"Normal Contrast Negative" - What is it?

Well all these Characteristic Curves we've uploaded in the past

couple days has got me started on tackling Sensitometry again. So

I've been reading through Chapter 4 of 'Basic Photgraphic Materials

and Processes' which discusses Photgraphic Sensitometry. All was

going well until the authors carelessly threw out a term...

 

Normal-Contrast Negative

 

Not only is the definition of this term nowhere to be found (that I

can find) elsewhere in the text, but they really throw a wrench in

the works by stating 'Interestingly, a normal-contrast negative

actually has significantly less contrast than the original subject'.

 

So I guess my question is two-fold - what is a 'Normal Contrast

Negative' and what do the authors mean in the statement above?

 

The authors do show some Characteristic Curves in the exmples that

show that the log H range is clearly greater than the Density range.

Could this be what they mean? Regardless, what on earth is 'normal'

in photography anyway??

Al, exactly what page are you referring to? I found a section for Normal-Contrast Films which is really any film that isn�t a specialty film. I couldn�t find the quote though. Let me know the page so I can better address your concern.

 

'Interestingly, a normal-contrast negative actually has significantly less contrast than the original subject'.

 

What they are saying is that under average conditions. The resulting negative will generally need to produce a gradient of around 0.50. An average gradient of 0.50 means that the output is 1/2 the input, or in other words, significantly less contrast than the original subject. The average paper has an average gradient of around 2.0. Put them together and you get 2.0 * 0.50 = 1.00 or a 1:1 tonal relationship between the original scene and the reproduction.

 

Normal is based on a statistically average set of conditions, a log subject luminance range of 2.2 minus a flare value of 0.30 to 0.40. The average gradient needs to be such as to fit this range onto a standard grade of paper, usually a grade 2. Generally this means about an average gradient of 0.42 for a condenser enlarger and a 0.56 for a diffusion. This can be expressed in the equation:

 

Desired Negative Density Range / Log Subject Luminance Range - flare

There is no absolute standard for a normal contrast negative, because enlargers produce differing amounts of contrast with their different illumination systems. For example, a condenser enlarger typically adds about 1/2 to 1 grade of contrast to the print when compared to a diffusion head enlarger (with the same negative).

 

Also, people have different opinions about what is the normal contrast paper (or which VC filter should be used for a normal negative). But most people agree that a normal contrast negative produces the best print when printed on a grade 2, 2.5, or 3 paper (or VC filter). If you are in doubt, and use VC filters, contrast grade 2.5 is probably a good choice when trying to calibrate negative contrast.

 

As I am sure you know, negative contrast is easily manipulated by varying the film development time. Of course, contrast also depends on the inherent contrast of the scene one is photographing.

Al,

 

It is a bit like "normally Salty Food" or "Normal music". There are extremes that most can

agree on but beyond that....

 

jmp

Al, Please remember what Mark Twain said about this subject.

 

"There's lies, damn lies and statistics."

 

A normal contrast negative (in spite of what the numbers might say) will print with a minimum of fuss on "grade 2" paper. This is different for grade 2 azo, graded paper, variable contrast paper or whatever you are using to print on (alternative process papers, platinum, etc.). However, what each of these have in common is that "normal" is defined by the paper being used.

The paper can "see" less contrast than the film. The film can see less contrast than the "real world" setting and the eye, so everything is being compressed to fit the scale of the paper.

 

This is normal?

Nothing in photography is "normal". Photographers with a tech bent have been arguing for decades about "H&D curves", where the "toe" and where the "shoulder" fall, the straightness of the "straight line portion of the curve", and a bunch of other crap that pre-digital techies played around with to sound knowledgeable.

 

Every enlarger is different, as are the lenses for them. Pick a paper you like, probably variable contrast, and start out with a #2 filter. Now go out and shoot film under a variety of conditions and bracket your exposures in half stops from one stop under to one stop over. Develop according to the suggested time/temperature. Next make the best print you can out of each negative. If they're a bit flat or too contrasty repeat the whole procedure but add or subtract 10% to your time. Now pick the best negative based on good shadow detail and highlights that aren't blocked up. In all probability you'll be on the money; at worst you'll know that you have to rate the film, say Tri-X, at 250 or 640, or the like to get optimum negatives.

