The purpose of this exercise is to see the depth of field available at different aperture settings – the smaller the aperture (the bigger the number) then the greater the Depth of Field, the range of the image which os sharp.
For the exercise the subject needed depth to give me something to clearly show the results, and as it was raining (again!) I chose the best thing I could think of, which would be easy to see the results on – hence my big sewing ruler!
Kit: Nikon D300 with 18-55mm lens, at 55mm focal length. ISO 400, aperture priority, allowing the shutter to look after itself, whilst I adjusted the aperture to suit the exercise.
The camera was monunted on a tripod to make sure all the images were from the same location, and I chose the 40 cm mark on the ruler as my focus point for all the images.
For the first image my aperture was set to the widest available – f5.6 and as the image shows, the DOF is extremely narrow – from the 39.5cm mark up to just over the 41cm mark. This image also shows the unequal areas in focus in front of and behind the focus point – the area in focus to the front of the focus point (40cm) is less than the area in focus to the rear.
For the second image I adjusted the aperture to f16 which increased the DOF by about 1.5 cm to the front and rear of the focus point.
In this final image I closed the aperture down to f36 which increased the acceptable sharp areas to around 15 cm.
Having played around with Depth of Field, otherwise known as the Hyperfocal distance, in the past, this is the first time I’ve actually had a go at measuring it, so quite an interesting exercise, albeit the narrowness if over emphasised by it being a very close-up subject.