how to use a Zelox enlarge-O-meter?

Discussion in 'Darkroom Equipment' started by Paul Byrnes, Nov 11, 2009.

  1. Paul Byrnes

    Paul Byrnes Subscriber

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    Hello all
    I have just come into a lovely old piece of kit - the Zelox enlarger meter - made in Sydney some 40 or more years ago by a family electronics firm (Steven Deratz, apparently now retired). Question is how to use it?
    It has 0-60 wheel at top for 'paper sensitivity', a middle knob that has 5-10-20 choices for timing, presumably seconds, and a VU-type meter at the bottom. A paddle with holes is attached by electrical cord to the unit, for placing on the easel (and it works fine). I realise the key is where you set the knobs - but with Ilford MG papers, where would that be? I'm assuming it was made for graded papers, but can I use it for MG papers?
    Anyone got one and using it? I realise it's a specialised piece of kit but somebody out there must have used one.
    Any help gratefully received.
    PB
     
  2. Tony Egan

    Tony Egan Subscriber

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    Hi, I had on once and found it to be completely useless! Probably says more about me than the equipment but nothing beats a proper test strip in my opinion and I saved time doing this rather than messing around trying to calibrate this meter for every possible paper, filter etc. etc. In the long run I think mastering production of a print is more satisfying than (trying) to master a tool like this.
     
  3. cowanw

    cowanw Member

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    Make prints and figure out the times, then pass your meter, with all darklights out, under middle gray of the projected negative, and white and black. then make notes. You will soon find the speed of your paper.
    Once you have got enough data that way you can use the meter properly. It may be possible to use the Delta black/white readings to indicate grade.
    It might be designed to have a ground glass appearing filter over the probe as a sort of averaging device.
    I agree with Tony, but the fun is in the journey.
     
  4. Paul Byrnes

    Paul Byrnes Subscriber

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    Thanks guys - with 2 mins searching on the net I found Mr Deratz, now enjoying his retirement on the Sunshine Coast north of Brisbane. He was very kind but couldn't really remember how it worked, since he designed and built it about 43 years ago! He did say he probably built about 100 of these - which makes me proud to own one even if I can't figure it out. I understood about half of what you suggest Bill, but will think on it. Not sure what Delta black/white readings are but will google that. The VU meter at the bottom has three sets of figures, corresponding to the speed choices above it - 5,10 or 20 seconds, so you read the amounts based on one of the three lines...which would appear to indicate seconds. He said it uses a cadmium sulphide sensor in the paddle, so it has some memory. Any suggestions on the sequence of how you use it would be appreciated - and yes, I do make test strips, but as Bill says, the fun is in the journey. I just can't help being curious. Thanks for your help so far.

    PB
     
  5. Steve Smith

    Steve Smith Subscriber

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  6. Chan Tran

    Chan Tran Member

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    If you can post a picture of the thing may be we can help you figure it out. I do believe that it's not very useful but it would be interesting for find out how it's supposed to be used.
     
  7. cowanw

    cowanw Member

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    I meant take a reading in the blackest part of the image and the lightest part of the image and the difference (delta) will be an approximation of the range of contrast of the negative. that info, plus actual enlarger exposure times, will gradually get you the info to use it as predicter of exposure times and possibly of grade.
     
  8. cowanw

    cowanw Member

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    There are only three variables 1 the speed, 2 the fstop, 3 the EI of the paper. Stick with one paper, keep lots of notes and the other variable will be come apparent.
     
  9. Paul Byrnes

    Paul Byrnes Subscriber

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    some pics

    Thanks to all posters - getting closer to the answers. Steve, the Ilford meter is similar but mine doesn't use a green light system. Here are some pics of what the actual thing looks like - might have been helpful earlier but I'm still learning abt how to use APUG (hope this works). Grateful for yr tips so far - and thanks for explaining what delta is Bill. I'm still learning the advanced stuff. :smile:.
    PB
     

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  10. Chan Tran

    Chan Tran Member

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    Looking at the pictures I think this is how you're supposed to use it.
    1. Make a good test print.
    2. Select the range switch that is close to your exposure time of the test print.
    3. Put the probe under the enlarger at the point you want to measure (it could be the shadow, highlight or midtone. it's your choice)
    4. Set the sensitivity knob until the meter read the same time as your exposure time for the good test print.
    5. Put an unknown negative on the enlarger and put the probe at the point where you want to be the same density as the good test print.
    6 Read the time on the meter. This is the exposure time for your new negative. I presume if your new negative is much lighter or darker the test negative you could use the range switch to switch it to different range for better reading.

