17-55 F/2.8 IS EF-S = 27.2-88mm... (wanting to upgrade, confusion...)

[realityinabox]

So, I understand the whole 1.6x crop factor because the sensor is smaller than 35mm, I just get confused on the conversion of the numbers.


A 17-55 F/2.8 IS EF-S = 27.2-88mm on a full frame body.


I currently have a Sigma 28-70mm f/2.8 EX DG on my Rebel XT. My queastion is, are these two lenses (roughly) equivelent in length when taking the 1.6x into consideration, or is the EF-S lens still 11mm shorter on the short end and 15 shorter on the long?





Sorry is this type of thing gets asked often, but I checked the first page and didn't see anything related.

[Jarhead5811]

is the EF-S lens still 11mm shorter on the short end and 15 shorter on the long?

Yes, check out Bryan's explanation: Field of View Crop Factor (Focal Length Multiplier).


The focal lengths listed in the specs are always actual focal lengths unless listed as 35mm/full frame equivalent.