Comparison Pentax FA28 versus F28
Contrast Comparison
The Pentax F28 and FA28 are both very good lenses and agree in almost all properties, except contrast wide open. This is demonstrated below.
One will probably not recognize this in the field, but only under defined test conditions.
Images below at f2.8, Pentax K20D, 100% crops.
1. Daylight:
2. Tungsten:
3. Infinity:
4. Contrast measurement:
Contrast has been measured using the method described here, using Image-J.
Do not give much on the absolute numbers (which depend on lighting) and not even much on the exact position of the points. The values have been obtained from only one image each and the error is probably quite high.
The test pattern:
Result:
The Pentax FA28 shows noticeably reduced contrast wide open compared to the F28.
From f4 on the contrast ist identical.
Else I have noticed that the focal length of the F is slightly shorter than that of the FA, about 3-4% (= ca. 1mm focal length), but I don't know which one is closer to 28mm.
In my view the best 28mm from Pentax is the M28/2.
It is optically and mechanically as excellent as the K28/2, but much smaller.
The K28/2 has the same optical construction as the Zeiss Distagon 28/2, whereas the M28/2 has the same optical construction as the Olympus Zuiko 28/2. Both designs are excellent.
BACK