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Re: [OM] Light meter

Subject: Re: [OM] Light meter
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Tue, 06 Sep 2011 19:34:24 -0400
Or, much more briefly, the E-1's histogram lies.

Chuck Norcutt


On 9/6/2011 6:47 PM, Ken Norton wrote:
>> I don't understand how the Kodak sensors don't lend themselves to
>> "Expose to the Right".  There's no metering involved other than running
>> the histogram to or near the right hand edge of the graph.  Are you
>> saying that those Kodak sensors can't handle a brightness level near
>> maximum?  Or that your histogram lies, or... what is it?
>>
>> I find the statement suspect.
>
> The Kodak sensors as used in the Olympus cameras utilize two different
> green pixels. They have slightly different color and brightness
> curves. Where most cameras mix the pixels of one each color at each
> intersection, the Olympus cameras require four pixels to be mixed.
> Unfortunately, the four pixels do not reach saturation at the same
> point.
>
> This causes major color shifts in the top stop of the range. If you
> made sure that absolutely none of the four color pixels reached
> clipping then there would be no shifts, but the histograms shown in
> the camera as well as in a RAW converter are derived and not literal.
>
> On the Zone-10 website, is a really good illustration of this. On the
> left side, look for "Product Reviews - Olympus E-1". Click on that and
> then on the "Olympus E-1 Dynamic Range Test". Go to page 2.
>
> The test photograph is 3 stops over-exposed. I did this to make sure
> that I was well into the world of clipping. The second image on the
> page is the same image converted with highlight recovery and exposure
> compensation to bring it back down to a normalized image.
> Inotherwords, this image is pulled 3 stops with maximum bit recovery.
>
> On the Kodak test target, look at column 13--Cyan. H13 is starting to
> lose color, but G13 and F13 are gray. In colunn 17 is red. H17 went
> pink, G17 and F13 went yellow. Column 18--green lost all color in G
> and F. But the Blues held one step farther. Meanwhile, the other two
> derived colors of magenta and yellow both topped out at I14 and I15.
> As you can see by the grayscale, highlight recovery pulled back four
> steps from 10 to 6.
>
> On Page 3 of that article you can see what happens when you push the
> exposure back up. Now, granted the image is quite noisy, but for
> crying out loud, this is SEVEN (7) stops of boost!!!! The second one
> is six.
>
> So, what I'm saying is that when it comes to color integrity, the
> Kodak-Olympus sensors don't handle the top very well and anytime you
> use highlight recovery you will get color shifts. It's actually kinda
> like Kodachrome in that manner.
>
> Granted, the E-1 isn't the cleanest sensor around and Olympus adds
> dithering noise across the entire image, so the acceptability of a
> severally pushed image might be beyond what you can stomach, but when
> it comes to color integrity, I'll gladly push an E-1 one stop than
> pull one stop and have to fight the highlights. Because of the added
> dithering noise, there is not as much noise reduction to be gained
> through pulling the exposure.
>
> These controlled tests, as illustrated in this article also have
> proven themselves out through empirical testing and usage.
>
> The E-1 is specifically a different animal than other Olympus cameras
> that followed. Even the E-300 and E-500 are a bit different because
> the times, they were a changing. The E-1 was introduced as a "Film
> Replacement". All other cameras following were "Digital Replacement".
> The E-1 was really the only Olympus camera designed to be used like a
> film camera.
>
> AG
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