ZBE INC. - Density Probe Manual

The Starlite 55 Colorhead offers many features designed to make your darkroom work easier. One of the most useful of these is the Starlite's ability to accurately change it's light output intensity, or light density. This allows the Starlite to automatically adjust the density of a print being made, not by only adjusting the exposure time as with conventional colorheads, but also by changing the density of its light output. This feature is realized to it's full potential in the Starlite Colorhead.

The Density Probe utilizes this feature of the Starlite by letting the colorhead "see" the amount of light at the baseboard of your enlarger. This allows the Starlite to automatically keep the light at the print consistent with the user's density value, or simply to give the user an accurate densitometer readout from under the lens.

HOW DENSITY WORKS

AN OVERVIEW OF DENSITY IN A PHOTOGRAPHIC PRINTING SETUP

Consider a basic enlarger setup for making prints from negative film. The light from the colorhead must pass through the negative and the lens before it gets to the photo paper. This means that both the negative and lens have an effect on the amount of light reaching the print.

Since we cannot change the density of the negative being printed, the things that can change a print's density are:

Amount of light from the colorhead: Of course, if you increase the light from the colorhead, you will get more light at the baseboard.

Exposure time: The more time light falls on the photo paper, the more exposed that paper becomes. It can be said that the paper "adds up" all the light that hits it as time passes, and that sum is the density of the print.

Aperture of the lens: The lens can vary the amount of light that passes through it using the aperture setting. A smaller aperture (higher f-stop number) will allow less light to reach the baseboard than would a larger aperture. Thus the lens has control over the light density at the baseboard.

The magnification of the enlarger setup: A larger baseboard image spreads the available light over a larger area, decreasing the amount of light per square inch (or "density") at the image area. As a result, the magnification of the enlargement being made also has control over the light density at the baseboard.

A conventional colorhead is not able to change it's light output (only the filtration), and for a normal enlargement, the magnification is not a viable way to achieve density changes. As a result, the operator would have to adjust the lens aperture or exposure time to affect density changes on the print.

But what if the colorhead had the ability to do two things: to see the amount of light falling on the baseboard, and be able to vary the amount of light it emits?

If the colorhead was told how much light at the baseboard makes a good print, it would be able to maintain that baseboard density, by varying its light output and reading the resulting amount of light at the baseboard. Changes in lens aperture (or the lens itself) and changes in magnification could easily be compensated for.

The Starlite Colorhead is able to vary the amount of light it emits, over a range of about 5 f-stops. The Density Probe, when used with the Starlite Colorhead, allows the colorhead to read the amount of light directly from the baseboard. This Density Probe will thus allow print size and lens aperture changes, while providing a way for the user to easily maintain a constant print density.

THE STARLITE DENSITY PROBE

The Density Probe is a precision electronic light measuring device designed for use with the Starlite Colorhead. It becomes the "eyes" of the Starlite when determining the amount of light currently falling on the baseboard. Using the Density Probe, you can freely change the aperture setting of the lens (or the lens itself), or even change the magnification. After the change, you simply probe the light at the baseboard, and the Starlite will correct the light back to the original density measured at the baseboard.

GENERAL NOTES ABOUT USING THE STARLITE DENSITY PROBE

Whenever you use the D-Probe, be sure to hold the probe unit as flat against the baseboard or easel surface as possible. Tilting the D-Probe will cause inaccurate readings.

When taking a probe reading, place the probe as close to the lens center as possible.

When activating the D-Probe button, be sure not to obstruct the probe's "eye" with your hand. Also, once you have started the probing cycle, it is best to leave the probe in place, removing your hand from it until the cycle is complete.

INSTALLATION

The Density Probe connects to the Starlite Colorhead at the top telephone-type jack on the left side of the colorhead's enclosure. The probe's cable can them be routed to allow the probe itself to rest on and around the baseboard area of the enlarger.