    That's how I think it should work. I think it's a primitive meter and doesn't take into account of the dynamic range of the negative. It simply tries to reproduce the same density on the print as that of the test print.
     
  11. Paul Byrnes

    Paul Byrnes Subscriber

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    Chan
    That makes perfect sense. Thankyou. I now understand what Bill was trying to tell me. And by metering different parts of the test neg, I can get an idea of the ranges in play too, which should teach me more about judging the densities of any given neg - which I am still having trouble with. I will give it a try. And I guess I need to do it again with different papers and film stock combinations.
    Mystery solved. Thanks to all.

    PB
     
  12. Nicholas Lindan

    Nicholas Lindan Advertiser

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    Pretty simple, really.

    First make sure the unit works...

    Check the sensitivity control:
    1. Place the probe under the enlarger with no negative;
    2. Set the 5-10-20 switch to 5;
    3. Turn the sensitivity knob to the max;
    4. Adjust the aperture and head height so the needle indicates the minimum time on the scale;
    5. Turn the sensitivity down and see the needle swings freely;
    6. Repeat for the 10 and 20 switch settings, the sensitivity control will need to be lowered with each change of the switch;
    7. When switching ranges the needle should indicate the same time on both scales.

    To check the the range switch:
    1. Set the switch to 5, adjust the aperture and sensitivity control so the needle is centered on the '5' scale, raise or lower the enlarger head if needed;
    2. Close the aperture one stop, the needle should indicate 10 on the '5' scale;
    3. Turn the switch to 10, make sure the needle points to 10 on the '10' scale;
    4. Close the aperture 1 stop, make sure the needle indicates 20 on the '10' scale;
    5. Set the switch to 20, the needle should indicate 20 on the '20 'scale.

    To calibrate for a specific paper:
    1. Make a just-not-white print with no negative - stop the lens down as the time should be around 7 - 15 seconds;
    2. Place the probe under the enlarger - all safelights need to be off;
    3. Set the range switch on 10, twiddle the sensitivity knob until the needle points to the time you used to make the print;
    4. Note the sensitivity knob setting - this is the speed/sensitivity to create a just-not-white tone on that paper;
    5. If you are out of range then use the 5 or 20 switch/scale;
    6. If you use VC filters then you should meter with no filter but make the print with a filter.
    7. You can repeat for any tone you wish. A paper will have a sensitivity setting for every tone it can produce.
    8. A step tablet can let you find the sensitivity settings for a wide variety of tones with just one print.

    Use:
    1. Place the probe where you want your white point to be - or any other tone for which you know the sensitivity setting;
    2. Set the sensitivity knob appropriately;
    3. Read the time from the meter, adjusting the 5/10/20 knob to let you use the most readable scale - ie, the needle towards the middle of the range;
    4. Adjust the aperture up or down if you want more or less printing time.
     
  13. Tony Egan

    Tony Egan Subscriber

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    ...and then stumble into bed exhausted without having made one print! Trust me, trying to master this will do nothing for your printing in the long run. The seduction of a "miracle meter" is enticing but ultimately futile. Keep it as a museum piece in a glass cabinet and let your eyes and your test prints be the judge...:wink:
     
  14. Paul Byrnes

    Paul Byrnes Subscriber

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    Thanks for the exhaustive advice Nicholas - but how do you know when you have made a good just not-white-print? Is there an accepted definition? I'll give it a try.
    Tony - I may never use it for much, but it's just one of those mysteries I had to solve. LRT. The tapestry that is rich.
    Thanks to all for the help.
    PB
     
  15. Nicholas Lindan

    Nicholas Lindan Advertiser

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    Not a print, a test strip/test patch/whatever. A just-not-white tone, the first one that is different from the white of the paper. Make the test strip at 10% intervals or so.
     
  16. Paul Byrnes

    Paul Byrnes Subscriber

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    Nicholas, thanks for the clarification. Much obliged. I get it now.
    PB