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.
Lighting. The lighting has much to do with relief, roundness and atmospheric effect. If the sunlight falls perpendicularly upon the scene as is the case during the noon hours, you will not secure the valuable shadows which add greatly to the effect of roundness and secure the necessary contrast which you must have in the snow scene to make it appear real. The best time of day to make an exposure is in early morning or late afternoon when the shadows are longest. At either of these times there is not as great a danger of over-exposure as at noon, when the sun is strong and the light falls almost perpendicularly, thus giving practically no shadows and a flat picture.
Snow Appears Dirty. This will be the result if you have over-exposed and under-developed your negative. There must be contrast between highlights and shadows and there must also be detail in the shadows, but the highlights should be developed sufficiently strong so the negative in these portions will be almost opaque, thus retarding the action of the light on the sensitive plate.
Highlights Appear Hard With No Detail. This is caused by over-development as well as by slight over-exposure; or perhaps too strong a developer. A correctly developed negative should be carried in the developer until the highest points of light are practically opaque, but the delicate half-tones in these highlights should be preserved. This is accomplished by careful development and will only result when proper judgment is exercised in stopping the action of the developer at the right time. A snow negative should be soft and delicate. In fact strive to reproduce exactly what you saw in the original. To be successful you must give particular attention to the exposure and then be able to develop the negative to exactly the proper density. Always use a normal developer and when the image first appears, if it shows signs of too much contrast, dilute with water. If the plate appears flat, add a few drops of bromide and conclude the development.