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

Subject: Re: [OM] RANT: Sample images taken with EP-1
From: "C.H.Ling" <ch_photo@xxxxxxxxxxxxx>
Date: Thu, 18 Jun 2009 00:27:15 +0800
I won't put my hope to the in-camera CA correction, I don't see Olympus is
working well here based on my DZ8mm experience. On the other hand most
of my OM lenses are having minimum CA when stopped down 2-3 stops
(even the F2 lenses) on 5D II, I believe 5D II don't know how to correct
the CA of my MF lenses and they are the old lenses that do not have
parallel rays to the sensor.

C.H.Ling

----- Original Message ----- 
From: "Ken Norton"
> >
>> 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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