There are two types of lens that we can talk about in this exercise, Zoom lens and Prime Lens. The prime lens is also referred to as fixed or standard. The prime lens has a fixed focal length, so if you want your subject to fill the frame then you would physically have to get closer to them, whereas with a zoom lens the focal point or closeness can be altered without moving. Prime lens’ are normally around the 50mm/55mm standard focal length. My wide angle lens has a focal length of 18mm to 55mm, but the tele lens I use has a focal length of 75mm to 300mm, as seen in the images below
In some cases lens’ may also have facility for Automatic Focus or Manual Focus. This is useful at times, I find when I want to really get the right focus, for say the DoF then I use manual as its easier than waiting for the lens to do the work for me and I can be more precise with the area I want in focus.
A variable aperture zoom lens will have a specified aperture range, normally indicated on the lens barrel. In my case the wide angle lens has a, 1.3 to 5.6 f/stop range.which means that maximum aperture is f/1.3 at the widest focal-length which is 18mm. So putting into plain language, if I set my focal length at f5.6 and zoom in, I will not have a problem with the aperture automatically changing, but if I set at f/1.3 and zoom in I will find that the aperture has changed and this will also affect exposure and perspective.
Select your longest length and compose a portrait shot fairly tightly with in the frame in front of a background with depth. Take one photograph. Then walk towards your subject while zooming out to your shortest focal length.
Focal Length 18mm
Focal length 55mm
Reviewing both shots the background looks completely different in the second shot. Paddy, my husband and our dog Harley, didn’t move, but I did altering the focal length as I moved, to make sure that I got Paddy filling the same amount of frame that I had in the first photograph. if we look at the arches behind him, we will see the difference. This is known as perspective distortion which will be explained further in Project 2; Part 1 – Exercise 2.3
Read more on Framing in a previous exercises