calibrating Canon light meter using sunny f16 rule

[andy_game]

In "Closeups In Nature" John Shaw stresses the importance of calibrating a camera light meter using the sunny f16

rule. He suggests that Canon camera meters are typically set to overexpose while Nikons underexpose. Seemed

like a good thing to try, so I ran a quick test on my EF and FTbn. Both gave the same meter reading, f12, ie

overexposing by about 3/4 stop. I wonder if anyone else has tried this. It does seem pretty important to have some

way of checking the meter calibration. Of course 3/4 overexposure in bright sun doesn´t mean the full range of EV

levels would be out by the same amount, and I do want to run the tests again to double check my results. Any

thoughts? Andy

[ronald_moravec1]

You need a reflective source equal to the % reflectance the meter is calibrated to. Might be 18% grey, might be 12,

 

When you aim the meter at a random scene, you have no idea if the reflectance is proper for meter calibration.

 

Without better tools, go by experience of how the film turns out. Also try metering and then underexposing by 2/3 stop to see if the film is more satifactory.

 

Lots of factors come into play like scene reflectance, shutter accuracy, film processing, battery voltage, actual sunlight ( bright blue sky in middle lattitues May to Sept), meter cell aging.

 

In other words it is way to complited for anything but an empirical test.

[egoldste]

Agree that reflectance meters can be and are calibrated to both 12 and 18% gray. With all due respect to John Shaw it is also a bad idea to try to calibrate off the reflectance from bright sunlight, because the finish and speculance of gray cards differ and this can easily cause variance of 1/2 stop of more from a very bright light source.

 

I'd offer that it is much more important to calibrate your entire work flow than your meter... that is the approach I would take...

[User_502260]

I use both Nikon an Canon cameras and I do not find that they show different exposure values. They have different patterns so it is still good to know what you are metering. If I am using a Canon F-1 I will look for a mid tone as a reference and point the 12 degree spot there. If I am shooting the same scene with a Nikkormat or a Nikon FE I will adjust the exposure if the part of the scene I am pointing at has is very bright or very dark.

[SCL]

The sunny 16 rule is an estimate, not a particularly fixed standard to actually calibrate by. It is nice as a reference, but for actual calibration, you need a known standard. If you have an exposure meter which you know to be accurate, that's a good start.

[andy_game]

Thank you all for your valuable responses. I guess I´ll have to go and buy some slide film (I normally shoot prints) and run some more tests! All the best, Andy