EF mount on Tamron lenses that are designed for APS-C cameras?

[Mharwood16]

Hi all!
OK this is strange, My mom just bought a 6d. and coming from a 7d she really liked the Tamron 18-270mm mark I and was disapointed that she couldn't use it on the 6d as its an APS-C lens. So I was looking at it today and saw that the mount indicator was red. Which, in the canon world, means its a full frame lens. So i take the lens and pop it on the 6d. Im thinking that i must have missed something and that it really is a full frame lens. But than I look through the viewfinder, and the image is compleatly warped and vignetted. so I look on Tamron's web site and it is indeed a APS-c lens. I then tried the Tamron 60mm f/2 macro which is also an APS-c lens and it looked perfect. So my question is why is there an EF mount on a lens that is designed for an APS-c camera when there is a EF-s mount that would limit it to only APS-c cameras? Is this a Tamron thing? And why does the 60mm Macro look fine while the 18-270 looks terrible? is it that its a prime vs. a superzoom?
Has anyone else had this experience?

 

[neuroanatomist]

3rd party lenses (Tamron, Sigma, etc.) do not use the EF-S mount style, mainly because they are made for multiple OEM bodies (Canon, Nikon, Sigma, etc.), and only Canon uses a short back-focus mount (Nikon FF bodies have a DX crop mode).

Usually, and APS-C lens will have severe vignetting on a FF sensor. Some lens designs use a larger image circle than necessary for better optical quality, which may account for the better perfomance of the 60/2 macro on FF.

 

[wickidwombat]

I still can't get over anyone liking the tamron 18 -270 ..... :-\

 

[Roo]

As far as I know Tamron APS-C lenses are coded as Di II for identification while their FF lenses are just Di.

 

[dgatwood]

I still can't get over anyone liking the tamron 18 -270 ..... :-\

When traveling, lots of folks would prefer a single lens that they can use for nearly everything, rather than hauling around a bag full of lenses and having to swap them constantly, even if that means some loss in IQ. A range of 18–270mm on a crop body is staggeringly good for that, as it is equivalent to ~28–430mm on a full-frame. If the IQ isn't horrible, I can certainly see the appeal. Is the IQ horrible?

 

[wickidwombat]

Is the IQ horrible?

Yes .. Yes it is And the build is atrocious too. I hear the newer one is better though but the Mk 1 is appallingly bad

 

[Mt Spokane Photography]

I still can't get over anyone liking the tamron 18 -270 ..... :-\

Kinda makes you wonder why buy a 6D, when just a good lens would be such a huge improvement.