Before the Density Probe can be used in making prints, it must first be calibrated to your standard negative (Shirley) setup. This is simply a process by which you tell the Starlite what amount of light at the baseboard corresponds to a given density value at the keypad screen.

SETTING THE STARLITE PREFERENCES FOR THE DENSITY PROBE

The following preferences in the Starlite Preferences menu pertain directly to the operation of the Density Probe. Please review these settings in your Starlite in order to know what to expect from the probe.

PROBING LIGHT - FILTERED / WHITE

If set to "FILTERED", the Starlite will leave the current color filter setting in place when a probing cycle is started. This way, any density contained in the color balance of the current filtration will be "seen" by the D-Probe's "eye", which reads white light.

If the probing light is set to "WHITE", any color filtration in the current filtration setting will be removed before the D-Probe starts reading the light at the baseboard. This setting, which is the factory default, will allow the D-Probe to track the neutral density of the Starlite's output. This means that the Starlite system's keypad density value will track with most video analyzers, even when using the D-Probe.

PROBE WITH AUTOCORRECTION - ACTIVE / INACTIVE

When set to "ACTIVE", the Starlite will change it's light output to make the D-Probe reading match the light level that corresponds to the current keypad density value, in accordance to the level at which the D-Probe was calibrated during the Starlite's Calibrate Master Color Balance procedure (see Advanced Operations). This is the factory default setting. Using the D-Probe in this mode will allow you to always be sure that the same amount of light is falling on the baseboard when a particular density value is shown on the keypad screen, regardless of lens, aperture, or magnification changes.

When set to "INACTIVE", the Starlite will simply provide a passive readout of the light level it reads at the baseboard. When the light is at the same level as that used to print the Shirley, the D-Probe's reading will display the keypad density value that was used when the Shirley was printed (when the D-Probe was calibrated).

The actual procedure for using the D-Probe depends on the setting of the Autocorrection preference. A description of each method can be found in the General Use section of this manual.

CALIBRATING THE DENSITY PROBE

The Density Probe is calibrated at the same time that the Starlite Colorhead's Master Color Balance is calibrated. This is the case whether or not a video analyzer is used with the Starlite. This procedure is given for both cases in the Starlite user's manual. A generalized procedure follows:

Summary:

Setup your enlarger for printing your Shirley negative.
Enter an exposure time using ( 5 seconds ).
Select Emulsion channel 0 (zero) from the Starlite menu.
Enter a filtration of C0 M40 Y40.
Enter a Density of 0.
Use the most popular paper stock that will be represented by Emulsion channel 0.
Press to make exposure.
Adjust Magenta, Yellow and Density to achieve a perfect print.
Make test prints until you have a perfect print.
Go into Starlite Calibration menu.
Select Calibrate Master Color Balance from menu.
Enter the video values for D,C,M, and Y. ( 64 0 30 30 ).
Press when asked to Calibrate Density Probe.
Place empty carrier in enlarger, turn room lights off.
Place probe directly under lens on baseboard.
Wait 6 seconds, then press to take probe reading.

Your Starlite can be aligned so your standard setup negative prints perfectly at any set of DCMY values you choose to use. In other words, the filtration at which your Shirley prints perfectly on the Starlite may be assigned any set of D,C,M, and Y color correction values, according to personal choice or in order to conform to the standard filtration of your lab or video analyzer. Many labs like their setup negative to print at D64 C0 M30 Y30, another popular setting is D64 C0 M16 Y16. You may find it more convenient to use a round number for the density such as 0 or 100; it's your choice.

