Daily Archives: October 3rd, 2012

Weston Model 854 DR

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Weston Model 854 DR exposure meter USAclick for manual
Maker: Weston Electrical Instrument
Model: Model 854 “DR”
Circa: 1958
Cell type: Selenium
Measure type:Reflecting/Averaging
Designer: Alexander Williams
US Patent: 2,667,809
click for larger adWeston’s last attempt at a simple, “direct reading” meter for the amateur niche: i.e. you just point it and read the exposure and that’s it. It actually has a good idea behind it: you use a revolving plate on the back that partially covers the selenium cell, and that calibrates the meter for the film speed (a faster speed uncovers more of the cell, so the reading is higher. Neat idea). There’s a knob on the side, and you turn the knob until your desired shutter speed shows up, and then direct read the aperture. Or turn the knob until you find an aperture you like, and read the resulting shutter speed.This is one of the most unusually styled meters that I own. Like other Westons, the cell is on the back and it was meant to be held upright at eye-level. So you hold the bottom portion (you can see the grip contours on the sides) and your thumb can roll the knob, making it one-handed. The truly neat thing is that the roll knob is on both sides, so you can use it in either hand. Most meters are laid out for right-handed use.

Despite the neat styling and features, and that fact that it is easy to use, it suffers from the same problem all direct-read meters have—by being simple, it’s severely limited. On this one, the E.I. settings only go to ASA 250, but high speed films rated at ASA 400, or pushed to E.I. 500 or higher, were becoming common.

via James’s Light Meter Collection: Weston Model 854 DR.

Zone system film speed test

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Zone system film speed test.

 

Black and white film speed is found by testing for the minimum exposure that will produce enough density in the negative to print as a tone just visibly lighter than maximum black. Zone I. You can shoot this test on a roll of film that you plan to develop normally. It only takes six frames.

 

Making Test Exposures

 

  1. Set up a target, white, gray or any medium color will do. It should be large enough to fill the frame from six feet away. The target should be smooth – wrinkles can cause shadows or uneven brightness.
  2. Light the target evenly. Meter readings in the center and at the edges should not vary more than 1/3 of a stop.
  3. Set your meter at the film’s ISO rating (e.g. 400 for Tri-x). This will be called the test speed.
  4. Take a reflected meter reading of the target; choose a shutter speed that will allow you to bracket without using the slowest or fastest speeds.
  5. Set your camera for manual exposure; any auto-exposure setting will make the test meaningless.
  6. Record your exposures as you make them.
  7. Make the following exposures

 

  1. Meter reading – Zone V
  2. Blank frame – FB+F film base plus fog
  3. 5 stops less thank the meter reading. (close down the lens, you may need to increase the shutter speed don’t forget to put it back at your original setting as soon as possible) – Zone 0
  4. 4 stops less than the meter reading -Zone I
  5. 3 stops less than the meter reading – Zone II
  6. 2 stops less than the meter reading – Zone III

 

  1. Develop the film normally. Using the developer, time temperature you usually use.

 

Evaluating the test

 

To get the true film speed you must determine which test exposure produces Zone I. There are two ways to do this: you could make a visual determination by judging prints or you could use a densitometer. The densitometer is more accurate but you need to have access to the equipment.

 

The Densitometer Method

 

 

  1. Take a reading of the blank frame (exposure b)
  2. Take readings of all other frames; the frame with 0.10 – 0.15 more density than the blank frame (b) is the speed frame.

 

If test frame c is the speed frame then your true speed is 2x the test speed.

 

If test frame is the speed frame then your true speed is equal to the test speed.

 

If test frame e is the speed frame then your true speed is ½ the test speed

 

If test frame f is the speed frame then your true speed is ¼ the test speed

 

For example: You tested Kodak Tri-x (ISO 400) and your blank frame (b) reads 0.23

 

Frame c reads 0.23

 

Frame d reads 0.26

 

Frame e reads 0.33

 

Frame f reads 0.41

 

Your speed frame is e; if your test speed is ISO 400 then your true speed or EI (exposure index) is ½ that or 200.

