Good Lens, Bad Lens

[jgbkab]

I've decided that I'm ready to make my next lens purchase and I've been doing extensive research. One site that I have been using is the Photozone web site because they have quite a few reviews on Canon lenses. One thing I have noticed is that they sometimes get bad lenses from Canon. How can you tell if a new lens you've purchased is good or bad? I would imagine that it would take a while to actually figure it out (unless you're a pro). So how would an amateur go about recognizing a bad lens?

[Dodge]

I always do a ton of reasearch on any lens before I buy. Just type it into Google with the word 'review'. This will give you a good idea on how more experienced users rate a lens. Regarding your own testing, you could search flickr groups that are dedicated to a particular lens and look at sample images, comparing them to your own etc. This will help discern wether your results are limited by either the lens or user experience, comparing colour/sharpness etc.

There's also more technical aspects to take into account, speed, glass quality etc, but I'll let guys more knowledgable go into that side of things. I guess the best test of wether or not a lens is any good for you though is the images you see produced with it and what you want to do with it. IE, once you decide what you want to shoot with it, which type of lenses are best suited, then you can narrow it down to the best one within your budget.

[Aegea]

With any new lens I always start by taking a set of shots of a test chart under controlled conditions indoors. I seem to end up returning about 50% of the lenses I try.

[jgbkab]

Thanks Dodge. I've already decided the lenses I'm going to purchase but not the order. What I meant was that for instance with the Canon 17-40mm f/4L, the reviewer had to send the first three lenses back to Canon because they were not within specs. What is it that I would look for to find out if the lens needs to be returned?

[jgbkab]

Originally Posted by Aegea

With any new lens I always start by taking a set of shots of a test chart under controlled conditions indoors. I seem to end up returning about 50% of the lenses I try.

Oh okay. I didn't realize that on the reviews they were taking pictures of actual pieces of paper *facepalm*

[Biomech]

You often get things like this:

http://www.informatik.uni-bremen.de/...0f4.0%20CV.jpg

Where they show parts of the text photo in various areas, so the centre is generally the sharpest, then the corners/edges the most blurry by comparison.

[Dodge]

Originally Posted by jgbkab

Thanks Dodge. I've already decided the lenses I'm going to purchase but not the order. What I meant was that for instance with the Canon 17-40mm f/4L, the reviewer had to send the first three lenses back to Canon because they were not within specs. What is it that I would look for to find out if the lens needs to be returned?

Oops. gotchya. More about getting a good copy of a lens