If you do not want to read the book titled
"the confused photographer's guide to On-Camera Spotmetering ISBN: 0966081706" simply read the following:
The on-camera spotmeter (spot meter /
partial meter) is the most powerful exposure tool in the world but you have
to know how to use it!
Read the following technique and decide for yourself if you understand the concept. If you do understand everything
on the following page, and you can apply the technique described and produce correctly
exposed images, then that is all you need! If, however, you even have the slightest doubt
about this technique, or if you are still the least bit confused, this book is for you.
Remember: either you know how to use your spot meter effectively or you
dont. There is no in-between! I believe this is the simplest, easiest, best
illustrated, and most practical exposure book in the world!
Cheat sheet: The entire book condensed onto
one page (well almost!)
on Farzad's 5-stop Film / Digital Zone System ©1987-2007)
Set the ISO
of your Canon EOS 20D to 100 and choose an outdoor subject. Activate
metering/Partial Metering option on your 20D and set your cameras mode to manual and
to the shutter speed to 1/125.
Observe your subject and break
it down into its simple subject (single tone) components. Choose a Reference Tone. A Reference Tone is a simple tone (one tone) usually
chosen from the most important part of the subject. Once you have selected the Reference
Tone, point your spot meter circle at this tone so that the spot frame falls WITHIN this
simple tone and find its normal exposure. If your subject does not have a distinct single
tone pick out a tone that is medium gray or brighter.
Lets assume the
"normal exposure" indicated by your camera for this Reference Tone is
(i.e., 1/125 sec. at an aperture setting of 8).
As you may know, the spotmeters "normal
exposure" from any simple (single toned) surface will always provide the photographer
with an 18% gray image tone (or a Grayscale density of 128 (out of 256) in photoshop on
your home computer when you convert the image to black and white/grayscale).
The image tone that your camera's normal exposure
provides is independent of the original tone of your
subject. YOU MUST UNDERSTAND THIS since this is the foundation of the
Zone System of Exposure!
System/spot metering, converting
the "normal exposure" to the "correct exposure" is what a photographer
must do. In other words, the "normal exposure" readings of the spotmeter must be
interpreted by the photographer to determine the subjects "correct
exposure." The principle behind this simplified technique is that if one tone of a
complex subject is exposed correctly, the rest of the tones follow and will also be
correctly exposed . Now decide which one of the following tones would most closely matches
your Reference Tone: Black, Dark Gray, Medium Gray, Light Gray or White. With this
simplified technique you must choose one of these five tones. Once you have decided which
one of these five tones best matches your Reference Tone, then adjust your camera settings
If you chose Black, you need
to decrease the "normal exposure" setting by two stops. Decreasing the exposure
time by two stops converts the 18% gray image tone to 4.5% Black
(028 on Gray Scale). The correct exposure is
now 1/125@f-16 or equivalent.
If you chose Dark Gray, you
need to decrease the "normal exposure" setting by one stop.
exposure time by one stop converts the 18% gray image tone to Dark gray
(078 on Gray Scale). The correct
exposure for this is 1/125@f-11 or equivalent.
If you chose Medium Gray,
leave the aperture and shutter speed as they are since the meter is already creating an
18% gray (Medium Gray - 128 on Gray Scale) image tone, i.e., the tone of the image matches the approximate
tone of the Reference Tone. Also remember that when metering from a medium gray surface,
the "normal exposure" and "correct exposure" settings are
approximately the same. In this case the correct exposure is 1/125@f-8
If you chose Light Gray, you
need to increase the "normal exposure" setting by one stop. Increasing the
exposure time by one stop converts the 18% gray image tone to Light Gray
(178 on Gray Scale). This results in
a correct exposure of firstname.lastname@example.org or equivalent.
If you chose White, you need
to increase the "normal exposure" setting by two stops. Increasing the exposure
time by two stops converts the 18% gray image tone to White (228 on Gray
Scale). The correct exposure would be
1/125@f-4 or equivalent.