Getting to know your camera: Focal length & angle of view

Ok first exercise.

This involved trying to determine how the different focal lengths would make the final image appear, and what the best viewing distance would be. I decided to start by checking out the manual for my Nikon D5000 and see what is said the 'standard' length was for my camera. I've scanned in the page describing how to work this out:

To start with it looked extremely complicated, and my maths is not the best! The diagram really helped me to understand what exactly is being described, its much easier to get to grips with something visual. After studying it for a little while I 'think' I've worked out that a standard size image for my camera would be at a focal length of 23.3mm. If this is wrong someone please correct me!

After establishing this I moved on to the exercise itself and took some shots of a scene at the standard focal length, the minimum and the maximum and a length that with both eyes open, appeared to be the same in the viewfinder as what I could see visually. It turned out that the closest length to what I could actually see was the longest length of 55mm, so below are the three shots I took in the following order: 55mm, standard 23mm and 18mm.

The first image, 55mm, was the one closest in the view finder to my natural vision with both eyes open. In fact if I could have zoomed in a fraction more it would have been perfect. When it was printed on to A4 paper I couldn't physically stretch my arms far enough to make the printed image appear the same size as what I could see, so the best viewing position for this image would have been if I could have pinned it to a wall and taken a step backward.

The second image, 23mm, was most like what I could see when I could hold the print right out at arms length. A little further would have actually been better.

The third image, 18mm, was best when held at exactly arms length.

What I have noticed is that the longer the focal length used, the further away the image must be for it to appear a 'normal' size. Smaller focal lengths produce images that have to be viewed close up to see all of the detail. What surprises me is how much the angle of view changes from what I perceive as normal and the standard focal length, an awful lot is lost. I will have to take this into account when I consider what shots I'm taking and where the final prints might be published. This will also help me to decide on print sizes for future assignments based on how I want to portray an image.