a hardware only solution. The hardware-solution
approach is exactly why Olympus 4/3 lenses are so huge!

The "New Think" allows lenses to be designed more like they were designed
for film cameras--allowing extreme light-ray angles to hit the sensor
surface. Unfortunately, the sensor surface isn't flat and just the sensor.
There are microlenses and UV/IR filters and AA filters.  As the lightray
approaches the edges of the sensor, the more distorted the lightray becomes
as it has to pass through these materials of increasing thickness.

What Olympus/Panasonic did to help resolve this problem is to remove or
degrade the AA filter and modify the microlenses. (Kodak removed the AA
filter nearly entirely from most medium-format and M8 sensors).
Unfortunately, modifying the microlenses still affects color artifacts as
well as vignetting so the in-camera processing is programmed to
automatically correct for this.

"New Think" means that since "perfection" is achieved through software, that
it frees the lens designers from the constraints of size and distance. They
can now make the lenses tiny. In essence, it's now marketing driving the
show and saying how large the lens can be and how thick it can be. Obviously
there are going to be issues.  No matter how you slice it, a 17mm lens is
difficult to make in any format. Had they designed it for optical
performance, the lens would be comparable in size to an old Zuiko 24/2.8.

AG
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