Trust the Film

[Sirius Glass]

... and the way you did not say it.

 

[Bill Burk]

What test was that?

Bracket a shot two stops and tell if there is a one-stop density difference between the resulting negatives.

 

[Bill Burk]

Among my recent haul of photographic books was this book: An Introduction to the Science of Photography, Katherine Chamberlain, 1951.

The book is written like a textbook with questions at the end of each chapter, and some questions, marked with a star, have answers in the back. Imagine my surprise to find that the test I described here... is very similar to one of the questions (and luckily one with an answer).

Chapter VII The Graphs of Photography...


*13. Devise a method by which the user of a miniature camera could get an idea of the gamma to which he is developing his negatives. Use only ordinary photographic equipment.

Answer: 13. Use the three frames at the beginning of the roll that are ordinarily wasted because there may be a light streak across them to make three exposures on a large white card. Illuminate the card evenly and focus carefully. Expose for 1/2, 1, and 2 times the meter reading, respectively. After development, measure the transparencies with an exposure-meter densitometer and compute the densities. Plot the D-log E curve for these three points. All should lie in the region of correct exposure on an approximate straight line. Gamma is the slope of this line.