LENSES ON DIGITAL CAMERAS
General Information:
Digital SLR (DSLR) cameras electronically capture images using a method similar to that of film. In place of film, an image capturing sensor is used—generally a CCD (Charged Couple Device) or CMOS (Complimentary Metal Oxide Semiconductor). Since the CCD or CMOS sensor in consumer-aimed DSLRs is smaller than a full frame of 35mm film (24x36mm), the focal length of any lens is effectively increased, usually by a multiplication factor averaging about 1.55x (most Canon models have a 1.6x factor while Fuji FinePix Pro and most Nikon's have a 1.5x factor). This holds true unless a 35mm-sized full frame image-capturing device is used. There are now a few serious “pro-sumer” DSLRs with full-frame sensors on the market, but they are generally quite expensive, averaging around $2,000 and up.
The multiplication factor used with APS-C-format consumer DSLRs (by far the largest number of camera-types purchased) is actually an advantage when it comes to using telephoto lenses because the effective focal length is longer—for example the equivalent focal length of a 200mm lens is 310mm (using an average multiplier of 1.55X), providing a longer reach because of the smaller-than-35mm format. However with wide-angle lenses it’s a different story. For example, a 14mm lens would be considered an ultra-wide angle on a conventional 35mm camera or full-frame digital camera, but it would be equivalent to about a 22mm (still wide, but covering a considerably narrower field) on most digital SLRs using the smaller image capture sensors. The same is true for zoom lenses as well; for example, a 17-50mm lens on a conventional 35mm camera is approximately a 26-78mm when used on a typical consumer digital SLR.
Auto Focus Performance and Image Quality:
When using a digital camera it is very easy to choose a specific area of the captured image, magnify it, and check it, either on the camera’s LCD screen or on a computer monitor. If this area is excessively magnified beyond the normal viewing capability, the image will appear pixilated, with imperfections and jagged edges. For example, viewing an image on an average 17-inch monitor with a pixel count of 6,000,000 (6MP) is like viewing a print made from a film image at approximately 32x21 inches! Under these conditions, it is also possible that slight auto focus errors will be visible that would normally go unnoticed on a normal size print or enlargement.
Auto Focus technology has been around for many years and has been improved dramatically since its inception; however, under certain conditions it can get confused. Sometimes the “best focus point” may shift slightly when certain conditions exist such as under low light conditions when the subject is quite dark or low contrast conditions when the subject is not well separated from the background. This is not a digital phenomenon—the same auto-focus discrepancy can occur with both film and digital cameras.
Tamron SP Lenses: (Super Performance)
Many photographers, amateur and professional, are using Tamron’s SP lenses on their digital SLRs. The SP series of lenses feature outstanding optical performance based on extremely demanding design and manufacturing specifications. In designing any SP lens, the first and foremost priority is given to attaining the highest possible optical performance and consistently attaining very tight tolerances on the production line. When using an SP lens on a digital SLR, we recommend that you shoot test images, then analyze and compare your findings to confirm their outstanding performance.
Tamron Di and Di-II Lenses: (Digitally Integrated; a new standard of lenses for Film and Digital SLR Cameras)
Di and Di-II are the designation Tamron puts on specific lenses featuring optical systems designed to meet the demanding performance characteristics of Digital SLR cameras currently on the market. Di lenses are optimized for both full-frame-sensor (24x36mm) digital and film cameras, and Di-II lenses are optimized for the smaller APS-C format sensors found in consumer DSLR cameras.
Tamron Di II Lenses: (Lenses designed Exclusively for Digital SLR Cameras)
Please note that Di-II inherit all of the demonstrable optical benefits of the Di design. Di-II lenses are made for exclusive use on digital cameras with image sensors 24mm x 16mm and smaller and are not intended for use on full-frame DSLRs or film cameras.
Tamron’s Warranty Policy:
Like all Tamron lenses, our SP and Di lenses come with a manufacturer’s 6-year limited warranty.
Contact Information:
If you have questions about the use of your Tamron lens on your digital SLR camera, please contact our service department at 631-858-8400 ext. 2502, or via e-mail at custserv@tamron.com. |
