Macbeth Slope Functions?

Discussion in 'Black and White' started by trooper, Jan 14, 2003.

  1. I've got a couple of Macbeth densitometers.... A TD902 transmission
    unit and just today, I picked up an RD514 reflection unit. Neither
    one has a manual and I've got the TD unit pretty well figured out and
    calibrated but was hoping someone could shorten the learning curve on
    the RD. I haven't got the slope function figured out and am not
    exactly sure how to calibrate. I can get it zeroed on a Stouffer RZ9
    zone strip chart and it goes to 1.73 on the black zone I. Is there a
    source for manuals? I left a message at the Gretag-Macbeth site and
    didn't find any pdf's or such for older machines.
     
  2. Craig, the usual method for the RD (reflection densi) is that you would have a reflection check plaque. This would have at the minimum a "white" patch and a "black" patch with the actual density values attached somewhere. I don't know what the Stouffer RZ9 is; if it's a transmission target, it won't help on your RD. If it is a reflective target, it's probably just what you needed.

    The general method for use is: hold down the probe on the white patch and adjust the "zero" (probably about 0.06 or so with the reflection target). Then, while holding down the probe on the "black" patch, adjust the slope control to get the proper reading. If it's way off, you might have to go back and forth a couple times.

    FWIW, the user manuals for machines like this were never very complicated; aside from calibrating instructions, they tell how to replace the lamp. Other than this, everything is pretty straightforward.

    PS; I'm not sure on those specific models, but some machines had a "master" zero control on the back; it's like a short post. Feel free to email me if you don't get anywhere with it.
     
  3. If you get a Kodak reference exposure target, it has proper reflective density steps incorporated as part of the pattern. The densities go up to 1.90, printed on matt finish photographic paper, and are with respect to the base paper reflection density. (ie the densities start at 0.0D)<br>I don't know what the tolerance of the densities is on that Kodak target, but it's got to be more accurate than using a transmission wedge (which you'd have to double the marked densities of, at least)<p>The usual function of a densitometer slope control is to set the maximum density correctly, while the zero control offsets the base density of whatever you're measuring.<br>Absolute densities are of less importance with reflective media, since you generally want to know what density of silver or ink you're getting, in addition to the unavoidable light absorbtion of the base medium.
     
  4. I was factory trained service for MacBeth Densitometers. If you get in touch with me I will send the calibration instructions from the RD514 service manual. I will also be glad to answer any questions. Also have TD924 manual (no difference from 902, just more functions).
     
  5. I have a MacBeth RD514 that I want to use for Epson Ultrachrome ink it seems to read the ink patches too low, it is a very stable instrument and I have the calibration plaque and all and I know how to use it. My prints are too dark when the charts read correctly, the charts are also too dark visually but they read as the MacBeth color checker 24 patch
     

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