This slight difference is a combination of experience, use and preference. Don't exclude Sigma, their 24-70 might be your preference over Canon's, but Canon's 85mm might be your preference over the Sigma. It's good to have something to compare too and to choose from! I love my Sigma 17-50 and my 1.8 135. Has full-time manual focus. Canon EF-S 10-22mm f/3.5-4.5 USM. Sigma 18-35mm F1.8 DC HSM A. With full-time manual focus, you can move the focus ring whilst it is in AF (autofocus) mode. This means that you can make manual adjustments once the AF has finished, without changing to manual mode. EF-A - The standard focus screen for EOS 40D. Standard Precision Matte surface, ideal with most lenses including zooms f/3.5 thru 5.6. All matte surface. Includes a special tool to remove existing screen. EF-D - Precision Matte surface, with etched grid lines to assist composition. The EOS 40D's AF points remain fully visible. Having no optics in the adapter means no loss of image quality. The same is also true for users of EOS M-series cameras with the EF-M lens mount who want to use EF or EF-S lenses - though EF-M has a shorter flange distance (18mm) than RF does (20mm), so you can't adapt EF-M lenses to the EOS R body without using optics. 200mm is 200mm is 200mm. Whether you measure it with a 300mm rule, with a 1 metre rule or with a 10 metre measuring tape. The main difference is the that the optical 'field of view' on an EF-S lens is designed for an APS-C camera and will give a wider 'field of view' (say, 100%) on an APS-C camera than an EF lens (62% field of view relative to Canon PowerShot SX230 HS Canon EOS 450D Canon EF 50mm F1.8 II Canon EF-S 18-55mm f/3.5-5.6 IS II Canon EF-S 55-250mm f/4-5.6 IS II +1 more Reply Reply with quote Reply to thread Complain PPbW6PL. A 50mm lens used on a Sony camera would yield an angle of view of 75mm instead of 80mm. Since Sony's and everyone else's APS-C crop factor is 1.5x opposed to 1.6x that Canon uses. -Demetrius. Current Gear: EOS 5D Mark IV, EF F/2.8 Trinity, EF 50mm F/1.8 STM, EF 85mm F/1.8 USM, 470EX-AI & 600EX II-RT. Has full-time manual focus. Canon EF-S 10-22mm f/3.5-4.5 USM. Sigma 18-35mm F1.8 DC HSM A. With full-time manual focus, you can move the focus ring whilst it is in AF (autofocus) mode. This means that you can make manual adjustments once the AF has finished, without changing to manual mode. But on an APS-C system, with its smaller sensor size, a "normal" lens is between 30 and 35mm, and a 50mm lens is a mild telephoto. So a normal APS-C zoom lens will typically have a range of around 18 to 50mm. Similarly, FF telephotos are longer, and FF WAs not as wide, as they "should" be for an APS-C camera. It’s the smallest and lightest EOS DSLR camera to date*, and is equipped with 4K recording capability, Canon’s Dual Pixel CMOS AF, and a vari-angle LCD for selfies and fun angles. Its 24.1 Megapixel (APS-C) CMOS Sensor combines with the powerful DIGIC 8 Processor for amazing performance and results, and the EOS Rebel SL3 even lets you The Canon EF 50mm f/1.8 II and the Canon EF 50mm f/1.8 STM have an aperture range of f/1.8 to f/22. However, the STM version does have 7 aperture blades whereas the older version only has 5 aperture blades. This means that the bokeh when using the STM version will appear rounder which some people prefer. By now you should know the differences

canon ef and ef s difference