Can an MTF chart tell you anything about a lens’s bokeh quality?

Question

I know MTF charts are mainly used to judge sharpness and contrast, but I’ve heard that they may also hint at bokeh quality. In particular, some people say the spacing or divergence between the sagittal and meridional lines can indicate whether out-of-focus rendering will look smooth or nervous.

Is that actually true? Can an MTF chart predict bokeh quality, as opposed to depth of field? For example, if a lens sometimes shows ring-shaped highlights instead of smooth blur discs, would that be visible in an MTF chart or review-style MTF bar graph?

user1375 · Accepted Answer

Supposedly the deviation between the Saggital (solid) and Meridional (dashed) lines on the mtf chart can be used to judge the bokeh. If the lines deviate widely from left to right the bokeh can have undesirable qualities.

Saggital contrast is measured using a pattern of fine lines parallel to the image diagonal whereas Meridional lines are set at 90 degrees to the image diagonal.

You have to compare pairs that correspond to the same f-stop and contrast rating (i.e they are the same colour and thickness).

Here is an example of a good lens, although contrast varies the S and M lines stay reasonably close together.

_{(source: canon.com)}

Here's an example of a less good lens (look closely at the thin blue lines):

_{(source: canon.com)}

Can an MTF chart tell you anything about a lens’s bokeh quality?

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