Calibrating a Sekonic light meter

Anyone hear of this method? I ran across it at another site. The old sunny 16 rule.

You set the ISO and shutter to 125. Take an incident reading on a clear mid day and you should get F16. Can't let any shadows get on the Lumisphere. I just tried it and I got F18 which required a -0.2 adjustment. It is 5:00 PM and I will try about 1:00 PM next time. Not sure it that matters.

Then I tried my 7D which I just aimed into the sky and it was bang on. My 5D2 is at Canon but I can hardly wait to try this out on it.

This place a great resource and a wealth of information so I'm wondering everyone thinks about this procedure.

Depending on what Sekonic Light meter you have.....

Click Here...

L-358

A better reference for calibrating a light meter is an 18% gray card. Very simple and rock solid. The L-358 doesn't allow for custom profiles but you can calibrate and dial in an offset.

What is the procedure for that method? I always prefer rock solid. When I thought about the sunny 16 method (that appears very close) tonight I could not get my head around factors like time of day, month, etc. I can just imagine Sekonic technicians running around outside calibrating meters

Leave the L-358 meter set the way it came from the factory unless you have a consistent exposure offset in your images over a variety of conditions.

Without a calibrated standard to compare readings against, it's very unlikely that you will be able to improve on the factory calibration of the L-358.

If you have a collection of five or more high quality meters that all can work in incident mode, you could compare the readings of all of them in precisely the same light condition and possibly find that one of them is off enough to consider making an adjustment. If you have a meter (such as the one in your camera) that only measure reflected light, then you can use an 18% gray card (one that is designed to be used for exposure measurement) to get an incident reading with that meter.

Simply pointing two meters which measure reflected light at a scene in front of you and comparing readings may easily give you false information because each could be "looking at" a different portion of the scene and thus be responding to light from different surfaces that reflect light differently.

Thanks. I really don't like messing around with that stuff. I'm not overly worried about a -0.2 difference and besides anything could be causing that. I do know they come calibrated from the factory. When I did some tests I found the white distribution more accurate using the L-358 than my 5D's meter when viewing the histogram after the shot.

I still found applying the sunny 16 rule was very interesting and surprisingly pretty accurate.

I wouldn't blow off .2 of a difference. It's not that hard to test if you have a good target.

What is the procedure? I just checked the manual and tells you how to change it but not how to measure.

digital paradise wrote in post #12432352
What is the procedure? I just checked the manual and tells you how to change it but not how to measure.

Calibration, by definition, is simply the act of comparing an unknown value to a known ("standard") value although many people incorrectly apply the term to the making of an adjustment. Adjustment is not, in itself, calibration. After making an adjustment, a device actually requires a second calibration (comparison with the standard) to make sure that the adjustment accomplished the correct change.

The calibration adjustment procedure published by Sekonic in the L-358 manual assumes that you have a calibrated standard as a comparison to the meter you may want to adjust. Very few photographers really have what is required.

The key is to use the L-358 in enough different situations to either be comfortable with the readings it provides (and your analysis of those readings) or to recognize a "need" to make a small adjustment.

Most new photographers assume that a meter should be "dead on" under all conditions but they do not realize that very often a skilled photographer needs to modify the values provided by a meter based on what the situations are for the image being made. For example, if the photographer needed to make sure that deep shadowed areas in the scene need to have detail in them while allowing the bright highlights to blow out, the exposure settings used may not quite match the readings on a meter. The bottom line is that any light meter is only a tool and the photographer needs to understand how to use the tool in a variety of conditions.

Calibration, by the way, was a major piece of my 39-year career working with industrial process control systems.

Thanks fo the explanation. Sounds like an interesting career.

digital paradise wrote in post #12432274
Thanks. I really don't like messing around with that stuff. I'm not overly worried about a -0.2 difference and besides anything could be causing that. I do know they come calibrated from the factory. When I did some tests I found the white distribution more accurate using the L-358 than my 5D's meter when viewing the histogram after the shot.

1. Different manufacturers calibrate their meters to different versions of the ISO standard, they do NOT use the identical value for Constant K or C within the equation...this applies to handheld meters and to camera meters. So it is rare to find all meters in agreement if you have a collection of photographers with 10 different meters and cameras.

Read about the K value differences for calibration of reflected light meters here

2. Your reflected light meter was integrating many portions of a scene (unless you used spot mode), so it is not at all surprising your camera reading did not agree with your L358 reading.

(BTW, my Canon 40D meters an 18% gray card identically to my Minolta incident light meter and also identically to my Minolta handheld spot meter that is pointed to the 18% gray card.)