Fast, ultra-compact mid-range zoom
High resolution full-frame digital SLRs demand the optical quality for which the SP 28-75mm F/2.8 XR Di is famous. Another in Tamron's selection of fast and constant F2.8 maximum aperture optics, its speed benefits photographers in several ways, including the ability to render cluttered backgrounds well out of focus, added low-light shooting freedom and a brighter viewfinder image. Featuring XR (Extra Refractive Index) and LD (Low Dispersion) glass in an optical formula employing 16 elements and 14 groups—assuring sharpness, optimal contrast and color accuracy, rendering striking images. Sophisticated aspherical element design and internal focus contribute to barrel size that belies a typically large F2.8 optic. With both an ideal picture angle range, fast aperture and outstanding optical properties, it's no wonder that so many SP 28-75mm F/2.8 lenses can be found in the bags of noted wedding and corporate shooters.
The designation “Di” (Digitally Integrated Design) marks a generation of lenses, which have been specially adapted to the higher requirements of digital SLR cameras (APS-C and full frame).
|Angle of View (diagonal)||
75° 32’ (with full-size SLR cameras)
32° 11’ (with APS-C sized sensor digital SLR cameras)
|Lens Construction||16 elements in 14 groups|
|Minimum Focus Distance||0.33m (13") (entire zoom range)|
|Max. Magnification Ratio||1:3.9 (at 75mm)|
|Diaphragm Blade Number||7 (circular diaphragm)|
|Standard Accessories||Lens hood|
|Compatible Mounts||Canon, Nikon with Built-In Motor, Pentax, Sony A mount|
Specifications, appearance, functionality, etc. may be changed without prior notice.
MTF (Modulation Transfer Function) curves describe to what extent the tested lens can faithfully reproduce contrast of the subject in images it captures.
The closer the 10 lp/mm (line pairs per millimeter) curve (the thick line for low frequency) in an MTF chart to "1" of the vertical axis (the higher up), the higher the contrast reproduction performance of the tested lens will be. The closer the 30 lp/mm curve (the thin line for high frequency) to "1" (the higher up), the higher the resolving power and thus the subjective sharpness of the lens will be.
Lens performance differs depending upon directions. Solid lines show performance in the sagittal (radial) direction while dotted lines indicate performance in the meridional (circumferential) direction. When sharp lenses capable of delivering uniform optical performance over the entire image field are tested, MTF charts show curves plotted in good balance.
Performance characteristics of photographic lenses cannot be expressed with only MTF charts. There are other factors that are expressed in different methods, such as taste of softness and degrees of compensation of various aberrations. But you can use MTF charts as a scale to measure lens performance.