Catpiano

Um ..  blurbackground, not means portrait lens wow ...  

Why nowaday, everyone want blur background?

Howabout buy a soft filter ? ( center one, keep all the NONE center object blur ) since you want the girl in the middle anyway ..

Base on what you want, I may say the 55-200 is a better choice for you, as you are new to photography, a Zoom lens may do the work for you better,  and the price for that lens is pretty decent ..

At ~ 100mm range, ( F4.5 area ) you should be able to capture a sharp object, and blur background, and you dont have to stand too far from the object.

55mm-200mm range for your sony DSLR, is a very good range!

Catpiano

   why people want blur effect ?/

I think now ..  most people want to see SHARP clean pic ??

Doesn't matter that day time u take the pic . . if you want blur background ..   u better use PS to process ..  or get a soft filter ..  or get a soft lens .. or get a lens baby ..

Catpiano

KTR, I think he means for APS camera .. the DOF is based on different calculation ..  

IE ..  take 2 pic, one with 85mm F1.2 on FF (36x24)  vs one with 50mm F1.2 on 1.6x crop (say 40D), which kind of ..  = 80mm  ( but not really )    even both pictures will look kind of identical ..  but diff DOF, the one with 85mm will be more SHALLOW ...   so I guess he means with APS camera, the DOF need to be added ?   ( I dont hv the calculation in my brain .. ask SB .. lol )

Anyway ...  

Catpiano

Oh ...  KTR .. let me use Nikon as example ..   

Kind of like D300 + 135 F2  vs D700 + 200 F2 ..

Catpiano

  so .. all of us OLD CAKES ..  are trying to explain??   lol ...

Catpiano

Yeah ..  jake .. what u read from that book .. is not totally true ..  

You may see the MAIN OBJECT  ..  look kind of the same ..  but not really .. ( ie more distortion )

It is really hard to explain ..    just like when I started doing 35mm .. people compared that to MF .. or FF ..  such as " 80 mm on MF = 50mm on 35mm format ..  "   I was ..   " what the heck ?? "    but once you try it, get the idea ..   then NO PROBLEM!!

Again, just buy some books from chapters ..  

I am happy with 2.0x, 1.6x, 1.5x , 1.3x as well ..  but never hv the same " AIR FEEL "  as FF ( or call old cake feel )  same as 35mm format, never get the "AIR FEEL"  ( or 3D feel ) as MF ..  

When we are here comparing APS  vs 35mm format ..   I am sure some DMF users are trying to explain to FF (35mm format) users as well .. lol