105_micro

Lens construction:	9 elements in 8 groups
Focus distance:	0.314 m to infinity
Angle of View:	23° 30'
Max. reproduction ratio:	1:1
Aperture scale:	f/2.8 to f/32
Attachment size:	52 mm
Diaphgram blades:	9
Lens hood:	HS 7
Dimensions:	75 mm (dia.) x 104.5 mm (length)
Weight:	555 g

In 1969 the compact Bellows-Nikkor 105/4, weighing just 230 g, was introduced. This lens did not have a focusing helicoid nor an automatic diaphgram, but its aperture could be set in 1/3-stops. The glass elements of the Bellows 105/4 were single-coated. Six years later (1975) the same five-element, three-group design was incorporated into the Micro-Nikkor 105 mm f/4, which now had a mount permitting focusing down to 47 cm (1:2). In 1981, the 105/4 received a new mount, with a locking screw to be used in reproduction work. In 1983 the AI 105/2.8 was introduced. This faster lens, with a ten-element CRC design, exhibited a better performance at infinity than its predecessor.

In 1990 the AF Micro-Nikkor 105/2.8 appeared and three years later the D-version was introduced. It was the first 105 mm Micro-Nikkor which could cover the complete range between infinity and 1:1 steplessly and without extension rings (namely, the PN-11), nor close-up attachment lenses (Nikon 4T). The AF 105/2.8 has a floating elements design, being 78.5 mm the effective focal length at the minimum focusing distance (31.4 cm). In fact, at 1:1 the effective focal length is given by the focusing distance divided by four. The plot below shows the variation of both the magnification and the effective focal length as a function of the focusing distance.

The shortening of the focal length in new macro lenses, determines also rather short working distances (WD). At 1:1, the WD of the AF Micro-Nikkor 105/2.8 is 13.6 cm. The table below shows the WDs of modern 100-105 mm macro lenses.

lens	WD (cm) at 1:1
Minolta AF 100/2.8 Macro	16.2
Contax Makro Planar J 100/2.8	15.5
Canon EF 100/2.8 Macro USM	15
Nikon AF 105/2.8 D	13.6
Sigma AF 105/2.8 Macro EX	12
Pentax FA 100/2.8 Macro	11.1
Tamron AF SP 90/2.8 Macro	10

The optical quality of the AF Micro-Nikkor 105/2.8 is very good. At f/2.8 lens sharpness at infinity is very good when checked by a 5X loupe. Surprisingly, borders are only slightly less sharp than the center, thus indicating a rather good correction of field curvature.

When viewed by 8X loupe, slides taken at f/2.8 are not as sharp as those shot at f/5.6, which exhibit a very good sharpness and contrast. At f/4 the performance is intermediate between f/2.8 and f/5.6.

Wide open I could not notice any vignetting. Distorsion is practically nil, as one should expect from a highly corrected prime macro lens.

I have used it with my Nikon TC-14A (1.4 X tele-extender) to take pictures of a distant building and I compared the slides to those taken using my AF ED 80-200/2.8 D. At f/2.8 (f/4 with TC) soft borders were clearly visible by 8X loupe (the 80-200/2.8 at f/4 and around 150 mm exhibits a better, more even performance). At f/4 borders' sharpness slightly increases, but to get an even sharpness, the AF 105 must be stopped down to f/5.6 when coupled to the TC-14A.

I have also shot dragonflies using the AF 105/2.8 and the TC-14A; in fact, at a given magnification, the use of the TC allows to increase the working distance. Pictures taken at f/8 or f/11 are very sharp when checked by 8X loupe.

Nikon compatibility tables state that the TC-14A cannot be used with the AF-D version of this lens.