The objective:
To correctly and accurately predict and reproduce the subject's tone that you are
photographing.
Very much like the previous examples, we can break down the tones (from black to white)
into five steps /tones /categories with each tone being one "Tone Step" away
from the other. In photography equivalent of a "Tone Step" is a
"STOP". For every stop, the amount of light reflected from a surface (or
entering the camera and exposing the film) "doubles" or "halves".
These tones in photography are called the "standard subject tones" or
"values" with the Standard 18% Gray / "middle gray" / "medium
gray" card (by definition) placed exactly in the middle of these black and white
subject tones.
Please remember that our unit in this case is 1 STOP
and we build our subject tones around the industry's medium
tone, the 18% gray card. You can buy this card from any serious photo
store for a few dollars .
| Black |
-2 |
2 stops darker than Medium Gray (4.5%
reflective) |
| Dark Gray |
-1 |
1 stop darker (less reflective) than
Medium Gray (9% reflective) |
| Medium Gray |
0 |
By definition 18% gray is the middle
of Black and White tones. Since it is separated from each of the tones by exactly 1 or 2
stops, it is exactly in the middle of 4.5% Black and 72% White as well as the middle
of 9% Dark Gray and 36% Light Gray. |
| Light Gray |
+1 |
1 stop brighter than Medium Gray (36%
reflective) |
| White |
+2 |
2 stops brighter than Medium Gray (72%
reflective) |
If
percentages in this illustration confuse you, please ignore them for now and stick with 1
and 2 stops
difference from the middle tone.
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