For some time now I've been suspicious at the accuracy of the meter readings on my 5D, so I've acquired a light meter to satisfy my curiosity.

Taking incident light readings across a range of subjects I've established my 5D consistently over-exposes.

Looking at the Sekonic site I was amazed to see the following statement:-

"Like film, imaging sensors vary in light sensitivity levels from one batch to the next. Despite manufacturers best efforts, fluctuations of native ISO sensitivities of up to plus/minus half-a-stop can be detected across the uncut wafers as they come off the manufacturing line. Depending on which ‘slice of the pie’ is inside your camera, the specs listed in the camera manual may not hold true to the characteristics of the sensor in your particular camera"

Here's the link if you want to see more:- http://www.sekonic.com/products/products_features.asp?ID=130

Interesting statement that I was completely unaware of.

Q. how does your camera fare?

Did you change the focusing screen of your 5D?

I also once wondered why the images from my 5D started to turn out over exposed. It turned out I didn't set the custom function to recalibrate (or readjust) the light meter reading which is required when you change the focusing screen (I changed from standard screen to Ee-D with grids).

I am shiping my Gossen Luna Pro SBC over this week along wth some other goodies. All I have here at present is an older analog meter. It will be interesting to compare the results once I have a good meter in hand.

No screen change - I mistakenly stated "over-exposed" correction 1/2 stop under-exposed on average

My Canon 40D is fairly accurate for daytime shots,

but I have had to dial in +0.6 of a stop when using the builtin flash.

I do not have a separate meter to make a more positive assessment.

By way of experiment set the camera to 100ASA. Today which is overcast

the camera gave an exposure of 1/125 at F8 which tallies with the rule of thumb

my father taught me.

My 5D seems accurate too, at least in the daylight shooting.

Although I do remembr how it often turns out overexposed on LCD display but it really wasn't in the saved images.

It's often the auto white balance that's not accurate with my 5D.

Just bring your 5D to the Canon Service Center in Sathorn (or fotofile on 5th floor of mbk) for light meter recalibration.

I have heard about users having calibrated range meter of cropped sensor dSLR which can yield slightly out of focus images when used with non-EF-S lenses, but never heard of light meter calibration.