Centon 18-28mm F4.0-4.5 Pentax KA mount
Centon 18-28mm F4.0-4.5 Pentax KA mount
By Steve Graham
Focal Length min 18mm, max 28mm
Aperture - max F4.0-4.5, min F22
Close Focus 0.49m
Weight 0.488kg
Note: This lens also seems to be sold under the Phoenix,Vivitar and Sirius brand names.
Build
About the same size as a 28-80 standard zoom, but with a large 72mm filter mount perched on the end, this lens is solidly constructed with a metal shell which, along with it's complicated optical construction, adds to it's weighty feel. Despite
being used quite a lot in it's year with me, there are no signs of wear, either on the body or on the metal mount. No case or hood was provided.
Optical
A 11 group, 14 element design, covering an aperture range of F4.0-4.5 to F22, with a domed front element, this is quite an unusual lens for the budget end of the market. Elements are supposed to me multi-coated, but flare has been a problem.
Heavy darkening of the corners can also be a problem, especially at the wider apertures, so stopping down to F8 and F11 is advisable. Colour rendition is fine, contrast seems good and results are acceptably sharp, if a little soft towards the edge of the frame.
Handling
A two-touch zoom, with reasonably wide focus and zoom rings, and a well weighted aperture ring, this lens has good handling characteristics, only being let down by the rather murky viewfinder image. No depth of field or infra-red index are marked however, which is a little annoying, especially as a lenses of this focal length do lend themselves to use of hyper-focal distances.
Compatibility
Mostly the Centon has been used on a Pentax P30T body, loaded with Fuji Velvia (which is not exactly noted for exposure latitude), where it has provided correct exposures under a
wide range of circumstances. Coupled with a Pentax Z1p, shooting Fuji Provia slide and Fuji Reala print film has also provided acceptable results, without necessitating the use of exposure bracketing so far.
Price
I paid 99 poumds Sterling (160 USD) for this lense (from Jessops). As there are no close competitors currently in the market I feel this is good value. B&H list the lens in it's Vivitar version for 139.95 USD.
Conculsion
I bought this as a introduction to use wide angles - to see if I liked the results and to find out whether I would be justified in spending more on a better quality replacement. For that purpose it has been an excellent choice, and some of my favourite images to date have been taken with this lens. At the present time I am only waiting for the Tokina ATX-Pro wide angle to hit the market before purchasing a replacement, but I expect the Centon to go on providing service, coupled to my P30T, for some time to come.
This page hosted by 
Get your own Free Home Page