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EF-S 17-55mm f/2.8 IS USM - Focal Length Confusion

Started Oct 10, 2012 | Discussions thread
Olga Johnson Forum Pro • Posts: 24,360
Re: EF-S 17-55mm f/2.8 IS USM - Focal Length Confusion

ryllz wrote:

Hi All,

I am very new to DSLR photography and have just recently purchased the T4i with the 40mm 2.8 lens.  To upgrade the lens kit that came with my camera 18-55, I am contemplating purchasing the 17-55 2.8 based on all the reviews I have read here and other sites.

My question is this: If the EF-S 17-55 was specifically made for the APS-C DSLRs and is not compatible with the FF cameras then why would the equivalent focal length still be at 27-88mm on the APS-C DSLR??  This confuses me a whole lot and i've read quite a bit.  I still have not found the explanation.

Based on my question above then what type of camera should I buy to take advantage of the actual 17-55mm focal length that I am planning to buy (obviously not an APS-C and this does not work on a FF so what are my other choices??)

Please forgive this very amateur question but it confuses me to no end.

Thanks in advance for the responses.

Ryll

Since the camera can use EF as well as EF-S lenses, imagine the confusion folks would have if the EF-S lenses were using a different focal length measurement than the EF lenses while providing the same field of view and depth of field.

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Olga

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