- Ed Dozier
MTF Mapper Version 0.5.8
This version of MTF Mapper has some new features and some changed features. This is the software that I use to evaluate both lens resolution and focus calibration. The author of this program is Frans van den Bergh.
You can get this software here: https://sourceforge.net/projects/mtfmapper/
This new revision can still use the original resolution and focus chart designs, which is a real relief if you have invested time, effort, and money in printing/mounting large versions of the charts. If you print the newer charts, you get some new and welcome abilities.
What’s changed? You may want to review my MTF Mapper Cliff’s Notes article, detailing the older version capabilities.
New Resolution Chart
The biggest change as far as I’m concerned is the switch from ‘relative’ measurements to ‘absolute’ measurements in the resolution charts (grid2d and grid3d). The chart scales of earlier MTF Mapper versions would only have a value range matching the actual measurements, but now the resolution range starts at zero.
Another big change is the switch to monochrome color coding in the 2d and 3d charts, instead of the ‘rainbow’ color coding that would auto-scale to the entire measurement range.
A small but welcome change is the addition of the photo name under the chart, so you know where the chart came from.
Original resolution chart design. You can still use this chart.
New resolution chart design, showing annotated photograph.
New chart up close. Good edge measurements are blue; “iffy” ones are in yellow.
2D Chart with absolute scale for MTF50 lp/mm
Older 2D Chart measurements with relative scale for MTF50 lp/mm.
3D new resolution chart showing the absolute (monochrome) scale
MTF 10 and MTF 30 Graphs
Camera companies have traditionally published MTF charts that show 10 lp/mm and 30 lp/mm “theoretical” values. I stress “theoretical” here, because those companies are merely blowing smoke. They don’t actually measure anything (at least Canon and Nikon don’t).
MTF Mapper can now plot the real-deal MTF10 and MTF30 charts, based upon actual reality. What a concept. These graphs use the same chart design used for "grid2d" and "grid3d".
MTF10 and MTF30 measurements using the new resolution chart
The new software can use the original focus chart. What’s new is how the ‘annotated’ version of the chart displays the measurements. The measurements are in “cycles per pixel”. The measurements are no longer embedded inside boxes, which makes reading the values and seeing the edges much easier.
Focus chart photo, showing the annotated edge measurements
“Profile” option for focus chart
The chart above shows a very slight focus error. The chart is oriented to make the left side farther from the camera than the right side. The ideal angle to shoot the chart is at 45 degrees relative to the vertical. The measurements above would indicate that the camera (or lens firmware) needs some “-” focus-tune adjustment, to pull the focus toward the camera.
I always recommend, by the way, to look at the annotated focus chart measurements. There are occasions when the numbers give you a better idea of how to adjust focus. Also, repeat this test several times to avoid reacting to normal focus variations. Lastly, perform the tests in good light for optimal reliability.
In the focus test above, the camera focus point was placed onto the right edge of the large central trapezoid. Because the chart is rotated, the trapezoid looks like a rectangle in the photograph.
Measure Longitudinal Chromatic Aberration
Focus chart with “fiducials” for measuring longitudinal chromatic aberration
Chart zoomed in. Shows green channel focus error.
The other major feature addition is the ability to analyze how a lens focuses in the red, blue, and green channels. When the different channel color focus measurements don’t coincide, then you have longitudinal chromatic aberration.
To create the charts shown above, the MTF Mapper needs to be configured as shown in the following picture:
Preferences dialog. Note the camera sensor “pixel size” must match your camera.
The new MTF Mapper version 0.5.8 brings many welcome additions. You might want to retain your older version, however, if you prefer the “relative” versus the “absolute” resolution measurements.
Please visit the Frans van den Bergh site and give him some praise for going through all this effort. Frans, you’re the man!