I would like to know the differences between:
- 50mm prime lens
- 50mm in a zoom lens
- 50mm macro lens
Let's start with what is similar with all three of these lenses:
They all have a focal length of 50mm. You should also be able to have a lot of overlapping focusing distances and aperture values.
When it comes to a zoom lens, they tend * to have a different maximum aperture values that are smaller than with a prime. The advantage is that you can zoom in and out so if your subject looks better at 55 then you can adjust your focal length to make your picture look "better".
The prime and macro lenses are very similar however, the difference comes in the focusing distance. With a macro lens you can do macro photography. This means if you want to take some very close pictures (normally people take pictures of bugs) then you can focus to that close of a range.
With a regular prime lens your biggest advantage is cost. Most non-macro lenses are cheaper than their macro counterparts.
Also, with primes you tend * to have a faster (or larger) maximum aperture. However, unlike your zoom lens you might not be able to get the picture you want and also may be unable to take a step forward (or backwards).
Some helpful definitions:
Aperture: also known as an f-stop this affects your depth of field. The larger the f-number number, the smaller your aperture is, and the larger your depth of field will be. For some pictures you may want to have a very large depth of field and then you can see everything behind your subject in focus. The downside is, when you use a smaller aperture, then you also decrease how much light is passed through the lens.
A bigger maximum aperture isn't always better. For example, people will spend more money on a 200mm with f/2.0 vs 200mm with f/2.6. It all depends on your requirements.
Minimum focusing distance: How close an object can before it will be in focus. All lenses should be able to focus to infinity; however, it is the minimum distance that is of importance (in this case). If you want things very close to you then you need a small minimum focusing distance. A macro lens will have the smallest; however, it has the tradeoff of cost.