Buying a lens

[bob hastie]

I've recently bought a Canon 30d and plan over the next few months to extend my range of lenses.
I have heard of particular lenes being bad copies of that lens. What can I do in shop to test the lens I'm about to buy in order to sort the wheat from the chaff?
Specifically my next lens (next week maybe) will be the canon 100-400, so any information about this lens willl be great but general information will help also.
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Bob

[eeyore]

thisis the link to the canon spec page http://www.canon.co.uk/For_Home/Prod...5-5.6L_IS_USM/

as far as dodgy copies go if you buy from a respectable canon main dealer this shouldnt be an issue, check out the add is the back of amateur photographer.

[Boddie]

I was thinking the same.

Certain reviewers intimate that their personal lens is a 'bad un'. I think what Bob means is that certain reviews state that the user has received 'one amongst a batch' which is not good throughout the range.

And to this point he wants to know how to test.

I dont think he means that they are counterfeit

[eeyore]

Originally Posted by Boddie

I was thinking the same.

Certain reviewers intimate that their personal lens is a 'bad un'. I think what Bob means is that certain reviews state that the user has received 'one amongst a batch' which is not good throughout the range.

And to this point he wants to know how to test.

I dont think he means that they are counterfeit

In that case the best bet is to put it through its paces , take shots at all points in the zoom range, test how fast it focuses, get a feel for how it moves, try the IS in both modes ete etc. Idf the salesman is impaitent with all this then find a more understanding dealer

Another good point is to remember to take your camera with you as it wont necessarily behave the same on yours as it does on a shop model.

and finally once you have bought it make sure you put it through its paces as soon as so if there are any issues you can exchange it asap - although it will have a 12 month waranty they are more likely to replace rather than repair if you go back as soon as possible after purchase.

[Boddie]

I have seen the sort of reviews Bob is talking off where people say that it is not sharp across the range etc, so they send it back and the replacement is far better. I guess thats just bad luck. What would you suggest is the best way to check a lens over itd length. Say a 300 mm lens.

I saw a good reveiew where a guy took photos of a plant pot which had a bar code on the side of it. The plant and barcode were obviously studied. But what sort of distance would you need it at for say a 300, 400 or 500 mm lens and would the lighting have to be perfect?

Cheers

[bob hastie]

Thanks for the quick replies guys.
Sorry I did'nt make myself too clear in my first post, I was indeed looking for tips on how to test the lens.
Is there any way to easily compare the optical quality of one lens against another. ie if I have 2 lenses offered to me what type of shot should I take to really show any slight diferences between them

[Boddie]

I think short of taking a laptop with you...

This chaps exercise is good http://kenmcvayphoto.clymbers.com/ar.../sigma800.html


See how he uses the plant and the barcode? But of course he did this at home

[eeyore]

Originally Posted by bob hastie

Thanks for the quick replies guys.
Sorry I did'nt make myself too clear in my first post, I was indeed looking for tips on how to test the lens.
Is there any way to easily compare the optical quality of one lens against another. ie if I have 2 lenses offered to me what type of shot should I take to really show any slight diferences between them

I'll have a thunk about that and get back to you - I have to say tho that I have never bothered, after all most canon lenses are excellent so you'd be very unlucky to get a duff one and you have the warranty to fall back on if you are that unlucky...

A lot of dealers dont routinely carry the 100-400is so the chances of them just happening to have two in stock is slight - you need to ring before travelling to make sure theyve got it at all in a lot of places.

[Boddie]

Is this a push pull lens. People complain of dust but where does the dust go, and how do you get rid of it?

[eeyore]

Originally Posted by Boddie

Is this a push pull lens. People complain of dust but where does the dust go, and how do you get rid of it?

yep its a push pull aka the pump - and the dust either ends up inside it or on your sensor - in the former case it needs to go back to canon , in the latter their are numerous methods of cleaning it which have been discussed on other threads.

However in normal use this wont be a prob, but it is in very dusty environments like beaches or raceways.

another thing to consider is if you are planning on using it in the street it isnt very "covert" resembling a bright white traffic cone - in tyhis instance you might be better off with a bigma or the tamron 200-500.