Gamma 1 Developers.

I have noticed that Lowell Huff describes Clayton F-60 & F-76 Plus

developers as "Gamma 1" developers, what is meant by this

description?

Could it possibly mean that with these developers you can easily get very high contrast, i.e. "gamma 1"? With many developers this is impossible, no matter how long the development time is. Especially on faster films, it is extremely difficult to reach more than 0.8 or 0.9 with many developers. Though, this is not actually a problem, bacause for normal use you need only gamma range of 0.55 - 0.7. But that is just my guess, I have never used these developers, they do not sell them here in Europe (Czech Republic).

Gamma is physically defined as the measure of the longest straight line portion of the charastic curve. Idealized, this is a 45ﾺ line that bsects the quadrant. Unexposed but developed film has a low density known as film base + fog. The useable area of the curve begins at .01 density above the density of film base + fog, where the film still has a low gradient and thus LOW CONTRAST. The shadow area of a subject will record on this low contrast 'toe" of the curve.The central part of the curve is a straight line. The longer this line is, the greater amount of information that will be recorded on the film. Above a certain amount of exposure the curve begins to level out(shoulder), which is why over exposed negatives often get low contrast highlights.

A gamma 1 developer will provide the most latitude to the toe and central portion of the curve.

Ultimately, Gamma is another way of discribing contrast.

Lowell, you're description of the term Gamma is misleading and confuses curve shape with contrast.

 

"Gamma is the tangient of the angle produced when the straight line portion of the characteristic curve is prolonged to meet the horizontal axis. It will be obvious that as the curve is steeper, or less steep, so the angle will vary and so, too, the Gamma, and therefore the gradation."

 

Jacobson, Jacobson

 

Developing, 18th revised edition

 

Gamma has nothing at all to do with the length of the straight line portion of the characteristic curve, but with the gradient of the straight line portion.

 

Jay

Thanks to Marek, Lowell and Jay for replying. Lowell mentioned F-76 Plus as being a "Gamma-1" type developer when replying to the `Maximum Sharpness` thread on the Digital Truth forum.

I am familiar with finegrain and acutance type developers etc, but not Gamma-1 developers.

Hi Keith.

 

Based on Lowell's explanation of the term, I don't think that "Gamma 1" could be considered as anything more than a marketing slogan, and certainly not a class of developers. By all accounts, these developers are analogous to other common developers like D-76.

 

Jay