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.
Storm Clouds. Cumulo-Stratus and Nimbus Clouds can usually be secured without employing a ray filter, for they are very often made up of heavy semi-dark tones and such shades of gray that the ordinary plate will photograph them perfectly. Many times, employing color corrected materials for these clouds will result in making them look exaggerated and unreal. The Cumulo-Stratus grows irregularly upward into piles of extremely striking magnificence. A hugh towering mass of heavy clouds rolls up from the horizon in striking form, full of grandeur, over-hanging its base and frequently foretells a thunder storm, especially when covering the sun so that its edges are given the appearance of gold. If striking pictures are desired this cloud provides the finest material for you to employ, but you must exert a certain amount of care, and bear in mind that the climatic conditions which exist at the time the cloud is secured must also have existed when making a landscape or seascape which is to be used in conjunction with the cloud negative.
409. The Nimbus Cloud belongs properly to the sea. It travels and increases in size at a great rate. It is very dense and dark, and is accompanied by rain and sometimes thunder and lightning. It often completely covers the entire sky with a dark mass that possesses no pictorial beauty, yet serves as a most effective background for storm seascapes. When the cloud is forming, or as it is dispersing, pictures of great beauty may be obtained; especially is this possible when the cloud has burst and the broken parts which are very dark at the edges, form into loose and jagged shapes. These broken and rapidly flying parts are called by sailors, "scud," and are the proper clouds for any picture representing very stormy weather.
410. From these different varieties of clouds you will observe that they arrange themselves into three distinct groups - fair weather clouds, wind clouds and storm clouds. If you will give careful study to the landscape or seascape into which you desire to print clouds, you will be able to obtain artistic and true-to-nature pictures. Three cloud negatives will answer the purpose for ordinary use. You should have one representative cloud negative of fair weather clouds, one of wind clouds, and another of storm clouds. These will be lighted, of course, from one particular side, yet if you wish to employ them with a landscape which is lighted in the opposite direction, you can reverse the cloud negative in the printing frame so that the film side is facing out instead of being in contact with the paper. A slight diffusion will result, but it will be practically unnoticeable, and not at all objectionable. In this way you have practically six cloud negatives - a sufficient number for the average worker. If you will watch the various transformations, especially in the higher clouds, you will see that the change is extremely rapid. Take, for instance, Cirro-Cumulus clouds and watch them for a few minutes; or even make a series of six or eight pictures at intervals of a couple of minutes. This will show very clearly the process by which the change takes place, and will prove of great interest and value to you. Storm clouds of any character should be similarly studied, in order that you may understand more perfectly the correct cloud effects to use in conjunction with various foregrounds.