Book Report: Customizing Film Speed and Development

edwardyung

Customizing Film Speed and Development

Way Beyond Monochrome
書入面提到3個不同層次的方法.
1. Quick and Easy  ←簡單易明, 1張圖就代表了
2. Fast and Practical  ←还能消化
3. Elaborate and Precise   ←吃完有点胃痛

有興趣找來翻一翻
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1. Quick and Easy
Here is a simple technique, which will improve picture quality significantly and does not require any testing at all. Use it if you dislike testing with a passion, or if you just don’t have the time for a test at the moment. This method can also be used to give a new film a test drive and compare it to the one you are using now. For a normal contrast, bright but cloudy day, cut the manufacturer’s recommended film speed by 2/3 stop (i.e. ISO 400/27° becomes ISO 250/25°) and the recommended development time by 15%. The increased exposure will boost the shadow detail, and the reduced development time will prevent the highlights from becoming too dense. For a high-contrast, bright and sunny day, increase the exposure by an additional 2/3 stop (i.e., ISO 400/27° now becomes ISO 160/23°) and reduce the development time by a total of 30%. Stick to the ‘box speed’ and suggested development time for images taken on a low-contrast, rainy or foggy day. A negative processed this way will easily print with a diffusion enlarger on grade-2 or 2.5 papers. Just give it a try (fig.1). It is really that simple to make a significant improvement to negative and image quality.

edwardyung

2. Fast and Practical

Here is another way to arrive at your effective film speed and customized development time. It is a very practical approach, which considers the entire image producing process from film exposure to the final print. The results are more accurate than from the previous method, and it requires three simple tests, but no special equipment.

a. Paper-Black Density Test
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This test will define the minimum print exposure required to produce a near-maximum paper density. Make sure to use a blank negative from a fully processed film of the same brand as to be tested. Add a scratch or a mark to it, and use it later as a focus aid.
1. Insert the blank negative into the negative carrier.
2. Set the enlarger height to project a full-frame 8x10 inch print and insert contrast filter 2 or equivalent.
3. Focus accurately, then measure and record the distance from the easel to the film.
4. Stop the lens down by 3 stops and record the f/stop.
5. Prepare a test strip with 8, 10, 13, 16, 20, 25 and 32-second exposures.
6. Process and dry normally.
7. In normal room light, make sure that you have at least two but not more than five exposures, which are so dark that they barely differ from one another. Otherwise, go back to step (5) and make the necessary exposure corrections.
8. Pick out the first two steps that barely differ from one another and select the lighter of the two.
9. Record the exposure time for this step. This is the exposure time required to reach a near maximum paper density (Zone 0) for this aperture and magnification. If you can, leave the setup in place as it is, but record the f/stop, enlarger height and exposure time for future reference.

b. Effective Film Speed Test
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This test will define your normal effective film speed, based on proper shadow exposure.
1. Select a subject, which is rich in detailed shadows (Zone III) and has some shadow tonality (Zone II).
2. Set your lightmeter to the advertised film speed.
3. Stop the lens down 4 stops from wide open, and determine the exposure time for this aperture, either with an incident meter pointing to the camera, or place a ‘Kodak Gray Card’ into the scene, and take the reading with a spotmeter. Keep the exposure time within 1/8 and 1/250 of a second or modify the aperture.
4. Make the first exposure.
5. Open the lens aperture or change the ISO setting of your lightmeter to increase the exposure by 1/3 stop (i.e., ISO 400/27° becomes ISO 320/26°) and make another exposure. Record the exposure setting.
6. Repeat step (5) four times, and then, fill the roll with the setting from step (4).
7. Develop the film for 15% less time than recommended by the manufacturer. Otherwise, process and dry the film normally.
8. Set your enlarger and timer to the recorded settings for the already determined Zone-0 exposure from the previous test.
9. Print the first five frames, process and dry normally.

An evaluation of the prints will reveal how the shadow detail is improving rapidly with increased film exposure. However, there will come a point where increased exposure offers little further benefit. Select the first print with good shadow detail. The film speed used to expose the related negative is your normal effective film speed for this film. Based on my experience, it is normal for the effective film speed to be up to a stop slower than the rated film speed. Fig.3a-c show just how much difference the effective film speed can make. Fig.3a is the result of a negative exposed at ISO 125/22° and then printed with the minimum exposure time required to get a Zone-0 film rebate with a grade-2 paper. The highlights are ‘dirty’, the midtones are too dark and ‘muddy’, and the shadows are ‘dead’ with little or no detail. In fig.3b, an attempt was made to produce a ‘best print’ from the same negative. The film rebate was ignored, the exposure was corrected for the highlights, and contrast was raised to optimize shadow appearance. The highlights and midtones are much improved, but the gray card is still a bit dark. The shadows are solid black, still without any detail, and the picture has an overall harsh look to it. Fig.3c is the result of a negative exposed at an effective film speed of EI 80, and then printed in the same way as fig.3a. The highlights are bright, but not as harsh as in fig.3b, the gray card is on Zone V as intended, and the shadows are deep black with detail. A big improvement, solely due to selecting the effective film speed.

c. Film Developing Time Test
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This test will define your normal film development time. A rule of thumb will be used to adjust the normal development time to actual lighting condition, where needed.
1. Take two rolls of film. Load one into the camera. On a cloudy but bright day, find a scene that has both significant shadow and highlight detail. A house with dark shrubs in the front yard and a white garage door is ideal.
2. Secure your camera on a tripod, and set your lightmeter to your effective film speed, determined by the previous test. Meter the shadow detail, and place it on Zone III by reducing the measured exposure by 2 stops.
3. At that setting, shoot the scene repeatedly until you have finished both rolls of film.
4. In the darkroom cut both rolls in half. Develop one half roll at the manufacturer’s recommended time. Develop another half roll at the above time minus 15% and another half roll at minus 30%. Save the final half roll for fine-tuning.
5. When the film is dry, make an 8x10-inch print from one negative of each piece of film at the Zone-0 exposure setting, determined during the first test. The developing time used to create the negative, producing the best highlight detail, is your normal film developing time. You may need the fourth half roll to fine-tune the development.

Considering your entire image-making equipment, you have now determined your effective film speed, producing optimum shadow detail, and your customized film developing time, producing the best printable highlight detail for normal lighting conditions.
However, film exposure and development have to be modified if lighting conditions deviate from ‘normal’. The rule of thumb is to increase the exposure by 1/3 stop whenever the subject brightness range is increased by one zone (N-1), while also decreasing development time by 15%. On the other hand, decrease the exposure by 1/3 stop whenever the subject brightness range is decreased by one zone (N+1), while increasing development time by 25%.
These tests must be conducted for every combination of film and developer you intend to use. Fortunately, this is not a lot of work and will make a world of difference in your photography.