Enlarging Meter: How to use it?

[jongcelebes]

I found this thing in flea market but I don't have any clue to use it. It has 3 parts:
+ Light sensitive part in a hole,
+ Display with needle. Printed value are 1 to 10 with special mark for number 8.
+ Radial table with 3 parameters.
- Value. With value 1 to 13.
- Sensitivity. With value 1 to 8.
- Time. With value 0.3 sec to 4 minutes.

I add some batteries and the needle position is change parallel-ly as light condition change.

Well, I've try Google but not much luck. Anyone know how it works? Thanks.

http://farm4.static.flickr.com/3514/3991143035_6639cc7c96.jpg

 

[MattKing]

Here are some off the cuff suggestions.

1) Prepare a good quality print example print. The example print should be from a reasonably well exposed negative showing a range of tones that is enlarged a normal amount. If you usually print 8x10 prints from mostly full framed 35mm negatives, then your example print should be like that. The scene photographed should include something like a medium reference tone - something reasonably common, such as a Caucasian flesh tone or a grassy lawn in sunlight or something similar;

2) Record the exposure time for the basic exposure, as well as the f/stop used (which should remain unchanged during this first part of the test).

3) Determine the "Value" on the meter that corresponds with the basic exposure time in your example print;

4) Put the photocell for the meter into the light path from the enlarger, so as to read the light from your reference tone;

5) Adjust the sensitivity until the meter needle reads the "Value" that is required so as to yield the basic exposure time on your print.

When you have done all that, you will have determined the "Sensitivity" for your paper. Now, in order to use the meter on another negative, you will just need to:

a) set the Sensitivity on the meter for the paper;

b) find a tone on the negative that corresponds to the reference tone;

c) put the photocell for the meter into the light path from the enlarger, so as to read the light from your near reference tone in your new negative; and

d) adjust your aperture on the enlarging lens until the meter reads the "Value" that is required so as to yield your chosen basic exposure time.

The range of sensitivity of the meter might be limited, so you may need to try different reference tones before you start getting results that are nearer the mid-range available.

You may be able to go through a similar process using an empty negative carrier instead, but you need to be sure that all other settings are the same as when the reference negative was in place.

Hope this helps.

Matt

 

[jongcelebes]

Thanks a lot. I will try it.

 

[Nicholas Lindan]

You should be able to use it much like a Darkroom Automation meter.

However, you should be aware it will not give you the precise results you can get with DA or RH equipment. The resolution of this meter is 1/4 of a stop and that really isn’t fine enough - as a comparison Darkroom Automation’s meter works in 1/100th of a stop and RH Designs’ in 1/24th of a stop.

If you are willing to settle for ball-park results then you can have some fun.

I am assuming (making an ass of you and me - as my first boss explained the effect of making assumptions in engineering work) the meter needle and the value and sensitivity settings are in stops. This will let you use the paper speed data available on the Darkroom Automation web site’s support section . Note the absolute speeds will be off - you will have to add or subtract a constant value from the Lucky’s meter reading to get it to correlate to the DA information. However, the contrast data will be useful without any changes.

The theory behind these charts, and behind the operation of both the Lucky and DA exposure meters can be found in the instructions for the Darkroom Automation meter and the DA exposure system.

You can make a first order calibration - fitting the Lucky readings to the DA charts:

1. Using a test strip with no negative in the enlarger find the exposure that gives just-maximum-black on Ilford MGIV RC with #2 contrast filtration;
2. Remove the filter and meter the light - place the meter reading on the VALUE setting on the dial;
3. Place the time you used on the TIME setting on dial;
4. Now calculate (Sensitivity - 9.8) - this is the correction to add to the DA paper speed data (the value may be negative, in this case subtract it).

Now, when you want a particular tone on the paper:

1. Look up the ‘paper speed’ for that tone and grade of paper in the DA chart;
2. Add the correction factor you found above;
3. Put that number on the SENSITIVITY setting on the dial;
4. Place the meter reading on the VALUE setting;
5. The exposure time will appear in the TIME window.

Metering the highlights to determine the base exposure is normally a good bet - prepare a small card with the corrected highlight speed for the paper(s) and grades you use. Then to find the exposure just put the SENSITIVITY setting to the highlight speed, meter the highlight transferring the meter reading to the VALUE on the dial and read out the exposure time.

To find the right grade of paper you can meter the highlights and shadows - the difference gives the contrast range of the paper. This contrast range can be read from the DA paper speed charts.

Another way to use the meter is with zone test strips. See http://www.darkroomautomation.com/support/zonestrp.htm

After you have made the test strip, meter the white light and set the meter reading to the VALUE scale. Set the time in seconds for each of the zone patches on the meter’s TIME scale and read the paper speed - for your meter and paper - from the SENSITIVITY window. Mark this reading next to the zone strip gray patch as shown in the application note. Now to get that tone just set the meter’s SENSITIVITY dial to the number you wrote down and the meter will give you the right exposure time.