Help My lens will not auto focus

[chunkey20012001]

hi guys just wondering if i can ask a quick question i bought my nikon 80 - 200mm lens 1:2.8 ED from jacobs a couple of days ago and i have been playing around with it in the house and i notice that the lens will only sometimes auto focus some times really fast as i would expect but other times the shutter just captures a blurry image is there any thing i can check before i take it back as i dont want to look like a wally but the lens has cost me alot and i want the best results from it.

I have the lens set to auto and same with the camera(D80) i notice that at the top of the lens it also has a switch saying limit and full which setting should i choose???

Any help is much appricated

Chunkey20012001

[Gareth_R]

you need to choose "full"

[digitalfailure]

the limit switch will prevent the lens from focusing on things within a certain distance limit.

For the sake of eliminating that as being a cause of the failure to focus, set it to full and try to get a focus lock on items ranging in distance. You should also be aware of the minimum focus distance as you'll never get it to work within that area.

[chunkey20012001]

ok thats a great help guys if this doesnt work then could it be the connection points ???

[digitalfailure]

if the lens is functioning and you have no error messages on the cameras display I'd say the contacts are fine.

give the lens a good test in the morning.

[fletch5]

i dunno bout nikons. but if the canon 40d cant focus it wont let you shoot unless you shift to manual, what shutter speed you using, from what i heard have you got the shutter speed above 1/200th or on a tripod?

[chunkey20012001]

i didnt know that about the shutter spped is this fact or myth???

[alex_m90]

i dunno bout nikons. but if the canon 40d cant focus it wont let you shoot unless you shift to manual,

The same is the case with the D80, unless you turn the AF off. :thinking:

[fletch5]

you didnt say it was the IS/VR model, so the general rule of thumb, is a shutter speed equivelant to your lens length, so a 200mm lens will mean a shutter speed of 1/200th in general to eliminate handshake, if your on a tripod or have a very steady hand you may manage to go lower, but im sure someone will pop along and confirm or tell you im talking rubbish shortly.

the vr model will eliminate some handshake so that you can go lower in shutter speed.

[chunkey20012001]

ok thanks guys great responses and really quick much appriciated

[chunkey20012001]

does the shutter speed apply to each focal length ofthe lens eg. if im using it at 80 mm should the spped still remain at 1/200 or should it be 1/80

[Chappers]

Rule of thumb Shutter speed= focal length. But you need to take into account the cropped sensor. so 80mm gives field of view equal to 128mm so shutter speed = 1/125 ( minimum).

Don't forget if you have fast moving subjects that you want to capture you need to increase the shutter speed beyond this

[chunkey20012001]

ok thank you very much

[pearce_jj]

I find that some lenses are better at focusing than others. I find the nifty a bit tempramental at times whereas the £30 28-90mm is always spot-on.

I usually shoot with one focus point selected - maybe it depends on something other than a smooth bit of colour being at that particular point.

[chunkey20012001]

yeah thats true thanks again for the help and i have tried the lens out and its working spot on now and im once again happy with my purchase