Tamron 18-250, not really 250. Really not 250.

[winniv]

Hi,
After a friend of mine alarmed me, I ran a test of my 18-250mm Tamron lens. This time, it wasnt about quality, sharpness, focus. This time, it was about the mm that the lens claimed to cover. The results were amazing: Compared to my Canon 70-200 F4, 250mm on the Tamron seemed the same as to 135mm on the Canon. And the max zoom of 200 with the Canon was way closer than the claimed 250 on the Tamron.

Because of it's versatility, this lens is often my walk-around lens. And I realize that, even if it were 135mm, it would still win that contest. But I do feel taken for a fool by Tamron.
Anyone care to test for themselves? Is this just my sample?
Anything we can do about this? Dont really know where to go. I dont expect any help from the shop.

Winni

PS I know I will use my 70-200 more often from now on. And I cannot wait for the tests on Canon's new lenses. I've always been disappointed about Canon's collection of walk-arounds on APS-C. Even with the recent news, I wish those 15-85 and 18-135 EF-S would have been with fixed aperture of F4 or so.

[Bob Atkins]

Focal lengths are defined for infinity focus. Some lenses drastically change focal length when close focused (it's one way to actually get close focus, especially with internal focus lenses), others don't change as much. It depends on the optical design.

I would not be at all surprised if the focal length of a lens was different from that stated when it's not focused at infinity.

Try the test again on a distant object and see what happens.

[winniv]

You were so right. At infinity, the Tamron clearly provides the extra 50mm. Amazing.
I find it strange that a 250mm lens provides only 130mm in a close zooming situation.
But thanks for your wisdom though.