Quote Originally Posted by AndreasT View Post
Who is this Henry you guys are talking about? I couldn't find where he is first mentioned in this long thread.
Andreas - we're referring to Dr. Richard Henry. He was a clinical chemist, but also a photographer. As a scientist he was frustrated by how in magazines, books etc., photographers would present things about materials and technique as fact without any evidence, and often without even a reasonable basis.

When he retired, he decided to equip himself with the appropriate tools and set about testing for the validity of many of the claims made by notable photographers, Zone System writers etc. He published the results in a book called Controls in Black and White Photography.

While the materials he used are mostly outdated, perhaps the most important takeaway is that just because a well respected photographer says something about exposure, development, contrast, chemicals etc doesn't mean we should simply accept it as fact, especially in cases where no evidence, or a proper description of the experiment is given. And the description of the experimental method is very important. Even when presented with data (a characteristic curve for example), if we don't know how the test was done, it is often difficult to conclude anything.