105mm focal length is ideal for portrait photography,
and this Sigma Macro lens can produce extremely high sharpness
at typical focusing distances. Note the excellent definition
of the lettering on this photographer's camera.
(Sigma SA-5 with flash; f/8; Ektachrome E100 VS at EI
Photos © 1999, Peter K. Burian, All Rights Reserved
As a manufacturer of a wide
range of lenses from 8-800mm, Sigma's line also includes true
macro lenses for extreme close-up photography. Both of the current models
will produce a full life-size rendition of the subject without accessories:
the AF 50mm f/2.8 EX Macro and, the model I tested, the new AF 105mm
f/2.8 EX Macro featuring the most popular focal length. Billed as the
"world's smallest tele macro lens capable of focusing down
to a 1:1 reproduction ratio" it proves that good things do come
in small packages.
Design And Characteristics. This is a very compact
lens and surprisingly lightweight, in comparison to other macro lenses
which tend to be rather heavy. Although the mount is made of stainless
steel, excess weight is avoided through the use of lightweight alloys
and polycarbonates. In comparison to its longer predecessor, the Sigma
AF 180mm f/2.8 APO, the new AF 105mm f/2.8 EX lacks some high-end features
as we'll see. However, it weighs 33 oz less and costs hundreds
of dollars less. The following information is worth noting:
· The AF 105mm f/2.8 EX Macro includes high grade optics for fine
performance from infinity to its closest focusing distance of 12.3".
Unlike the previous Sigma 180mm f/2.8 APO Macro lens (discontinued but
may still be available) this one does not include low dispersion glass.
Hence it is not labeled as APO. Considering the relatively short focal
length, this omission is not significant as chromatic aberration is
not a problem. (Very few lenses under 180mm include low dispersion glass,
regardless of the brand.)
very high magnification, depth of field is extremely shallow
even at small apertures, a fact of life with any lens. The
defocused areas should not be interpreted as a sign of low
resolution. (Sigma SA-5; at 1:1; f/16; Bogen/Manfrotto tripod;
PhotoFlex reflector panel; Ektachrome E100 VS at EI 200.)
· Instead of internal
focusing (common on longer lenses) this one incorporates helical focusing;
the front barrel does not rotate so using a polarizer is a pleasure. However,
the effective aperture does reduce in size in extreme close focusing because
of light loss due to extension (the lens barrel increases in length).
It's f/4.2 at a 1:2 reproduction ratio and f/5.5 at 1:1. With in-camera
TTL metering, exposures will be accurate. When accessory light meters
are used (not common in extreme close-up work) exposure should be based
on the effective aperture as per the chart in the Owners Manual.
· The focus ring does not rotate during F operation if it is pushed
forward to the "AF" mark. This nicety ensures that your hand
does not impede it while autofocusing. Remember to set the ring to the
correct position when autofocusing; this speeds up the operation and avoids
the risk of damage to the motor during.
· The test sample was for the Sigma SA-5 camera so it included an
Autofocus/Manual Focus switch also found on the Canon mount lens. Lenses
for other cameras do not include this control as all functions are set
on the body. Naturally, a mechanical aperture ring is included on lenses
intended with Pentax AF and Nikon AF mount. The smallest maximum aperture
is f/45 (f/32 with models intended for Nikon and Pentax), which is useful
for maximizing depth of field. (To determine depth of field at any aperture,
use the camera's preview control (if so equipped) as no scale or
chart is included.)
this Sigma Macro lens can be employed for extremely high
magnification photography, it is also useful for more moderate
close-focus work. (Sigma S-5; at 1:3; f/22; Bogen/Manfrotto
tripod; PhotoFlex reflector panel; Ektachrome E100 VS at
· A focus limiter switch
is provided. Use it to restrict autofocus operation to only very short--or
great--focusing distances. This helps maximize focus acquisition speed
especially in autofocus as the AF system does not search the entire range
of possibilities. No focus adjustment is required when using infrared
· A non-slip, non-reflective, and scratch-resistant matte EX finish
is used. Sigma includes a screw-in lens hood, although it is not really
necessary except in extreme sidelighting. The front element is recessed
so stray light rarely strikes it in any event.
· A distance scale (in feet and meters) is provided and the reproduction
ratio from 1:4 to 1:1 is marked on the internal barrel that extends in
focusing. This is useful when you want a specific level of magnification.
Simply set the focusing ring to the desired reproduction ratio and move
the camera back and forth until the subject appears sharp. I used the
Adorama Macro Focusing Rail for maximum convenience during my tests, but
you can move the entire tripod if you don't have such an accessory.
Mechanical Performance. Overall, I would rate mechanical
quality as very high. This lens mounted onto a Sigma SA-5 with an authoritative
click and fit perfectly. There was no looseness or "play"
whatsoever. Manual focus operation with the 1.5" wide knurled/rubberized
ring is smooth and well damped for a familiar feel. For focusing from
infinity to 12.3", a 300° turn is required. I found this useful
because the slightest change in focus makes a significant difference in
extreme close-up work. Setting the precise point of focus proved to be
easy and convenient with the AF 105mm f/2.8 EX Macro.
close-focus work, stopping down to f/22 is often necessary
for adequate depth of field, and the Sigma 105mm EX Macro
lens produces excellent results. Even smaller apertures
can be selected but the effects of diffraction then begin
to degrade sharpness, as with any lens. (Sigma SA-5; at
1:2; f/22; Bogen/Manfrotto tripod; PhotoFlex reflector panel;
Ektachrome E100 VS at EI 200.)
Autofocus operation is fairly
fast with the Sigma SA-5 but not silent, producing a low pitched hum.
