10-15-2013, 05:20 AM
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
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 ^_^
Quote:<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 ^_^