According to the theory of the great Ansell Adams the contrast of film may be adjusted with a combination of exposure time and development time. The master discribes this in his writings on the so called zone-system (I think "The Negative, N.Y.Graphic Society"). A longer exposure and shorter development time will result in a lower contrast. On the cotrary a shorter exposure time with a longer development time enhances the contrast. Mr. Adams perfected this system to such an extend, that he was capable of defining the contrast in the final print during exposure (with an accompanying devellopment-time in mind, even using filters). He printed his positives always with the same exposure- and development-time, on the same grade of paper. That asked and asks for the making af trial exposures.
This can be done by taking a photograph of a white towel at the standard time as indicated by a standard procedure (following for example sensitivity and apertuere on a light meter, , that gives you an exposure time. Write this time down, for example 16 seconds. This is Exposure time 1. The printed result should give a result af 18% reflection = neutral grey card. If you have found this time (you should follow exactly the right temperarures and development-time given for your printing paper), you have the beginning. Remember to write down the exposure- time for the paper print. This is exposure time 2 and will not change for the period of your testing. It must be clear that you should not change any filter, if any filter is used, using MC, nor in exposing nor in printing during this research. 1 Now make exposures of half, a quarter etc. and twice etc. the found time with your pinhole of the same towel in the same light level (artificial (day-) light may be most consitent (flash). A good range is 1/2, 1, 2, 4, 8, 16, 32, 64, 128, 256 second. Print them all with exposure time 2 and develop under the same circumstances as before. Put the results in a successive row from light to dark. Count the number of different greys you see, Mr. adams called this zones. According to what you write you se too limited a number af different greys in your result. Now do exactly the same experiment twice (step 2 and 3). 2 In the first case under-expose your negative 50% in the first case. Over develop 30% time (keep all conditions unchanged, only vary with exposure-time and development time. Print according to the found procedure using time 2 for the printing exposure time. Place the results in a successive row from light to dark. Count the number of different greys you see. 3 Do the same by over-exposing 50% and developing 30%. Print according to the found procedure using time 2 for the printing exposure time. Place the results in a successive row from light to dark. Count the number of different greys you see. You will notice more zones in 2 than in experiment 1 and less zones in experiment 3 than in 1. Thus you can use the gained knowledge to adjust a combination af exposure-time and development time to suit the contrast of your subject in the print without changing time or filter in the printing stage. I have only done this experiment with film, and not with paper-negatives. But it should work. May be some of our group will give their comments on my approach, so that we can interact before the actual experiment takes place. -----Oorspronkelijk bericht----- Van: pinhole-discussion-admin@p at ??????? [mailto:pinhole-discussion-admin@p at ???????]Namens William Erickson Verzonden: vrijdag 12 juli 2002 16:30 Aan: pinhole-discussion@p at ??????? Onderwerp: Re: [pinhole-discussion] Why is paper "contrasty"? I understand the behavior of VC paper, but my comments intended to deal with the fact that the tonal range of brightly lit scenes exceeded the tonal range of any paper. "Ratcheting down" the exposure time in such situations would bring the highlights more into the tonal range of the paper, at the cost of shadow detail, advantage being that you at least don't lose both highlights and shadow. Thanks for your thoughts. ----- Original Message ----- From: "Guy Glorieux" <guy.glori...@sympatico.ca> To: <pinhole-discussion@p at ???????> Sent: Friday, July 12, 2002 8:05 AM Subject: Re: [pinhole-discussion] Why is paper "contrasty"? > William, > > If you go to the Ilford web site, on the B&W products page, > http://www.ilford.com/html/us_english/bw.html > you will find hiding somewhere towards the center of the page an Acrobat > document called "CONTRAST CONTROL" that deals with your question. > > Basically, contrast on B&W variable-contrast paper is determined by the > amount of blue that hits the paper. Under the enlarger, low contrast is > achieved by reducing the amount of blue from the enlarger lamp with a > yellow filter. > > VC paper is calibrated for tungsten, which is yellow in color, compared > to daylight which is much more blue. So, it's only natural that paper > exposed to "blue" daylight will be more contrasty. > > To reduce contrast, use a yellow filter similar to the 00 that you would > use under the enlarger for minimum contrast: it works very well. It > will block some light, compared to not using a filter. But, if you use > Ilford paper, its speed is higher at lower contrast grades than at > higher contrast. As for me, I use ISO 4 when I shoot paper negatives > and it works well for me. > > Hope this helps, > > Guy > > ----- Original Message ----- > From: "William Erickson" <erick...@hickorytech.net> > To: "ppinhole discussion" <pinhole-discussion@p at ???????> > Sent: Thursday, July 11, 2002 8:45 PM > Subject: [pinhole-discussion] Why is paper "contrasty"? > > > > I've thought this through but haven't completely verified it yet, but > I > > wanted to see what others reaction is. B&W paper used as a negative is > said > > to be "contrasty". What does this mean? B&W paper has a sensitivity > range of > > a little more than four stops for any given exposure. Burning and > dodging > > increase tonal range by shortening or lengthening the exposure. If you > meter > > a scene that has an eight stop tonal range and give the average > exposure for > > the scene using a paper negative, you risk having the highlights blown > out > > because they are more than two stops above average, and shadows go > black > > because they are more than two stops below average. If the scene has a > tonal > > range of only four or five stops, your negative won't be contrasty > because > > all the tones lie within the range of the paper. What, then, to do in > > sunshiney scenes, for instance, where the tonal range might be eight > or nine > > stops? If you place the highlight tones of the main object of your > > composition about two stops above average, you will get good tonality > in > > important spots, no blown out highlights, even though you may get lots > of > > black shadows. The implication is, much shorter exposure times (read > higher > > ISO) in bright scenes than in shadowiy scenes (effctively lower ISO), > using > > the same paper. My first tests suggest that a good ISO for Ilford > multigrade > > in bright sunlight might be as high as 15, while 5 works well in > shaded > > scenes. Any comments? > > > > > > > > _______________________________________________ > > Post to the list as PLAIN TEXT only - no HTML > > Pinhole-Discussion mailing list > > Pinhole-Discussion@p at ??????? > > unsubscribe or change your account at > > http://www.???????/discussion/ > > > _______________________________________________ > Post to the list as PLAIN TEXT only - no HTML > Pinhole-Discussion mailing list > Pinhole-Discussion@p at ??????? > unsubscribe or change your account at > http://www.???????/discussion/ > > _______________________________________________ Post to the list as PLAIN TEXT only - no HTML Pinhole-Discussion mailing list Pinhole-Discussion@p at ??????? unsubscribe or change your account at http://www.???????/discussion/
