Samyang 14 mm f/2.8 vs. Irix 15 mm f/2.4

[soldrinero]

I've been thinking of getting a Samyang 14 mm f/2.8 for a while. I specifically want to use it to try night sky shooting, but I hope to be able to explore daytime UWA photography as well. For flexibility, I was planning to get the Dandelion chip for AF confirmation. While I was looking around, though, I realized that the Firefly version of the Irix 15 mm f/2.4 is only $100 extra at $400, or an even smaller difference once the chip is factored in. Are there other lenses I should be considering? I am price constrained, so the new Samyang/Rokinon f/2.4 seems a little too expensive at this point for a very specialized lens.

I saw TheDigitalPicture's review of the Irix and looked at the comparison tool (http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=1059&Camera=979&FLI=0&API=0&LensComp=1129&CameraComp=979&SampleComp=0&FLIComp=0&APIComp=0). Overall, the Irix seems better. But theres no direct comparison of the coma, which is the Samyang's near-superpower. So, has anyone used both lenses for astrophotography? Which would you recommend?

 

[Khalai]

Lenstip does review coma in their articles and just coincidentaly have Irix 15/2.4 Blackstone review:

http://www.lenstip.com/486.7-Lens_review-Irix_15_mm_f_2.4_Blackstone_Coma__astigmatism_and_bokeh.html

Pros:
Solid, sealed casing with an interesting design
Sensational image quality in the frame centre
Good image quality on the edge of the APS-C sensor
Imperceptible longitudinal chromatic aberration
Low lateral chromatic aberration
Lack of distinct problems with spherical aberration
Noticeably lower distortion than that of its direct rivals
Very low astigmatism
Sensible blurry areas for this angle of view
Very rich accessory kit

Cons:
Monstrous vignetting on full frame
Weak performance against bright light

 

[BeenThere]

I've used the Samyang, and it does a good job for night photography. It has some weird distortion, but it's not real noticeable in landscape images. I've not used the Irix, but lenstip does a good review.

 

[KeithBreazeal]

It's hard to imagine a lens better than the Samyang 14mm 2.8. I really am enjoying the lens for night work.

Milky Way at Shot Rock 21 June 2014 © Keith Breazeal by Keith Breazeal, on Flickr

 

[soldrinero]

Lenstip does review coma in their articles and just coincidentaly have Irix 15/2.4 Blackstone review:

...

Cons:
Monstrous vignetting on full frame
Weak performance against bright light

I found that vignetting measurement odd. They say the vignette is 72%, or -3.64 EV. Aren't EVs factors of two in light? They're using 1 EV = sqrt(2). If I'm right, it should be -1.84 EVs.

 

[Khalai]

Lenstip does review coma in their articles and just coincidentaly have Irix 15/2.4 Blackstone review:

...

Cons:
Monstrous vignetting on full frame
Weak performance against bright light

I found that vignetting measurement odd. They say the vignette is 72%, or -3.64 EV. Aren't EVs factors of two in light? They're using 1 EV = sqrt(2). If I'm right, it should be -1.84 EVs.

I would not get too caught up in the math. If they stated -3.64 EV, that means simply almost four stops of darkening in the FF corners. Which is quite a lot.

Then again, Photozone measured Samyang's vignetting also over -3 EV:
http://www.photozone.de/canon_eos_ff/532-samyang14f28eosff?start=1

Granted, they are not using identical method of measuring that, I guess Samyang has a small lead, but that vignetting is pretty considerable as well.

Canon 14/2.8L is a little better, but also MUCH more expensive as well:
http://www.photozone.de/canon_eos_ff/541-canon14f28mk2ff?start=1

There is also "cosine-fourth" law, so natural vignetting affecting wide angle lenses is something you can't really avoid...
https://en.wikipedia.org/wiki/Vignetting#Natural_vignetting

 

[soldrinero]

I decided on the Irix Firefly 15mm f/2.4. Thanks for your help! I've only had one chance to shoot the night sky so far, but I'm liking what I see. My location had too much sky brightness to shoot the galactic core, so this is pointed North. 11 exposures, 20 s each with in-camera dark subtraction, stacked with Starry Landscape Stacker.

BG9A4638-composite-2.jpg by soldrinero, on Flickr

 

[applecider]

soldrinero

Im looking at your image both on CR and Flikr and both seem really dark to me. Your settings are in the ball park but just for comparison I find that with a 14mm 2.8 25-30sec at iso 3200 or 6400 give me images bright enough to manipulate. And an aperture of 2.4 is not even a half stop faster than 2.8, so times and iso won't vary much.


Bottom line can't see stars in your posted images for what ever reason.