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  1. #11

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    Unless the colorstar 3000 has built in recognition of 18% grey, then it really doesn't matter what calibration target you use. A Macbeth colour chart is probably a far better option to put in the image as you get a whole range colours as well as greys. A slight deviation from grey will show up more on its complimentary and opposite colours on a colour chart than it will on grey. Infact it doesn't have to be a macbeth chart. You can design and print your own. The actual colour values are not that critical. The name of the game is reproducing a colour in the print that is on your target. Every print you make will likely be tweaked for colour so it is a starting point only for the particular film you are using that you are looking for.

  2. #12

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    The calibration program does require a grey negative. It automatically adjusts the calibration. You'll never the thing to work using anything else.

  3. #13

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    Yes but a Macbeth colour chart does have grey swatches which can be put under the probe. So does the colour star require an 18% gray card and how does it know if the grey card was exposed correctly. It would need a known reference then and not a photograph of a known reference which could throw the reference off.

    Square 22 of the chart is 18% grey (density 0.7).

    http://usa.gretagmacbethstore.com/in...lorChecker.htm

    Bloody expensive:o

  4. #14

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    It needs a grey negative. The built in densitometer handles the rest. You could stick a 35mm negative into the probe and check exposure if you really wanted to.

  5. #15

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    Ok I misunderstood. You are saying the actual negative needs to be grey/neutral in colour as opposed to a colour negative which has a colour mask in it. Yes?

  6. #16

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    No it needs to be a photo of a grey card. C-41 for RA-4. E-6 for positives.

    Really doesn't need to be much more then a full frame shot.

  7. #17
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    Tom, the light temperature of the first negative you should use to calibrate your analyser with, is easiest if you use mid morning or mid afternoon light on a clear day.

    Then you print a genuine neutral grey, presumably using the inbuilt programme as mentioned by Nick.

    Once you have these enlarger settings correct, you tell the analyser, with these filtration settings in place, this is a neutral grey with this paper.

    Obviously at this stage you will print a frame from that roll, at least I did.

    From then on, when you decide to take a set of colour pictures, you take a frame with the Expo/Disc attached as before, first up.

    When back in the darkroom you take that first grey Expo/Disc exposure, place it in the enlarger, place the probe under, set the analyser to the correct settings, then you change the enlarger settings until the analyser is happy.

    At this stage, without using any paper, you have analysed the light and corrected for a near exact light temperature from your previous testing.

    You then make a test print, within reason it should be virtually colour perfect. The only thing you really have to adjust for is density.

    Remember that Red and Cyan are obtained by density. A dark print will have a red cast and a light print will have a Cyan cast. This assumes all other colours have been corrected first.

    You normally use two of the three filters for colour negative printing, these are Magenta and Yellow. The Cyan filter is not used, the amount of correct Cyan or Red you have in your print, is generally determined by print density.

    Hope this helps.

    Mick.

  8. #18
    Ed Sukach's Avatar
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    Calibration of the Colorstar 3000 does NOT require an 18% gray negative. It would be helpful to either use a uniformly exposed frame or one where the same spot can be accurately accessed on each trial.

    A test exposure on the media in question is made, and the ColorStar will measure the deviation from a density of 0.55 on cyan, yellow, magenta - and overall integration - and utomatically compensate for these deviations. Another test is made - and the results further refined, until the ColorStar will be able to accurately determine the filtraiton necessary to produce an average "gray" from the TEST strip.

    Do you have a copy of the ColorStar 3000 manual?
    Carpe erratum!!

    Ed Sukach, FFP.

  9. #19

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    Ed,

    Yes I have a copy of the ColorStar 3000 manual, but I've been working from the Frances Schultz article which is based on using a grey negative to calibrate the machine. I was under the impression that the grey negative was to insure colour neutrality as a starting point.

    Mick,

    From your description of how to use the Expo/Disc, a new grey negative is made per film / lighting situation etc, and so a new set of calibrations are made per grey negative?

    Tom

  10. #20
    Mick Fagan's Avatar
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    Tom, once you have your enlarger set for a perfect grey picture, you set the analyser.

    The next time you are out shooting, you take an Expo/Disc negative for every different light situation.

    You take a merry-go-round with tungsten and daylight, take a Expo/Disc frame with the camera pointing to the merry-go-round and if possible, some daylight as well. On your walk you take seascapes, take an Expo/Disc negative of the seascape, on the way home you take pictures of your friends in a restaurant, take an Expo/Disc negative.

    In the darkroom you decide to do the merry-go-round shots, put a neg in and compose the picture, replace it with the Expo/Disc negative and adjust the enlarger until the analyser is happy, change negs, focus and print, process and see just how good you and your technique are.

    Then you do the restaurant frames, put a neg in and compose, replace with the restaurant Expo/Disc negative, set the enlarger, change negs, focus and print.

    You should have virtually perfect colour balance, density is another issue, but you should be able to work out from a contact sheet the fine density changes required.

    I enlarge in 1/8 f stop increments, put a chart on the wall where you can glance for the changes.

    Kapish?

    Mick.

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