Setup your enlarger for printing a Shirley negative. Use your normal lens, carrier, easel, etc.
Enter an exposure time, say 5 seconds.
Select Emulsion 0 (zero) in the Starlite main menu. This channel will represent the type of photo paper on which you are about to test-print your Shirley.
Enter a filtration pack to start with. A setting of C:0 M:40 Y:40 is a good starting place.
Enter a Density of 0 to start with.
Turn off the darkroom lights and place the paper on the easel/baseboard. Use your most popular paper stock, that which is to be represented by paper Emulsion 0 in the Starlite Colorhead. When handling paper, you may turn off the keypad lighting by pressing .
Make the exposure by pressing .
Adjust the Density, Magenta, and Yellow values in the Starlite and make the next test print.
Continue making adjustments and test prints until you achieve a perfect print.
Once you have made a perfect print, the next step is to make the Starlite's display read the correct DCMY values (e.g. D64 C0 M30 Y30) for printing a Shirley in your lab. Any values may be used. To do this go into the Starlite menu and then into the Starlite Calibration menu.
Select item 2,"CALIBRATE MASTER COLOR BALANCE" from this menu and press .
You will see the current filtration values displayed, with the cursor flashing on the density value. You may now replace these values with any numbers you wish. To advance the cursor to the next color, press . If the values are Density 64, Cyan 0, Magenta 30, and Yellow 30, enter: "64 ENTER, 0 ENTER 30 ENTER 30 ENTER." If the density number is negative and should be positive then press , which will toggle the sign of the number. After the entry for Yellow, pressing will complete the entry of DCMY values. If you enter an incorrect number, press to regress to the previous value.
Once all the filtration values are entered, you will be asked if you would like to calibrate the Density Probe. To calibrate the Density Probe, press now. The colorhead lamps will turn on.
You will be asked to take a probe reading. Remove the test negative from the carrier and then put the empty carrier back into the enlarger.
Place the Density Probe on the baseboard, centered directly under the lens.
Wait for about 6 seconds to let the probe stabilize, then press to lock in the probe reading.

When the lamp goes out, the Master Color Balance is now set to print a perfect Shirley at the DCMY values entered in step 15.

GENERAL USE OF THE DENSITY PROBE

As mentioned earlier, the way in which the Density Probe is used differs depending upon the setting of the Autocorrection preference in the Starlite Preferences menu. The probing methods in each case are described below.

PROBE WITH AUTOCORRECTION SET TO ACTIVE

Load your negative and compose and focus the image as desired.
Enter the color filtration values and density value at which you are going to print this negative into the Starlite's keypad. These values may be entered directly from a video analyzer.
Remove the negative from the carrier. This allows the light at which the negative will be printed to be visible at the baseboard.
Place the D-Probe in the center of the baseboard area, directly under the lens.
Press the button on the D-Probe.

The Colorhead lamps will turn on, then the light level will change until the amount falling on the D-Probe matches the D-Probe's expectation for the current keypad density value. When the system is satisfied it has a stable reading, the lamps will turn off automatically, completing the probing cycle.

PROBE WITH AUTOCORRECTION SET TO INACTIVE

Load your negative and compose and focus the image as desired.
Enter the color filtration values and density value at which you are going to print this negative into the Starlite's keypad. These values may be from a video analyzer.
Remove the negative from the carrier. This allows the light at which the negative will be printed to be visible at the baseboard.
Place the D-Probe in the center of the baseboard are, directly under the lens.
Press the button on the D-Probe. The Colorhead lamps will turn on, and the keypad display will read "PROBING…" On the keypad, a density value from the probe will be displayed. At his point, the D-Probe is simply reporting what it "sees." Make any adjustments to lens aperture needed to achieve the density number you want. (Note that this density number is independent of the Starlite's main-screen density value, which represents the light emitted from the head).

When finished, press the button on the D-Probe again to terminate the probing cycle.

USING THE DENSITY PROBE FOR FLESH-TONE PRINTING IN COLOR MODE

The Density Probe used with the Starlite Colorhead is usable for matching the density of flesh-tones on different images. Although this method will not match the color balance of the images, it will work to match the density. The generalized method is to make a perfect print from a standard (Shirley) negative, then calibrate the Density Probe while reading a flesh-tone area of the image. Thereafter, new negative images' flesh-tones can be matched simply by probing the appropriate area.

