Lens porn: Sigma 50-100mm F1.8 Art

[Timotheus]

Seems Sigma has done it again:

http://www.sonyalpharumors.com/leaked-first-picture-of-the-crazy-sigma-50-100mm-f1-8-lens/

Yet another uniquely fast zoom (for crop). You guys excited? I know I am :-) Now let's wait for RRP

[TheRenaissanceMan]

Man, this would make a great kit with the 18-35. 

Big, though. Big and heavy and 82mm filter thread.

[Cinegain]

Pretty sexy! 

-- Would be nice to have both the 18-35mm f/1.8 and 50-100mm f/1.8 making use of that advanced AF system... but I have already the 18-35mm f/1.8 in Nikon mount, because: M43. Will Canon e-adapters work better than let's say this Commlite Nikon one? http://www.commlite.com/en/product_show.php?id=205&img_sl_lm1=upimg/2015112012350794.jpg&title_lm=E-Mount%20Ring&title=CM-ENF-E%281%29 . Because I'd still prefer the Nikon mount: still gives you the cheaper options for dummy adapters and lens turbos with M43 (BMD Micro Cinema Camera for example) and adapts then natively to D5300/D5500. Although having the A6300 will probably render those cameras completely useless anyways. I just don't want to go the Canon route if I don't have to. I see no future there.

[Timotheus]

2 hours ago, Cinegain said:

...Because I'd still prefer the Nikon mount: still gives you the cheaper options for dummy adapters and lens turbos with M43...

I remember Sigma announced a 'mount conversion service' when their Global Vision lenses were introduced. So you can switch mounts on all Art, Contemporary and Sports lenses...although I never heard anyone actually do this or what it would cost.

[Don Kotlos]

2 hours ago, Cinegain said:

Pretty sexy! 

-- Would be nice to have both the 18-35mm f/1.8 and 50-100mm f/1.8 making use of that advanced AF system... but I have already the 18-35mm f/1.8 in Nikon mount, because: M43. Will Canon e-adapters work better than let's say this Commlite Nikon one? http://www.commlite.com/en/product_show.php?id=205&img_sl_lm1=upimg/2015112012350794.jpg&title_lm=E-Mount%20Ring&title=CM-ENF-E%281%29 . Because I'd still prefer the Nikon mount: still gives you the cheaper options for dummy adapters and lens turbos with M43 (BMD Micro Cinema Camera for example) and adapts then natively to D5300/D5500. Although having the A6300 will probably render those cameras completely useless anyways. I just don't want to go the Canon route if I don't have to. I see no future there.

For E mount sony users the only problem would be getting AF with the adapted nikons. Since Sigma will also announce an Canon to Sony auto-focus adapter If I have a Sony E cam then I would go with the Canon version. 

[AaronChicago]

Hell yeah.

[Inazuma]

The thing is that a 70-200 f2.8 becomes a 50-142 f2 on a speed booster...

[Grim Fandango]

Just now, Inazuma said:

The thing is that a 70-200 f2.8 becomes a 50-142 f2 on a speed booster...

And don't forget that while it has the DOF of a 1.8, in light terms, it is illuminating like a 2.8 on a crop frame sensor - making the speed boosted 70-200 faster

[Cinegain]

Yeah, the article didn't convert currency and I didn't bother to convert it myself, so I wasn't expecting 1499 USD/EUR quite yet until I read another. Also... I didn't see a mention of optical stabilization, so I take it, like the 18-35mm it has none? Things are starting to look a little grim, not to take your name in vain, Grim. I don't know... resorting to a speedboosted Tokina 50-135mm f/2.8 (that cinemodded goes for 4499 USD) might not seem so far fetched after all...

[Nikkor]

36 minutes ago, Grim Fandango said:

And don't forget that while it has the DOF of a 1.8, in light terms, it is illuminating like a 2.8 on a crop frame sensor - making the speed boosted 70-200 faster

That's incorrect, the fstop is a standart, if after speedboosting you get f2, it will be slower than f1.8

[AaronChicago]

1 hour ago, Inazuma said:

The thing is that a 70-200 f2.8 becomes a 50-142 f2 on a speed booster...

