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Photo Forum / Film Photography / Darkroom / October 2004Contact Printing: How Black To Go?
How do I determine what is "black enough" on a contact print? I've done an exposure test strip 5, 10, 15, 20, 25, 30 secs. and have determine there is just a smidge of discernable difference between 20 and 25 and no difference (that I can see anyway) between 25 and 30 I think. New Dektol. Silver Paper. I'm trying to build a curve to apply to my digital negatives. My thinking is that I have to establish my enlarger time first because it shouldn't be a variable. Then build the curve from my step wedge. I could probably get away with 15-20 seconds because that was an OK black. What's the thinking on this? > How do I determine what is "black enough" on a contact print? I've done an > exposure test strip 5, 10, 15, 20, 25, 30 secs. and have determine there is [quoted text clipped - 5 lines] > with 15-20 seconds because that was an OK black. What's the thinking on > this? What I do projection print a step wedge that goes from 0 (actually 0.06) gross density up to about 3.15 (IIRC) and my usual time, height, and aperture. I process this normally and when dry, examine it under a light somewhat stronger than normal (but not ridiculously strong). I look for the last step that I can distinguish from the darker ones. The next one is, for me, maximum black. Now my "reflection densitometer" is that Kodak Densiguide, Q-something, with holes in it. By that standard, this black has a reflectioin density greater than 2.0. Now for making negatives, since printing step wedges gets old very fast, I print so that the clear edge of the negative matches that maximum black. Now the first time I tried that, the rest of the print was way too dark. But to get maximum black, I _must_ expose the negative at least that long. Since the contrast index was correct, the only way to manage is to expose the negative more in the camera so that the mid tones come out right. That way, the clearest parts of the negative _will_ print maximum black, the midtones will look "right" (i.e., what I expose for Zone V will, when printed, match the 18% gray card), and the highlights will be right too (if the contrast index was correct). The only thing that might be unexpected is that the net densities for Zone I come out around 0.25 to 0.3 instead of the 0.1 Ansel Adams recommended in his books. So what?  Signature.~. Jean-David Beyer Registered Linux User 85642. /V\ Registered Machine 241939. /( )\ Shrewsbury, New Jersey http://counter.li.org ^^-^^ 14:55:00 up 4 days, 16:47, 3 users, load average: 4.21, 4.15, 4.05 > How do I determine what is "black enough" on a contact print? I've done an > exposure test strip 5, 10, 15, 20, 25, 30 secs. and have determine there is [quoted text clipped - 5 lines] > with 15-20 seconds because that was an OK black. What's the thinking on > this? What are you talking about? The question is mostly geek speak to me. However, I will tell you how I (chemicals only) determine the correct exposure for a contact sheet. I run a test strip, but NOT of the pictures! I run a test strip across all the negative strips in a holder and I make sure that each of the sprocket strips are exposed for progressively longer amounts of time. Then I examine each strip to determine what amount of exposure causes the sprocket holes to become so dark that can no longer be distinguished (just) from the strips between them. That is the "correct" exposure for the entire contact sheet, and I think it will produce the best overall result. >> How do I determine what is "black enough" on a contact print? I've done >> an [quoted text clipped - 13 lines] > > What are you talking about? > The question is mostly geek speak to me. However, I will tell you how I > (chemicals only) determine the correct exposure for a contact sheet. [quoted text clipped - 5 lines] > between them. That is the "correct" exposure for the entire contact sheet, > and I think it will produce the best overall result. I'll explaing a little more. My inkjet is printing to Inkjet transparent media (e.g. Pictorico OHP or White Film, Epson Overhead). My inkjet is capable of producing densities in the 3.0 range (possibly even higher on some of this media) at 5760 DPI . I create (inPhotoshop) step wedge of blocks ranging from 0 (clear) - 100 (black) per cent to transparency film using my inkjet. I contact print this step wedge to my wet media (Kodak Paper). I scan the resulting contact print (Epson 3200). I adjust for black and white points in Photoshop. I take a density reading on each of the squares to build a table used to develop a curve which is the characteristic relationship between my inkjet negative and my wet printing media (silver paper, Pt/Pd et al.). The data from table is inputted into photoshop in the "Curves" menu and saved as an *.ACV file. Now I call up a B&W photo in photoshop, put the curve on a layer, invert the photo (turn it into a negative) and print it to my inkjet at whatever size I want the final print to be. Contact print the inkjet transparency and in theory I have a perfect print. (The Burkholder method more or less) The original question was to ascertain what people considered an acceptable method for determining how "black" a perfect black should be in a print, why and what's the best method to use. I'm new at this darkroom thing, but not at this computer thing...cheers. Thx. > > The question is mostly geek speak to me. However, I will tell you how I > > (chemicals only) determine the correct exposure for a contact sheet. [quoted text clipped - 35 lines] > at this computer thing...cheers. > Thx. This makes no sense. Although this makes some sense, since you are rescanning the print your scanner's 'curve' is also being applied, the rest or your process will be biased, won't it? If your final output is a chemical print, it seems to me that you should do the analysis there, either visually or with a densitometer. > > The question is mostly geek speak to me. However, I will tell you how I > > (chemicals only) determine the correct exposure for a contact sheet. [quoted text clipped - 35 lines] > at this computer thing...cheers. > Thx. > Although this makes some sense, since you are rescanning the print > your scanner's 'curve' is also being applied, the rest or your process > will be biased, won't it? If your final output is a chemical print, > it seems to me that you should do the analysis there, either visually > or with a densitometer. At