I saw this test strip prcocedure:

http://www.natcam.com/Darkroom/tips/Test/strip.htm

on the Natcam web site. They refer to as printing for base density plus fog. How does it work? Thanks.

-- Buck Cochran (hjc@duke.edu), November 10, 1999

Answers

The rest of that page explains it. What don't you understand?

All they are doing is ensuring that the clearest part of the film (the part that is totally unexposed) actually comes out black on the print. They are finding the mimimum print exposure time that gives the maximum black.

I would quibble with that web page in two regards: firstly, it is more convenient to give logarithmically increasing exposure times, rather than linear. Secondly, the mimimum-time-for-maximum-black usually varies for different contrasts.

-- Alan Gibson (Alan.Gibson@technologist.com), November 10, 1999.

The only thing I might want to do, it change the time to be stops or fractions of a stop. The way they set it out, you have a one stoop change between the first and second segment, but less than a stop for each additional segment.

-- Terry Carraway (TCarraway@compuserve.com), November 10, 1999.

I wonder why people accept that you should expose for the shadows on a negative, the thinnest part of the negative but they always want to expose for the densest part on the print. Exposure and contrast work the same on both materials. Printing for maximum black is alright for making sure that exposure and development of your film are in the ballpark but I think it is the wrong approach for making creative prints.

-- Jeff White (zonie@computer-concepts.com), November 10, 1999.

I would say that learning how to make a print that uses the full paper scale from black to white is an important step in learning how to print. If I can't make a full-tone print, I probably can't control anything else. Certainly, it is only a first step, and many good images shouldn't use the full scale.

-- Alan Gibson (Alan.Gibson@technologist.com), November 10, 1999.

Isn't the rule for a straight, full-scaled print analogous to that for negatives, namely

Determine exposure on the basis of the minimum density (of the print, i.e. the densest part of the negative that must still exhibit some detail), and determine grade on the basis of what you want to be black

(provided, of course, that the scale of the negative is long enough)?

-- Thomas Wollstein (thomas_wollstein@web.de), November 11, 1999.

I agree with an earlier post that the progression of exposure for the test strip should be in stops. 2 4 8 16 32 64 and then from that you can tailor it in half or quarter stops. Now you will never acheive a full tone balanced print if you dont have a negative that is correctly exposed at your film speed and developed in your developer at your process time. Exposure of the film controls the information in the shadows and then you control the density of the highlights by the time the film is in the soup. You will never get a rich luminous print until you provide the paper a negative it can handle. You dont have to be obsessive about testing thousands of rolls of film but when you get it right you will be the happiest darkroom gnome on the planet. When you know the way your film/paper combinations work together you can "forget" that information and create wonderful full toned photos and enjoy photography. Just a thought from a very happy darkroom gnome.

-- Steve Nicholls (gl1500@chariot.net.au), November 11, 1999.

Print test strips for maximum black with the clear part of the negative (b+f) negates one of the big advantages of negative film: latitude. Also, the test would have to be redone if there's significant cropping. Tedious. Go to http://www.aseonline.net/~brownt/darkroom.htm to see what I do.

-- Tim Brown (brownt@ase.com), November 12, 1999.

Here's a very interesting paragraph from Photographic Sensitometry by Todd & Zakia:

In general, it was found that only a part of the paper curve was used in making excellent prints. Specifically, almost no preferred print contained the maximum density of which the paper was capable. The darkest shadow was quite uniformly found at a point on the D log E curve well below the maximum, and at a point where the slope was equal to the average slope of the curve, as shown in Fig. V-4. The inference from this discovery is that for pictorial prints, viewers want to see detail in the shadows, even at the expense of the deepest possible black tone.

So wadaya think of that? It would seem that maximum black isn't as essential as thought. In fact, if you achieve maximum black, the print may not be as good!

-- Conrad Hoffman (choffman@rpa.net), November 12, 1999.

Conrad

I do not know the details of the measurements made to substantiate that claim, but I would suspect that you can't measure very small spots. For larger areas, on the other hand, it has always been clear that (as a rule) there should be some detail.

Also, whether or not you need max. black might also depend on the subject and the general mood of the image, on personal preferences, asf. Therefore, this small excerpt may be misleading.

-- Thomas Wollstein (thomas_wollstein@web.de), November 15, 1999.

On the issue of whether to make the basic print exposure based on highlights or the shadows: I've always felt it depends on the image. I usually want to make the basic exposure in a way that minimizes the amount of complicated dodging necessary, since it's generally easier to do complicated, multiple burns than dodges. Sometimes--usually if overall print contrast is low and shadow areas need to be darkened--this means exposing for the highlights so I can burn in the shadows (rather than exposing for the shadows and dodging the highlights). If overall print contrast is high, it's usually the opposite. But I suppose everyone has his or her own way of working.

