A tip for newcomers to SLR photography.
I often hear: “Why do I need so-called “fast” lenses – like the 50mm f/1.8 lens Michael keeps talking about? Surely my 18-55 lens also covers 50mm?”
Well yes it does. But:
- Less sharply. A “prime” (i.e. non-zoom) lens is sharper.
- A prime lens is also smaller and lighter.
- And especially: the prime lens has a lower minimum “F-number” – i.e. a larger aperture. The lower the “F”-number, the better. Your kit lens is f/3.5-5.6 (meaning zoomed out it can go as low as 3.5; zoomed in it can go only as low as 5.6. The 50mm f/1.8 can go as low as 1.8).
Why is this important?
So in today’s class I took two shots of a student in available room light. One at f/5.6, and that is what you would get with your standard “kit”-lens. It looks like this:
Two things happen:
- Because of the small aperture (high “F-number”), the camera has to keep the lens open for a long time. This means that unless I use a tripod and tell the subject not to move, in indoors light I will get camera shake (the shot needed 1/10th of a second). And sure , do.
- The lower the “F” number, the shallower the depth of field, i.e. the blurrier the background. The higher the F-number, the sharper the background.F/5.6 gives a background that is somewhat blury.
Now look what happens when I use an aperture of f/1.8 (for which you need a lens that can do that, like the 50mm f/1.8 lens):
Much better – a pretty dramatic difference on both counts!
So the best way to immediately get great portrait shots is to:
- Get yourself a 50mm lens. On most cameras this is simple; do note that on a Nikon D40/D60/D3000/D5000 you need to manually focus this lens (that is why I recommend Canon cameras at the entry level).
- Learn Aperture Priority mode (A/Av) and use a low “F-number”.
- Turn the camera sideways and get close!
(Wow, three numbered lists in one blog post!)