Understanding the MTF graphs
We have been testing lenses with Hasselblads
Ealing MTF equipment since 1991. All MTF reports are made with the same equipment
and by the same operator (Per Nordlund at Victor Hasselblad AB). So far we have
tested lenses only at infinity. We measure MTF at 10, 20 and 40 lp/mm, where
10 lp/mm (line pairs/ mm) means 10 black lines with 10 white lines in between,
for each millimeter.
The graphs
The graphs show MTF in percent for the three line frequences of 10 lp/mm,
20 lp/mm and 40 lp/mm, from the center of the image (shown at left) all the
way to the corner (shown at right). The top two lines represent 10 lp/mm,
the middle two lines 20 lp/mm and the bottom two lines 40 lp/mm. The solid
lines represent sagital MTF (lp/mm aligned like the spokes in a wheel). The
broken lines represent tangential MTF (lp/mm arranged like the rim of a wheel,
at right angles to sagital lines). On the scale at the bottom 0 represents
the center of the image (on axis), 3 represents 3 mm from the center, and 21
represents 21 mm from the center, or the very corner of a 35 mm-film image.
Separate graphs show results at f8 and full aperture. For zoom lenses, there
are graphs for each measured focal length.
Resolution, contrast, MTF
Many terms - but what do they mean? In an article about lens performance, the
terms are discussed in an understandable way. Read more.