Tamron SP 70-200mm f/2.8 Di VC USD G2 Lens for F - Manual (Page 27)

An electromagnetic diaphragm system, which is
a standard feature for Canon-mount lenses, is
now utilized in Nikon-mount lenses*. More
precise diaphragm and aperture control is
possible because the diaphragm blades are
driven and controlled by a motor through
electronic pulse signals.
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*Available only with cameras compatible with the electromagnetic diaphragm (D3100, D3200, D3300, D3400, D5000, D5100, D5200,
D5300, D5500, D5600, D7000, D7100, D7200, D300, D300s, D600, D610, D700, D750, D800, D800E, D810, D810A, D3x, D4, D4s, Df,
D500, D5). (As of January 1; Tamron)
Electromagnetic diaphragm system for
Nikon-mount lenses