Tamron SP 70-210mm F/3.5-4 Model 52A: Tamron's SP 70-210, introduced in 1979, changed the thinking of optical engineers throughout the industry by showing what could be achieved in terms of properly balancing optical performance throughout a 3:1 zoom range and throughout a continuous focusing range of infinity to 1:2 macro at 0.75 meter. There were no macro buttons to press, and this lens could even be zoomed while in macro mode without affecting the focus. This lens clearly offered far more convenience and flexibility compared any other telephoto zoom lens available at the time of its introduction, with the exception of Vivitar's Series 1 90-180mm medical macro zoom, and is an excellent example of Tamron's frequent genius for optical design. Tamron's lens features a broader zoom range plus better control off off-axis aberrations compared to the Vivitar Series 1 lens.

While overall optical performance is average (in terms of a conventional telephoto zoom lens), the inherent features of this lens were in a class unto itself when this lens was introduced to the marketplace. Some have suggested that this model 52A lens is better than Tamron's completely redesigned and later model 19AH lens merely because this lens reaches 1:2 in macro mode whereas the 19AH lens only reaches 1:2.66 in macro mode. This quite simply is not the case. Tamron's later SP 70-210 model 19AH is significantly sharper and produces much higher contrast for the fine details within the image, and is superior in all respects except for maximum macro magnification. Nevertheless Tamron's Model 52A, for a zoom lens, provides very good close focus and macro performance.

The SP 70-210 was the first 3:1 telephoto zoom lens which continuously focused from infinity to 0.75 meter and which was capable of 1:2 telephoto macro magnification at the long end of the zoom range. Previously, telephoto zoom lenses which featured a "macro" mode employed a button which was pressed to allow rotation of the zoom collar past the minimum focal length setting and into macro mode. Optically, this operation merely shifts the position of the compensator group such that the lens will only focus on extremely close subjects. The problem with this compensator group shift method is that, while on-axis macro performance will be acceptable to fairly good at best, off-axis macro performance will usually be quite poor. Tamron's lens resolves these issues rather successfully. Look carefully at the four elements employed in the front focus group within this lens, as shown above. You will note that these elements are quite thin and feature very gentle curves. Why, you wonder? Quite simply because this type of optical prescription minimizes focus induced aberrations such as spherical aberration, off-axis astigmatism and off-axis coma.

Did you know that this lens came in two flavors, both labeled as model 52A? Look closely at the focus scale in the photo at the top of this page and the photo to the right (click on photo at right to view a high resolution). Note that the foot scale in the top photo reads 20 and then infinity whereas the foot scale in the photo to the right reads 30 and then infinity. The original mechanical version of this lens featured a mere 1/2 turn of the focus ring to go from infinity to the minimum focus distance of 0.75 meters. The later mechanical version looks identical except for the focus scale. The later version features a 3/4 turn of the focus ring to go from infinity to the 0.75 meter minimum focus distance. The focus on the later version, unlike the earlier version, doesn't creep when the lens is tilted up or down. The original version is fairly rare since it was quickly replaced with the later version within a matter of a few months.

Two other manufacturers, one an independent (Vivitar) and the other an OEM (Konica), produced functionally similar lenses to the Tamron. Vivitar introduced their their Series 1 90-180mm F/4.5 in either 1976 or 1977, and Konica soon introduced 80-200mm F/4 UC Hexanon AR a year after the Tamron. Both of these lenses, like the Tamron, featured continuous focusing to 1:2 macro at the telephoto end of their zoom ranges. For a while these three lenses were the only telephoto zooms which provided continuous focusing 1:2 tele-macro capabilities. The performance of the Tamron and Vivitar lenses, considering the features and optical design parameters, was quite good for the era and represented the best that could be achieved by any manufacturer. The Konica lens, as tested by Modern Photography, displayed some decentering on the optical bench and would have performed better had Modern sought out another example as was normally their policy. Unfortunately the Konica test report fell prey to the publishing deadline and a correctly manufactured example was not obtained by Modern for testing. Konica fanatics, please keep this in mind when reviewing the Modern Photography test reports shown further below, as a good production example of the Konica lens performs somewhat better compared to the results which Modern Photography published.

The Tamron's 3:1 zoom ratio is more versatile than the 2.1 and 2.5:1 zoom ratios of the Vivitar and the Konica lenses respectively. It should be noted that the Tamron SP 70-210, unlike the Vivitar and Konica lenses, possesses virtually zero chromatic aberration or lateral color. Also note that, while the Vivitar and Konica lenses do display some off-axis lateral color, the lateral color in these lenses is considered to be small in amount compared to conventional zoom lenses. Off-axis astigmatism and coma are very well controlled within the Tamron since, in addition to the four element focus group, Tamron chose to also use four elements in the zoom group and four elements in the compensator group. Thus Tamron was able to achieve fairly high off-axis aberration correction and performance throughout a somewhat broader 3:1 zoom range and throughout the very wide focusing range.