 

The Visual Method

 

 

  1. Print a test strip from the blank frame (b)
  2. From the test strip choose the shortest exposure that turns the paper maximum black. If your not sure what maximum black looks like compare your test to a piece of paper that has been exposed to white light then developed.
  3. Print the rest of the frames from your test (c,d,e,f,) using the exposure time you determined in step 2 which would maximum black in the minimum time.
  4. When the prints are dry judge which print is a tone just visibly lighter than max black. That is the speed frame.

 

For example: You test Kodak Tri-x (ISO 400) and your blank frame (b) prints max black in 5 sec.

 

At 5 sec frame c is max black

 

At 5 sec frame d is max black

 

At 5 sec frame e is just lighter than max black

 

At 5 sec frame f is almost gray

 

Your speed frame is e; if your test speed is ISO 400 then your true speed or EI (exposure index) is ½ that or 200.

 

Another variation on the Visual Method is to place your target in a scene with recognizable tones. These tones will help you determine which is the correct exposure.

 

 

The Practical Method

 

This method is not as scientific or accurate as the densitometer tests however it works. You will need a gray card for this method

 

  1. Choose an evenly lit stationary subject.
  2. Set your meter at the film’s ISO rating (e.g. 400 for Tri-x). This will be called the test speed.
  3. Take a reflected meter reading of the gray card; choose a shutter speed that will allow you to bracket without using the slowest or fastest speeds.
  4. Set your camera for manual exposure; any auto-exposure setting will make the test meaningless.
  5. Record your exposures as you make them.
  6. Make the following exposures.

 

  1. Blank frame – FB+F film base plus fog
  2. 5 stops less thank the meter reading. (close down the lens, you may need to increase the shutter speed don’t forget to put it back at your original setting as soon as possible) – Zone 0
  3. 4 stops less than the meter reading -Zone I
  4. 3 stops less than the meter reading – Zone II
  5. 2 stops less than the meter reading – Zone III
  6. 1 stop less than the meter reading – Zone IV
  7. Meter reading – Zone V
  8. 1 more than the meter reading –Zone VI
  9. 2 more than the meter reading –Zone VII
  10. 3 more than the meter reading –Zone VIII
  11. 4 more than the meter reading –Zone IX
  12. 5 more than the meter reading –Zone X

 

 

Develop the film normally. Using the developer, time temperature you usually use.

 

 

Evaluating the test

 

 

Contact the film for the minimum time it takes to reach maximum black.

 

Choose the frame with the best detail in both high lights and shadows.

 

If frame g – zone V is correct then your EI is equal to the test speed.

If frame f – zone IV is correct then your EI 2x the test speed

If frame h – zone VI is correct then your EI half the test speed.

If frame i – zone VII is correct then your EI one quarter the test speed.

 

For example:

 

You test Tri-x ISO 400 and frame looks best then your EI would be 200. ISO/2=EI

 

Determining Film Speed

Determining Film Speed.

What is Film Speed?

Expose for the shadows. Develop for the highlights.”
So, how much exposure is needed for the “shadows”? ….It depends on the film speed!

  1. Film “speed” depends on –
    • the film’s sensitivity to light intensity and color, AND
    • to a lesser extent, the developer and development procedure used.
  2. Your individual film “speed” may also be affected by –
    • the sensitivity, color response, and accuracy of YOUR light meter,
    • the quality and condition of your camera lens, and
    • the accuracy of the diaphragm and shutter of your camera.
    • whether you are “exposing for the shadows” or using an auto-exposure camera, gray card, incident light meter, etc.
    • The film’s characteristic curve or “personality”.

