A Review of the Sigma 35mm f/1.2 DG DN Art Lens

The Sigma 35mm f/1.2 DG DN Art lens is one of the newest from the company and one of the first designed specifically for mirrorless cameras. With its ultra-wide aperture, it looks to be an interesting option for Sony E and Leica L shooters, and this great review takes a thorough look at it.

Coming to you from Dustin Abbott, this great video takes a look at the Sigma 35mm f/1.2 DG DN Art lens. The 35mm f/1.2 Art features three Special Low Dispersion (SLD) elements to reduce aberrations, three aspherical elements to reduce distortion, a Hyper Sonic motor with full-time manual focus, de-clickable aperture, rounded 11-blade diaphragm for smoother bokeh, and weather-resistance. 

I have to admit that I was really impressed by the sharpness of the lens wide open, even compared to some of the top lenses from other manufacturers. I have always loved my Canon f/1.2 lenses, but I long ago accepted that shooting at the widest aperture was more about that characteristic look than it was about technical image quality. The idea of being able to have the unique look of such an ultra-wide aperture in tandem with a sharp rendering is certainly very intriguing. Check out the video above for Abbott's full thoughts. 

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It will be interesting to someday find out if this really performs anywhere near f1.2 when someone like DXOmark publishes the T-stop. Sigma is known for exaggerating theoretical f-stop values, their 85mm f1.4 Art actually has a terrible T-stop value of 1.8! Which is completely ridiculous since it's enormous and when you consider the Sony/Zeiss 85mm f1.8 is cheaper and has the same 1.8 T-stop value at half the size and weight. I'd be pretty pissed if this 35mm f1.2 is more like an f1.4 or more, which I suspect.

F-stop is only a measure of aperture vs focal length. T-stop IS a measure of light transmission. A lens with different f- and t-stop numbers is NOT exaggerating its f-stop value.

A lens' F-stop is only a valid measure of light transmission when compared against itself (same lens at f1.4 vs f2, for example). You should never compare the light transmission of two different lenses based on only their f-stop numbers.

What are you talking about? I misspoke, what I meant to say is I doubt the Sigma 35mm f1.2 has a T-stop value anywhere near 1.2, okay happy? By the way you're not going to teach me anything about F-stops or T-stops, because I know exactly what they are and have been a professional photographer for 18 years. Everything I said is 100% true and accurate, I don't come on here to spew lies. Sigma in my opinion greatly exaggerates many of their lenses f-stop numbers. They have poor light transmission compared to many native lenses. The only reason I compared the Sigma to a Sony lens is to show how ridiculous it is that that Art lens is so massive, yet has a T-stop of 1.8! Are you like a member of the f-stop police or something, all you're trying to do is make me sound like an idiot, but not adding anything to the discussion. Are you saying that I'm wrong about Sigma exaggerating? Just take away the whole semantics, do you think a massive lens with a f1.4 aperture should have a T-stop of 1.8?

i'll ignore the parts were you went flying off the handle.

and yes, you ARE wrong about Sigma exaggerating. or maybe you don't quite understand f-stop vs t-stop as you claim, because there's nothing particularly wrong about f-stop and t-stop numbers not matching up.

Sigma would only be exaggerating if their listed f-stop numbers do not match up to to what their lenses are actually. since there's no indication of that ever being true, it means that Sigma is NOT exaggerating their f-stop numbers.

once again, f-stop and t-stop numbers on a lens often DO NOT match. in fact, the more glass elements are in a lens (and Sigma lenses tend to have a lot of glass), the bigger the difference. after all, glass is never 100% transparent. the more glass is in a lens, the less light makes it out of the other end.

Sigma advertising f1.2 means that they'll actually give you f1.2. there's no such thing as "f1.2 of light" in a universal sense, because f-stops are USELESS in telling you the light transmission between two different lenses.

and if you still don't believe me, check out the DXOmark measurements on the Canon 35mm f1.4L mkII: https://www.dxomark.com/Lenses/Canon/Canon-EF-35mm-F14L-II-USM-mounted-o...

f1.4, T1.7. the equivalent Sigma 35mm f1.4 is actually brighter, at T1.6

All your doing is arguing that I misspoke and I have already admitted what I was trying to say didn't come out right. You're welcome to look me up and see my work and trust me I know what a T-stop is and what an F-stop is. You just brought up one example of a Sigma lens having better light transmission than one Canon lens, but overall SIgma's have pretty terrible light transmission because they are solely focused on center sharpness and many of their lenses therefor suffer from field curvature. I've read countless articles and seen countless videos of people explaining that many lenses are more like an f4.5 than an f4, so I'm not alone in my argument. There is probably a more technically correct way to describe what I was trying to say, but you're like an f-stop Nazi here, because you know damn well what I'm talking about, so stop being high and mighty.

Adam Palmer's picture

If you aim for sharpness wide open you will need more elements which means light will be lost. It's a design choice. Sigma is guessing that people will want sharp at 1.2 vs the 1/3 stop of light. I think I would prefer the wide open performance.