Sigma/Tamron lenses
 

I have a Canon EOS 600D with
[LEFT]Canon 18-55mm EF-S F/3.5-5.6 II
Canon 55-250mm EF-S F/4.5-6 IS II
Canon EF 50mm F/1.8 II

I like photographing landscape / Birds please suggest Sigma or Tamron Lens which is better than 55-250 and I am on budget so prime lenses are out of question
[/LEFT]

I have the exact same kit as you've listed. On recommendations and having done some research I have added the following Sigma lenses:

[B]10 - 20mm F4-5.6 EX DC HSM[/B]

[B]70 - 300mm F4-5.6 DG MACRO[/B]

They are both great lenses in my opinion and produce good quality images. As well as both coming with a lens hood the 10 - 20 is the EX variant ( Sigmas answer to Canon L series ) and is supplied with a carry pouch.
With the 1.6 crop factor the 70 - 300 gives you 480 zoom equivalent, I've had some great images of the moon and birds using a nest box at the end of my garden.
On Amazon the 10 - 20 is around £300 and the 70 - 300 is £95.
Hope this helps and happy shooting.
Pete.

thanks a lot Petethebear

i would say the canon 55 - 250 is a better lens than the sigma 70 - 300mm apo dg macro lens
first and foremost is the canon lens is IS the sigma is not
the sigma is quite soft at the 300mm end where the canon is acceptable at 250mm

the difference in the lenses isn't worth the extra 50mm and if it's garden birds you are taking photo's of you would be much better off saving a little extra cash and going for a sigma 150 - 500mm OS lens

if your really on a tight budget there is a sigma 170 - 500mm apo dg lens that can be had for not a lot of money second hand ( no longer in production ) but if you come across one make sure it is the DG version and not the older model
the older model is not suited to digital SLR's inless it has been re chipped by sigma

the sigma 170 - 500 stays sharp up to around 420mm after that things starts to get a little softer but still acceptable

i have been down the sigma 70 - 300mm route and it's price reflects it's performance it's pin sharp at 70mm but above 200mm it's not that good i replaced it with the sigma 170 - 500mm apo dg lens ( before th 150 - 500mm OS existed ) and found it to be a much better lens but as already mentioned above 420mm it started to lose sharpness

I have to agree the 55-250 is a really nice lens and scores in iq stakes. If you are looking for something longer then look at a second hand canon 100-400L

[QUOTE=wave01;84331]I have to agree the 55-250 is a really nice lens and scores in iq stakes. If you are looking for something longer then look at a second hand canon 100-400L[/QUOTE]

The canon 100-400 lenses seem to go for silly money on EBay as I have been watching them.

One ended today @ £840 + £15 postage.

I have been looking on a website called Panamoz.com and they are selling for £967 New with 12 month warranty I know they are grey imports but when you are saving around £300 its worth looking at they also pay any import taxes etc.

Thanks Cosmicma and Wave01 but I think I will go for [URL="http://smartshoppers.in/product/canon-ef70300mm-f456-is-usm-lens/"]Canon EF 70-300mm f/4-5.6 IS USM Lens
[/URL]

[QUOTE=acmerchant;84381]Thanks Cosmicma and Wave01 but I think I will go for [URL="http://smartshoppers.in/product/canon-ef70300mm-f456-is-usm-lens/"]Canon EF 70-300mm f/4-5.6 IS USM Lens
[/URL][/QUOTE]

In reviews I have read that lens has come out worst on image quality than the 55-250mm IS, I had the canon 70-300 and never liked the images it produced they seemed soft and lacked definition but then I may of had a poor sample, I changed to a Tamron SP AF 70-300 F/4-5.6 Di VC USD and found it to be much sharper and has better IS than the Canon!

[QUOTE=wavemachine;84383]In reviews I have read that lens has come out worst on image quality than the 55-250mm IS, I had the canon 70-300 and never liked the images it produced they seemd soft and lacked definition but then I may of had a poor sample, I changed to a Tamron SP AF 70-300 F/4-5.6 Di VC USD and found it to be much sharper and has better IS than the Canon![/QUOTE]Yes, not well reviewed at all.

[QUOTE=donoreo;84384]Yes, not well reviewed at all.[/QUOTE]

Mind you the L version is a different story but it isn't cheap!