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Canon EOS 40D Guide to Digital Photography by David D. Busch

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But First, a Word from Our Sensor

One pervasive consideration that will trip us up in this chapter (and throughout this book) is the omnipresent lens crop factor. If the sensor is smaller than the standard 35mm film frame (24mm × 36mm), then any given lens will produce a field of view that’s cropped from that full frame. To express the “real” field of view in 35mm terms, you must multiply a lens’s focal length by the crop factor, which in the case of the EOS 40D is 1.6X. Canon also sells dSLRs with 1.3X and 1X (full-frame) sensors, which provide the fields of view shown in Figure 6.1. At this writing, Canon’s camera line includes the Canon EOS-1Ds Mark III and Canon EOS 5D, which both provide a full-frame, 1X crop (or non-crop) of the image, ...

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