SETTING UP THE STARLITE FOR DENSITY PROBE MATCHING OF FLESH-TONES

Choose a medium or large printsize. A minimum of 8x10 is recommended for flesh-tone matching (depending on the size of the flesh area in the negative). This is due to the fact that the aperture on the D-Probe itself must completely lie within any flesh-tone area in the image; a larger print size tends to allow a given patch of flesh tone in the image to completely cover the D-Probe's aperture.

Make a perfect print from the negative at this size. Do as many prints as necessary to achieve a print that is good in both color and density. Even though the Density Probe will not be able to match this color, the color balance will affect the density reading.
Once the perfect print is made, begin re-calibrating the Starlite's Master Color Balance by selecting the "CALIBRATE MASTER COLOR BALANCE" option from the Starlite Calibration menu.
Enter the filtration values to be associated with the perfect standard print made in step 2. Keep in mind that the Density number will be the same for all future prints. This is due to the fact that the Density Probe will always be looking for the same level of light in the flesh-tones of future negatives, regardless of each negative's overall density.
Recommended filtration values for most setups are D:64 C:0 M:30 Y:30.
After entering these values, the Starlite will prompt on the keypad, "WOULD YOU LIKE TO CALIBRATE THE DENSITY PROBE NOW. PRESS ENTER IF YES." Press to confirm this. At this point turn the room lights off.
The keypad will then prompt "PLEASE REMOVE NEGATIVE FROM CARRIER. REPLACE CARRIER TAKE PROBE READING." When setting up for flesh-tone printing, do not remove the negative from the enlarger! Position the D-Probe on the image being projected, in a flesh-tone area that is free of excessive highlights, shadows, jewelry, or anything else. Look closely at the Density Probe's aperture to be sure that it is entirely within the flesh-tone area.
Press to take the reading.

After the Starlite reads the current amount of light representing the flesh-tone, the keypad display will read "PROBE CALIBRATION COMPLETE," after which the display will revert to the normal main screen. The filtration values displayed will reflect the values that were entered into the Master Color Balance calibration.

The setup for printing using the D-Probe to match flesh-tones is now complete. The next section outlines the use of this system in day-to-day printing.

USING THE DENSITY PROBE TO MAKE PRINTS USING FLESH-TONE MATCHING

Load the negative to be printed into the carrier. Compose and focus the print at a medium-to-large printsize. Set the lens to the desired aperture.
Enter a starting filtration pack into the Starlite. Remember that the Density value will be the same for all negatives when using the D-Probe for matching flesh-tones. If you calibrated the standard negative to a Density value of 64 (given as an example in the previous section), always start printing at D:64, regardless of the thickness of the new negative.
Position the Density Probe on the image so that it's aperture lies completely within a flesh-tone area. Press the button on the D-Probe, making sure that nothing (fingers, etc.) is blocking the probe's aperture.
The Starlite will take the probe reading by turning it's lamps on, then adjusting it's light output so that the amount of light reaching the probe will be the same as it was when the probe was calibrated.
Once the Starlite is finished, the lamps will turn off. The Starlite is now ready to make a print.
Turn off the room lights, load the paper, and make the print by pressing .

Please note that this method has limitations. As mentioned earlier, the print size will be limited to the smallest size that will allow the D-Probe's aperture to lie completely within a flesh-tone area of the image. Also, since this setup is done explicitly for flesh-tones, printing other subjects will be a little tricky. For instance, when printing a landscape image (with no flesh-tone areas), an area comparable in density, if not color, will need to be used for the probing. This method of printing also excludes using any kind of video analyzer with the system.

USING THE DENSITY PROBE IN BLACK AND WHITE PRINTING MODE

The use of the Density Probe is very similar in Black and White printing mode as for Color. A very important thing to note however, concerns the use of safelights. Whenever you probe using the Starlite's Density Probe, be sure all safelights are OFF. The D-Probe will read the safe light as additional density at the baseboard, causing inaccurate operation.

