Know Your Camera – Focal Length

For this part of our Know Your Camera assignment we have been concentrating on focal length.

In the days of 35mm cameras, all lenses worked in a similar way and everyone know what it meant to have a focal length of 50 mm or 100mm. Now that we are in the digital age, lenses affect cameras differently depending on the size of the camera’s sensor. For example a 50mm lens on a DSLR is one thing but because a camera phone has a much smaller sensor a 50mm lens would be very much more zoomed in.

I had always thought that my Sony a77 had a full sized sensor and that my lenses worked the same as they did when I had a 35mm camera but in doing this exercise I see that it isn’t.

I started by taking a photograph with my lens on its widest setting then taking three more photographs at different focal lengths, trying to keep my subject at the same size and position in the viewfinder. The last image was taken with my lens at its most zoomed.

Focal Length 18mm / Focal Length 35mm 27mm
Focal Length 18mm / Focal Length 35mm 27mm

Focal Length 55mm / Focal Length 35mm 82mm
Focal Length 55mm / Focal Length 35mm 82mm

Focal Length 100mm / Focal Length 35mm 150mm
Focal Length 100mm / Focal Length 35mm 150mm

Focal Length 200mm / Focal Length 35mm  300mm
Focal Length 200mm / Focal Length 35mm 300mm

I have labelled each photograph with the focal length of my lens and the 35mm equivalent.

In Lightroom I changed the image to black and white and increased the contrast. In black and white you are not distracted by the very green grass around the graves.

 

Know Your Camera – Autofocus

For the first part of our Know Your Camera assignment we have been concentrating on autofocus. It can be useful and its sometimes quicker and more accurate than manual focus.

With my camera set on autofocus, at its widest aperture and a medium telephoto I found a smallish subject close to the camera and a background with some detail in it. Then with the subject positioned at one edge of the frame I was asked to make two images, one with the subject in focus and the other with the background in focus.

I had a wander round a dilapidated graveyard and took these two photographs.

The first focuses on the moss on the edge of the grave while the second focuses on the urn, the dead plants and other graves in the background. To achieve this I focused my camera on the moss then locked it in position while I framed the shot and then took the photo. Staying where I was I then pressed the focus again and took the second image.

In Lightroom I changed the image to black and white and increased the contrast. In black and white the lines of the graves are emphasised and you are not distracted by the colours of the grasses and dead plants.

Autofocus-1 Autofocus-2