Should I get the Samyang 14mm or 16mm for astrophotography on APS-C?

[HenryHunt]

Hi,

I've never properly got into astrophotography (though I have experience with it) before and am going to Yosemite in July. This is a great (no light pollution) opportunity for me to try to master astrophotography and get some great shots there, but I'm having a hard time deciding on a lens to buy for this. I'm torn between the Samyang 14mm f2.8 and the Samyang 16mm f2.0. I have two APS-C cameras (Canon EOS 60D and 700D).

I had initially decided to go for the 16mm because of its wider aperture and the fact that it is specifically designed for APS-C cameras (according to the description). However, I am now not sure and am considering the 14mm instead because of its shorter focal length.

How much difference will f0.8 make and how much difference does the fact that the 16mm is specifically designed for APS-C cameras make (I'm not actually sure what designed for APS-C means anyway)? Will images turn out bad if I use the non APS-C designed 14mm on my APS-C cameras?

Ultimately, would you recommend I go for the 16mm or 14mm? I know the 14mm is very widely used, but the wider aperture and 'designed for APS-C' is swaying me towards the 16mm. Which one would you say is best?!

Thanks.

 

[mdruziak]

Why not consider the 12mm f2.0? It's a great lens that you can use for a lot more than astrophotography. I use one on my Fuji camera and it's every bit as sharp as my Canon 17-40 L Series lens but a LOT cheaper.

One other reason to consider going as wide as you can is that you can always crop your image in post if you need to. There is nothing you can do if your lens isn't wide enough especially when doing astrophotography.

So the deal with APS-C vs full frame lenses - With the Canon system, you can use a Samyang APS-C lens on a full frame body, but you will get big time vignetting (actually the frame will be masked and only use the center portion of the sensor). The "designed for APS-C" lenses are usually smaller and cost less than the full frame lenses.

 

[HenryHunt]

I had looked at the 12mm f2 but unfortunately they only do it in M mount for canon. That's what led me to choose the 16mm.

 

[TCampbell]

I have no experience with either lens. Sometimes lenses exhibit some poor optical effects at extremely low focal ratios (coma, field flatness, vignetting, etc.) If the lenses are optically equivalent at their respective lowest focal ratios, then f/2 wins over f/2.8 because you collect twice the light at f/2 as compared to f/2.8 and the difference in (assuming no tracking mount) isn't much different (23 seconds vs 26 seconds).

However, if the f/2 lens is optically inferior at f/2 and needs to be stopped down... then it's no longer necessarily the winner.