Cannot a prime lens change its aperture
Are you trying to confuse DLSR newbies classcams? I'm not sure if that's a smile or a smirk!
TO those uninitiated, on almost all lens you can change the aperture (the A on your dial if you've got a Sony like me, or possibly "An" on others?) which impacts the amount of light going through the lens:
Larger aperture = small f number = more light
If there's more light going through your lens, then the less time you need it flowing through the lens to make your picture = quicker shutter speeds = steadier shots = sharper pictures
Large aperture also impacts on the depth of field (dof) - the amount of your photo that's in focus and the amount that's blurry:
Larger aperture = small f number = shorter depth of field = more blurry background
With zoom lenses, the maximum aperture (small f number) changes as you zoom in. So as you zoom in, the aperture decreases (f number gets bigger), your shutter speed needs to slow down = less steady shots, and dof gets longer (less blurry back grounds).
So if you're getting used to taking photos at one zoom length with a certain shutter speed and depth of field, and then try again at another zoom length you could get confused.
With prime lenses, this isn't a consideration as you can't zoom!
To be honest, I'd recommend using primes to start with
- you get sharper images because the lens is designed to be perfect at one length rather average at varying lengths
- you can play with aperture and compare easily (you know it's not the zoom changing the pictures)
- they're cheaper
- they typically have high maximum apertures so youi can really tell the difference in DOF and shutter speeds
my 10c anyway...