Enlarger Meter and Computer - EPOI Analite II

The last time I made a silver print was when I was a teenager and my big BROTHER made a silver print(s). So I never really did it. I've read about it and of course scoured the internet. I'm an old hat at developing negatives and scanning them, put I've yet to make a silver print. So recently, I have been getting my darkroom ready. I have an enlarger and will be attaching a baseboard soon. Everything is going according to plan and I am having fun getting ready for actual printing.

 

In my quest to find affordable darkroom accessories, I found an "Enlarger Meter and Computer", new old stock, and as the price was nice, I bought it. I probably will only have it for my display collection, but I was wondering if anyone has ever used a similar meter to make prints. As a lark I may try to use it after I do the tried and true method of exposure strips, but I am curious to hear other folks experience with this method.

 

Have it, used it in past years - works just fine. May not get "perfect" results, but always usable prints.

Have it, used it in past years - works just fine. May not get "perfect" results, but always usable prints.

Were meters common or targeted for gear heads? I don't see much about using meters. I was watching some videos by Timi Hall who mentions using a meter. He has very interesting experience with printing.

There were all sorts of devices - I had a Kodak template, like a negative that you put on the paper - link kodak enlarging exposure template - Google Search

they still make them! There were a variety of DIY test strip devices - one a simple series of strips held together with tape, that you folded back while watching the timer. There were all sorts of Pro enlarging meters (expensive) - my recollection is that this was the first one that was affordable for the average enthusiast

I still have a meter that I build from a Popular Electronics article many years ago.

 

Similar to the one shown, it gives a high/low indication.

 

With many meters, you need the usual test strips or exposure scale to get started,

and then it will allow many prints to match the exposure. I usually meter on a face,

as a spot with known similar shading. The one shown seems to have calibration

to ANSI speed ratings, though I would still do some tests.

 

As well as I know, meters were more common for color for many years, before

ones meant for black and white came out priced for ordinary photographers.

 

The low gamma of color negative film, and correspondingly high gamma for

print materials makes exposure accuracy much harder. (Not to mention

getting the color balance right.) This is also true for the higher grades

of paper or high numbered variable contrast filters.

 

Yes, do test strips first, then compare to the ANSI ratings in the table.

It is likely that your paper, which might not even be in the table, is

different enough. Once you get used to it, it will get you to the

right exposure, even with test strips, faster.

At one time my wife took photos of two dozen teachers at her school. She wanted me to make an 8x10 inch print of each one for display in the school.. She used a Kodak Instamatic camera and the exposures were all over the place. Doing test strips would have taken a good deal of time. I had an enlarging meter and took readings off of the faces. Most prints came out well on the first print and saved me a lot of time, paper and chemicals.

The template mentioned above is called a "Kodak Projection Print Scale" (though others make them, too).

 

The size is 4x5, such that it can be placed on a 4x5 sheet of paper, but that wastes much of the paper.

 

A 2x2 sheet centered appropriately and, as noted above, usually on a face, usually does it.

 

But yes, a meter on the face usually works well, too.

That's basically a spot meter for printing. Not terribly useful IME, and an averaging or integrating meter is a better bet.

 

I suspect it might have been supplied with a diffuser to fit under the enlarger lens to turn it into an averaging meter.

 

FWIW, in the distant past I designed and built a centre-weighted metering/timing device for my enlargers. The novel bit was the sensor. It consisted of a CdS cell plus small lens fitted adjacent to the enlarger lens and pointed at the baseboard image. The output of the CdS cell was amplified to drive a timer, such that exposure timing was entirely automatic. A knob to set paper speed and a 'go' button being the only controls on the device.

 

The timer also automatically switched the safelight off so that it didn't interfere with the exposure sensing.

 

It worked really well and I've never seen a commercial device with a sensor that simply clamped next to the enlarger lens. I thought of patenting and marketing the thing, but I was too busy trying to run my own photography business at the time. The opportunity's now long passed, but if anyone wants to run with the idea; feel free.

 

These niche-market inventions are sometimes a good way to lose your investment money quite quickly, IME.

 

P.S. I later used a Philips made meter/timer. Not as automatic, but it worked well.

