This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
Cultivate Observation. Before attempting to photograph subjects of this class, study them at other seasons and note their characteristics. The knowledge thus gained will help you materially in your work, and also aid you to secure results with greater dispatch and comfort when the proper moment arrives.
The Camera. A hand camera is perhaps the most serviceable instrument for securing snow pictures, because of its lightness and portability. It will also be found convenient for long winter tramps over the open country.
429. A waterproof focusing cloth affords the needful protection against weather conditions. Even with this equipment the practice of snow photography is difficult. The difficulty lies in the great contrasts which, as just stated, exist between the brilliant snow and the dark objects of the landscape. The same procedure should be adopted as in other cases of strong contrast - the use of specially prepared plates and proper development. Non-halation or backed plates should be used.
Exposure. The greatest of care must be exercised that you do not over-expose when making snow pictures. The white snow reflects the strong light and the whole scene is of practically an even tone, and if the plate is at all over-exposed it will be extremely flat. If anything, you should err on the side of under-exposure. With a F. 16 stop and an ordinary rapid plate or film, 1-100 of a second will be a great sufficiency of exposure. If the light is very diffused it may be permissible to use an exposure of 1-50 of a second; but even in diffused light there are so many cross reflections and the whole scene will be so evenly illuminated, that it will be a very easy matter to misjudge the correct amount of exposure necessary. Usually one-half the exposure of a scene without snow is sufficient for one with snow. For example, if you would give l-50th of a second without snow, 1-100 would be approximately correct for the same scene with snow.
Lens Shade. Some times reflections from the snow, difficult to avoid, will be cast into the lens. To overcome them make a cone of black cardboard and fit it around the lens. The cone must not be long enough to interfere with the angle of view of the lens, yet should cut off the direct reflection from the snow that would otherwise come into the lens. Holding the slide of your plate holder or any black object under the lens will prevent reflected light from striking it. Reflections will not always occur, much depending on the angle of light into the view. The reflection can, of course, be detected on the ground-glass when focusing. (See Illustration 48a, Page 232.)
Advantage Of The Ray Filter. The sensitive plate is always affected by the strongest lights, whether reflected or direct; and, in consequence, the more subdued lights are very hazy and misty in the shadows. The best way to overcome this haze and mist is to give quick exposures and to use a ray filter.
433. A strong sunlight on the white snow, especially where the sun faces the instrument, will have the same effect upon the lens and plate as it would upon the human eye when looking at the snow with the sun shining upon it. In the latter case the eyes are weakened and almost blinded by the dazzling whiteness.
434. Lens vs. Human Eye. - If you were looking at some distant object across a field of snow it would be almost impossible to see it, and the longer you looked the less you would be able to see. This is exactly what happens to the lens and sensitive plates. The longer the exposure, under the above conditions, the less the lens will see, which results in your obtaining very little detail on your sensitive plate. Like the human eye the plate will have fogged over and the image appear veiled. When you first looked at the snow your vision was perfectly clear and you could see all of the detail. Now, transferring this example to the "seeing power" of the lens, you can realize why the short exposure on your plate will give the best results, rendering plenty of detail, while a longer exposure will produce fog.
435. By the Use of a Ray Filter (which has been previously described) the activity of this curtain of strong light - the reflection of sun on the snow - will be reduced enough to give a good rendering of the highlights in the negative and secure sufficient detail in the shadows. Thus the ray filter acts on the lens like smoked or blue glass upon the eye. The blue glass prevents the yellow rays of light from affecting the eyes, enabling one to see distinctly the various objects which are situated on the glaring snow. When the ray filter is used on the lens it keeps the chemical rays of light from acting in a similar manner on the sensitive plate, and little or no fog will result.