Canon 24-70 f2.8 - need some help

I have an opportunity to purchase a 24-70 for below what I think is below the current market price. It is a local sale, so I will have the opportunity to inspect and try the lens before finalizing the sale. Date code is UR (2006), and the price is $900.

My research has uncovered the issues that have been raised regarding lens creep, and back focusing / calibration issues. My question is: How can I test for image quality, and focusing adaquately prior to buying? Sale will be a face to face meeting (first time meeting) at the local Starbucks. Besides viewing the sample image on the camera LCD (40D), is there any other way to test for image quality.

Second follow up question - is this as good a price as I think it is for this lens?

Thanks for any feedback you can offer.

Smacatl

UR is actually 2003. Good luck with the transaction.

Yep, there are a few used UR around here too, and looks like they will sell for about $1,200 AUD

Best way is bring your notebook, take few pics, fast shutter to determine sharpness, and also take pic of the sky to check if there are dust spots etc, transfer the pics to your notebook and blow up to 100% or bigger, shouldn't take longer than 15 mins, takes 10 mins to wait for your coffee at Starbuck these days anyway...

Bring tripod w/ 2sec delay to eliminate camera vibration as a potential issue.

1) Check focus w/ shots at f/8 from 3, 10, 20ft
2) Check wide open performance w/ shots at f/2.8 from 3, 10, 20ft

Shoot at something w/ lots of color and contrast but static. Check all the images at 100% center and edge.

Always try to separate btw AF, wide open and user error.

djvkool wrote in post #8902055
Yep, there are a few used UR around here too, and looks like they will sell for about $1,200 AUD

Best way is bring your notebook, take few pics, fast shutter to determine sharpness, and also take pic of the sky to check if there are dust spots etc, transfer the pics to your notebook and blow up to 100% or bigger, shouldn't take longer than 15 mins, takes 10 mins to wait for your coffee at Starbuck these days anyway...

Don't mistake a dirty sensor for dust in the lens. I doubt that this method would provide hard evidence of dust in the lens.