Sigma Slr & Dslr Lenses | Sigma 18-200Mm F/3.5-6.3 Ii Dc Os Hsm Af Lens For Nikon Aps-C Dslr {62}

This Series Of Zoom Lenses Was Created To Give A Lightweight Lens That Could Be Wide Angle Or Telephoto Or In-Between. The Focal Length Rules Still Apply To Zoom Lenses. The Focal Length Is For The Format The Lens Was Designed For. This Focal Length Is Based On 35Mm Full-Frame Cameras Or Digital Full-Frame Cameras. An Slr That Uses A Lens Such As Dx Or Aps-C Most Be Multiplied By A Factor To See The Actual Focal Length That Comes From Using A Sensor That Is Smaller Than 24X36 Size. If The Lens Is Used With A Full-Frame Slr, The First Number Is The Widest Angle, The Second The Maximum Focal Length. If The Second Is Less Than 50Mm, Then It Is A Wide-Angle Zoom. If It Goes Higher Than 50Mm, It Is A Wide-Angle To Telephoto Zoom. If The Base Maximum F/Stop Is A Fixed Number, The F/Stop Range Will Remain Constant Throughout The Zoom Range. If This Number Is Two Part, Such As F/2.8-F/4, Then The Lens Will Only Be An F/2.8 Lens At The Smallest Millimeter. This Will Vary Throughout The Zoom Range And Will End At The Maximum Telephoto At The Second F/Stop. With A Camera That Meters Through The Lens, This Change Will Be Automatically Adjusted. If You Are Using A Flash That Is Not Coupled To The Meter, You Must Adjust The F/Stop To Compensate