There's something about the Sigma Art lenses that are special though.

[Grim Fandango]

Just now, araucaria said:

That's incorrect, the fstop is a standart, if after speedboosting you get f2, it will be slower than f1.8

This explains things better than I can:

 

[Geoff CB]

1 hour ago, Cinegain said:

Yeah, the article didn't convert currency and I didn't bother to convert it myself, so I wasn't expecting 1499 USD/EUR quite yet until I read another. Also... I didn't see a mention of optical stabilization, so I take it, like the 18-35mm it has none? Things are starting to look a little grim, not to take your name in vain, Grim. I don't know... resorting to a speedboosted Tokina 50-135mm f/2.8 (that cinemodded goes for 4499 USD) might not seem so far fetched after all...

I love that lens. I've seriously regretted selling my copy when I went to Nikon Full Frame, will get another one day.

[JurijTurnsek]

2 hours ago, Inazuma said:

The thing is that a 70-200 f2.8 becomes a 50-142 f2 on a speed booster...

Makes you wonder what kind of sharpness and AF speed you could get with A6300.

[The Chris]

2 hours ago, Grim Fandango said:

And don't forget that while it has the DOF of a 1.8, in light terms, it is illuminating like a 2.8 on a crop frame sensor - making the speed boosted 70-200 faster

F/1.8 is F/1.8 on any sensor, the only thing that changes is the effective FOV and DOF relative to full frame when using the same lens on a smaller sensor. A speed boosted 70-200/2.8 will not be faster than a 1.8 lens on a  APS-c body. It will have more reach than the Sigma 50-100 however.

[Grim Fandango]

Just now, The Chris said:

F/1.8 is F/1.8 on any sensor, the only thing that changes is the effective FOV and DOF relative to full frame when using the same lens on a smaller sensor. A speed boosted 70-200/2.8 will not be faster than a 1.8 lens on a  APS-c body. It will have more reach than the Sigma 50-100 however.

The F-Stop number is a ratio, between the focal length and the aperture, so if you have a 100mm lens with an aperture opening of 50mm, it is set to f2.0.

But a 100mm lens that covers a full frame sensor and a 100mm lens that covers a m4/3 sensor are very, very different to each other, despite sharing those two common measurements. The difference in designs manifest in the size of the image projected by the lens. The aperture blocking certain angles of light reaching the sensor is the same, thus the out of focus areas will be the same amount out of focus, but your 100mm lens on a m4/3 lens will show a much narrower DOF - as you so correctly point out. So to achieve the same frame as the full frame, you actually need to mount a 200mm lens on the full frame. What happens, the DOF changes because to maintain f2, your aperture is now 100mm wide, blocking far less of that light coming in.

Therefore, you cannot achieve the same picture. In order to do that, you will need your 100mm to open up more, in this case, also to 100mm diameter - f1.

So you see, for any particular picture, you cannot recreate it by matching the lens numbers and plopping it on any old sensor (we all understand this) not can you only multiply the focal length crop factor (becuase the out of focus character is different) but if you want to achieve the same look, you have to also apply your crop factor to the f number, your lens needs to be faster for the crop sensor to achieve the same shot.

Thus when comparing two lenses for the same sensor, one a lens designed for that crop frame sensor, and one a full frame lens with a speed booster, not only is that speed booster concentrating the light, increasing it's brightness on the smaller lens (F2.8 becomes an F2), but you are bringing the full frame characteristics of the lens to that crop sensor efectively making that sensor a full frame. Therefore to achieve the same look that the full frame lens brings, you need to use that crop factor on the aperture too for the crop lens (which remember is not going through a speed booster).

[Cinegain]

1 hour ago, Geoff CB said:

I love that lens. I've seriously regretted selling my copy when I went to Nikon Full Frame, will get another one day.

