S Dilworth
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philip_pj wrote:
S, do you think Wayne's Nikkor so relatively inferior in those characteristics as to be responsible for the differences in the images he posted, and the luminosity handling he notes? It's a modern, high end Nikkor we are talking about...
It is a modern Nikkor, but it's one stop faster than the Zeiss (though they both have ten groups, I notice) and the coatings are different. The rear element of the Distagon is also much smaller, so it presents a smaller reflective surface for the image projected onto the sensor during exposure.
We're going by Wayne's comments here, and I don't know if he shot directly comparable images. Contrast is affected by many things. But if the Zeiss offers higher contrast than the Nikkor, that would be in line with my own general experience of the two brands.
It's S for Samuel, by the way.
wayne seltzer wrote:
What is interesting is that with the right bottom corner crop you can see the blurriness in the wall and the street lamps in the bottom right crops but the boat in the foreground is sharper. So it looks to me like field curvature causing the extreme corner blurriness.
I'm sure field curvature is at least partially to blame for the corners, but I think the boat is sharper – where it is sharper – simply because it's farther from the corner proper than the street lamps. The sharpness fall-off towards the corners is unusually abrupt for this Distagon, which means 1 mm in this area makes a big difference.
Most of the features of the boat are higher in contrast than the background on the far side of the Thames; this increases the perception of sharpness. Colours and atmospheric disturbances may also play a role.
In addition, the boat is far enough away to be at infinity for practical purposes. Field curvature would not cause a noticeable difference in sharpness between the boat and the far side of the river.
Finally, field curvature may swing away from the camera in the extreme corners, meaning distant objects would be imaged with better focus than close objects (when the lens is focused at infinity in the centre).
Other things to note:
- The photos were taken at 1/125 second, which is a bit slow for careful comparisons unless a pretty hefty tripod is used.
- Simon doesn't tell us where and how he focused. Since there's only sky in the centre of the images, this would be very useful information!
- In these images, the Zeiss reveals slightly more subject detail throughout most of the bottom-middle crops, and on objects in the corner crops that are closest to the centre (i.e. not the extreme corners). But two factors complicate this comparison: (1) the Zeiss has a longer focal length (this puts the Canon at a disadvantage), and (2) because the Zeiss has a longer focal length, the same objects are positioned closer to the corners for the Zeiss than the Canon (this puts the Zeiss at a disadvantage).
- In these images, the Canon has less chromatic aberration, distortion, and off-axis light fall-off than the Zeiss. The corners are obviously much better. Objective, indeed!
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