18-200 vr vs 70-300 vr

Started May 15, 2007 | Discussions thread
Tom Christiansen Senior Member • Posts: 2,239
Re: 18-200 vr vs 70-300 vr

msnikon wrote:

Now i am starting to lean towards the 18-200 because the few times
i will need the 300mm i can just crop it a bit and the 18-200 has
the capability to handel most situations.

I'm afraid it's a bit more complicated than that. At infinity focus, fine,
but when you're focusing on something that's 10 or 20 feet away,
you'll find that the internal focus strategies taken by the more versatile
zoom cut your image into something that looks more like it's been
shot at 135mm instead of the 200mm you'd had it set to. The 70-300
will give you a much larger image when set to 200mm than the 18-200mm
will give you when set to 200mm -- at other than infinity focus. This may
sound crazy, but it really is a very dramatic effect.

You can see this when you try to use a close-up lens as an attachment
to attempt macro work. This doesn't work very well on the 18-200,
but works very well on the 70-300. Here are discrete numbers:

I would say they're not likely to be accurate to more than ¼cm, so I've
rounded in most cases:

18-200 @ 200mm and near focus

ratio close-up maximage
1/3.6 none 8½cm
1/2.7 500D 6½cm
1/3.2 5T 7½cm
1/2.5 6T 6cm
1/2.1 6T+5T 5cm
1/1.7 6T+6T 4cm
1/1.5 6T+6T+5T 3½cm

70-300 @ 300mm and near focus

ratio close-up maximage
1/3.8 none 9cm
1/1.3 500D 3cm
1/1.3 5T 3cm
1.2/1 6T 2cm
1.6/1 6T+5T 1½cm
2.2/1 6T+6T 1.1cm
2.6/1 6T+6T+5T 0.9cm

The very curious thing is that while a 500D lets you capture an image
that's about a third larger than without it if you stick it on the 18-200VR,
on the 70-300VR it is MUCH more effective, suddenly permitting thrice
the normal size! Going from 8½cm to 6½cm isn't all that impressive, but
going from 9cm to 3cm is!

As far as build quality goes, both are mid-grade lenses, neither flimsy
like the 18-55 nor tank-like the way the 17-55 is. However, the 18-200
zooms in two stages, and the 70-300 in only one, which seems a smidged
less prone to wobble.

If you only have the cash for one, then you really should get the 18-200.
Otherwise you'll be walking around with something that's often too telephoto
for the job at hand. However, it's not a substitute for the 70-300 at all.

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