Ah! Great to see someone already in love with this lens.  I've got to admit, it was andy lee (of course) who kind of planted the seed that put the Tokina 50-135mm f/2.8 on my radar. Found a nice Canadian fellow to ship me a new one, which came in just before lunch. Had some errands to run, so I hope I can put it to the test in the next few days at least.

Supposed to have APO qualities and it does appear to be parfocal too! So, it's fair to say that the initial impression was a good one! Thing is built to see some shit and the rendering is kinda nice, takes the edge offa brittle 4K, although perhaps not really squeezing out the optimum performance of this baby at the f/2.8 I'd wish to just leave it on. I was about to try Zeiss primes now, but this is like a 50mm, 85mm and 135mm f/2.8 in one. Speedboosted and voilá, Hollywood vibes.

It's a nice alternative to the Nikon 80-200mm f/2.8 D, which is gorgeous and the better performer I think, but the Tokina's wider range might appeal a little more. All for a fraction of the costs of a Zeiss primes set or the Sigma for that matter, although, I guess in the end the Sigma probably has a fair enough price... the Olympus 40-150mm f/2.8 PRO isn't far off and the Sigma is a f/1.8.

[bamigoreng]

40 minutes ago, Grim Fandango said:

The F-Stop number is a ratio, between the focal length and the aperture, so if you have a 100mm lens with an aperture opening of 50mm, it is set to f2.0.

But a 100mm lens that covers a full frame sensor and a 100mm lens that covers a m4/3 sensor are very, very different to each other, despite sharing those two common measurements. The difference in designs manifest in the size of the image projected by the lens. The aperture blocking certain angles of light reaching the sensor is the same, thus the out of focus areas will be the same amount out of focus, but your 100mm lens on a m4/3 lens will show a much narrower DOF - as you so correctly point out. So to achieve the same frame as the full frame, you actually need to mount a 200mm lens on the full frame. What happens, the DOF changes because to maintain f2, your aperture is now 100mm wide, blocking far less of that light coming in.

Therefore, you cannot achieve the same picture. In order to do that, you will need your 100mm to open up more, in this case, also to 100mm diameter - f1.

So you see, for any particular picture, you cannot recreate it by matching the lens numbers and plopping it on any old sensor (we all understand this) not can you only multiply the focal length crop factor (becuase the out of focus character is different) but if you want to achieve the same look, you have to also apply your crop factor to the f number, your lens needs to be faster for the crop sensor to achieve the same shot.

Thus when comparing two lenses for the same sensor, one a lens designed for that crop frame sensor, and one a full frame lens with a speed booster, not only is that speed booster concentrating the light, increasing it's brightness on the smaller lens (F2.8 becomes an F2), but you are bringing the full frame characteristics of the lens to that crop sensor efectively making that sensor a full frame. Therefore to achieve the same look that the full frame lens brings, you need to use that crop factor on the aperture too for the crop lens (which remember is not going through a speed booster).

Smaller format lenses have exactly the same light gathering capabilities as larger format lenses at the same f-stop, for their native sensor sizes - link:

https://photographylife.com/sensor-crop-factors-and-equivalence

[Grim Fandango]

Just now, bamigoreng said:

Smaller format lenses have exactly the same light gathering capabilities as larger format lenses at the same f-stop, for their native sensor sizes - link:

https://photographylife.com/sensor-crop-factors-and-equivalence

Then you will have literally no problem proving that! Get two cameras with different size sensors, stick two lenses on the front of them set to the same f-stop number, and try to take identical photographs with them. When you give up because the bokeh in one is far more out of focus than the other for the same frame, apply my formula and then take those same photos. Or just watch the video I posted above where they perform that precise test.

[TheRenaissanceMan]

17 minutes ago, Grim Fandango said:

Then you will have literally no problem proving that! Get two cameras with different size sensors, stick two lenses on the front of them set to the same f-stop number, and try to take identical photographs with them. When you give up because the bokeh in one is far more out of focus than the other for the same frame, apply my formula and then take those same photos. Or just watch the video I posted above where they perform that precise test.

Light gathering, not bokeh.