Noritsu Densitometer - Nailing Films and Prints B&W Workflow

[zarrir_junior]

<p>I have just received my first densitometer. It is a Noritsu DM-201 <strong>Transmission and Reflection</strong> Colour unit. Working perfectly. Tried to Google for a detailed workflow so i can nail down exposure and development times for specific <strong>developer-film-paper combinations</strong> but found some very vague information. Can someone provide me some straight instructions on how to proceed? The Noritsu manual simply provides technical info, no workflow suggestions.</p>

[Tony Evans]

<p>Zarrir,<br>

I am no expert in this field and leave more sophisticated recommendations to others. Years ago I went through this exercise in the following way. For each Film/Dev combo, shoot a full Zone I- X series of a Kodak Gray Card, plus a blank (Lens Cap on). Measure the transmission densities and plot. Helpful if you also shoot some scenes on the same roll. Read Ansel Adams to interpret your new info.</p>

[Alan Marcus]

<p>To wet your whistle:<br>

Using the visual (yellow filter) measure the highlight density of a black & white negative. Say it is 1.20.<br>

Now measure the shadow density, say it is 0.15. Now subtract to obtain the density scale of this negative. Thus 1.20 - 0.15 = 1.05. We print using grade 2 paper.<br>

Paper grade vs. scale<br>

Scale 1.40 or higher grade 0<br>

Scale 1.20 thru 1.40 grade 1<br>

Scale 1.00 thru 1.20 grade 2<br>

Scale 0.80 thru 1.00 grade 3<br>

Scale 0.60 thru 0.80 grade 4<br>

Scale 0.60 or lower grade 5</p>

[leicaglow]

<p>This is very useful. My gray scale chart is long gone, and I can't seem to find one (at least with 10 zones) anywhere. Any tips on finding one that is reasonably priced?</p>

[Alan Marcus]

<p>Gray Scales Kodak<br>

 

<p>Uncalibrated, No. 1A 152 3380<br>

Uncalibrated, No. 2 152 3398<br>

Calibrated, No. 2 152 3406<br>

Uncalibrated, No. 3 152 3414<br>

Calibrated, No. 3 152 3422</p>

</p>

[zarrir_junior]

<p>Hi Alan, so by measuring this density range of any negative it is possible to determine a starting point for the contrast of the print. How about the exposure time?</p>

[Alan Marcus]

<p>Known negative exposure time vs. unknown negative exposure time calculation:</p>

<p>The densitometer directs a beam of light of known intensity causing it to transverse the negative. The instrument measures the light loss due to this passage and assigns this loss a numerical value.</p>

<p> By convention, the value is written in logarithmic notation base 10.</p>

<p>We select a typical negative to use as a standard. We measure its highlight density; it is 1.40. We print this negative via trial and error using time as the adjusting factor. The best print of the series results from a 12-second exposure.</p>

<p>We select an unknown negative to print. We measure its highlight density; it is 1.30. This negative is less dense thus less exposure time will be needed.</p>

<p>If we know the density, we can calculate another value known as opacity. This is the total amount of light that hits any area of the film ÷ amount of light that gets through. We can use a table of density to opacity or we can use a scientific calculator. Opacity is 10 elevated to the power of the density value. Example density 0.30 = opacity 2 or, stated another way, the light reduction is 2x or 50% or 1/f stop. Density 0.60 =opacity 4 or 4x reduction or 2 f/stops. Density 0.90 = 8 or 8x reduction or 3 f/stops.</p>

<p>If we know the density of the test negative and the density of the unknown negative and we know the time used to print the test negative, we can derive the revised exposure time -- an unknown negative.</p>

<p>The test negative was printed at 12 seconds.</p>

<p>The test negative has a high density of 1.40. Using a calculator or table we calculate the opacity -- it is 25.12.</p>

<p>The unknown negative has a highlight density of 1.30; we calculate its opacity -- it is 19.95.</p>

<p>Now we calculate an exposure time for the unknown negative.<br>

The math:<br>

19.95 ÷ 12.12 x 12 = 9.5 seconds.</p>

[Alan Marcus]

<p>All this gobbledygook starts with Ferdinand Hurter (Swiss 1844 -1898) and Vero Driffeld (England 1848 - 1915). Together they pioneered the twin sciences of sensitometry, exposing with precision, films and papers and densitometry, the measurement of the blacking yield that results from exposure. Today we expose test materials, measure, and graph. When we graph, we call them H&D curves to honor them.</p>

<p> Hurter & Driffeld made the first light meter; a thermometer that measured the heat produced by sun light and tables that converted the reading to camera settings.</p>

<p> The sensitometer, densitometer, light meter, enlarging meter, automated printer exposure control, the built in exposure logic and the histogram, all trace back to their work published in 1890.<br>

<br>

If we can see further than other men, its because we stand on the shoulders of giants (Isaac Newton).</p>

[zarrir_junior]

