Great info guys!
Prime means it's a fixed lens not a zoom.
1.2 is a faster lens than 1.4
So when your saying faster you mean it is able to capture enough light more quickly in order to produce a decent photo?
After doing a quick google search for 'prime f1.2 or .4 it was apparent to me very quickly that a 1.2 was much more than a 1.4, about 3x as much or ~$1000.
Like Graph said its a fixed focal lenght (they are most often referred to as prime lenses) the F number refers to the apature,the lower the F number the larger the apature and hense the faster the lense(can capture light) F1.2 can be quite expensive in primes and anything lower that F1.2 goes into stratispheric costs (not that the average person would need it). 50mm f1.4 is a good compromise as it can perform very well for most of the situations you will be likely to use it in, you will also get some exercise from it due the "manual" (walk closer or further away) focus element to using one.
no bashing from me as its all about the image produced and not about the equipment that produced it.
I like setting my camera to manual and doing the tuning (not sure what the proper term is but this seems like it will get my point across).
So to put it in lay terms. A 50mm prime lens would be like taking pics with the lens my camera came with (18-55), all the way zoomed in or all the way zoomed out? I'm thinking zoomed out.
I would just have to put the lense right up to the glass to get a good close shot of say a bristle nose plecos face where the nostrils, eyes and bristles were in the shot?
If money is an issue, the 50mm f/1.8 is an excellent lens and can be had for about $100. Very sharp, great walk around lens. The other suggestions are good though. If you can swing it, the Tamron 90mm Macro, Nikkor 60mm Micro, and Sigma 150mm Macro are all great lenses but will set you back $300-400.
For macro, I personally suggest a tripod and shutter release. Of course with some practice you can certainly do it free handed.
Okay so with a 90mm prime lens it would be like taking pics with the lens I have (again, 15-55) roughly at about twice the distance? Pretty sure the nikor lens that I have is f1.8.
Right now I took a break from taking all the hardscape out of my L183 starlight tank to see how the plecs are doing and to snap some pics. I'm allowing the mulm/pieces of DW to settle so the water clears and I can get better shots.
But I think after that I'm going to hot up Craigslist and see what's doing on there lens wise...