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[OM] Re: can your digital do this?

Subject: [OM] Re: can your digital do this?
From: "Carlos J. Santisteban Salinas" <cjss@xxxxxxxxxxxxx>
Date: Fri, 6 Feb 2004 13:44:13 +0100
Hi again -- forgot to say something...

>Your picture looks, to me, like longitudinal chromatic aberration which is
>due to different colors having different focal lengths
<SNIP>

This *may* be something related with the sensor...

Although much less noticeable than in CCDs, those Can*n's CMOS sensors
suffer from 'pixel bleeding' too, which leads to purplish fringing around
the very bright highlights.

As someone said before, lateral chroma is best judged on a sharp, high
contrast pattern (e.g. small black text over white). *Uncorrected* lateral
chroma shows in the form of blue-violet fringing at one side, and
red-orange at the other. But *residual*, corrected lateral chroma is
usually on the 'apple green + cherry red' scheme, though it may differ a
lot from this pattern.

*Longitudinal* chroma is just one-colour fringing (usually purple), but it
may shift towards yellow when defocusing.

However, I'm afraid there's some lateral chroma associated with digicams:

-I've seen chroma on the Zuiko 28/2 when fitted to the EOS-300D (Digital
Rebel), which I don't recall when using film -- OK, this lens was not
designed for digital, but...

-I've seen chroma on the crappy 18-55mm bundled with the 300D -- OK, this
is a cheap rebadged APS lens, with even *shorter* back focus distance,
but...

-I've seen chroma (lateral type, with the aforementioned colour scheme) on
E-1 shots taken with that telecentric-blah-blah-blah 14-54mm -- Hmmmmmm...
;-)

Enjoy,

...

Carlos J. Santisteban

<cjss@xxxxxxxxxxxxx>
<http://cjss.galeon.com>



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