Edited November 19, 2019 by rodeo_joe|1

At one time my wife took photos of two dozen teachers at her school. She wanted me to make an 8x10 inch print of each one for display in the school.. She used a Kodak Instamatic camera and the exposures were all over the place. Doing test strips would have taken a good deal of time. I had an enlarging meter and took readings off of the faces. Most prints came out well on the first print and saved me a lot of time, paper and chemicals.

That makes sense!

I have one of those, bought it new back in the 70's and used it quite often. When used correctly it did give consistent results but its use was rather finicky, there cannot be any safelight on in the room when you are using it. I used it with a diffuser under the lens. It is basically a comparator?, you first make a properly exposed print via test strips, then with the diffuser in place you null the meter. As you change to other negs or you change enlargement size the meter will give you an exposure time that will be in the ball park. You then can fine tune your exposure with more tests. The meter can be a big help for production work especially if you have established consistent exposure/development procedures. I stopped using mine because I now have safelights on all the time over the print sink and they screw with the meter reading plus I no longer do production printing.

Over the years I have used several types of exposure meters but have always found that using test strips was the best way to determine print exposure.

but have always found that using test strips was the best way to determine print exposure.

Sure, if you have the time, but I often had to bang out dozens of proof prints in an hour or so. The automatic timer gizmo I built made the task quite easy, with very few reprints needed due to incorrect exposure. It only needed adjusting for different batches of paper.

 

We regularly rely on TTL exposure metering in the camera. What's the difference between that and automating the enlarger exposure? Do you think minilabs make a test strip for every print?

(snip)

We regularly rely on TTL exposure metering in the camera. What's the difference between that and automating the enlarger exposure? Do you think minilabs make a test strip for every print?

 

Not so many years ago, I got 200 Christmas cards printed by Shutterfly, very underexposed over

just about the whole card. It seems that there was one bright spot in one corner that it used to

make the exposure. Also, no-one seems to have looked at them, or it would have been noticed.

 

Shutterfly nicely gave me credit for the cost, though I then had cards made somewhere else.

 

I am not so sure how they metered them wrong. Others printed the same image right.

 

I have had many others printed from Shutterfly right, but not that one.

 

Which leaves the question, similar to that for cameras, of spot or

average metering.

Over the years I have used several types of exposure meters but have always found that using test strips was the best way to determine print exposure.

That's pretty much what my research shows. Still, I can see they are useful with large productions. One would need to know the variances and accept them for the process.

This old man is 81 and retired. I worked in the photo industry, starting with a photofinishing job after school. In my calling, I designed giant photofinishing plants and the high-speed developing and printing equipment. I worked at various photo manufacturing jobs. At three, such businesses I designed and marketed enlarging meters for both black & white and color printing. They work and they are the heart of the photofinishing printer, both super high speed and mini-lab. Towards the end of my career they became super suffocated meaning they blended light measurement with computer logic.

 

Not to brag but how about a look at the math of black & white projection meter.: The devise measures the density (light blocking ability of the film) based on the amount of light reflected from the spot being examined. Actually the best results are obtained by measuring two spots. One is a highlight, the other is a shadow. Often the highlight is considered the same as the clear base film.

 

The math is highlight density minus shadow density.

 

Highlight 1.18

Shadow 0.13

Scale 1.05

 

What contrast grade for this scale?

 

Grade 0 = 1.4 or higher

Grade 1 = 1.2 thru 1.4

Grade 2 = 1.0 thru 1.2

Grade 3 = 0.8 thru 1.0

Grade 4 = 0.6 thru 0.8

Grade 5 = 0.6 or lower

 

Find exposure time:

 

Test print grade 2 was calibration negative 12 second’s exposure its scale is 1.10

Unknown negative is in the gate. This negative has a scale of 1.30

 

Exposure time factor is Density – Opacity

Opacity of density 1.10 = 1.10^10 = 25.59

Opacity of density 1.30 = 1.20^10 = 19.95

Exposure time for unknown = 19.95 ÷ 25.59 X 12 = 9.5 seconds.

 

You might think this is nonsense but this is the computer logic. By the way, color printing requires more logic.

Some gobbledygook from Alan Marcus

Edited November 22, 2019 by alan_marcus|2

The last time I made a silver print was when I was a teenager and my big BROTHER made a silver print(s). So I never really did it. I've read about it and of course scoured the internet. I'm an old hat at developing negatives and scanning them, put I've yet to make a silver print. So recently, I have been getting my darkroom ready. I have an enlarger and will be attaching a baseboard soon. Everything is going according to plan and I am having fun getting ready for actual printing.

