Focus at different apertures Exercise 3

Monday 11th April 2011
Focus at different apertures

Using the same 50mm prime lens with the camera mounted on a tripod and the shutter release cable, I took 3 photo's - f1.8, f11, f22 and compared them after printing.

50mm prime lens f1.8

The red elipse demonstrates the limit of sharpness. I was interested to see it was an elipse shape, as I had assumed the aperture would be a circle. I expected this to be a small depth of field as for obscuring backgrounds and portrait photography I have been taught to use the smallest depth of field possible with the lens used. We have had this lens in the kit bag for some time and I have not worked with it much, so I was keen to experiment as it a good lens for still life photography and low light indoor work.

50mm prime lens f22

The red elipse demonstrates the limit of sharpness.

The middle of this picture is sharp. I expected the whole picture to be in focus. This could be because of bokeh (blurring) and the lens only having 5 blades so it creates a pentagon shape. I have researched this lens on the internet http://www.the-digital-picture.com/Reviews/Canon-EF-50mm-f-1.8-II-Lens-Review.aspx

There is a marked difference between the f1.8 and f22 or f11 because a large aperture gives a small depth of field.

50mm prime lens f11

The red elipse demonstrates the limits of sharpness. I think this is the best photo when printed out as there is more in focus than with the f22. For example, the collars are easy to read. 

Focus with set aperture - Exercise 2

Focus with a set aperature

As the weather was against me, I set up a row of wine bottles as my scene with depth. I mounted my camera on a tripod and took a series of 3 photographs. These demonstrate the effects of focussing in different places on the same picture. For this arrangement, I prefer the focus in the middle because it gives the eye a place to start from. The viewer can then move outwards to view the whole scene.

Focus on the left bottle

Focus on right bottle

Focus on middle bottle

All photos were taken with 50mm fixed lens with an aperture of 1.8mm to let lots of light in and produce a small depth of field. I manually selected the focus points and kept the camera in the same position mounted on the tripod. I used the shutter release cable to minimise movement.The picture I prefer is the one where the right hand side is in focus. This is because it is nearer to the viewer and I think it leads your eyes down the line of bottles.

16/2/13 – from experience gained throughout the course, I would now use my 24-105mm F4 lens with a circular aperture because it has a circular aperture rather than a pentagon shape.