-- Chris Patti (cmpatti@aol.com), November 15, 1999.

By the way, I took a look at the test strip site, and I'm struck by the following statement: "Making a test strip for each negative is definitely not consistent. Each photo will be exposed randomly, based on the way you happen to feel about the relationship between incrementally darker stripes of print that you have developed." I guess exercising artistic judgment about the needs of each individual image is "random" and "inconsistent." Let's not let the way we feel about the image influence our printing!

-- Chris Patti (cmpatti@aol.com), November 15, 1999.

Making the test strip based on minimum exposure to produce maximum paper black in the unexposed (margin area) of the film is a valid procedure. I use this approach for all my contact sheets. It shows immediately how my negative exposure and development are doing. It also comes very close to how the final print will look when made with a diffusion enlarger. And by comparing the contact to a print made with a condenser enlarger the amount of highlight detail that is compressed can be judged.

The key is to expose the paper through the neg until the clear film edges just match the black from an area with no neg covering the paper. Since the darkest shadow areas should be exposed to be at about 0.10 above film base plus fog, this method establishes a consistent starting point. All usable image densities will lie above the maximum black.

If I have made the contact sheet with the enlarger set at the right height for an 8 x 10 print, I can take exposure information directly from it and apply to the final print and be quite close on the first try.

-- Tony Brent (ajbrent@mich.com), November 17, 1999.

Tony,

Determining exposure by the shadow areas has the one drawback that on changing to a softer grade, the former max. blacks won't be max. blacks any more (provided they were in fact just on the threshold). So you have to make another test strip. To me it seems much more logical to determine exposure by the desired density of the highlights, and to choose the grade you need to get the desired shadow detail and density (be it max. black or not). That way (assuming identical speed for all grades, or a conversion factor such as half the speed with grades 4 and 4 1/2, as is the case with many VC papers), the exposure stays constant when you change the grade, and all you have to do is choose harder grades until you have the desired local contrast and density. This is in fact the conversion of the old rule "Expose for the shadows and develop for the highlights" to the printing process.

Both test-strip methods will invariably fail to give satisfactory results for long-scale negatives, i.e. negatives whose scale exceeds that of the softest paper grade, or negatives where local contrast becomes insufficient when to choose the grade to accommodate the ends of the scale. In such cases, you will need more test strips - separate strips for different regions of the image, and you will have to dodge and burn.

I agree with you that going for max. black is a good way to print contact sheets (for the reasons you mention in your post), and also that one can get a pretty good idea on the exposure and grade of the print from a contact sheet on a somewhat soft grade. But you need not expose your contact sheet at the same enlarger-head height as for the print itself to be able to get a clue as to the exposure time. Times can be extrapolated to different heights with reasonable accuracy.

-- Thomas Wollstein (thomas_wollstein@web.de), November 22, 1999.

Let's try to straighten this out once and for all. After all, science is science, but art is many times much more complcated. And, to paraphrase Adams, "Making a negative is a science, making a fine print is a art." Printing a negative at the minimum exposure to achieve maximum black in the print is an excellent check on the exposure and development of you negative. If blacks are black, and you have the desired detail in the shadows, and whites are white, and you have the desired detail in the highlights, then whatever exposure/development combination you have used is in the ballpark. If shadow detail is missing, the neg is underexposed. If the shadows are too high, the neg is overexposed. If the highlights are wrong (but the shadows OK) then the development time is wrong. All of this works great for Zone System calibration. I routinely proof all of my negatives at this "proper proofing time" in order to monitor my eyuipment and techniques (not to mention changes in materials). However, when I make a fine print, I treat it just like I do a negative: i.e. I expose for the least dense part (highlights in a print) and adjust contrast for the most dense part (the shadows) of the print. This means choosing the test strip exposure that has the desired highlight detail and quality and then going on from there to find the desired contrast and the correct dodging and burning scheme, etc, etc. In short, using the proper proof to keep an eye on your negative making techique will insure that you have negatives that are adequate for the making of a fine print. Print making, on the other hand, is a highly personal and intensly creative endeavor that simply cannot be reduced to an exposure formula for a given negative density. One needs extensive knowledge of one's materials and the necessary experience, not to mention a modicum of talent! Regards, ;^D)

-- Doremus Scudder (ScudderLandreth@compuserve.com), November 27, 1999.