Should i swap lenses would appreciate someone's input? - 1

I currently have a D3100 with kitlens Nikon 18-55mm f/3.5-5.6G AF-S VR DX NIKKOR
and a tamron 70 mm - 300 mm - F/4.0-5.6 which I bought last week.

I like to take pictures with a short DOF to really draw attention to the subject getting it as sharp as possible with soft blur around of things like flowers objects and people.

This is with my tamron lens:

I'm usually out taking pictures of scenery in woods and such.
I'm thinking a prime would be more suited for the pictures i want to take.

Should i Swap my tamron 70-300mm for a prime lens:
Nikon AF-S 35mm f1.8 G DX Lens: £125
Nikon AF-S 50mm f1.8 G Lens: £160
Nikon AF-S 40mm Micro f/2.8 DX G Lens £200

"Selective" DoF is 50% equipment, and 50% technique, and is achieved by three factors.

1.lens focal length - the longer the lens, the shallower the DoF.
2.focus point - the closer the subject is to the lens, the shallower the DoF.
3.aperture - the wider the aperture, the shallower the DoF.

Of the three, the lens focal length has the most influence, the focus point next, and the aperture has the least influence.

Myth #1: it takes a lens with a large aperture to get a good DoF. Nothing could be further from the truth. While aperture does have some influence over DoF on any lens, the focal length trumps all other factors.

So a long telephoto with a f/5.6, under the right conditions, can achieve good results.

What are those conditions?

If you set your Tamron to 300mm @ f/5.6 and shoot with the subject as close as you can (within a few feet), you will achieve a much of a shallow (or perhaps even more) DoF than say, a 50mm lens @ f/1.8.

Want proof? Look at this website for tips on selective focus. There you will see that you can indeed get a pleasing DoF blur with an inexpensive lens.

http://www.althephoto.com/concepts/selectivefocus.php

The trick though is to compose the photo so your focus distance is short, and your telephoto length is long.

However, the lenses on your list are all great lenses and will also perform well. But at least try the tricks I have given you on your Tamron before buying a new lens.

You will already have observed that you can get minimal D of F by using your 70 to 300 at about 100mm or beyond, making sure that you have the lens at max aperture (smallest number). The main way to get shallow d of f is to have your subject close to the camera and the background far away. Try to borrow on or other of those lenses you have listed and see what you can do with it. For serious macro (close-up of flowers etc) I recommend a lens longer than 40mm; there are lenses of 60mm and 70mm with full macro facilities.

Your existing kit should be perfectly capable of what you want to do - once you learn to get the best out of it.

Though your current kit is capable of bokeh, you definitely wouldnt regret atleast getting a 50mm. The example you provided is a clear example of why, the picture isn't sharp at all. Looks like it might have a bit to do with focus as well, but everyone will tell you to learn to work with what you have, its up to you