[frank]

http://nikonrumors.com/2013/10/14/sigma-...site.aspx/

 

Looks nice but bulky. At wide end the resolution does not look promising at border/corner, however.

 

[youpii]

It's official now

http://www.sigma-global.com/en/lenses/ca...index.html

[JJ_SO]

Frank, thanks for posting.

 

Bulky, you're saying? Any design suggestions, how Sigma can get the constant f/4 into a smaller tube? Pass it forward to them...  But I have to say, I don't want to re-buy my 77mm filters for 82mm, so that's a dealbreaking thing for me, too. As for weak corners: Apparently not that much weaker than the genuine lenses, when comparing PZ results of 24-85 and 24-120/4 VR.

 

Also, not everybody's a friend of extending tubes. Anyway, I'll save my money for a 85/1.4 in the quality level of their 35/1.4 

[Rainer]

Looks like a nice lens.

The main question will be: How does it compare to its direct competitors

(EF 24-105/4L IS and 24-120/4 VR), and how will its streetprice be.

If it has an optical edge over these two lenses, it might find its share in

the market.

The 82mm threadsize for filters might help to reduce vignetting a bit.

Albeit, I do not like the dual/coaxial tubes ... in this regard, I prefer the

construction of the EF 24-105.

Nevertheless, it will be interesting to see first hands-on reports and

reviews.

 

Rainer

[frank]

Size/Weight comparison:

 

Sigma 24-105mm f4:  88.6mm x 109.4mm, 885g, 82mm filter

Canon 24-105mm f4: 83.5mm x 107mm, 670g, 77mm filter

Nikon 24-120mm f4:   84mm x 103mm, 670g, 77mm filter

 

MTF chart comparison:

 

The Sigma:

 

The Canon:        

 

The Nikon:

[frank]

Frank, thanks for posting.

 

Bulky, you're saying? Any design suggestions, how Sigma can get the constant f/4 into a smaller tube? Pass it forward to them...  But I have to say, I don't want to re-buy my 77mm filters for 82mm, so that's a dealbreaking thing for me, too. As for weak corners: Apparently not that much weaker than the genuine lenses, when comparing PZ results of 24-85 and 24-120/4 VR.

 

Also, not everybody's a friend of extending tubes. Anyway, I'll save my money for a 85/1.4 in the quality level of their 35/1.4 

 

When compared to the Nikon/Cannon counterpart, 215g increase in weight, and 82mm vs 77mm in filter size. These two numbers made me say that the Sigma is "bulky". 215g increase in weight is significant, I think. In absolute numbers, I also think ~900g is too weighty for a constant f4 and standard zoom lens.

[JJ_SO]

The MTF curves look similar but let's keep in mind: Nikon MTF curves stop at 30 lines/mm. They don't say anything about max. resolution or contrast at higher frequencies. I'd like to quote the user Ade from NR Forum who made me understand MTF a bit better: See more at: http://forum.nikonrumors.com/discussion/...fWIK4.dpuf


 

<b>Nikon MTF</b>


Nikon measures the amount of contrast preserved at various areas of the lens (from center outward) at 10 lines/mm and 30 lines/mm. They do it with lines parallel and perpendicular to the diagonal of the lens. The result is a plot of distance (x-axis) vs. contrast (y-axis).


Since they stop at 30 lines/mm, the absolute resolution of the system is not tested.

<b>Imatest MTF50</b>


Imatest plots the preserved contrast at different frequencies, from zero lines/mm to > 200 lines/mm. The reported resolution is the max resolution at 50% contrast. The absolute resolution of the system is not tested.

<b>Further notes</b>


I'm simplifying a lot of the above. For example, on modern charts, there are no "physical" line pairs anymore. Instead, a "slanted edge" is used and the number of equivalent line pairs is calculated.


But I hope everyone gets the point that MTF testing does not attempt to find out the absolute maximum resolution the system can produce. Resolution is defined at a contrast level, and we can arbitrarily define a contrast level where more and more resolution could be detected (at 1%? At 0.1%? At 0.01%?) 

 

I'd also consider it a heavy lens. On the other side, if 82mm filter thread would reduce the vignetting, it could become acceptable. So, I'm wondering how the rumored 24-70/2 will look and feel alike.

 

On another other side: The new Zeiss 55/1.4 otus is over 1000 grams, with no AF and no zoom and no possibility to re-adjust the lens' AF by a dock.

 

I'm wondering about the pricing of that Sigma, it can't be much under it's competitors. After all, the lens performance still is more than those curves and I wait to see some sample pictures before judging anything, I know that's a bit old school. So far, Sigma surprised me twice with two lenses. Nikon needed 10 lenses to surprise me three times. It will become interesting if Sigma can hold on it's surprise rate  ^_^

[Klaus]

Size/Weight comparison:

 

Sigma 24-105mm f4:  88.6mm x 109.4mm, 885g, 82mm filter

Canon 24-105mm f4: 83.5mm x 107mm, 670g, 77mm filter

Nikon 24-120mm f4:   84mm x 103mm, 670g, 77mm filter

 

MTF chart comparison:

 

The Sigma:

 

The Canon:        

 

The Nikon:

 

The MTFs are not comparable.

[Brightcolours]

The vignetting at wide angle will remain, because for most part that is sensor-caused. I already found the Canon one heavy for a standard zoom... 

[frank]

The MTFs are not comparable.

 

Yes, I know. But I think the trend is comparable, e.g. borders vs center resolution/sharpness,  astigmatism, etc.

 

Even without knowing the specific definition of the manufacture's MTF, I think from the green lines in the Sigma chart it can be inferred that the astigmatism is quite pronounced at 24mm, at least wide open.