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One addition that previous answer did not make clear is that EF-S lenses are also measured in full frame focal length sizes just like EF or full-frame lenses. In other words, an EF-S lens listed at say 60mm would have an effective focal length of 96mm, just like a full frame lens. The only real difference between the EFS and EF lens is that the EF-S lens is designed to fit only Crop Sensor or APS-C cameras. But the focal lengths are the same as Full Frame cameras, even though the effective focal lengths are 1.6 (times) what it says on the EF-S lens. So, go figure!
Sorry, there was a problem. Please try again later.EF lenses are designed for 35mm sensors and, going back more than 30 years, 35mm film cameras. The EOS 90D is an APS-C sensor which is 37.5% smaller than a standard 35mm sensor. EF-S lenses are designed for the smaller APS-C sensor. That being said, the EF lenses still work on APS-C sensor cameras, like the 90D, there is just a difference in how the lenses perform. Primarily, the effective focal length will be increased by 1.6x, resulting in a 50mm EF lens having an effective focal length of 80mm on the APS-C sensor camera. There are also changes related to depth of field related to the lens' aperture. While EF lenses are compatible with APS-C sensor cameras, EF-S lenses are not compatible with full frame, 35mm sensor cameras (without an adapter, at least, but there would still be an impact on the image).
Sorry, there was a problem. Please try again later.The mount that goes on the lens
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