I have a two part question - and probably something that has been thrashed to death before so excuse my ignorance please.

Firstly, how do people do their own lens tests? I have read somewhere about putting a sheet of newspaper on the wall and shooting at all apetures - is this how it is done? Or do people prefer to test out in the field?

Also, do you shoot 100asa slide to test the lens, or print film - (given the inconsistancy of print processing I'm guessing slide)?

In lens 'tests' the word "soft" will often be used, especially when talking about a lens wide open. Is this softness a perceptable thing in 8x10 enlargements, or more of a scale thing that you would have to be a scientist to appreciate and identify?

The reason I ask is because I am at the stage of A: wanting to test my Nikkor 70-210 4.5/5.6 which I'm not sure is all that "sharp" - and also B: looking to purchase another lens in the 28-80 zoom area.

For the price, lenses like Sigma's 28-70 f2.8 and Tokina's 28-80 f2.8 look very attractive (I haven't got a huge budget, and am going to have to save for a while to get it anyway). But owning a Nikon, I would of course rather get a Nikkor for it - but the money is a factor (I can't really aford a Nikkor 2.8, even second-hand) and would have to start looking instead at the Nikkor 28-105 3.5/4.5 - foregoing the 2.8 fstop.

But then there are those lens test again that talk about "softness" in the sigma's and tokina's, and that scares the hell out of me. Does anyone have any experience with these lenses (or other sigma's, tokina's, tamron's etc).

Does anybody test their lenses before they buy?

Sorry about all the questions, but this whole lens question gets me uptight - especially since it's the lens that determines image quality (yeah, I know - buy the most expensive one you can afford - right)? But how good are Sigma's etc... if that is what I can afford?