Since I have recently bought a Pentax SLR, I was naturally browsing for some nice lens to go with it. However this is easier said then done, especially if you do not understand the meaning of the initials that mark every model.
Let’s explain the meaning of the symbols on the example:
smc DA*16-50mm F2.8 ED AL (IF) SDM:
- smc – refers to the multicoating applied to the optics to reduce reflections and UV light, resulting in improved contrast.
- DA* – DA and DA* are Pentax series of lenses developed specifically for digital cameras, i.e. smaller sensor than the traditional 35mm camera. DA* denotes a higher quality lens with tighter sealing, thus more resistant to dust and weather and featuring supersonic motors for quicker and quieter focusing.
- ED – stands for Extra-low dispersion glass that is used in lens to reduce chromatic aberration. These types of lens focus colors more equally for sharper, crisper images.
- AL -means aspherical lenses are used. Wide-angle and mid-focal length lenses use aspherical designs to correct the challenges of spherical aberration in such focal lengths. Spherical aberration is a problem caused by lens elements with extreme curvature (usually found in wide-angle and wide-angle zoom lenses). Glass tends to focus light differently through different parts of such a lens, causing a slight, overall softening of the image even though the lens is focused sharply. Aspherical lenses use a special design that compensates for that optical defect.
- IF – means Internal Focus. The lens barrel does not contract and expand with different focus settings and the front filter ring does not rotate when you adjust focus.
- SDM – stands for Supersonic Drive Motor that is used to move the optics in the lens to achieve focus.
*Images of the Pentax K200d and smc DA*16-50mm F2.8 ED AL (IF) SDM are courtesy of Pentax.