Thanks Jonathan. I could have sworn I bought a copy of Phil Davis' BTZS book years ago, but I can't seem to find it now. I'll start there. Skip. mail1 wrote: > Phil Davis's "Beyond the Zone system" is the definitive work on this > subject. > http://www.btzs.org/ is the web site for articles and info on the book, and > software > > http://www.btzs.org/Software/Plotter.htm This windows base software plots > both film and paper curves and the matcher feature graphically compares the > film and paper relationship. > > I have seen some really good buys on eBay for densitometers that have the > ability to measure both film, and paper densities. > > > http://www.btzs.org/Software/ExpoDevPalm.htm > I have used a Palm Pilot loaded with info from Plotter software to determine > exposure and film development times. The Palm creates a log that saves some > time with note taking. > > I will admit it took some effort to get up to speed on all this. This system > has provided me with a method to use Subject Brightness Ratios and metered > EV values to determine film exposure and development that yield negative > density ranges to match the papers I use. > > > "The Book of Pyro" by Gordon Hutchings > "Edge of Darkness" by Barry Thornton > Both of these authors write about there experience with staining developers > and VC papers. > Barry Thornton wrote about the effects of stain color and there effects on > VC papers. He also formulated different developers that optimized the stain > for VC papers > Now available from, > http://www.photoformulary.com/DesktopDefault.aspx?tabindex=0&tabid=1 > > The BTZS Plotter software will graph projected or contact prints from step > tables. The density values from the stained negative can bet entered in the > step table column and the corresponding reflective print densities enter to > complete the plotting. > Unfortunately the negative density values are not linear like a step table; > therefore I suspect this would skew the curves. > I have used transmission densitometers, reflection densitometers, and on > easel photometers to determine negative density range, paper log-exposure > range, and paper exposure, only to find the local gradation causes me to > change exposure, and paper grades (paper log-exposure range). To make an > analogy all this testing gets me in the ball park for sure, I see fewer > balls, and strikes, and some times I get a home run. > Remember negative exposure and development are finalized upon completion > of development, and all this effort is to make fine negatives that are a > delight to print. > > Jonathan Ayers [mail1&redwoodhorses.com] > > > > > > -----Original Message----- > From: pure-silver-bounce@xxxxxxxxxxxxx > [mailto:pure-silver-bounce@xxxxxxxxxxxxx] On Behalf Of Richard Knoppow > Sent: Saturday, November 10, 2007 12:16 PM > To: pure-silver@xxxxxxxxxxxxx > Subject: [pure-silver] Re: Densitometer for print exposure calibration > > > ----- Original Message ----- > From: "vellum" <vellum@xxxxxxxxxxxx> > To: <pure-silver@xxxxxxxxxxxxx> > Sent: Saturday, November 10, 2007 6:02 AM > Subject: [pure-silver] Densitometer for print exposure > calibration > > > >> Shannon's interesting thread about multigrade paper has >> made me want to >> test my enlarger and paper to better understand it and >> calibrate my >> system. It's something I've never done before. I'm fuzzy >> on some of >> the concepts and what they really mean, like Log Exposure >> Range, but >> I'll figure it out as I go. >> >> I have a Jobo Colorstar 3000, but I don't have the B&W >> density probe for >> it. I just have the standard color probe. >> >> What densitometers might be the best candidates for B&W >> print exposure >> densitometry if I were shopping used on ebay? I'd rather >> buy a new one >> but I suspect new ones may be costly. Ease of use on the >> enlarging >> easel and accuracy (or consistency) would be priority. An >> exposure >> timer function would be nice, but not essential. >> >> Ability to use it to measure density of negatives would be >> nice too. I >> develop using both MQ and pyro developers. Having one >> densitometer that >> "does it all" would be cool, but probably there may be >> none that do >> everything well. In that case, it is the printing >> densitometry that >> matters most to me. >> >> Skip. >> >> > > I think the key here is understanding that there are > two media to be measured: negative and print. A transmission > densitometer will allow you to measure the densities, but > more important, the contrast, of the negative (with some > qualifications). The resulting range of densities on the > paper will also depend on the characteristics of the > enlarger. Nearly all transmission densitometers measure > diffuse visual density. Some enlargers use semi-specular > (condenser) light sources which produce different effective > densities than a diffuse source. This is called Callier > effect and varies with the film. It is nearly absent for > color film and greatest for coarse grain silver film. > To measure the print one needs a reflection > densitometer. A number of these have been made and are > available. Both types of densitometers are made for either > white light or standardized colors. > The effective density of a negative with a stain image > such as produced by Pyro is dependent on the color > sensitivity of the printing material. If its printed to a > panchromatic material the effect is nearly absent. For blue > sensitive material the effect is to increase the contrast > but not the shape of the film curve. For variable contrast > materials the stain image may look like a masked filter > causing the contrast to vary with the negative density. > Since the filtering effect is strongest in the dense regions > the effect is greatest on the print highlights. Since VC > paper prints lower contrst for blue exposure than for green > the effect will be to lower highlight contrast in about the > same way a shoulder in the film characteristic would do. The > amount of this effect willd depend on the relative density > of the stain versus the silver density, the spectral > characteristics of the paper, and the light source. > Beacause the paper characteristics affect the resulting > curve it is difficult to measure using a densitometer. You > would have to have filters at the correct colors to match > the two components of the printing paper. I don't think the > blue and green filters used for color work are at the right > wavelength. > One could presumably print a step tablet onto the film, > process it, and make prints from which a reflection > densitometer could measure the resulting density curve. I am > pretty sure I have seen published results of such tests but > can't cite a source. > > --- > Richard Knoppow > Los Angeles, CA, USA > dickburk@xxxxxxxxxxxxx > > ============================================================================ > ================================= > To unsubscribe from this list, go to www.freelists.org and logon to your > account (the same e-mail address and password you set-up when you > subscribed,) and unsubscribe from there. > > No virus found in this incoming message. > Checked by AVG Free Edition. > Version: 7.5.503 / Virus Database: 269.15.28/1123 - Release Date: 11/10/2007 > 3:47 PM > > > No virus found in this outgoing message. > Checked by AVG Free Edition. > Version: 7.5.503 / Virus Database: 269.15.28/1123 - Release Date: 11/10/2007 > 3:47 PM > > > ============================================================================================================= > To unsubscribe from this list, go to www.freelists.org and logon to your > account (the same e-mail address and password you set-up when you > subscribed,) and unsubscribe from there. > > > ============================================================================================================= To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there.