The SP 70-210's only weakness is a lack of contrast in fine details at all zoom settings when photographing distant subjects. Why? Because the correction for spherical aberration within the four element focus group was optimized for closer distances rather than for infinity. This is fairly similar to the Vivitar lens which was optimized for 1:10 magnification, yet is much more tolerant for both further and closer focusing distances. The result in slight spherical aberration at infinity, particularly at the telephoto end, and is why we noted that this lens is merely "average" when used as a conventional telephoto lens for distant subjects. When shooting subjects which are more than 20 feet away from the lens, stop this lens down to F/8 to suppress the slight spherical aberration. Image quality is noticeably sharper within the 5 to 10 foot range. Why? Because the front focus group is optimized for this range, producing nearly zero spherical aberration.

The macro performance of the Tamron SP 70-210 and Vivitar Series 1 90-180 lenses is superior to the Konica lens. The Tamron's macro performance is very good on-axis, but shows some off-axis astigmatism with larger apertures at the shorter zoom settings. When in macro mode, stop the Tamron down to F/8 or F/11 and the off-axis astigmatism disappears to yield very good image quality across almost the entire field. The Vivitar lens, when in macro mode, exhibits some off-axis coma and lateral color which are reduced by using smaller apertures. Again, note that the Tamron lens exhibits virtually zero lateral color. Overall, the Tamron lens has somewhat better off-axis image quality compared to the Vivitar when both lenses are used in the 1:4 to 1:2 macro magnification range.

The SP 70-210's ergonomics are much better in comparison to the Vivitar lens. The Tamron's focus, zoom and aperture rings are all of the same diameter which makes moving your hand back and forth for adjustments much more convenient. The Tamron also has a much wider zoom ring (in terms of gripping area along the barrel, not diameter) compared to the Vivitar and features a focus ring which, unlike the Konica and Vivitar lenses, does not move forward when turned. Ergonomics of the Konica lens are surprisingly good with the exception that the focus ring does move forward when the lens is focused toward closer focus distances. In terms of ergonimics, the Tamron ranks first, the Konica second, and the Vivitar a more distant third.

Both the Tamron and Vivitar lenses feature nicely labeled macro reproduction ratio scales. The Tamron scales are most convenient since they are color coded for three zoom focal lengths, namely 70, 135 and 210mm, whereas the Vivitar lens features three individual orange colored scales which are labeled for focal lengths of 90,135 and 180mm. Note that the Konica lens does not feature any macro reproduction ratio scales. Although the Konica lens was a beautifully engineered and constructed lens, the lack of color coded macro scales to match the color coded zoom ring definitely was a detriment to sales of the Konica lens. The Konica lens could have, should have, and would have sold much better in its day had Konica provided similar color coded scales as featured on the Tamron lens. The room was there on the barrel of the Konica lens. It is not that these scales would have been particularly handy; but rather would have immediately implied to the prospective buyer that the Konica lens was indeed something special in terms of inherent features.

The Vivitar lens featured a built-in tripod socket whereas the tripod ring for the Tamron was an optional accessory. The Konica lens didn't feature any tripod ring, and Konica never produced an accessory tripod ring. Notably, both the Tamron and Konica lenses featured built-in lens hoods which are quite useful for shading these lenses against flare.

So, what are our overall conclusions regarding these three lenses?

• Overall, this Tamron lens features not only a broader zoom range, but also features slightly better off-axis macro performance compared to the Vivitar Series 1 lens.
• This Tamron lens features virtually zero chromatic aberration and lateral color, making it virtually an APO lens in terms of these aberrations which, by nature, define an apochromatic lens. Why didn't Tamron promote this feature, we will never know! We consider this to be a gross oversight in Tamron's advertising for this lens.
• This Tamron lens features extremely tight control of off-axis aberrations yet exhibits spherical aberration for subjects which are further than about 15 or 20 feet away.
• This Tamron lens, since spherical aberration is its only predominant aberration for distant subjects, responds very well to mild to moderate unsharp mask techniques in image processing programs such as PhotoShop to yield very good results.
• Both this Tamron lens and the Vivitar Series 1 lens perform very similarly in macro mode; its just a difference in off-axis aberrations.
• The Konica lens performs somewhat below both the Tamron and Vivitar lenses in macro mode, particularly in terms of off-axis performance.

Lens Specifications:

Lens Model	52A
Focal Length	70 — 210mm
Aperture Range	f/3.5~4 — 32, AE
Angle of View	34°~11°
Optical Construction (Groups / Elements)	15 / 16
Min. Focus from Film Plane	29.5" (0.75m)
Macro Mag. Ratio [w/2X Converter]	1:2 [1:1]
Filter Size	58mm
Diameter in. (mm)	2.5" (64.5mm)
Length at [w/Nikon mount]	6.5" (165mm) [6.7" (169.5mm)]
Weight oz. (gm)	26.5 oz. (750g)
Lens Hood	Built-in type, retractable.
Accessory	Accepts SP 2X tele-converter #01F. Tripod mount ring available as optional extra.