Thank you Shannon for the more detailed description. Shannon Stoney wrote: > It was pretty simple really. Sorry if I made it seem complicated. > > I got a stouffer step tablet in the 4x5 size from The View Camera > Store. I printed it using six different filters: 00, 1, 2,3,4, and > 5. Then I looked at the results. Each paper had a step tablet > printed on it, but on the 00 one for example, more steps had a shade > of grade on it. Grade 5 would have relatively few steps with a color > of gray. > > So, I would mark on each paper the step that printed at near black > (zone 3 in zone system terms) and the one that printed near white > (zone 7). Then I took the step tablet negative to the densitometer > and measured the density of those steps, say step 5 and step 11. Step > five might have a density of 0.4, whereas step 11 would have a density > of 1.4. The difference between them--1.0--is the paper scale. > > That's all. > > Alternatively, you could send the paper tests to The View Camera Store > and then they would measure them for you. > > The way I use this information is: when I have a negative I want to > print, I could measure its shadow density on the densitometer, measure > the highlight density, subtract, and know approximately what > filtration the paper will need, or indeed if I can print the negative > at all on that enlarger. > > (If you use the Beyond The Zone System method, you also use this > information to carefully expose and develop your negative to fit the > paper scale you want. Most of the time this works, but with roll film > obviously the results are chancier and more uneven because all the > exposures get the same development.) > > --shannon > > > On Nov 10, 2007, at 11:26 PM, vellum wrote: > >> Thanks Richard. I saved your post to review in the future when I might >> hope to have a better idea what it means. What I really want to do is >> whatever it was that Shannon did, so what I was asking for was advice on >> acquiring equipment that could help me do that. That's probably what I >> should have said to start out with. I'm no longer certain I understand >> what what it was Shannon did though, so I'll shelve that idea while I >> assess the matter further. >> >> >> >> Richard Knoppow wrote: >>> >>> ----- 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. >>> >>> >> ============================================================================================================= >> >> 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. > > ============================================================================================================= 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.