I often get the question from aspiring photographers, "Which lens should I buy?" This post is for you. If you never could quite understand why in the world I would ever recommend a lens that doesn't zoom, here it is. The fastest most expensive zooms have f/2.8 as their widest aperture. The fastest primes in production go down to f/1.2 What does aperture mean and why is it important?
Well in layman's terms, it's the amount of light a lens allows into the sensor to capture an image. The best way I've ever heard it explained is picture a bucket and a faucet. The larger the faucet, the less amount of time it's going to take to fill the bucket. In the example below, the exposures are all the same but the amount of light required to properly expose the f/1.2 image is actually over 5 stops lower than the amount of light required to expose the f/8.0 image. That's 5 times less light at f/1.2! Have you ever wondered why your images are blurry inside when you don't use a flash? This is why. It takes 5 times as long to get the same image.
Do you notice anything else about the images? Does that f/1.2 image look strange? That's because of the VERY shallow depth of field. I'll let you judge for yourself which one you find most appealing and I'll leave that topic for another day! : )