 

If the photos are REALLY flat or contrasty add or subtract 20% to your developing times. Just remember that the authors make their money by writing and selling books! They'd be mighty poor if they summed it up in just two paragraphs. It takes a lot of skill to flesh out two paragraphs into an entire chapter, or maybe even a whole book. Go shoot a roll and find out what you need to do, and don't worry about the technical gobbledy-gook unless you're really interested. Sorta like you don't really need to know the actual chemical reactions that take place when you fry eggs; you soon learn what heat setting works best on your stove.

Al-when you publish "Practical Approach to B&W Photography" by Al Kaplan I want to be the first in line at your Barnes and Noble meet the author night. I like your style!

Way back, a smart guy named Lootens suggested in his books that you're wasting your time with 1 stop bracketing. He said if you shoot one normal, one at +2 and one at -2, you were sure to come back with something printable. I think his logic was based on films having a fair amount of latitude, and photographers often making larger mistakes than they realized.

Well folks, mystery solved. I re-read the chapter and found the following description...

 

Actually the answer was earlier in the chapter...

 

"For pictorial photographic negative emulsions, a total negative constrat of approximately 1.1 is considered normal (for diffusion enlargers) and is based on the printing characteristics of the negative."

 

Sounds pretty dogmatic to me...I agree nothing can be called 'normal'. Expect two lines drawn orthogonal to one another. But then I'll leave such matters to a Perpendicularity Consultant.

 

But not completely nonsensical. Given a relative log exposure range of about 1.6 for an average scene (luminance ratio of 160:1 or 7 1/3 stops...guess I know where that magic number comes from now), that works out to a Gamma of 0.6875.

 

Sorry for the confusion. I think we can consider the case closed.

Al, just a quick correction. The average log subject luminance range is 2.2 (160:1 or 7 1/3 stops). 2.2 / .3 = 7.33. Also, you don't want a total negative contrast of 1:1. You want a total reproduction of 1:1. This includes the print. Keep reading guy. It comes slowly.

I told you Mark Twain was right. tim

 

P.S. Sorry, couldn't resist. Q.F.

I read a good test in the Zone system for 35mm to determine proper contrast and film development time. Shoot a roll of film alternating Zone III on a gray card and blank frames. Cut into three pieces. Vary the development times a few minutes for each piece. Then shoot a 8x10 of half of each frame. Do a test print. When the Zone III appears at maximum black you have your proper contrast and development time. This is a great test as it seems to eliminate all the variables of the printing stage because the relationship of the film values should be a constant.

Should be Zone VIII above, oops.

Defining a Normal contrast negative doesn't come so much from the desired negative density range, but from what is considered average conditions. What is the average scene's luminance range? What is the average flare factor? A Normal negative is whatever the CI is that will reproduce these conditions satisfactorily under the desired printing conditions, be it platinum or point source, be it printing-out-papers, or gum bichromate, be it grade 1 or grade 4.

Hope that these thread is still active.

 

Since I returned to B&W just less than a year ago I've been reading and re-reading Ansel Adams "The Negative" book. He suggests normal negatives for condenser enlargers to have Zone I around 0.8-0.11 and Zone VIII around 1.15-1.25. Using my Sekonic meter with diffusor-disk attached as rough densiometer I check my films as part of my film process and get values 0.1 and 1.2 respectively. But I'm not satisfied with the results - have to print nearly all negatives with grade filter #1/2 or #1 (one even with #0).

 

I found this odd given that my negatives are withing suggested range. Then an idea came to me: 1) Adams used mostly large format camera (I have to be content with 35mm), so his negatives have more details (apparently higher local contrast in shadows and highlights); and 2) he most likely refers to fiber-based grade 2 paper, while I'm using multigrade resin-coated paper. I checked Ilford curves for Ilfobrom and Multigrade RC, and former has just very slightly more exposure latitude. Based on that rought data (why didn't Ilford put more readable curves in their PDF?) Ilfobrom should be capable to reproduce one stop (sorry for this clumsy definition) more than MG RC paper. Unfortunately I can't try Ilfobrom myself, but I've found that Agfa's paper has the curve very close to Ilfobrom. Will check this as soon as I have chance to get hold of that paper.

 

To anyone who prints 35mm negatives on both RC and fiber paper (preferably on condenser enlarger): try making a test shot with both deep shadows and highlights in the frame, develop negative that it fits range mentioned above and see if you can print it on grade 2 FB-paper so that good details appear in both shadows and highlights, then print it on RC paper and see if either highlights or shadow details disappeared. (I assume the test is done with Ilford's Multigrade RC and Ilfobrom or with papers that have similar density )curves. Whould be nice to see whether FB papers "picks up" more from the negative.