As to the difference in spacing of Zones along in the two examples. Everyone should be familiar with the exponential scale of exposure:
For a seven stop scene:
1, 2, 4, 8, 16, 32, 64, 128 for a ratio of 1:128
Add one stop (unit) of flare and it becomes:
2, 3, 5, 9, 17, 33, 65, 129 for a ratio of 1:64 (six stops)
Even though the original scene is 7 stops, you are only dealing with 6 on the film curve. What are the implications of this?
Processing normal for a seven stop scene is really processing for a 6 stop scene. Without the presence of flare, development would have to be one stop less for normal.
The log-H range on the film curve for a seven stop scene would be 1.80 for a one stop flare factor and not 2.10. That means, the place where you determine the density range of the negative would be one stop (0.30) to the left. You can see this in the two examples. While not perfect since the flare factor in the examples is slightly higher than a stop, the density range for Zone I to Zone VIII in Curve B (flare example) is the same as the density range for Zone I to Zone VII in Curve A (no flare example).
The two examples only differ in the interpretation of the information. So, in a shooting situation, there would be no difference in the negatives as they will be subject to the exact same conditions. The question becomes, which one reflects the way it works in the real world and which one is using the same set of conditions and coming out with the wrong interpretation / answer?
The two curves are an example of the importance of correct interpretation of the data.
Last edited by Stephen Benskin; 09-08-2011 at 08:50 AM. Click to view previous post history.