Sigma Pentax 28 - 70mm consistently overexposed?

Hi All,

I recently bought the following old (but autofocus) lens on ebay:-

Sigma Pentax Fit 28 - 70mm f3.5 - 4.5

The image quality is good (considering most reviews online slate it) but I'm finding the K-x consistently over-exposes images. Or perhaps, it lacks contrast (throughout the focal length). I typically use shutter or apperture priority modes - I've yet to try fully manual but I suspect the results will be the same.

Images to me look overexposed and very 'flat' - some raw post editing brings things to life (with great results), but I'd expect better straight from the camera.

Is this my first example of a poor lens or are there metering problems between the old lens and new camera?


Steve

For "over exposing", you don't say what metering you are using. Try filling the frame with a white sheet of paper. With no correction it should come out a mid grey.

For "flat" you don't say if you are shooting in jpeg or raw.

Why not post some images complete with exif.

ok, I have one example taken randomly yesterday - but I have others which are all lacking contrast / over exposed in a similar way. I can improve things dramatically by some post processing of the RAW files but I'm confused how the auto-exposure can be wrong. If anything, with such a bright sky, I'd expect the camera to underexpose to compensate.




f/14.0, 1/60 sec, 42mm, ISO 100 (other EXIF should be intact)

I must admit I haven't compared lenses side by side, but this does seem different to what I'm used to (kit 18-55, 50-200, 35mm prime).

Spot metering maybe?
Or it can high class reverse back engineering...
If it isn't the spot metering i would try to see what Sigma says if your other lenses act normally.

I'll have a play with metering and perform some side by side tests.

I guess I can't really complain for £15 anyway

Steve

First thing I thought of was that the lens wasn't stopping down far enough when the picture was taken due to mechanical stiffness of the aperture mechanism of the lens.

Is the lens still over exposing when shot wide open ( no mechanical stop down ) ??