 

In my quest to find affordable darkroom accessories, I found an "Enlarger Meter and Computer", new old stock, and as the price was nice, I bought it. I probably will only have it for my display collection, but I was wondering if anyone has ever used a similar meter to make prints. As a lark I may try to use it after I do the tried and true method of exposure strips, but I am curious to hear other folks experience with this method.

 

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That is a newer model than the one that I used.

The early model did not have the white plastic circular disks, so were more limited in capability.

 

I use a different meter now.

 

I use it as Alan said.

#1 - To determine the brightness range of the negative. This helps me determine what filter grade to use, to start with.

#2 - To determine the exposure to use.

 

For some reason, some/many darkroom people say you should learn to print with your eyes.

But the same people (and most everyone else) shoot the photo using a meter.

So what is the difference?

In practice you can do both with your eyes.

BUT it requires a LOT of practice, which most people won't do.

 

As RJ said, you have to KILL all the safelights to use it, as they will distort the readings.

Also, it ain't braggin' if it's true.

This old man is 81 and retired. I worked in the photo industry, starting with a photofinishing job after school. In my calling, I designed giant photofinishing plants and the high-speed developing and printing equipment. I worked at various photo manufacturing jobs. At three, such businesses I designed and marketed enlarging meters for both black & white and color printing. They work and they are the heart of the photofinishing printer, both super high speed and mini-lab. Towards the end of my career they became super suffocated meaning they blended light measurement with computer logic.

 

Not to brag but how about a look at the math of black & white projection meter.: The devise measures the density (light blocking ability of the film) based on the amount of light reflected from the spot being examined. Actually the best results are obtained by measuring two spots. One is a highlight, the other is a shadow. Often the highlight is considered the same as the clear base film.

 

The math is highlight density minus shadow density.

 

Highlight 1.18

Shadow 0.13

Scale 1.05

 

What contrast grade for this scale?

 

Grade 0 = 1.4 or higher

Grade 1 = 1.2 thru 1.4

Grade 2 = 1.0 thru 1.2

Grade 3 = 0.8 thru 1.0

Grade 4 = 0.6 thru 0.8

Grade 5 = 0.6 or lower

 

Find exposure time:

 

Test print grade 2 was calibration negative 12 second’s exposure its scale is 1.10

Unknown negative is in the gate. This negative has a scale of 1.30

 

Exposure time factor is Density – Opacity

Opacity of density 1.10 = 1.10^10 = 25.59

Opacity of density 1.30 = 1.20^10 = 19.95

Exposure time for unknown = 19.95 ÷ 25.59 X 12 = 9.5 seconds.

 

You might think this is nonsense but this is the computer logic. By the way, color printing requires more logic.

Some gobbledygook from Alan Marcus

 

This is god baby! GOLD!! Thank you for posting.

This old man is 81 and retired. I worked in the photo industry, starting with a photofinishing job after school. In my calling, I designed giant photofinishing plants and the high-speed developing and printing equipment. I worked at various photo manufacturing jobs. At three, such businesses I designed and marketed enlarging meters for both black & white and color printing. They work and they are the heart of the photofinishing printer, both super high speed and mini-lab. Towards the end of my career they became super suffocated meaning they blended light measurement with computer logic.

 

(snip)

 

Unrelated to this discussion, and actually for one outside of photo.net, I was looking through a book

on color reproduction. (That is, more generally than just photography.)

 

There is a chapter on color printing, going back to the original Kodacolor, and then to

the improvement after that, including automated color printing. I have known for a long time

that the usual way to do automated color balance is integrating to gray (the term used

in the book). I also know how averaging light meters work on cameras.

However, I never thought about both at the same time. The result is that integrating to

gray color balance weights on the light intensity through the negative, so more weight

for parts that are darker in the original.

 

The surprising result is that it works pretty well most of the time, even for images

with a fairly large part of one color. In days long past, the small fraction were it

failed would be individually reprinted.

 

(The actual reason I was looking this up was related to color temperature

of photoflood lamps, and corresponding films, for a Wikipedia article.)

