Sigma 10-20 on Four Thirds... crop questions.

cokebottles · 31 Jan 2008 at 10:44

I've mentioned before, that Im planning to move away from my Olympus E-330 in the near future, onto a Canon or Nikon where I have a greater choice for lenses. My first planned purchase after a body+lens kit would be a Sigma 10-20mm BUT it has just been released on Four Thirds (which fits my existing camera).

I'm not sure if this is sufficient in meeting my wide-angle needs as the crop factor on Four Thirds is 2.0x as apposed to 1.5x on a Canon or 1.6x on a Nikon. This would be mean I could achieve a 35mm equivalent range of 20-40mm if I buy the Sigma 10-20 for my current cam, or roughly 15-30mm if I change over to Canon (at an obviously larger cost).

My question is: how much would I lose (field of vision wise) being at 20mm as apposed to 15mm? Does anyone have any pictures that could help me visualise this. Also is there a way to work out the field of vision angle for different focal lengths.

thanks guys.

Messiah Khan · 31 Jan 2008 at 10:49

cokebottles said:
Four Thirds is 2.0x as apposed to 1.5x on a Canon or 1.6x on a Nikon.

Other way round.

Four thirds: 2X
Canon: 1.6X
Nikon: 1.5X
Canon 1D: 1.3X
Canon 1ds/Canon 5D: 1X
Nikon D3: 1X

a1ex2001 · 31 Jan 2008 at 11:45

I'm not sure that the 4/3rd's cameras would really benefit from this lens the oly kit lens is already 14mm so your spnding a lot fo not much more and and 20mm is not really super wide.

this was one of the key things that put my off the oly stuff I was seriously considering an e510 but I live ner the peak disrict and really wanted to be able to have a wide option when out there for a sensible price!

cokebottles · 31 Jan 2008 at 12:38

It is a shame. I really like my E330, its far from perfect, but has some cooool feature. I imagine the E510 with IS in the body would be pretty sweet, shame about the lack of wide angle lenses, except for the $$$$ Zuiko Digital ones. I think I will stick with the idea of switching over still then.

Still: some pics of diff focal lengths would be cool - and still if anyone knows how to work out FoV angles- would be nice to think about this stuff.

sean · 31 Jan 2008 at 20:05

cokebottles said:
Still: some pics of diff focal lengths would be cool - and still if anyone knows how to work out FoV angles- would be nice to think about this stuff.

I used an FOV calculator for these. At 10mm the horizontal FoV would be ~96 degrees on a 1.6x crop Canon or 82 degrees on a 2x crop system. The 10-20 on 4/3rds projects and APS-C image circle so using the sizes of each sensor I made this simulated comparison of the crop on 4/3rds:

Image courtesy of J. Star on Flickr. Used under a Creative Commons license.