I skipped the the first part if this exercise, due to the suggestion that it was unlikely to work with a digital camera.
Firstly I had to determine my camera’s standard focal length. The camera is a Nikon D5100 and according to the manufacturer has a cropped imaging sensor and therefore a crop factor of 1.5X. This would therefore give it a standard focal length of just over 38mm. I then mounted an 18-105mm Nikkor zoom lens onto the camera for this exercise.
The scene I decided to capture lay just outside my rear balcony. A new apartment block just completed in construction. Something of an eyesore actually, but useful at least as something quite definite in form and easy to measure against. The camera was mounted on a tripod for a repeatably stable from which to take the next series of photos.
First photo was at the cameras’ standard focal length – 38mm
When this photo was printed and then held at enough of a distance so that it appeared to be the same size as its subject, I measured this to be 35cm.
The next photo was at its’ widest angle of view – 18mm
I found this photo when printed had to be held at such a close level I think I ended up cross-eyed! It wasn’t practical to make a measurement, but I would say length somewhat shorter than my nose, about 4 cm
And the last photo at the narrowest field of view (or longest telephoto length) – 105mm
This photo had to be held at just beyond an arms’ length away to make the comparison, at about 95cm (does that mean I have short arms?).
When I printed these photos out on A4 sized paper I wasn’t sure whether to do so with a borderless reproduction, or as the print software determined a “100%” print size to be, which had quite a wide border. I opted for 100%. The images had to be straightened slightly in software. I very rarely print my photos, so it really was quite interesting to have actual photos in hand, even if they were printed on plain copier paper.