Several years ago I took part in a Great American Photo Workshops workshop.One of the participants provided participants with a great tool or aid.
Using an old 35mm slide mount on a string enables the photographer to view in the standard aspect ratio of most digital SLR cameras.
When I lead a photo outing I will ask participants to leave their cameras othe car and only bring the viewer and their tripods. All too often we as photographers walk into a scene and plant the tripod with the lens that is already on the camera or the favorite lens and begin captures.
To purposely make images it is best to walk the area with your viewing tool
and look for the best compositions. Once you are satisfied you plant your tripod and retrieve your camera with the appropriate lens. There are 2 scales on each mount. Pictured here is the Film side and the Digital of original unit I have carried for more that 6 years. The digital side uses the Nikon 1.5 crop factor for ease of math. The Canon 1.6 or 1.3 are close and a good start.
When using these tools you can look through the Void in the mounts and once you have the composition you want you then hold the string to your eye and then calculate the distance from the mount to your eye.This measure provides you with the approximate lens you will need to make your image.
I have used a permanent marker to put a coloured scale on the crop or view tool. The measurements are all 1″, 2″, 4″ and 8″ for Full Frame and 1-1/2″, 3″, 6″ and 12″ for Digital.
Try using this device to previsualize your image making rather than planting your tripods and then hoping you have the right spot.
Please excuse the image quality. I took these images in the lounge at Heathrow with my iPad and then sent to laptop top post.