Hi,
The 120/4 has significant field curvature.
Best regards
Erik
The mtf literature from Zeiss states:
"This is the must-have lens for every photographer doing serious
close-up work. We believe that no studio photographer
specialised in advertising, product, food, technical or industrial
photography can really do without it. Combined with a motorized
Hasselblad SLR or the Hasselblad FlexBody for creative
selective tilting of the sharpness zone, the Makro-Planar® T*
4/120 CFE lens is the compact workhorse lens for day-to-day
studio work - be it analog or digital.
Optically well-designed makro-lenses like the Makro-Planar® T*
4/120 CFE lens differ from other lenses in two ways.
First: Their performance is optimized for subjects like the one
you’re just looking at: A flat page slightly larger than a human
head with intricate detail plus color. Which means that the image
quality and light distribution is extremely good, even in the
corners and even at full aperture. This is exactly what is needed
for serious professional copy work of subjects that are smaller
than the ones ideally photographed with the Carl
Zeiss Planar® T* 3,5/100 CFi lens, e. g. delicate drawings (so
the two lenses complement each other very well in the hands of a
demanding photographer).
Second: A basic type of lens design is chosen that maintains its
performance characteristics very constantly on a high level over a
wide range of reduction ratios or distances.
Like from half life-size (1:2) to infinity, in the case of the
Makro-Planar® T* 4/120 CFE lens.
It is based on the Carl Zeiss Planar® lens design type, which
offers very good close-up potential and is therefore also chosen
as the basis for the ultra high resolution Carl Zeiss S-Planar®
lenses for the micro-lithography, which are - in their new version -
called Starlith, the most sophisticated lenses of our day.
Although the Makro-Planar® T* 4/120 CFE lens can and should
be used for subjects as small as postcards, the built in focussing
helicoil allowes only to focus down to a single page. This has
been done for safety reasons: Since most of the Hasselblad SLR
cameras in use with professional photographers today do not
incorporate TTL exposure metering, we believe that the lens
should not easily focus down to such reduction ratios without
warning, where exposure compensation is absolutely unavoidable
for professional results. Adding an extension ring for closer
focussing should remind the photographer to apply the
necessary compensation.
The CFE version of the Makro-Planar® T* 4/120 lens allows for
fully automatic compensation of exposure in extreme close-up
photography provided a Hasselblad camera with built-in TTL
exposure meter is used.
Preferred use: Close-ups of all kind, products, industrial,
documentation, copy work, digital photography"
It looks like here it is supposed to be very flat field,
but only for close distances, and that is likely why the infinity curves show such a drop towards the edges...otherwise, it has been described by Zeiss personnel as being better chromatically corrected than most other makers' apo designs, and in my experience (nowhere as much as many of you though, no doubt) is a really nice piece of glass...just building on your comment and trying to give a more comprehensive idea of this lens, as many people dismiss it out of hand.
Also, if I remember correctly, Leica showcased their initial S camera with this lens before they created their own S lenses.
Hope this helps.
Martin