Book"Basic photographic materials and Processes"

[Neal Shields]

Would somebody tell me if the log scales in the Sensometry chapter of this book are wrong, or did I smoke too much dope in high school. They seem to be fine un til you get into negative numbers and then they go haywire. I.E. for an actual lux sec exposure of .0064 they show a log of -3.8. (my computer says it should be -2.2) Half that; .0128 shows a log of -2.1 (my computer returns -1.89) then half that .0256 shows -2.4 which seems to go in the wrong direction!

[Bill C]

Hi Neal. I had to take a look because I couldn't hardly believe they'd be wrong (this book is relatively mature, etc.). But I think you're right on this. I'm going from the 1990 edition on table 4.2. In the third column ("Actual Log H") they have: -3.80, -2.10 ? 0.80.

The correct numbers should probably be (from top): -2.20, -1.90, -1.60, -1.30, -1.00, -0.70, -0.40, -0.10, 0.20, 0.50 and 0.80. There are slight rounding errors; I just changed each successive number by a nominal +0.30 which I think is in the spirit of what they are trying to show.

I'm still almost amazed you found this error. Good eye!

[Neal Shields]

Please disreguard prior question. It is answered in the back of the book. It is just a different (and to my taste confusing) way of notation for negitive logs. Sorry for the fuss.

Neal