This is the review of the IF that appeared in Popular Photography a few years ago:
A great performance—and no distortion!
WHAT YOU SHOULD KNOW: The
40mm f/4 Carl Zeiss Distagon T* IF CFE
lens, a new floating-element formula, is the
first major redesign of the 40mm Distagon
in decades. The 40mm (35mm equivalent:
26mm) is popular with Hasselblad shooters
using digital backs with smaller sensors.
The new 40mm f/4 Distagon T* IF
CFE has mechanical connections for
V-series Hasselblads (e.g., the 500CW)
and gold-plated contacts compatible with
200-series Hasselblads with electronically
controlled focal-plane shutters. It claims to
be up to digital standards.
HANDS ON: Average in size and weight
for a lens of its type, the lens is magnificently
finished in semigloss black with
very legible white-on-black numerals
except for the EV scale (EV 3–21) in
orange on black. There are adjacent
metric and footage distance scales, the
latter calibrated in inches below 3 feet,
down to the minimum focusing distance
of 19 inches. The wide, dual-focusing
collar and narrow shutter-speed (1–1/500
sec plus B) collar are rubberized, ribbed,
and very grippable. The f/4–22 aperture
ring is easy to grasp. You can lock both
aperture and shutter-speed rings together
by holding in a button as you turn them, to
make equivalent exposure settings. Other
features include an aperture-stopdown
switch, locking PC terminal, “F” shutter
setting, comprehensive depth-of-field
scale, and a screw-in lenshood. The new
lens balances extremely well, and all controls
operate very smoothly, with very well d&ed
action.
IN THE LAB: Resolution results indicate
outstanding performance at all apertures,
both center and edges, at f/4, f/5.6, and
f/8. Barrel distortion (0.1%) was virtually
undetectable. At the minimum measured
focusing distance of 18 inches (1:7.5), center
and edge sharpness were excellent at
all apertures. Optimum aperture was f/16.
IN THE FIELD: Test slides were uniformly
sharp and contrasty from center to corners
at all apertures, and flare was very well
controlled throughout. Light falloff was
gone by f/5.6. An excellent result.
CONCLUSION: Expensive, but for the
pros who need it, worth every penny. The
best ever tested for a medium-format lens
of this type
How they came up with no distortion is beyond me. What where they smoking?