Manaen wrote:So what is the main difference between a 35mm, 50mm & 85mm prime lens? (apart from the cost)
There's a number of differences, all related, and they each can have a distinctive affect upon your photographic work. Please don't think that this is an either/or proposition either: each of these lenses can and probably should have a place in your kit.
Let's start by going back to describing everything in terms of full frame photography, because that's how this is measured.
The 50mm presents an angle of view to your camera's sensor that is very close to what we see with our eyes.
The 35mm lens is what is called a wide angle lens, and thus it presents a wider field of view. This means that it can fit more (of what you may be seeing) into what your sensor can capture. As such, those picture elements will appear to be reduced in size and further away.
The 85mm lens is what's called a telephoto lens, and it presents a narrower field of view to the sensor. In contrast with a wide angle lens, it will fit less into what your camera's sensor can capture, and consequently, those picture elements will appear to be increased in size and closer to you.
Telephoto lenses permit you to take close-up photos of subjects that may be some distance away - say of a bird in a tree, or perhaps bring your view of an event such as a sporting game closer to the action than otherwise possible given where you might be physically located.
Wide angle lenses permit you have a greater overall view of .... something. They're great for landscapes where you want to fit the whole expanse of water or a distant mountain range into your image.
Ok, I think that's the basics.
Your D60 is what we call a crop format camera: its sensor is smaller than what you will find on a full frame camera, and thus any image that you make will already appear to be cropped, relative to that same image made on a FF body. The crop factor is 1.5 and the primary effect of this is that this is narrowing your field of view. Effectively, this gives your camera a perceived advantage when shooting in a telephoto
mode, because it's as though your lens's focal length has been increased by 1.5. Thus your 50mm seems to be like a 75mm, and your 35mm seems to be like a 52mm.
Which means that, on a DX body, the 35mm presents an angle of view closely aligned to the way that a 50mm presents on a full frame camera.