It\'s the MTF charts for the lenses shown across the image frame at different resolutions (10, 20 & 40 line pair/mm) and directions (sagittal and tangential).
If we look at the 28/35/50 comparison:
and we look at one of the charts:
The X & Y axis are simply the horizontal and vertical edges of the image. The Z (vertical) axis shows the MTF (i.e contrast). This is at a specific resolution, namely 40 lp/mm. For the M9, this corresponds to elements that have a radius of about 2 pixels. So it\'s the fine detail. The direction in this case is sagittal or radial, meaning that it\'s the resolution in the direction towards the image center. The other direction that is in a separate graph is tangential which you can visualize as circles around the center.
So what does this particular graph tell us:
Well, that the center sharpness for fine detail in the sagittal direction is very good (the red center) but that it drops off somewhere around mid frame (the dip in the surface/ green area) and gets better in the corners again. So if you have in your shot say a sandy beach, or anything with a fine texture, you can expect a drop in contrast in the direction towards the center of the image. This was from the 35 Lux. If we look at the same chart for the 28 Cron we see this:
We can see that the transition from the center to the edges is smooth. There is a drop in contrast for fine detail in the corners, but the transition is much more graceful without any wobbly parts in the middle.
If we look at them side by side just colorized by sharpness (MTF), 28 Cron on top:
That\'s how the sharpness for fine detail in the sagittal direction will vary in the shots that you take with the 28 Cron vs the 35 Lux. This tells you for instance that the Cron is definitely a better landscape lens - you don\'t want big swings in resolution in different places on the image when you are doing traditional landscape photography (i.e stopped down at infinity)
It\'s the MTF charts for the lenses shown across the image frame at different resolutions (10, 20 & 40 line pair/mm) and directions (sagittal and tangential).
If we look at the 28/35/50 comparison:
and we look at one of the charts:
The X & Y axis are simply the horizontal and vertical edges of the image. The Z (vertical) axis shows the MTF (i.e contrast). This is at a specific resolution, namely 40 lp/mm. For the M9, this corresponds to elements that have a radius of about 2 pixels. So it\'s the fine detail. The direction in this case is sagittal or radial, meaning that it\'s the resolution in the direction towards the image center. The other direction that is in a separate graph is tangential which you can visualize as circles around the center.
So what does this particular graph tell us:
Well, that the center sharpness for fine detail in the sagittal direction is very good (the red center) but that it drops off somewhere around mid frame (the dip in the surface/ green area) and gets better in the corners again. So if you have in your shot say a sandy beach, or anything with a fine texture, you can expect a drop in contrast in the direction towards the center of the image.
