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Re: [OM] Digital resolution - was IMG: An Occasional Flower on Friday -

Subject: Re: [OM] Digital resolution - was IMG: An Occasional Flower on Friday - Jim N.
From: "Jim Nichols" <jhnichols@xxxxxxxxxxxxx>
Date: Mon, 9 May 2011 12:16:59 -0500
Thanks for the dissertation.  I learn more about the E-1 each time you pass 
on your knowledge of the subject.

For me, the E-1, with the Kodak sensor, is great for family photos, 
close-ups, macro, and general walking around with the 14-54 attached.  For 
the Leica Telyt-R, where cropping is often necessary, the E-510 is a much 
better choice.

Jim Nichols
Tullahoma, TN USA
----- Original Message ----- 
From: "Ken Norton" <ken@xxxxxxxxxxx>
To: "Olympus Camera Discussion" <olympus@xxxxxxxxxxxxxxxxx>
Sent: Monday, May 09, 2011 9:28 AM
Subject: Re: [OM] Digital resolution - was IMG: An Occasional Flower on 
Friday - Jim N.


>I wasn't trying to disagree with Chuck on the diffraction limits
> thingy. The hard facts are that F16 is going to stink on the E-1 as
> you are far enough past the theoretical limit that it doesn't matter
> if it is F8, F11 or F2 that the calculators come up with.
>
> Another aspect of this discussion which isn't taken into account very
> well. The diffraction limits for digital imaging assume that each
> sensing pixel position is a stand-alone affair on the sensor. It is
> not. In fact, this whole calculation is based on pixels being isolated
> from each other, but the very nature of the bayer array utilizes
> "nearest neighbors".
>
> With most cameras, the algorithm is a variation of the following:
>
> Take one green, one red and one blue pixel and create an RGB value for
> an implied pixel at that intersection. The Olympus is a little
> different and harkens back to some early sensor designs which use four
> pixels for the algorithm. In fact, the Olympus (specifically the Kodak
> sensors, but even the Panasonic sensors show this characteristic) use
> two different types of green sensors. If you don't include both greens
> as part of the algorithm, you'll get lots of artifacts in the image
> and any variation of the color yellow will turn UGLY on you.
>
> OK, so with the E-1, as we average four pixels together to get the RGB
> value, but that would result in a 50% drop in effective resolution.
> Not quite. Most algorithms will step forward one pixel at a time to
> recalculate. But with the Olympus E-1 files, most algorithms that do a
> single pixel step will not map the greens correctly and will produce
> artifacts. To get around that, they usually do a two-pixel step. Those
> algorithms DO result in a 50% drop in effective resolution. The
> in-camera JPEG engine of the E-1 does this very thing. However, from
> my own testing it appears the higher-res engine that was found in
> Olympus Studio actually did a per-pixel step. However, where most
> algorithms for most sensors are tri-pixel based, an E-1 sensor needs
> the algorithm to calculate the intersection of four pixels.
>
> In essence, the E-1, with the dual-color greens, is one of the most
> complex sensors to convert the images from. Your choice is to have
> improved resolution (but if you do that, make sure that NO channel is
> within one stop of clipping), or to have color fidelity without
> artifacts.
>
> Back to the diffraction-limits. The E-1 image files are the spongiest
> files around. Getting anything super-duper sharp is an impossibility.
> There is no such thing as pixel-sharp, no matter how many times in the
> past I've referenced it. Canon cameras can produce pixel-sharp images,
> Olympus cameras generally can't. And the E-1, with the combination of
> the hyperactive AA filter and the 4-by pixel-matrix takes it into
> another whole dimension of futility.
>
> Therefore, whatever the calculator says is the diffraction limits of
> the E-1 are probably a whole stop off and even at that you are really
> hard pressed to see where it makes much of a difference. F16? Yes, you
> are well past the edge of the cliff, but depending on the focal-length
> and lens, the diffraction limits are pretty much theoretical.
>
> As always, test your own equipment. Know your own equipment. Don't
> take Chuck's word, my word, or some calculator's word for gospel. No
> two lenses are the same. No two camera models are the same. And no two
> RAW converter algorithms are the same. In-camera JPEG will look
> different than an Olympus Studio converted file which looks different
> than an ACR converted file.
>
> AG
> -- 
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