This is not intended as a full discussion of the topic and primary references should be consulted for complete understanding. I have found Fred Picker’s Zone VI Workshop especially helpful in clearly outlining the steps necessary to find (1) your personal film speed, and (2) your “normal” film development time. Both are very helpful and will ultimately save a lot of time and money!


Finding your individual film speed (often called “exposure index” or EI) for a film-developer combination is a little like finding the “home” key on a typewriter, or “middle C” on a piano. It gives you a reference around which you can maneuver.

Kodak Publication No. F-5, KODAK Professional Black-and-White Films states that “..densities less than about 0.10 density units greater than gross fog level usually print as black.” This gives rise to the notion that the part of the negative which is to print darkest (other than pure black) in the print, should have a density of 0.1 above film-base plus fog (fb+f), or in Zone System terms, ..enough exposure to provide a Zone I density of 0.1 above fb+f. This is the Zone System equivalent of “Expose for the shadows” in the the ageless rule that heads this page.

Since exposure meters are supposed to interpret what they read as middle gray (Zone V), a Zone I exposure can be made by metering any uniform surface and providing 4 stops less exposure.

To determine one’s own film speed rating for any film-development combination, it is necessary only to …

  1. Meter a uniform surface using your best estimate (or manufacturer’s rating) of the film speed.
  2. Starting with the meter’s recommendation (Zone V), make a series of exposures, reducing the exposure one stop per exposure for at least six frames. I like to put a Zone V exposure at the end to mark the end of the blank frames and double-check the Zone V value.
  3. Develop the film according to the procedure you are testing.
  4. There should be frames with no density other than fb+f (film base plus fog), followed by a frame in which additional density is clearly identifiable. Theoretically, this frame should have a density of 0.1 above fb+f, but in the absence of a densitometer, your guess is probably adequate.

  • If the frame four stops from the Zone V frame is too light (or clear), your speed (ASA) setting is too high (you think your film is faster than it is).
  • If your “Zone I” frame is too dark and/or there is density in the lighter frame next to it, your film speed may be set too low and you are getting more exposure than you need.

If further adjustment is needed, you may either repeat the process with a new estimated film speed, or estimate how much you would have to change your estimated film speed to give the fourth (Zone I) frame a density of 0.1.


It is an hour after sunrise. The sky has light clouds with a little blue sky. The sun is hidden behind a cloud. With a Pentax Digital Spot Meter, the clouds read EV 151/3 – 161/3 while the ground under the edge of the deck reads 61/3. That is a 10 stop range, in subdued light! If you desire tonal separation in the clouds AND definition in the leaves on the ground, you need a film that can record more than 10 stops in a reasonably linear way. Interestingly, in bright afternoon sunlight, the range between bright cumulus clouds and forest shade is about the same, from 7 – 171/3.

Photographing a Kodak Gray Scale in either sun or shade exposes the film in only about a 5 stop range. This is adequate for short scale color reversal films like Kodachrome, but color negative and black-and-white films typically have a much longer scale and exceed the range of light reflected from the Gray Scale. If you want your negative to have both Zone I and Zone IX exposures, a single photograph of the Kodak Gray Scale won’t do it. Adding the exposures from BOTH sun and shade does, however, approximate (EV 8 – EV 171/3) the 9+ stop range of light available in a normal outdoor scene.

A Kodak Gray Scale was examined with a Pentax Digital Spot Meter. Two sets of readings, one in bright sun and the other in shade, resulted in the EV readings shown above. The slight difference in range is probably due to the way light is reflected from the glossy paper in diffuse and direct light. The illustration above shows that the black square is read by the meter as EV 8 in the shade and EV 112/3 in the sun, while the white square is read at EV 13 in shade and EV 171/3 in the sun.

Solutions have been suggested through the years in which two cards are mounted, one to the front surface of a box in direct sunlight, and another in a recessed shaded area inside the box. This allows a single photograph to reproduce the full range, but retains the problem of getting uneven illumination to the “shaded” card, since light inevitably “bounces around” inside the box.

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