digital tele lens advice please

I'm currently using an old but very good Vivitar series 1 (markII) 70-210 zoom on my new *istds. It works very well at the football as you can see here http://www.ephotozine.com/gallery/showlargepic.cfm?photoid=189066

The manual focus is relatively simple as everything is almost at the infinity setting anyway fom my seat in the stands, so very little adjustment is required. For things like woodland shots of birds though it is very difficult to focus quickly, just because of the wide area covered on the barrel, and usually by the time i have focussed the bird has flown.

I have looked at a couple of sigma autofocus lenses
http://www.jessops.com/search/viewproduct.cfm?PRODUCT=SIG703004DMS2PAF&BRAND=&CONTINUE=false&FEATS=&FIRSTPRICE=0&KEYWORD=&LEVEL=&MODELNUMBER=&NEWQUERY=True&NODE=143&ORD=ASC&ORDERBY=&QUANTITY=10&RECENT=0&REFINE=&SEARCH_FOR=&SEARCHNODE=0&SEARCHURL=dointellisear


http://www.jessops.com/search/viewproduct.cfm?product=SIG552004DCSAF&BRAND=&CONTINUE=false&FEATS=&FIRSTPRICE=0&KEYWORD=&LEVEL=&MODELNUMBER=&NEWQUERY=True&NODE=143&ORD=ASC&ORDERBY=&QUANTITY=10&RECENT=0&REFINE=&SEARCH_FOR=&SEARCHNODE=0&SEARCHURL=dointellisear&SECONDPRICE=&SHOWCASEID=&STARTROW=1&SUBS=&WORD_SEARCH=N&
and wondered what others thought of them or any (cheap!) pentax gear on the market. My budget is low, around 150 quid max.
thanks in advance
john

this is a better link http://www.jessops.com/search/viewproduct.cfm?PRODUCT=SIG703004DMS2PAF&BRAND=&CONTINUE=false&FEATS=&FIRSTPRICE=0&KEYWORD=&LEVEL=&MODELNUMBER=&NEWQUERY=True&NODE=143&ORD=ASC&ORDERBY=&QUANTITY=10&RECENT=0&REFINE=&SEARCH_FOR=&SEARCHNODE=0&SEARCHURL=dointellisear

John,
I have an old Sigma 70-300mm, and it's not very brilliant. Cheap and cheerful I think is the term! Lacking in contrast, and generally a bit wishy-washy on the *ist-D.

On the other hand, I picked up a second hand Pentax SMC-F 70-210 off ebay, and that is wonderful. Lovely and crisp, with great contrast. I've used it along with the Pentax SMC-F 1.7x AF convertor and the two work well together.

Hope that helps,
Matt

The Pentax lenses have the edge IMHO.

With the 1.5x focal length multiplier, because of the APS sized CCDs, telephoto lenses are not really the problem with digital SLRs. Just choose a good quality one to avoid chromatic abberation.

Wide angles are more difficult, although the new digital-only zooms look very promising.

Thanks chaps, for the wide end i got the 18-55 pentax DA which i am so far happy with. I saw a new 75-300 FAj on the park cameras website yesterday at 109.99gbp and thought it would be worth a go at that price. It came today and I'm hoping to try it out tomorrow. I have seen negative comments about it above 200mm, but because of the 1.5x multiplication i doubt I'll use it at that sort of focal range very often (nice to have it in the bag though!). I also wonder if people who are complaining are using the correct support/settings for such a long focal length.
At least if it is a bad 'un it's a cheap bad 'un and i can get rid of it and try something else.
John

I invested in a Sigma 70-200mm f2.8 lens and a matched teleconverter.
Loving it!

Keep an eye on e-bay because second hand decent ones come up from time to time.

I'm not a good photographer but my half decent efforts have becone 25% better with the new lens... and 25% on to half decent makes 62.5% decent. Which I call a result!