CALIBRATING THE DENSITY PROBE IN BLACK AND WHITE MODE

The Starlite Colorhead has separate facilities for aligning the Density Probe in Color mode or Black and White mode. This is necessary since in Color mode the Emulsions, Process offsets, etc., can have density offset values that effect the Density Probe reading, whereas in Black and White operation, the Emulsions and Process offsets are disabled. Consequently there is a separate, simple procedure to align the Density Probe for Black and White printing. This procedure differs from that in the Color printing mode.

Before performing this procedure, make sure that the Density Probe is properly connected.

First select Black and White printing mode in the Starlite main menu.
Select a "regular" black-and-white negative, one that represents an average negative printed in your lab.
Make a good print from this negative. See the section in the Starlite user's manual How To Make A Black And White Print By Testing.
From the Starlite's main menu, select the Starlite Calibration menu and then select the "CALIBRATE B&W PROBE DENSITY" option.
You will be instructed to remove the negative from the carrier and take a probe reading. At this point you should remove the negative from the carrier.
Place the Density Probe on the baseboard, centered directly under the lens. Be sure the room lights and any safelights are off. Wait 4 seconds for the probe to stabilize and then press .

The Density Probe Black-and-White calibration procedure is now complete. The Density number now displayed will represent a good probe reading for this negative. If this negative was selected properly, most other black-and-white negatives will print near this density value. The alignment set up here has no effect on any of the Color printing settings.

GENERAL USE IN BLACK-AND-WHITE MODE

The use of the Density Probe in Black-and-White mode is the same as in Color printing mode. Generally, you set your print up as desired, place the D-Probe under the lens, then press the button on the probe. If Autocorrection is on, simply wait for the Starlite to adjust the density, and the lamps will automatically shut off, ready for printing. If Autocorrection is off, adjust the lens aperture until the desired density readout number is displayed, then press the probe button once again to terminate the cycle. A more detailed description of the procedure by which a black-and-white print is made, appears in the Starlite user's manual.

CALIBRATING THE DENSITY PROBE FOR FLESH-TONE PRINTING IN BLACK AND WHITE MODE

To align the Density Probe for probing flesh tones in Black and White mode follow these steps:

If the Starlite is not in Black and White mode, select Black and White mode from the Starlite main menu.
Using a black and white negative that is representative of the type of negatives you normally print, make a good print, preferably close to grade 2.0.
Once you have a good print, go into the Starlite main menu, then the Starlite Calibration menu and select " CALIBRATE B&W PROBE DENSITY." Don't remove the negative or change the lens aperture etc. at this point: you must do the calibration procedure with everything the same as when you made the good test print.
You will be asked to remove the negative, but do not. Place the Density Probe on the baseboard directly under a good patch of flesh tone that is not too far from the center of the image. Be sure that the flesh tone completely covers the reading aperture on the Density Probe. The room lights and safelights should be off. Wait 4 seconds and then press . That completes the alignment procedure for flesh tone probing. Write down the density number displayed on the main screen now: it is your new target flesh tone Density number 7.

BLACK AND WHITE PRINTING BY PROBING FLESH TONES

The Density Probe can be used for "density analyzing" when in Black and White mode. Instead of using the Density Probe to simply maintain the Starlite's Density calibration (probing with no negative), you can use the Density Probe for simple density analyzing of flesh tones. In this way you can select the contrast grade first, then probe a flesh tone to set the density automatically.

The following is an outline of how printing is done when probing flesh tones:

Take a new negative and place it in the enlarger to make a print.
Set the contrast grade to 2.0, or whatever grade you wish to use.
Focus and compose the image as usual.
Enter your flesh-tone target density value. This is the value to which the Density Probe was calibrated initially. (See the previous section: Aligning the Density Probe for Flesh-tone Printing in Black and White)
Take a probe reading by positioning the Density Probe on the baseboard under a flesh tone. Click the probe once to start probing, then wait a few seconds for the probing to finish. After the lamps go off you are ready to make the print.