You may sometimes find that the actinometer indicates a very different exposure from what the eye would lead you to expect. For instance, one day last September I went to Bothwell Castle, to get a picture I knew of in the grounds. It was one of those strange yellow days we had then, and the sun, though shining with all his might, was apparently shining through orange glass. The actinometer indicated an exposure of thirty seconds where in good light one would be right. I was rather incredulous. Thirty seconds in broad sunshine! However, I gave this exposure, but for my own satisfaction I gave another plate fifteen seconds only.
On developing, the latter was hopelessly underexposed while that having thirty seconds gave a negative which furnished one of my exhibition pictures.
I have shown you how to reduce the quality of the light to a certainty, also how to reduce to rule the exposure with different lenses and stops on certain classes of subjects, and it remains with you only to guess correctly to what class the view you wish to take belongs; I can assure you from my own experience that there is enough uncertainty about that point to prevent good negatives ever becoming monotonous.
The only aid I can suggest in this case is the continual use of a note-book. Note every plate you expose, and when you have a failure be careful to record the fact, and you will gradually find these accumulated notes becoming a great help in cases of doubt. One hint I can give to beginners is that a great number of the pictures to be met with in this part of the country are intermediate between "Open Landscape" and "Landscape with heavy foliage in foreground;" and it is scarcely needful to say that if you are in doubt, let the exposure be rather too much than too little; you may make a negative of an overexposed plate, but never of an underexposed one.
We take from the Br. Jour. of Photo. the following interesting paper read by W. Goodwin before the Glasgow and West of Scotland Amateur Association.