Sigma 50 1.4 sharpness wide open

Hi, I'm new to the forum and wondering if anyone can offer me advice on a Sigma lens I'm using (Nikon mount) - 50mm 1.4.

I have read claims by some that their lenses are just as sharp at 1.4 as 2.8. Is this really the case? Given my past experience with old 1.4s I have found the Sigma 50 to be very good at 1.4, a little PP giving nice portraits but it is not as sharp there as at 2 or 2.8. Has anyone else found the same thing? Am I expecting too much or is my lens not performing as it should?

Any help would be appreciated, thank you.

f1.4 (1/1000, manual focus, no filter, no PP)





f2





f2.8

While this lens is sharp (in the center) at f/1.4, it is definitely not the same as f/2.8. I did some tests of it (on Olympus mount, but optically it is still valid), you can find my results at http://digitalcave.ca/resources/photography/sigma5014.jsp

Cheers
--
--Wyatt
http://photos.digitalcave.ca
All images (c) unless otherwise specified, please ask me before editing.

Sigma is much sharper even in center when stopped down compared to f/1.4:

http://www.lenstip.com/177.4-Lens_review-Sigma_50_mm_f_1.4_EX_DG_HSM_Image_resolution.html

Same applies to Nikon 50/1.4g as well:

http://www.lenstip.com/162.4-Lens_review-Nikon_Nikkor_AF-S_50_mm_f_1.4G_Image_resolution.html

Since the Sigma is sharper at f/1.4 than the Nikon some people make the wrong claim that it does not need to be stopped down for sharpness.

Lenses differ in how sharp they are wide-open, and in how much sharper they get when stopped down, but I don't think there's any lens that doesn't change at all. Even a lens that is "optimized" for shooting wide-open, such as the Noct-Nikkor 58mm f/1.2, gets sharper when stopped down. However, its sharpness curve may not be as steep as, say, the 50mm f/1.4G, so while it may be sharper wide-open, the G catches up or surpasses it a few stops down. (Speaking hypothetically; I don't know how their sharpness curves actually compare.)

I think the general consensus is that the Sigma is sharper in the center wide-open, but the Nikkor catches up by f/5.6. The Nikkor is sharper than the Sigma in the corners at every aperture. However, Thom Hogan's sample of the Sigma was less sharp in the center wide-open, then sharper by f/2, then equal by f/5.6.

Images above looks very much like the Sigma 50 I had.. before I sold it off. I heard a lot of praises about how sharp it is at f1.4, but I can't agree to it. Like yours, I can only see it being sharp from f2.0 onwards. I didn't expect it to perform at best in widest aperture, but it's result is just not my liking.

Got myself the 50mm 1.8G after that, really satisfied with the lens at f1.8.

Bokeh still the best for Sigma though.

Thank you for those who responded. It is good I suppose to assume I don't have a bad copy. A little sharpening and contrast in PP normally solves problems anyway.

Has anyone here had experience with Sigma in the UK for calibrating auto-focus to your camera? Mine back-focuses badly, I normally focus manually, certainly at wide apertures but would like to get it corrected if possible and would be curious to hear how others have fared with sending the camera and lens to sigma?

Thanks.