When printing color negatives using color photo paper, the trick is to avoid use of a cyan printing filter. The yellow printing filter is a perfect blue blocker. The magenta is a fair green blocker. The cyan filter is a poor red blocker, we avoid it’s use (if possible). The actual task is to adjust the red, green, and blue exposing energy to obtain a faithful print. Think of the paper as having 3 emulsions (red, green, blue sensitive).

 

We start with the color negative in the gate with the enlarger lens wide-open. The exposing energy for all thee emulsion is excessive. We stop down the lens aperture. This act equally reduces the red, green, and blue exposing energy. The paper speeds of the thee emulsion are not equal. The red emulsion will be satisfied as you stop-down. The green and blue emulsion will be over-exposed. In other words, the emulsion speeds are fixed at the factory to avoid the use of a cyan filter.

 

Now the task is to adjust the green exposing energy, usually by employing a variable magenta. Same for the level of the blue exposing light, a variable yellow filter is dialed in.

 

Now with the correct red, green, and blue exposing energy, the exposure time is adjusted to obtain the desired print density

 

Such a scheme requires calibrated test negatives. I managed a department that made test negatives. Usually sold in sets, over-exposed, normal exposed, and under exposed. We could supply most any film type and make.

 

These test negatives were used to calibrate enlargers, high-speed photofinishing printers and mini-labs.

 

If you put a typical pictorial color print on phonograph platter and spin it, the colors typical blend to make an 18% reflective surface (battleship gray). Lots of exceptions.

 

More gobbledygook from Alan Marcus

Edited November 23, 2019 by alan_marcus|2

Exposure time factor is Density – Opacity

Opacity of density 1.10 = 1.10^10 = 25.59

Opacity of density 1.30 = 1.20^10 = 19.95

Exposure time for unknown = 19.95 ÷ 25.59 X 12 = 9.5 seconds.

Sorry Alan, but there are a couple of mistakes in there.

1.10^10 does not equal 25.59, but 12.59.

Also, the higher density negative will need more exposure time, not less.

Making the corrected time: (19.95/12.59) x 12 = 19.015 seconds. Or 19 seconds for all practical purposes.

 

In addition - pun intended - since densities are simply the logarithm to base 10 of opacity, they can be used directly, and in a much simpler way, to calculate the time correction.

 

(Density) 1.30 minus (Density) 1.10 = 0.20. Antilog 0.2 = 1.585, and 1.585 x 12 = 19.02

 

And once again we arrive at a practical exposure time of 19 seconds.

 

In short, there is no need for a conversion to opacity from density readings, and the correction algorithm simply becomes:

Unknown time = Antilog (DensityX - Reference density) multiplied by Reference time.

 

In your above example:

T = 10^(1.3 - 1.1) x 12

 

That's a much simpler calculation for any computer or human to perform.

 

The above works correctly for densities lower than the reference too; since the antilog of a negative number is fractional.

Edited November 23, 2019 by rodeo_joe|1

@ rodeo_Joe This old man makes many mistakes.

Opacities are directly proportional to exposure times. Assume unknown negative has a highlight density of 1.30 and our calibration (test) negative highlight density is 1.40.

Then the Opacities are 10^1.3 = 19.95 and 10^1.4 = 25.1d. That is what I wanted to say. If the test negative's exposure time is 12 seconds, then the unknown negative's exposure time is 19.95 / 25.12 X 12 = 9.5 seconds.

 

Anyway - my formulas are valid my math may need some help.

PS. No disrespect or criticism of Alan was meant by the above. I'm all too aware that everyone makes mistakes. I'll own up to making more than my fair share.

 

In fact Kudos to Alan for taking this discussion to a higher level, and for his doubtless invaluable contribution to the processing and minilab industry.

 

However, if there's a simpler and easier way to do things, I'd feel remiss in not pointing it out. Over-complexity brings more chances for mistakes to creep in - as evidenced by that simple and understandable error in converting density units to opacity.

 

No hard feelings I hope Alan?

 

In my simplified algorithm there's still a conversion from logarithmic representation to linear, which is performed by the Antilog (ten to a power) function. The prior subtraction of two (logarithmic) density values is exactly the same as dividing their linear opacity equivalents one by the other.

Edited November 23, 2019 by rodeo_joe|1