Inspecting a lens for purchase

I'm 87% sure I'm going to buy the 85L f1.2 mkII. I've been told that one should take time to physically inspect the glass before buying a lens.

How should I inspect this? What should I look for?

The cost of this lens is significant to me so I want to make sure I get the best lens possible.

Thanks for helping.

Well, I don't think I've ever had an issue with the lens elements when purchasing a new lens, and I'm not sure why you were given this particular bit of advice, but if I were to follow it, I would look at the front and rear elements and inspect for scratches or chips on the lens elements, or bubbles within the glass. Some people get all upset with minor discoloration of the lens coating, but it won't affect the image quality and in my opinion is not worth fretting about.

Mark

DaleRob wrote in post #2106068
I'm 87% sure I'm going to buy the 85L f1.2 mkII. I've been told that one should take time to physically inspect the glass before buying a lens.

How should I inspect this? What should I look for?

The cost of this lens is significant to me so I want to make sure I get the best lens possible.

Thanks for helping.

Only 87%, that's a very precise amount of 'sureness'

Just do a visual inspection for anything obvious, marks, scratches etc. and dust inside the lens assembly itself - just common sense really.
Try the focus ring to see if it's smooth and not too stiff, although these can 'loosen' with a bit of use.
If you can try it on the camera and check the images in the store then even better.

I'm guessing the advice is to look for scratches or other flaws in the actual optics.
It's certainly the first thing I do. I only once had a lens that came with the "Dealer installed scratch option". But I did in fact return it without even trying it. (fortunately I was in the shop and simply handed it back to them, in all likelihood the scratch had occured at the shop )

DaleRob wrote in post #2106068
How should I inspect this? What should I look for?

The problems I see here most often with any lenses are focusing errors and image quality issues. Thus, when I buy a lens, I mount it on my camera, take some pictures inside the store and of the landscape in front of the store, and inspect them at high magnification on the camera's screen.

So far, I've never found a lens that wasn't acceptable, but it's an easy test to conduct. It also gives you an opportunity to determine if the ergonomics of the lens are workable.

If they have several, they might let you compare them. But I would be exceedingly careful with them if you do that, and if you have a problem, show them clearly what concerns you--it might be a usage issue.

Rick "who would rather pay more to try it out first" Denney