<p>Pretty nice, Marcus. Thank you. So if i have a good negative that prints nicely on a certain paper, at a specific grade, at a known exposure time, then all i need is a transmission densitometer to make an unknown negative to be printed (the best it can be) on THAT SAME PAPER. Correct? That´s where my second question comes: What if i decide to change the paper for the unknown negative print? Can i benefit from the reflection capability of the Noritsu to achieve good results with this new paper? How?<br>

Sorry to ask you so many questions, but this equipment was bought so cheap that i am pretty much inclined to find out how it works and perhaps save me some precious time at the darkroom. It is a DM-201 model, with Visual and Blue, Green and Red individual colours. Status M for transmission mode. Four digits show Visual, B, G and Red separately and simultaneously (nice!). Printer is working and it is in pristine cosmetic condition. Should i always rely on RED for my Black and White measurements?</p>

[Alan Marcus]

<p>First, we use the visual filter only for black & white readings. This is because in the days of Hurter and Driffield, electronic light measuring did not exist. For many years, densitometry used a split field instrument like a microscope. The instrument displayed simultaneously a view of a natural density filter and a view of the film. One rotated a wheel that held different values of natural density filters. These were juxtaposed against the film. Since the human eye has magnificent ability to judge the likeness of two simultaneous views, the density of the film was easily and accurately obtained via this direct visual comparison. The visual filter is a Wratten 106 Amber, it converts the response characteristics of the light source and the photo sensor of the densitometer to match the values obtained is you had used a visual split view densitometer of the past.</p>

<p>The red - green - blue filters are used to evaluate color film. The red filter position is also used to evaluate the correctness of the exposure of the color film. This is because current color printing systems are biased to avoid the use of cyan filters in light path of the enlarger / optical printer. Cyan filters are very poor as to their band pass accuracy, thus, we avoid their use. The cyan filter, if it were accurate would be used to adjust the energy level of the red exposing light during the printing exposure. Due to the poor performance of the cyan filter, we use the iris diaphragm of the enlarger lens for this purpose. Or other means to adjust the overall brilliance of the exposing light. Therefore, the red density of the negative provides good insight as to the correctness of the exposure received by the color film.</p>

<p>To get the most value from the densitometer for determining printing exposure, the test negative and the photo paper and the activity of the process are all taken into account. The more accurate the test material, that is the more relevant the test film and paper combinations, the better. Now the densitometer is used for off easel evaluation. For on easel evaluation we use an enlarging meter which is a cross between a densitometer and a light meter. In high-speed printing equipment, we additionally use computer logic with look-up tables. Many types of negatives and paper combinations are pre-tested and the offsets stored. During the printing cycle the type of film, even down to the generation of the film is determined and offsets are factored in taking into account different paper types. We have been doing this with black & white films since the turn of the last century and with color films since the early 1950's. </p>

[Alan Marcus]

<p>The transmission densitometer is used to evaluate film. The reflection densitometer is used to evaluate photo papers. A light meter is used to evaluate the exposing light so the camera exposure can be set to best benefit. An enlarging meter is used to evaluate the exposing light of an optical printer such as an enlarger or high speed printer. A color analyzer is a highly advanced densitometer using a video display as an aid for the operator to determine printing off-sets for a high speed photo printer.</p>

<p>I think most are not sufficiently bored. After all this stuff is just gobbledygook. </p>

[paul_hoyt]

<p>In Ansel Adams' basic photo series on the negative he has a complete discussion on what negative densities you should have for Zone I, Zone V and Zone VIII. He also has a complete step by step instruction for film testing. Buy the book(s) and follow the instructions. If you change your film or developer, you will need to retest. I don't really know how a reflection densitometer will be of any real value; zone system densities are determined with a transmission densitometer and negatives.</p>

<p>Paul</p>

[zarrir_junior]

<p>I read something about contact printing a step wedge and then reading the results with the reflection densitometer to plot a curve. Maybe related to paper speed only?</p>

[paul_hoyt]

<p>Stouffer Industries makes negative step wedges; both calibrated and uncalibrated and 10 or 12 or 14 or 21 or 31 or 41 steps tablets. They come in various sizes depending upon your needs. I have used a 31 step, calibrated, 4X5 step tablet.</p>

<p>See: <a href="http://www.stouffer.net/TransPage.htm">http://www.stouffer.net/TransPage.htm</a><br>

You might also read the discussion from Paul Wainwright (<a href="http://www.paulwainwrightphotography.com/biblio_by_me.shtml">http://www.paulwainwrightphotography.com/biblio_by_me.shtml</a>) on using a step tablet for plotting density curves.</p>

<p>Paul</p>

[zarrir_junior]

<p>Excellent tip, fascinated with his first phrase: "<strong>The world needs another article in densitometry as much as it needs a bullet in the head</strong>". In fact, many books and articles have been written and re-written, but most of them lack the friendly approach i could find, for example, here in the forums.</p>

[zarrir_junior]

<p>Paul, those articles actually summarize everything i needed to know and that were also cleverly exposed by Alan above. It is now shortened to a simple task to be done: Discover the correct exposure time for the test negative contact print. Thanks a lot you guys!</p>