| Maker | Pentax |
|---|---|
| Technical data | |
| Type | Prime |
| Focal length | 55mm |
| Focal length (35mm equiv.) | 82.5mm |
| Crop factor | 1.5 |
| Aperture (max/min) | f/1.4 / f/22 |
| Close focus distance | 0.45 metres (18 in) |
| Max. magnification | 0.173x |
| Diaphragm blades | 9, rounded |
| Construction | 9 elements in 8 groups |
| Features | |
| Manual focus override |  |
| Ultrasonic motor | |
| Weather-sealing | |
| Unique features | Weather-resistant |
| Application | Portrait |
| Physical | |
| Max. length | 66.0 millimetres (2.60 in) |
| Diameter | 70.5 millimetres (2.78 in) |
| Weight | 375 grams (13.2 oz) |
| Filter diameter | 58mm |
| Accessories | |
| Lens hood | PH-RBH 58mm |
| Case | S90-100 |
| Angle of view | |
| Diagonal | 28.6° |
| History | |
| Introduction | 2008 |
| Retail info | |
| MSRP | $799.95 USD |
The smc Pentax-DA* 55mm f/1.4 SDM lens is a professional prime lens for the Pentax K-mount. It is designed for portrait use [1] with a 35mm equivalent focal length of 82.5mm. The lens features weather sealing, an SDM ultrasonic motor for quiet autofocus, and has 9 rounded diaphragm blades for smoother bokeh. Autofocus speed is similar to an equivalent screwdrive lens. [2]
The Pentax K-mount, sometimes referred to as the "PK-mount", is a bayonet lens mount standard for mounting interchangeable photographic lenses to 35 mm single-lens reflex (SLR) cameras. It was created by Pentax in 1975, and has since been used by all Pentax 35 mm and digital SLRs and also the MILC Pentax K-01. A number of other manufacturers have also produced many K-mount lenses and K-mount cameras.
Portrait photography or portraiture in photography is a photograph of a person or group of people that captures the personality of the subject by using effective lighting, backdrops, and poses. A portrait picture might be artistic, or it might be clinical, as part of a medical study. Frequently, portraits are commissioned for special occasions, such as weddings or school events. Portraits can serve many purposes, from usage on a personal Web site to display in the lobby of a business.
An ultrasonic motor is a type of electric motor powered by the ultrasonic vibration of a component, the stator, placed against another component, the rotor or slider depending on the scheme of operation. Ultrasonic motors differ from piezoelectric actuators in several ways, though both typically use some form of piezoelectric material, most often lead zirconate titanate and occasionally lithium niobate or other single-crystal materials. The most obvious difference is the use of resonance to amplify the vibration of the stator in contact with the rotor in ultrasonic motors. Ultrasonic motors also offer arbitrarily large rotation or sliding distances, while piezoelectric actuators are limited by the static strain that may be induced in the piezoelectric element.
