Tamron SP lens 911331 tested, 90mm f/2.5 macro, Olympus-fit.     Tested April 1981.

Lens number 911331                  

Specifications: 90mm f/2.5 Tamron SP, No. 911331; Adaptall-2 mounts for Olympus OM, Canon FD, Minolta MD, Konica AR, Contax / Yashica; Adaptall mounts for Pentax K, ES, Universal, Nikon A1, Fujica ST, Mamiya (SX and ZE), Topcon, Rollei, Canon FL;accepts 49mm filters, f/2.5 to f/32, with click stops at ½ stops except between f/16 and f/22;, min. foc. dist. 15 5/16 in. (0.39m), 2 5/8 in. long, 2½ in. diam. (66 x 64.5 mm); close-focussing to 1:2, 1:1 with 2X converter; $360.

Practical comments: Well-finished 90mm f/2.5 is conveniently short, very well balanced on camera: 1¼ in.-wide textured rubber focussing ring is easy to grasp, with smooth, precise action; all scales very legible; f/32 minimum aperture very useful in macro and with fast films, magnification ratios with and without 2X converter clearly indicated on barrel, 49mm front thread often enables use of existing filters, but front element isn't well shielded from stray light unless accessory hood is used..

        PERFORMANCE

Our Standard As Tested
Focal length: + - 5%
(85.50 - 94.50mm) 		88.49mm
Max. Aperture: + - 5%
(f/2.38 - 2.63) 		f/ 2.58
Distortion: ( ± 2.0%) less than 0.5% (pincushion)
Light falloff; at f/ 5.6
+1 stop from theoretical limit
(0 - 1.15 stops) 		0.15 stops


                    RESOLUTION

TAMRON SP 90mm f/2.5
at 1:49 magnification
f/no. Center
(Lines/mm) 		Corner
(Lines/mm)
2.5 Excellent 49 Excellent 55
4 Excellent 62 Excellent 55
5.6 Excellent 62 Excellent 55
8 Excellent 69 Excellent 62
11 Excellent 69 Excellent 62
16 Excellent 62 Excellent 62
22 Excellent 55 Excellent 49
32 V. Good 44 Excellent 44
                      CONTRAST

TAMRON SP 90mm f/2.5
at 30 lines / mm
f/no. Center
( % ) 		Corner
( % )
2.5 Medium 49 Low 28
4 High 72 High 54
5.6 High 76 High 60
8 Medium 66 High 55
11 Medium 64 Medium 52
16 Medium 53 Medium 47
22 Low 45 Low 40
32 V. Low 33 Low 30


                    MACRO RESOLUTION

TAMRON SP 90mm f/2.5
at 1:2.07
f/ Center
(L/mm) 		Corner
(L/mm)
2.5 ******** 33 V. Good 33
4 Accept 37 Good 33
5.6 Good 47 Accept 33
8 V. Good 53 Excellent 47
11 Excellent 59 Excellent 59
16 Excellent 59 Excellent 59
22 V. Good 53 Excellent 53
32 Excellent 53 Excellent 47
                      MACRO RESOLUTION

TAMRON SP 90mm f/2.5
at 1: 4.06
f/ Center
(L/mm ) 		Corner
( L/mm )
2.5 Good 41 Excellent 46
4 Excellent 58 Excellent 52
5.6 Excellent 65 Excellent 52
8 V. Good 58 Excellent 58
11 Excellent 58 Excellent 58
16 Excellent 58 Excellent 52
22 V. Good 52 Excellent 52
32 Excellent 52 Excellent 52


******* Not recommended, macro seldom used at this aperture.

Field test slides: Crisp, snappy transparencies at all apertures, with good contrast, fine image detail across the field. Sharpness improved somewhat in f/8 to f/16 range. Some flare noticeable under adverse conditions (sun just outside picture) due to shallowly recessed front element..

Optical bench analysis: Tight, bright central image core on axis at f/2.5, with slight spherical aberration, reduced to very slight levels at f/5.6 with touch of yellow-orange flare. Image quality optimal by f/16.
Toward corners of field, some reddish and surrounding yellowish flare near the image core at f/2.5, but greatly improved by f/4, diffraction limited (optimal) at f/16.
(April 1981)

Modern's Photo Buying Guide '85
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