how to measure MTF

[BetterSense]

How can I measure MTF of enlarging and taking lenses? I have seen manufacturers MTF charts...how do they measure them?

 

[Christopher Walrath]

It's a little above my paygrade but here is a .pdf on Schneider's website, for those interested, that seems to lay it out pretty good.

 

[Nodda Duma]

The professional way: MTF station such as made by Optikos. It costs about as much as a nice home. We just got a new setup at work and it is sweet. It allows me to see how my assembled designs compare directly to predicted performance.


The poor man's way:

Pay someone else to measure it.

If you want to measure the MTF of an imaging *system* (including lens, film or digital imager, scanner), use a slant-edge technique described in ISO 13322 and as implemented in software such as Imatest.


MTF is not easy to measure, which is why most photographers hadn't heard much of it up until a decade or so ago. Now MTF is reported by camera reviewers primarily due to Norman Koren's development of Imatest software.

Edit: that Schneider PDF is good for theory except that the illustration of spatial frequencies is incorrectly showing a square-wave pattern (black and white bar pattern). A square wave consists of many frequencies, and in optics gives you CTF (contrast transfer function).
MTF is based upon repeating sinusoidal patterns, which is created from a single spatial frequency (Google terms that are unfamiliar)

 

[AgX]

The poor man's way:

Make yourself or buy respective charts that have patterns of stripes in varying frequencies (stripes per lenght-unit).
Check at the final reproduction step the highest frequency that still can be discerned by you as stripe pattern.
That will give you with a bit of calculating a personal resolution test. No MTF though.
But good enough for your personal gear or material qualifying, if done the same way each time.

 

[Sirius Glass]

The poor man's way:

Pay someone else to measure it.

+1

 

[Nodda Duma]

AgX if you scan your reproduction and calculate the contrast for each group of stripes, then you can get a rough plot of the CTF of the imaging system. This will include the CTF of the optics, film, and scanner. But for just the CTF of the lens....well It's difficult to separate out the component CTF's but theoretically you can. Use sinusoidally varying light/dark patterns instead of stripes and you get MTF.