With any AF system, response is quickest at wide apertures such as f/2.8
because more light is transmitted to the sensors. This is an f/2.8 lens
at least at common focusing distances. Effective aperture does diminish
in extreme close focusing, but autofocus is rarely practical in such photography.
Because depth of field is minuscule, it's best to focus manually--on
the most important subject area, such as the stamen of a flower.
Quite short at infinity focus, the barrel does extend by 2.5" when
set for the minimum focusing distance. Since the internal barrel is so
light in weight, overall balance on a tripod does not shift noticeably.
At times, I do want a longer focal length in a macro lens: for greater
working room between the lens and subject or for a narrower angle of view
to avoid including a large expanse of a cluttered background. Like most
macro lenses however, the Sigma AF 105mm f/2.8 EX will not accept a tele-converter
directly. A short extension tube would solve that problem but one was
not supplied for my tests.
the Sigma 105mm EX Macro lens includes autofocus, it's
best to disengage this feature in extreme close-up photography.
Set focus manually for the most important subject element
instead of allowing the system to make its own "decision."
(Sigma SA-5; at 1:2; f/22; Bogen/Manfrotto tripod; PhotoFlex
reflector panel; Ektachrome 100EC.)
The loss of light transmission
with lens extension did make focusing more difficult in low-light conditions,
but then I remembered an important fact. My own macro lens--like some
other affordable models--has only an f/5.6 maximum aperture and only provides
magnification to 0.5x (half life-size). In comparison, the Sigma AF 105mm
f/5.6 EX Macro is still ahead on both counts.
Performance Evaluation. I used this macro lens often
in greenhouse gardens for close-ups of tiny blossoms or details inside
larger flowers. The primary advantage of shooting indoors is that there
is less wind-induced motion. The fans do move the subject slightly, but
not nearly as much as the wind outdoors would. After discarding the slides
blurred by subject motion, I made the following notes while reviewing
the others under an 8x loupe.
· At a 1:2 (and lower) reproduction ration, macro performance as
excellent overall with the optimum results obtained at f/16. This produced
very high sharpness, definition of intricate detail, and contrast at the
f/stop we all use most frequently in such photography. (I did not hesitate
to shoot at f/11 or f/22 either when those f/stops were required to achieve
a specific effect.) Center sharpness was high while edge sharpness nearly
matched that level. I considered the slides suitable for a fine 11x4 print,
impressive indeed for a lens in this price range.
· At the 1:1 reproduction ratio (full 1x magnification) optimum
results were obtained at f/16 and f/22, small apertures essential for
adequate depth of field. Image quality is suitable for a fine 8x12 print
or a full page reproduction in a book or magazine.
matter how high the optical potential of this Sigma Macro
lens, the slightest camera or subject movement will lead
to unsharp images. By shooting indoors, using professional
techniques, I was often able to avoid motion blur. (Sigma
SA-5; at 1:1; f/16; Bogen/Manfrotto tripod; PhotoFlex reflector
panel; Velvia 50 at EI 100.)
· At very wide apertures
such as f/2.8 or f/4, sharpness and definition were lower, especially
at the edges of the frame. Frankly, this is merely academic. In close-focus
photography, depth of field is far too shallow at wide apertures, so most
such work is done at small apertures.
· When desired, I was able to stop down even further, to f/45 for
maximum depth of field. This is tempting for anyone who finds the range
of sharp focus so frustratingly shallow in extreme close-up photography.
However, as with any lens, stopping down beyond f/22 does extract a penalty:
due to the effects of diffraction, image sharpness is degraded. This is
an optical fact with any lens, caused by the bending of light rays as
they pass through an extremely small aperture. Select f/32 to f/45 only
when depth of field is more important than a razor sharp image as in some
interpretive (non-documentary) photography.
· At greater focusing distances from 8' to infinity, optical
performance was very good indeed. A 105mm focal length is great for portrait
photography, and this lens would do well in that application, too. For
the optimum results, shoot in the f/5.6 to f/11 range to take advantage
of the optical "sweet spot." When the background is defocused,
you'll notice a very pleasing effect in the out of focus highlights.
This is caused by the eight (vs. the usual six) blades in the diaphragm
which make the opening nearly circular even at wide apertures.
In order to avoid disappointment in any extremely high magnification work,
use professional photographic techniques. That means a rigid tripod, cable
release, and reflex mirror pre-lock at the 1/4 sec to 1/30 sec shutter
speeds where the effects of internal vibration are most noticeable. And
make sure the subject is not being moved by the breeze, even slightly.
Finally, do recognize the effects of shallow depth of field. The zone
of apparent sharpness is very limited in high magnification photography;
the out of focus areas should not be interpreted as an indication of low
In a nutshell, the Sigma AF 105mm f/2.8 EX Macro produced image quality
much higher than its moderate price would suggest. Aside from the factors
already evaluated, there is virtually no vignetting by f/5.6, flare is
well controlled, color rendition is very close to neutral, and pincushion
distortion is minimal. Overall, this lens is a bargain. It's one
that would suit the needs of the photo hobbyist who is interested in trying
some extreme close-up work whether for nature or for stamps, coins or
other inanimate subjects.
elements in nine groups
Minimum Aperture: f/32 (Nikon D and Pentax); f/45 (Sigma
SA and Canon)
Angle Of View: 23.3°
Minimum Focusing Distance: 12.3" (31.3 cm)
Maximum Reproduction Ratio: 1:1
Diaphragm: Eight blades
Filter Size: 58mm
Dimensions: 2.9x3.7" (74x95mm)
Weight: 15.9 oz (450 g)
Mounts: Nikon D AF, Canon AF, Pentax AF, Sigma AF