first sight one would expect the scanner's "curve," or any CCD's "curve," to be a straight line. But postprocessing may be going on in the software which would alter that. The scanner's curve when scanning a print in flatbed mode is almost negligible when compared to the curve of the paper. I find that the scanner makes a not bad densitometer too. One drawback I'm finding is that the digital negative produced on the inkjet requires a lot of ink to block light. So in part my question stems from trying to limit how black I need the print. Right now I'm noticing the "flat line" portion of my silver paper's curve seems to fall on the inkjet's 1.5 to 2.3 density range. In other words disproportionately on the darkest parts of digital negative. The trick is to make the inkjet's output stretch over the usable range of the paper. Hence a curve is needed to "re-map" the inkjet's output. The inkjet's negative output looks wrong to the eye but perfect to the silver paper if done correctly. I believe this method of using curves can also be applied to negatives with "difficult" contrast. > Although this makes some sense, since you are rescanning the print > your scanner's 'curve' is also being applied, the rest or your process [quoted text clipped - 41 lines] > > at this computer thing...cheers. > > Thx. > The original question was to ascertain what people considered > an acceptable method for determining how "black" a perfect black > should be in a print, why and what's the best method to use. > I'm new at this darkroom thing, but not at this computer > thing...cheers. Thx. I've looked at scores of prints evaluating black vs black; step tablet and fb+f. As you pointed out there is black and then there is black. The very blackest will perhaps pull all print values too dark. That very black may be one or two stops more exposure than needed to produce a black only faintly less dark. Print papers vary in their max black. Developers can influence to a small degree final maximum density and of course toners. I'd say it is a subjective call in practice. Prints given a little of a high-key finish may have less dense blacks. Life may not be so simple. Dan Dan Quinn wrote (in part): >>The original question was to ascertain what people considered >>an acceptable method for determining how "black" a perfect black [quoted text clipped - 6 lines] > is black. > The very blackest will perhaps pull all print values too dark. Usually does with typically exposed negatives, but as I have posted previously, you can correct that, without affecting your contrast, by exposing your negatives more (usually one stop more is enough) so that Zone V on the negatives come out with a net density of about 0.85 to 0.9. > That very black may be one or two stops more exposure than needed > to produce a black only faintly less dark. Signature.~. Jean-David Beyer Registered Linux User 85642. /V\ Registered Machine 241939. /( )\ Shrewsbury, New Jersey http://counter.li.org ^^-^^ 17:35:00 up 5 days, 19:27, 4 users, load average: 5.92, 5.77, 5.14 This is the type of comment I was waiting for. Thank you. I think I'm coming to that realization that the blackest black may not be the easiest to work with. > > The original question was to ascertain what people considered > > an acceptable method for determining how "black" a perfect black [quoted text clipped - 13 lines] > a little of a high-key finish may have less dense blacks. > Life may not be so simple. Dan > This is the type of comment I was waiting for. Thank you. I think I'm coming > to that realization that the blackest black may not be the easiest to work [quoted text clipped - 17 lines] > > a little of a high-key finish may have less dense blacks. > > Life may not be so simple. Dan Frankly, I never worry about it. Obtaining a "proper" black is as simple as taking a developed, but unexposed piece of film, cutting a hole in part of it and increasing the print exposure until the black of the film's fb+f cannot be differentiated from the black produce by the hole. That's the basic (i.e., minimum) exposure for any developed film/paper combination to produce a good "black" assuming your negtive has areas of "zero" density." In actual practice, I never bother. I know my negatives and the typical contrast range they have. I print for the highlights. "Contrast" is the range of tonalities, not the maximum black, one sees in a print. If the highlights aren't right the print is simply too dark and heavy to my eye. Blacks are much harder to differentiate, while subtleties in highlight tonalities are more easily discerned. To me, good highlights are what make the print "sing." All my prints have good blacks; I often burn them in. But I generally just let them fall where they may. The difference between a print reflection density of 1.8 and 2.2 is rarely noticed, while the _range_ of overall tonality is. Of course, Ansel Adams used to claim he could tell the difference between a Zone I value and a Zone II print value. Maybe. I leave everything below a Zone III shadow density to the subjective area we call "black." > How do I determine what is "black enough" on a contact > print? I've done an [quoted text clipped - 13 lines] > the thinking on > this? The maximum black on a print depends on its surface and how its illuminated. Most papers are capable of deeper blacks than are useful for reflection prints as can be demonstrated by looking at the print by transmitted light. Typical maximum reflection density for glossy paper is around log 1.8 to 2.0. Your negatives should be made to get close to this value. Visual perception of black depends on the nature of the image. Small dark areas in an otherwise light print will appear darker than the same value on a low key print. If you can achieve good tonal rendition overall it probably does not matter if the blacks are at the absolute limit of the paper. Because the curve of a digital negative can be adjusted at will it is possible to compensate for the paper curve, this is very commonly done when making ink jet negatives for alternative printing methods. There is a great deal of material on making digital negatives for alternative printing on the web, much of this will be of use to you even though you are printing on standard paper. A google search will find some of this. Also look at the Bostick and Sullivan site at http://www.bostick-sullivan.com for links to more. Signature--- Richard Knoppow Los Angeles, CA, USA dickburk@ix.netcom.com |
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