Canon EOS Rebel T1i EOS System Brochure 2010 - Page 15

Floating System Typical lenses correct for optical aberrations only at commonly used focusing distances. Not surprisingly, at other focusing distances, especially close range, aberrations can compromise image TS-E 24mm f/3.5L Floating System Closest shooting distance Focal plane Floating Floating Effect (TS-E 24mm f/3.5L) Astigmatism quality. Rather than using fixed spacings, Canon's floating system dynamically varies the gap between key lens elements based on focusing distance. Most aberrations are effectively suppressed throughout the focusing range, assuring high image quality in all shooting situations. Dust- and Water-Resistant Construction Most L-Series EF telephoto lenses are highly dust- and water-resistant thanks to rubber seals at the switch panels, exterior seams, drop-in filter compartments and lens mounts. Moving parts, such as the focusing ring and switches, are also designed to help keep out environmental contaminants, providing reliable performance under harsh conditions. EF 24mm f/1.4L II USM •f/2.8 •1/30 sec. Full-Time Manual Focusing Canon EOS cameras with EF lenses deliver impeccable AF precision. Manual focusing capability, nevertheless, can enhance flexibility. Canon EF lenses with full-time manual focusing enable the photographer to manually tweak focus without switching out of AF mode. Since AF action does not cause the focusing ring to turn, it can be made wider for improved grip and comfort. TS-E Movements Tilt Movements alter the angle of the plane of focus between the lens and focal plane, and Shift Movements move the lens's optical axis in parallel. Circular Aperture Canon lenses featuring circular aperture diaphragms employ curved blades to create a smoothly rounded opening as the lens is stopped down. As a result, most out-of-focus background highlights are rendered as natural-looking rounded shapes rather than as distracting polygons. These lenses deliver smooth, consistent stop-down action (even at 10 fps), near-silent operation and excellent optical characteristics. Reverse tilt and shift greatly reduces the range on which focusing is possible. Shift was used to adjust the image to keep the building perpendicular all the way to the top. Inner and Rear Focusing An inner focusing lens has the focusing lens group(s) in front of the diaphragm, while a rear focusing lens has the focusing lens group(s) behind the diaphragm. Both designs allow for compact optical systems that produce faster AF. And because the front of the lens does not rotate to focus, filter orientation remains constant. AF Stop Feature Pressing the AF Stop button (featured on several EF IS telephoto lenses) momentarily locks the AF to help prevent the focus from shifting to a passing obstruction. After the obstruction has cleared, the focus will still be on the subject, and you can quickly resume shooting. AF Stop buttons are positioned at four locations around the lens grip for easy access. 30 The lens's tilt mechanism is used to achieve a pan focus effect that allows focusing all the way back. Tilt Movements -Using a normal lens, shallow or deep focus is controlled by the size of the aperture used to adjust depth-offield. Canon TS-E lenses can help achieve this by the tilting of the lens barrel in relationship to the focal and subject planes. This allows for the appearance of extremely deep focus even at wide open apertures, and shallow focus at smaller apertures. Depth-of-field with tilt movements Plane of optimum focus Film plane Using Tilt Movements to Focus an Oblique Subject Plane Without using shift causes the image of the building to lean in at the top. Shift Movements - By keeping the camera level, and using the shift function to raise the lens instead, this perspective effect can be corrected. With the camera's focal plane set parallel to the building, shifting the lens upward will obtain a more rectangular-looking building. With a normal lens With a TS-E lens Using Shift Movements to Focus Tall Building EF LENSES EF 15mm f/2.8 Fisheye •f/16 •1/640 sec. Specialty Lenses EF-S Lenses - Designed for the Canon EOS 7D, EOS 50D and all EOS Rebel models with APS-C sized sensors (with a 1.6x crop factor), Canon's EF-S lenses take advantage of the sensor's smaller size to help deliver optimized performance in compact, lightweight designs. The EF-S 15-85mm f/3.5-5.6 IS USM is a perfect example of this technology. With a compact design, a 35mm equivalent range of 24-136mm, and Optical Image Stabilizer technology, it's a superlative walkaround lens... possibly the only lens you'll need to enjoy basic Canon digital SLR photography. Fisheye - Perfect for super wide-angle and special effect photography, Canon's full-frame fisheye can focus as close as eight inches (0.2m), and delivers exceptionally sharp images throughout its focus range. Up to three gel filters can be inserted into its built-in rear filter holder. TS-E - TS-E lenses are capable of tilt and shift movements, which bring many of the advantages of technical view cameras to the EOS System. Tilt movements alter the angle of the plane of focus between the lens and film plane, making broad depth-of-field possible even at larger apertures; shift movements slide the lens's optical axis along the film/sensor plane, enabling photographers to correct or alter perspective at almost any angle. Macro - Canon's EF lens lineup has a number of options for true close-up and macro photography. With five macro lenses for precision, and three screw-on close-up lenses for convenience-in addition to Life-Size Converter EF and two Extension Tubes-Canon's macro lenses and close-up accessories can uncover detail that is nearly impossible for the unaided human eye to detect. EF Mount In designing the EF lens mount, Canon engineers gave photographers a lot more than a way to quickly attach a lens to a camera body. As the communication conduit between camera and lens, this fully electronic mount system has none of the shock, operational noise, abrasion, play, lubrication requirements, slow response, lever operation limitations, or other design restrictions related to mechanical linkage mechanisms. A self-test system, using the lens's built-in microcomputer, can even warn of malfunctions through the camera's display. The EF mount makes possible high-speed autofocus, precise aperture control and preview, automatic compensation with lens extenders, and both forward and backwardcompatibility with new lens technologies-such as USM and IS-as they are developed by Canon. About Macro Magnification A life-size macro lens-that is, a 1x magnification-records an image on film at its actual size. If you're photographing a flower, for example, and it has a diameter of 1 in., it will occupy 1 in. of your actual slide or negative. With a digital SLR, at 1.0x magnification, the image projected onto your camera's sensor will likewise be the same size at the sensor plane as the actual subject itself. Other macro lenses have lower or higher 0.25x magnifications. A lens with 0.5x magnification will produce an image on film that is half the size of the actual subject. Your 1 in. flower then would only occupy 0.5 in. on film. 0.5x In the other direction, a 5x magnification lens will convert the 1-in. flower to a 5-in. diameter image. Since the entire image won't fit in the frame of your film, you will have an enlarged image of a detail of the flower. 1.0x Magnification is not the same as focal length. A 50mm lens and a 180mm might both be macro lenses with, for example, 1.0x magnification. The advantage of the longer lens is that it allows greater distance from 3.0x a subject, while allowing the same magnification in the final image. The 180mm lens is ideal for shooting tiny subjects without disturbing them; the 50mm is better choice for copying flat documents. 5.0x FOCAL LENGTH COMPARISON 15mm Fisheye 14mm 17mm 20mm 24mm 28mm 180° 114° 104° 94° 84° 75° 35mm 50mm 63° 70mm 46° 85mm 100mm 135mm 34° 28° 30' 24° 18° 200mm 300mm 12° 400mm 8° 15' 500mm 6° 10' 600mm 5° 1200mm 4° 10' 2° 5' 31