My favourite piece of kit: Viewing Card by Ian Raabe
The image above is my highly portable viewing card. It is made from thin flexible black plastic, but could also be made from a piece of black cardboard.
It is 20 X 16 cm with a cutout of 4 X 5 inches. The same size as the film you are using. I know other photographers use viewing devices with lenses, but I have never seen anyone else use this device in the field.
While out photographing, all my equipment is carried in a backpack, while the viewer is held in the hand ready for use. The viewer is used for composition and to help choose the appropriate lens. As an example, consider this scene : For this composition using a 4 X 5 field camera, if I choose a 210mm lens, then the card is held 210mm from the eye.
Moving towards the subject I stop when the composition seems right. I drop the card and then set up the camera on this spot. Any other adjustments are made and the image is taken. If constrained by only being able to stand in one spot, moving the viewer away or towards you will help choose the most appropriate lens.
I first saw this device in Ansel Adams book, Camera and Lens, Basic Photo One, 1976 edition, page 29. His caption for the photograph reads “The card suggests possible compositions… We do not necessarily (if ever) place the camera where the card was held!”
– Ian Raabe