modulation transfer function

[dachyon]

Hi Experts,
I am looking for a way to measure image quality using Modulation Transfer Function (MTF) measurements, but can find no reference to this concept in the Vision Development module docs, or on this forum. Does anyone know if NI supports this kind of image quality testing ?

Thanks in advance.
D

[Zealous]

I'm also interested about MTF so if someone could explain is it possible to measure, calculate and draw MTF?

[viksiv]

The standard for measuring the resolution of both scanners and digital cameras is set out in ISO-12233 and is based on slanted edge method. The Standard defines test target, illumination conditions and numerical procedure to calculate the MTF. The technique uses image of a sharp edge, slightly slanted relative to the vertical and horizontal axes, which transitions from near full black to near full white.  Imaging this edge with a camera produces an Edge Spread Function, a measure of how much the camera resolves or blurs the edge.  Spatial differentiation of the ESF results in a Line Spread Function, a measure of how the camera resolves and blurs lines.  By orienting the spatial differentiation along the axis closest to the edge rather than the axis across it, the ESF is essentially oversampled. This enables the LSF to be determined at many times the limiting resolution of the digital structure, effectively multiplying the Nyquist limit.  Using a Fourier Transform, the Modulation Transfer Function is determined directly from the LSF.

Here http://www.i3a.org/downloads_iso_tools.html  you can find both Matlab and Labview tools to perform ISO-12233 test on RECORDED image. If you need to calculate MTF during live video you will have to write your own program. Labview together with Vision module has all necessary basic functions (extraction, differentiation, FFT) to calculate MTF, although processing of oversampled slanted edge has to be developed in a way similar to how it's done in above mentioned tools.

Imatest http://www.imatest.com/docs/sharpness.html has commercial program that implements ISO-12233 test technique and has enhanced capabilities. They also describe in more details how actual processing is done.

Please note that this technique gives MTF of complete system (camera lens + detector) and not of camera optics alone.

Subject of MTF is quite wide to be covered here. This digital photography site http://www.normankoren.com/Tutorials/MTF.html  has good  and simple introduction into the issue.

[dachyon]

Thanks a lot, thats very helpful. 

D

[Zealous]

Thanks a lot! That helped much 🙂

[harjeemann]

hello experts,

               i am  bit confused for getting MTF curve and know verty little about it . i am having a picture i am taking its FFT i get an edge detected image after that what i have to do to get an MTF curve graph. bit complecated for me and http://www.i3a.org/downloads_iso_tools.html  link is not existing now i think. 

i read some where to take a FFT of your image and thenmultiply with "frquency response" what frequency response means i have no idea here if any on e help me with the steps to have a MTF curve will be appreciated.

cheers

harry 

[viksiv]

Hi,

If you do a search for "ISO-12233 test tools" you'll find that a new location for the test tools is http://www.i3a.org/resources/iso/iso-tools/

Also the only way to overcome your confusion about "getting MTF curve and knowing very little about it" is to start experimenting and learning more...

V.

[harjeemann]

thanks viksiv that will help me

[okurtsev]

Also you can try Quick MTF - www.quickmtf.com

[UweV]

Thank you, viksiv, for the posted links ( http://www.i3a.org/downloads_iso_tools.html ).

However, this link seems to be dead. Does anyone know where to find a LabVIEW (or Matlab) implementation of an ISO-12233 test?

Thanks a lot!