New Lens Arrives
Anyway I was concerned for a while and then I realsied most of the issues lay with the way I was using the elns so take heart!
Just for fun test it on a flat wall and use different focus positions - the mode where the buttons shift the focus point for the AF about and see what happens.
Mike
My own theory for what it's worth is that the AF sensor struggles to locate any sharp contrasty edges in some shots becuase the field of view is so wide and that it can sometimes latch onto an unexpcted bit of contrast.
The most disappointing shots I have at the moment are those nominally set to infinity focus.
What I did was stick my lens on a tripod in the garden and then take the same shot with the Sigma, the kit and a an old prime. This went a long way to reassuring me that all was well and also tended to make me think that the AF struggled to focus on very distant things or things without much contrast. A wall a few feet away no problem although I did also test to make sure that the red focus area (I was on spot) fell onto either a course of mortar which at 10mm was quite hard or the front door frame and then the focus was fine.
Basically I'd suggest you do sokme tests like that. I also did the front and back focussigng test which showed all was well. As I say it's the distant view shots that seem the most troublesome.
Mike
I've not really noticed the lack of sharpness but after looking at a lot of pics - you're right you can see it.
Was out and snapped a few yesterday - you can notice the non-sharpness but the flexibility of the lens far outweighs it for me.
ISO 500 - a bit soft and noisey close in
1/125 7 500 18mm
1/50 7 320 18mm
1/50 5,6 100 20mm
Sharpness looks OK here to me - don't know if this is contrary but 12 at 1/25 seemed sharper to me than 20 at 1/50?
1/25 4.5 100 12mm
Even a bit soft, its still loads of fun
I doubt I've used the lens wide open much though.
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and I wasn't using much PP sharpening at the time as I didn't understand why it was needed. The ficus is off but I thin k it's sharp.
Pretty close up and this prints a dream.
I forgot to sharpen again in PP.
Very misty morning
I'm not sure what you'd make of any of these at these sizes
Mike
I was after a 10/20 having seen some amazing shots taken with it!,,,that was until now!. I'm afraid I cant see a sharp shot amongst them,You would be much better of trying a smaller aperture and using a tripod methinks!,the dof shooting around the 5.6 mark cant be very great at all.The stonework on the church tower is terrible,not a patch on what I can produce with the 18/55.......I'll hang on a bit I think until you get the hang of it!.....good luck...............Ken
I agree with the other posters that MX's problems are probably down to incorrect focusing (and perhaps camera shake in some, despite the SR). If not that then it may be a faulty example.
What do you think of mikew's shots? They look alright to me.
Also see: www.pentaxuser.co.uk/forum/viewtopic.php?t=6637
Better still, search Google, Google Images and pbase.com. You will find some stunners.
Re infinity focusing: I can't remember if this applies to the Sigma 10-20, but bear in mind that many modern lenses are designed to focus beyond infinity. This allows for any future expansion/contraction in the materials. So don't just use the nominal infinity setting without checking it's correct.
I have had focusing difficulties too with this lens, but usually being more careful about what I'm focusing on, or simply letting the AF have another go, does the trick.
You can't just assume everything should be in focus because it's a wide angle. Remember it's not ultra-wide at 20mm anyway - the equivalent of 30mm on a film camera.
Here are links to some rather large images that I took almost when I got the lens. they seem sharp enough. I warn you now they are in total 6 meg plus.
At 10mm
www.drmikewebb.com/Cornerhouse.jpg
at 16mm
www.drmikewebb.com/porch0409.jpg
They look sharp in PS.
Mike
Mike
I can't believe that the autofocus gets it wrong EVERY time.
I have contacted Sigma who want to look at some of my pics.
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4839 posts
17 years
South West London
No tripod, but shake reduction on, which should be good enough for 10mm @ 1/15
It "should be". But it is not advisable to rely on either SR or the 1/(focal length) rule of thumb if you're trying to judge the sharpness of a lens.