02-19-2015, 12:08 AM
Not sure if anyone can dig up MTF info for the 55/2.8 micro AI-S but I have tested one today.
Real focal length: 54.881mm
On-axis MTF results:
10lp/mm - 90%
20lp/mm - astigmatism becomes real - tangential plane at about 86-87% sagittal plane at 70%.
30lp/mm - 60% / 55%
40lp/mm - about 45% in each plane
The field curvature / astigmatism at infinity is "pretty strong" - the two planes peak in MTF almost 100um apart. In terms of raw values this is quite intense - 100um is almost 20px of blur or so but in terms of the grand scheme of things it is not bad. .1mm astigmatism is alright - because this is on-axis it points to some misalignment within the lens or tilt in the test system but it is not a bad result.
Here is the spot from the lens: http://i.imgur.com/82BxEKE.jpg
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To break things down - MTF50% is about 35lp/mm here. 35lp/mm * 2 * 36mm = 2520px of "real resolution" on a full-frame sensor which could realistically be pushed to about 3000px.
Real focal length: 54.881mm
On-axis MTF results:
10lp/mm - 90%
20lp/mm - astigmatism becomes real - tangential plane at about 86-87% sagittal plane at 70%.
30lp/mm - 60% / 55%
40lp/mm - about 45% in each plane
The field curvature / astigmatism at infinity is "pretty strong" - the two planes peak in MTF almost 100um apart. In terms of raw values this is quite intense - 100um is almost 20px of blur or so but in terms of the grand scheme of things it is not bad. .1mm astigmatism is alright - because this is on-axis it points to some misalignment within the lens or tilt in the test system but it is not a bad result.
Here is the spot from the lens: http://i.imgur.com/82BxEKE.jpg
---
To break things down - MTF50% is about 35lp/mm here. 35lp/mm * 2 * 36mm = 2520px of "real resolution" on a full-frame sensor which could realistically be pushed to about 3000px.