QUOTE(seather @ May 29 2012, 03:59 PM)
the 50mm 1.8g will only have a 50mm Field of View (FOV) in a full frame body... the D7000/D5100 has a crop sensor which is 50% smaller than a Full Frame (FX) sensor..
u can read more here:
http://www.bobatkins.com/photography/tutor...and_lenses.htmlin summary, for Nikon, if u buy a FX lens... u need to multiple by 1.5 to get the correct FOV/focal length...
example: in ur D7000, u will see the same picture through the 50mm 1.8g, and ur 18-105 when u zoom to 75mm

f1.8 means it can have a wide aperture... meaning good for low light... plus wide aperture = thin DOF = nice bokeh...
btw... u take the D7000 to lower budget, not D5100 meh??

Doesn't matter you get FX or DX lens, still need to multiply crop factor.
DX lens means is meant to use on DX sensor, if you use on FX sensor body, it will not be able to utilize the full sensor area, hence vignette.
Even if you buy a compact camera, you still need to multiply crop factor.
You buy mirrorless like GF3, also need to multiply crop factor (e.g. 14-42mm kit lens, becomes 28mm-84mm which is the standard zoom).
Even handphone, you need to multiply crop factor to get the focal length in 35mm Format.
In short, to make it simple doesn't matter whether it's FX, DX, CX, etc. When you mount a lens on crop body, you need to multiply by the crop factor to get the focal length in 35mm format.
QUOTE(Acquainted @ May 29 2012, 04:07 PM)
so the 18-55mm kit lens + 50mm 1.8G will be perfect for d5100 starter? XD
basically i will be using the dslr for travel pics, graduation pics (which is very soon- expecting lots of portraits, i mean, 2-3 people shots), besides will the 50mm 1.8g applicable for group pics? around 10 people.
(wow, great knowledge u have there, looks like ive to cling to this thread more often)
Since you have knowledge already and you mention you want to venture into this, I'd suggest you to get D7000 straight.
D3100 & D5100 is more for people who want simple and easy to use. If you want to get more serious you'll find the hassle and troublesome to adjust settings as these 2 models caters more for casual users.
Besides, if you get D5100, later you learn more and want to have more control and have better handling, you'll regret and it'll be a waste of money when you cannot stand and want to change.
But if you just want for casual use and can live with the limitations, then you can go for D5100. Personally, my advice is if you want to venture into this field, you will want at least a D7000 or a proper body which gives more control and handling.
Just try them both together and you can tell the difference immediately.