Testing Continued

Today, I setup a grey card on a wall and took a series of shots, using a tripod, and a Canon 5d, gradually over exposing and under exposing the greycard.

Here is the file that is exposed according to the meter. I will call this MIE, [Meter Indicated Exposure].

greycard meter indicated exposure

Here is the 2nd shot which is one stop over exposed. I will call this MIE +1.

grey card mie +1

Here is the 3rd shot two stops over-exposed, I will call this MIE +2

greycard mie +2

Clearly, given that MIE has the histogram to the left of centre and no RGB values anywhere near 127, I'm guessing that this CCD is NOT recording things correctly. Given that MIE+2 gives me a histogram that appears correct and a set of values closer to 127, I'm going to assume that, this camera, a brand new Canon 5d is under exposing by 1/2 to 1/3 a stop, the next file is far to bright and the histogram is way to far over to the right for it to even come close in this test.

There are several other issues that are bothering me about the results of this test, the vignetting, mainly, so much so I am going to attempt this again under more controlled conditions.

At one level this test is inconclusive, why is the CCD not recording an even set of values for example? So, I'm asking both my readers to stay tuned.

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This page contains a single entry by s2art published on August 17, 2007 11:06 PM.

Testing was the previous entry in this blog.

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