Whether or not you use a filter, a lens hood will protect both FAR better than either filter or sans filter. Particularly on a lens like the 24-70, where the hood is 2+ inches deep. It has to be one heck of an impact to destroy the hood to the point that anything can even touch the front element. You might think "oh it's only plastic, it'll shatter in a million pieces" but no, that's not what happens. Even if you strip the mounting bayonet, it will tend to ride up around the lens, and unless you hit it EXACTLY straight on with SIGNIFICANT force, it will bend and not break. If you hit it with enough force to really disintegrate the hood, you not only have the potentially of a broken front element, you probably have other elements decentered and you're very likely looking at a bent lens mount on either the lens or the camera.
How much does it take? Well, this summer I tripped and fell on my 60/f2.8 AFS Micro, which has a small but very exposed front element. The hood was mounted, and I had no filter - it was a bright sunny day. The mounting bayonet was shattered into about ten pieces, but the hood stayed roughly around the lens, despite hitting a railroad rail - and a man (me) falling on it from behind. No damage to the front element, but one or more elements were decentered and the mount was bent. That cost $220 to repair. Plus another HB-42 hood cost $33. I know from experience that an HB-40 used on the 24-70 is about the same price range.
_____ Brian... a bicoastal Nikonian and Team Member
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