TriX Loc: Raleigh, NC

Since the 18-135 is an f 3.5-5.6 aperture lens and the 24-105 is an f4 constant aperture, then the focal length range and the f stop are two of the most relevant aspects of the discussion and the OP's decision. If he were to believe the misinformation, he might think that the 24-105, being a FF lens, would be either f6.6 or f2.5 depending on whether the f stop was multiplied or divided by the crop factor (the person who posted wasn't too clear as to how the "crop factor" affected the f stop), and that could be a deciding factor in his decision.

Now whether simply stating that it was incorrect is enough or whether actually providing a reason is required is open to debate, but generally, when someone gives me information, I want to actually understand the reason why - you (or the OP) may have a different opinion or interest in learning. Either way, understanding aperture and what f stop means seems pretty basic to me, and I think something that would be important to anyone learning about photography, but again, that's just my opinion. Just trying to provide useful information here, it's not especially complicated, and you or the OP can easily disregard it if you find it unhelpful.

Gifted One Loc: S. E. Idaho

Perhaps it just comes down to dollars and cents or sense. In any case it leaves people talking to their selves.

J. R.

Architect1776 Loc: In my mind

So what useful information have you given about this lens specifically that answers the question of getting it?
Aperture theory is fine but you have not quantified if the lens is worth an upgrade? Explaining FF and crop sensor relationship of the aperture is pretty distant as to a quantifiable quality question. I would dare say knowing if the lens is sharp, easy to handle, perhaps weight being a factor if it is very heavy or light, durability lots of far more important "Upgrade" reasons or not.

To the OP as I said at the beginning. This is a great lens, sharp, uses 77mm filters like the next step you would make the 100-400mm does. It is a great standard lens to keep on your camera. I have found mine to be a great upgrade from the non-L glass you are using.
One other thing it will function perfectly on any EOS camera ever made whether it is a film or digital EOS. You will not lose any functionality no matter the camera so as you upgrade a camera or find an old classic EOS film camera to try film with this lens will have absolutely no problem working with any of them. Nice perk of the L glass.

jhs7931

I want to thank you for "refocusing" on my original question. Very helpful comments. ...:)