Originally posted by Ira I'm looking for a seller of hard metal lens hoods like this, but for the OP, this linked listing is incorrect and giving erroneous information:
Well, if I'm reading the OP's intent right, this (the 58mm tele hood) should work OK on a 100-300, especially on a digital sensor. (I'm speaking anecdotally, basically, Samski, but you should be pretty safe there. There are a few variables about it: essentially it has to do with angle of view and how wide the actual element being covered is, as well as the diameter of the hood. )
Definitely isn't going to work on a 24mm of the same filter size, though: you'd need something less deep.
(If you're looking, Ira, this seller carries just about everything in S&W hoods, which I favor when I can't find round hard plastic. Looks like he has a couple of styles of wide ones, even. They're good quality for the money, probably as much as you'd need (Occasionally a finish blemish turns up, but they're usually actually kind of pretty. We used to stock the brand in a store where I worked, a long time a go.
He's a good seller, too. Cause he stocks this brand, he's pretty much my go-to-guy for hoods and step rings. )
For the OP: Petal hoods usually aren't the way to go for teles: if so, the only one you'll likely find that's good is one made by the lens' manufacturer for that lens: most aftermarket petal hoods are made quite short. If you like the idea of a rubber one, the kind sold as three-position ones are probably the only ones deep enough to provide good coverage for a longer lens.
They can be convenient except that they tend to be kind of big in diameter, which is a drawback for me because I usually like to carry my lenses front-down in bags. I have one for a rather hood-fussy wide to-tele zoom which I actually call 'The Front Porch' (it's a much bigger size than you're looking at, but you actually can't see me when I'm shooting behind it.
Really does the job well, though, for that sort of lens. )
I'd choose the metal one for that 100-300, though, nice and deep.