Distortion in SMC Pentax-DA 18-250mm F3.5-6.3 ED AL [IF]

MBK · 10-15-2008, 02:01 PM

Hi

I am new to this forum.

Recently I acquired a new Pentax zoom smc-DA 18 – 250mm/3.5~6.3 ED AL [IF]
for my Pentax DS *ist and K200. It seems the lens has some vignetting that
I am not used to seeing.

I have attached two downsized images - one taken at 100mm focal length
and the other at 250mm

- Does anyone know if this is normal behavior (vignetting) with this lens or do you
think there is a problem with this lens i.e. worse than what can normally be expected?

I can correct some of it, but what is the opinion?

kind regards
Morten Bech Kristensen
Denmark.

kristoffon · 10-15-2008, 02:11 PM

Yes, for this lens it's normal. Lightroom has a vignette correction feature which is great. Since I shoot RAW anyway, you don't lose any noticeable amount of image quality by eliminating it that way.

You may want to check the review at www.photozone.de for this lens and for the Tamron 18-250 for the Canon/Nikon systems (pretty much the same lens).

Lowell Goudge · 10-15-2008, 02:18 PM

aside from what has been stated, do you have stacked filters or one with a large ring on it that may be causing some of the problem? Have you tried with and without the hood?

Also, on many lenses this is a condition usually found wide open, and one that corrects as you stop down? have you tried different apatures?

This is.may be only a question of knowing the limits of your lens. My lenses don't vignette, but that is because except for my 10-20mm Sigma, every thing I own is a full frame lens. In all honesty, I am not waiting for a full frame camera but that is the biggest benefit of full frame lenses, they are designed to cover so much more area that these issues just don't exist