Thanks JoJu.
I never mentioned MF because the OP was only asking about APS-C and FF. I felt that discussion on the subject might be relevant for the OP in selecting a lens for his use.
I was about to reply "5D has 12.8 MP, 30D 8.2MP, so any lens will outresolve those bodies, but I made very good experiences in getting FF glass. Bodies come and go, the lenses are to stay longer". Depending on how much lenses toni-a has already bought, one could also be tempted to suggest abandoning the old Canon steamer and go for a brand which has more MP and better dynamic range to offer. But then I read some rumors about high MP Canon to come, with a Sony sensor - at least… off course, such a jewel won't be cheap.
Full-frame is generally the best format for ultrawide imaging. It presents the best balance of detail/quality price and size. Of course medium format can be superior, but it also costs much much more, weighs much much more, and may not actually yield a higher quality image. There are many medium format lenses available that are quite bad, terrible even, for the price asked for them.
I know of a Canon Pro who adapted it to his 1D, he said at 18mm there are no visible distortions. Interior shots are great. I like it very much, except that front light behavior with direct sunlight. Just getting a 15 × 15 cm Filterholder, I waited until one is available for less than 100 €.
But it's excellent that Canon now has to offer also a cute lens in that range.
Thanks guys for your unput
Well DOF and details are not major concerns at least for me when talking about ultrawides.
It is more about the perspective and the total look of the photo
my 50mm f1.4 on 30D behaves almost the same as my 100mmf2.8 on 5D when it comes to DOF and IQ however I prefer portraits made with the 100 macro.the faces just look better
Like I said above, perspective is FOV dependent, so equivalent UWA lenses on APS-C and on FF will give the same perspective.
Perspective is not dependent on the field of view at all - it is dependent solely on the geometry between the entrance pupil of the lens and the object.
You may be thinking of f-theta distortion, which necessarily grows as the field of view widens. This is the type of distortion you see in lens evaluations - both barrel and pincushion are types of f-theta distortion. At about 120 degrees f-theta explodes 'inherently' (and I do mean explodes - it increases by almost 5%/degree at 120deg, 7%/degree at 122deg, 10% at 125deg...)
At about 90-95 degrees it may become noticeable, being on the order of magnitude of 1/2% per degree. This inherent increase in distortion is known as rectilinear distortion colloquially. It can be counteracted or removed through strong barrel distortion (this is why fisheyes do not have it, or have little of it) but then of course you have a fisheye lens.
That said, if you increase the focal length you do reduce the angle dependence. A format 5x larger than full-frame that uses a 100mm lens to replicate the look of a 20/21mm lens on FF would have a noticeable amount less...
However, in the Canon scope, the new 16-35/4 IS seems to change the game quite strongly......
Aside it's "problems" with front light (not everybody wants flare in each front light picture), the 14-24/2.8 for Nikon is still a cute lens - but since the thread opener is Canon based, that might be not helpful. Manual focus with Samyang or Zeiss is also something to consider. Yes, full frame has a lot to offer - but compared to the 12.8 MP of the 5D, a couple of APS-C cameras (like the 70D) will show more details in better quality and higher ISO.
), I was only referring to the available lenses. 14-24 is a mighty lens - I never shot with one, but I've worked with files shot with it (on a D3 series camera), and the picture was sharp into the corners at 14mm, f/2.8. Nuts. :wacko: