[felix]

Hi everyone! 

I didn't think I'd ever see an f/1.8 zoom, but here it is: http://www.sigma-global.com/en/lenses/ca...index.html

 

Sounds pretty interesting! 

[mst]

Wow, interesting indeed!

-- Markus

[Brightcolours]

Pretty nice going into FF territory, but that weight makes it a bit curious on APS-C... 810 grams for a ~28-55mm f2.8 lens... The Canon EF 24-70mm f2.8 L USM II weights 805 grams and the Tamron 24-70mm f2.8 VC USD weights 825 grams.

That is one hefty APS-C standard zoom.

[PuxaVida]

Cool design... I think the zoom range is also well chosen. One can pair it with various alternatives from UWAs. And for the short tele range, I guess we'll be seeing another "new standart" from Sigma soon  ... A 35-120mm f/2.8 would be nice for instance...

 

And as BC mentioned, I agree this one's quite heavy compared to the 24-70mm f/2.8 FFs... Maybe because of the build material and 17 glass elements.

 

Serkan

[popo]

Very interesting. This specific range is not a major interest area for me, but I'm hopeful that is an indication they will try longer focal lengths in future. Having said that, the tradeoffs are tricky. This could replace budget primes, but I can't see this lens being in any way cheap! Still could be a poor mans alternative to a high end prime set.

Actually, this lens would be far more interesting if they were to attempt this on APS-C mirrorless systems. The reduced need for retrofocus should hopefully simplify the design somewhat, reducing size and weight, and cost too. Imagine pairing this with a future X-Pro2!

[Brightcolours]

Cool design... I think the zoom range is also well chosen. One can pair it with various alternatives from UWAs. And for the short tele range, I guess we'll be seeing another "new standart" from Sigma soon  ... A 35-120mm f/2.8 would be nice for instance...

That then would have to be a 35-120mm f1.8, of course

Sigma already has a 50-150mm f2.8 EX DC OS HSM, which will pair it nicely. Only this APS-C lens rivals the 70-200mm f2.8 full frames almost in size and weight... But it does have very sharp optics.

 

And as BC mentioned, I agree this one's quite heavy compared to the 24-70mm f/2.8 FFs... Maybe because of the build material and 17 glass elements.

 

Serkan

Well, obviously it also is heavy because of its f1.8-ness... f2.8 standard zooms for APS-C weight between 500-650 grams already.

[JJ_SO]

Brightcolours, I've no idea how you calculate a f/2.8 - it has f/1.8 and you can't just multiply the aperture by the crop factor - that would only be fair, if the lens would have to bring enough light to a double as large sensor.

 

It has an aperture which is hard (if ever) to get for a range between 18 and 24mm - except some pricey 24/1.4 FF lenses. I can see that as a standard zoom for D7100. Given what the 35/1.4 performs, Sigma is really reaching for a high place in lens heaven. 

[mst]

Brightcolours, I've no idea how you calculate a f/2.8 - it has f/1.8 and you can't just multiply the aperture by the crop factor - that would only be fair, if the lens would have to bring enough light to a double as large sensor.

It's absolutely fair if you want to compare lenses with equivalent DOF. In this regard a f/1.8 lens on APS-C is the equivalent of a f/2.8 lens on full frame. Which also shows: there is actually no size advantage if you take as much as possible into account.


-- Markus

[Brightcolours]

Brightcolours, I've no idea how you calculate a f/2.8 - it has f/1.8 and you can't just multiply the aperture by the crop factor - that would only be fair, if the lens would have to bring enough light to a double as large sensor.

That is just the nature of things. To get an equivalent lens, you multiply the focal length to get similar field of view. You multiply the f-value to get a similar aperture size and similar DOF. 

 

You can just multiply the focal length by crop factor, and similarly, you can just multiply the f-value by crop factor.

 

Simple example:

Suppose we have a 85mm lens on an 1.6x crop camera (compared to 135 format "full frame), with an focal length/aperture ratio of f/1.8.

To get a similar FOV we multiply by crop factor: 85 x 1.6 = 136mm.

To get a similar aperture we multiply the f-value by crop factor: f1.8 x 1.6 = f2.88, so lets say about f2.8.

Lets check if that is correct. 

Size of the aperture of the 85mm f1.8 lens:

85mm / 1.8 = 47mm aperture.

Size of the aperture of a 135mm f2.8 lens: 

135mm / 2.8 = 48mm aperture.

 

The 85mm f1.8 lens on 1.6x crop and the 135mm f2.8 lens are equivalent. They offer each respective sensor the same FOV angle, they offer a similar aperture size for the light to pass through, they will offer a similar DOF.

 

So this Sigma lens offers for APS-C what the f2.8 standard zooms offer on FF.

 

It has an aperture which is hard (if ever) to get for a range between 18 and 24mm - except some pricey 24/1.4 FF lenses. I can see that as a standard zoom for D7100. Given what the 35/1.4 performs, Sigma is really reaching for a high place in lens heaven. 

[JJ_SO]

Brightcolours, a f/2.8 is slower than f/1.8 no matter which sensor size.

 

That was the reason I wrote "you can't just multiply the aperture by the crop factor" - only if it comes to DOF, but not to a gain of 1.5 f-stops faster shutter speeds, not to a gain of a relatively narrow DOF in wide-angle (for APS-C). To compare that shutter speed, it has to be a 28-55/1.8 for FF! And that sounds much less cheap than a 28-55/2.8 - each manufacturer can do that.

 

I admit, 1.5 f-stops are easily done by contemporary VR/OS devices, one can handhold up to 4 f-stops - but one doesn't get short shutter speeds by VR//OS.

 

It looks long and thin in the pictures, but given the filter size 72mm, it's a huge piece of gear.