Focus problem with Sigma ..advice please

[Yardbent]

not been too happy with sharpness of landscape shots lately
in the park last week, it was noticeable that objects focused on at 100m away were really OOF...tripod mounted, no OS, remote release

Sigma 17-70mm 2.8-4.5 DC Macro HSM

with advice from here [ thanks greatly to CJS - ..], I've done many tests and these seem to show the problem

1st ..........a 100% crop, focused on rear light
EXIF = 1/125, f11, Focus Range = 6m - infinity, Focus Distance 12.59m
all seems reasonable and image is OK
.

.
2nd ..........a 100% crop, focused on house in distance
EXIF = 1/125, f11, Focus Range = 6m - infinity, Focus Distance 12.59m

note ..still at 12.59m......all the shots i took from f5.6 to f11 the Focus Distance was 12.59....why..?
.

as a ''control'' I used a Nikkor 50mm Ai manual lens, f11 at infinity
this is far far sharper on the garage door slats, the hedge, and the yellow tree
.

sorry if this is long-winded, but need some advice/thoughts
I'm sure it will be Sigma focus prob - back to Sigma ...

their web-site quotes £85 - anyone recommend anyone else..?

 

[Yardbent]

.

 

[menthel]

Difficult to tell with the second set, it does look more blurred BUT the light is completely different and there may be some element of the wind blowing things around. I am sure one of our resident lens testing experts will be along with better advice soon though!

 

[woof woof]

It's difficult to tell with these small images but it looks a lighting / metering thing as much as anything as in the first shot the garage door slats look almost blown. Ten seconds in PS to try and bring the lighting down and the slats out a bit makes it look a lot closer to the other shot.

 

[odd jim]

...and remember the prime will almost always be sharper and suffer less distortions, CA etc that a mid range zoom, even a very good one.

 

[Yardbent]

***EDIT to first post

"removed incorrect reference to f-stops"

 

[Yardbent]

thank you all ....still inconclusive then....

RTFM all day in the taxi...nothing

what is BUGGING me - why is the ''focal distance' always 12.59m regardless of the scene - even the distant garage

i did use the remote release - wonder if this 'locked' the focus between subjects....:shake:

I'll try a number of shots this evening on different spaced objects

if I focus on a distant object, surely the 'focal distance' should be 100s of metres..? and not 12.59m

[all the above were 100% crops as i thought this was the size to view]