Attached Link: Sigma lens designations

I believe that the DC designation is designed for the crop sensor while DG is how Danny described DX. I think there may be a little confusion here with EX which is the designation for Sigma’s Pro range lenses.

http://www.sigma-imaging-uk.com/support/abbriviations.htm

 

35mm is the closest you will get to a FF 50mm on a canon 1.6 crop.

Yes you will inherit the distortions associated with wide angle. That is because you are not changing the actual focal length on the lens, all you are doing is changing the FOV

 

Using a 50mm lens will be your best bet if room is available.

 

Let us not forget this is not really a new issue, the difference in FF to crop censor can also be compared to a 35mm and medium format film, where a 50mm lens would be a 50mm lens, the same lens would be much wider on a MF body (if it fitted it)

If I remember correctly (long time since I used MF) an 80mm lens on a FF body is approx equivalent to 50mm on MF so the conversion factor is approx the same (from fading memory so I could be slightly wrong)

 

I think it is probably time to forget about the equivalents to a certain degree when buying lenses, and think more about what the apparent focal length is and the effects it will give you.

They wouldn’t have made the cane if you weren’t meant to break the rules