Lens Question

mangobreeder

mangobreeder

mangobreeder

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3 Mar 2008
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Im looking to get a

Tamron 10-24mm f3.5-4.5 Di II LD AF SP Aspherical (IF)

It will be going on mt 450D, which as we all know is not full frame. but the lens aboveis designed for crop sensors.

My (dumb) question is, what effective Focal length do i get with this lens, is it 10mm or 16mm, (10mm X 1.6)?
 
AtticusFinch said:
Always x1.6
Click to expand...

What he said.
For reason of marketing and to lessen confusion, all lenses focal length are market at 35mm film size, even if it's for cropped. Took me a little while to get use to it.

By the way, I'm looking to sell my Tamron 11-18mm if that floats your boat. It's in MM.
 
mangobreeder said:
but arnt Di-II Lens designed for crop cameras? if so i though you would get the 10mm not 16mm eqv?
Click to expand...

What this essentially means is that the lens will not work on a full frame camera. This is due to the image "circle" that the lens provides to the sensor being only large enough to cover a crop sensor. On a full frame camera you would get significant vignetting (not to mention possible rear of the lens clashes with the mirror!).

As said all lenses specify their 35mm equivalent focal length, this should always be then modified by the multiplier value of your crop, which is 1.6x in this case.
 
Also

mangobreeder said:
but arnt Di-II Lens designed for crop cameras? if so i though you would get the 10mm not 16mm eqv?
Click to expand...

The ff vs cropped frame issue means that the cf lenses are not designed to prodcue effective images on ff cameras.

ff lenses are designed to work on both ff and cf cameras, on a cf camera less of the lens area faces the sensor and this is where the 1.6 multiple on fl appears.
 
All lenses designed for crop sensor cameras (Including Canon's EF-S lenses, among others) still have their focal lengths advertised in 35mm format.

So yes, you still need to multiply by 1.6.
 
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