bad lens?

Flying giraffe

Flying giraffe

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Neil
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in this thread i was advised my lens may have a problem with focusing, its a sigma 17-70mm, im going to try what one kind chap has suggested, but would love any other help you may have, thanks
http://www.talkphotography.co.uk/forums/showthread.php?t=324106
and photo here
IMG_2554a.jpg
 
Where was the focus point, did you use centre point, individual points or auto?

Notice the aperture was f/5 and am I right in thinking that on the right hand side the trees etc are leading away?

Not so sure there is anything wrong with your lens and need more info, also did you focus then recompose

As an aside might also be better to switch to using a native ISO rather than an auto defined one like your ISO 500
 
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If you bought it new get it back or get it properly serviced. At f/5 DOF is certainly large enough to have everything nice and sharp. That lens has bad centering defect which very typical for this maker. Get rid of it and get Canon.
 
I'd say the lens has a problem - nothing to do with how you focussed or howe many focus points you used. It's not a DoF issue either. Something very weird going on.
 
Not saying the lens isn't faulty, but need all the facts so one more question

Is a filter fitted?
 
also if it is a problem with the lens is it fixable or no worth the expense, if it is where would you recomend?
 
Looks a duffer to me. Check your other lenses for any sign of right side softness. If others do it then it could be a problem with your lens mount on the body. If you can return the lens then I'd return it and get a replacement.
 
Must be my eyes or laptop screen, but the 2nd and 3rd pictures don't look that bad to me
 
Not the best of subjects for a test - but still doesn't look ok to me.
 
second one was witha 50mm to show any difference
Click to expand...

That explains why that one looked the best then, first isn't great and can see a slight difference on the right of the 3rd one

Know its often used, but a plain brick wall isn't too bad a test subject
 
Something totally flat left to right - with good even light and contrast.
 
ok best i can find at the moment, all on 70mm end
this one appears oof to me on the right
IMG_4172.jpg

not to sure on this one
IMG_4173.jpg

or this
IMG_4175.jpg
 
Think you will need to use it tripod mounted (OS turned off) on a good test subject to get a definitive answer.

Bit closer in on a flat wall with uniform light should work, guessing any deviation will show up more at the longer end

Still not sure and must be very annoying, have you noticed it in any of your other shots?
 
havent been doing it that long, so just put any thing like that down to user error, thanks for all your help
 
also can you make sure the camera and the subject (wall?) are parallel to each other.
Hope that's not your roof - looks like it needs a bit of work too! :)
 
awp said:
also can you make sure the camera and the subject (wall?) are parallel to each other.
Hope that's not your roof - looks like it needs a bit of work too! :)
Click to expand...

ien stand right in front, will the above wall do if i correct the angle, i see sigma want nearly £90 to work on it, seems abit steep, and its my parents roof, and were all scared of heights lol
 
just taken these, and they appear to do the same, looked on sigmas site and its £86 for Focus / zoom / aperture / circuit, is it worth it?, or could it still be user error?
IMG_4185.jpg

IMG_4184.jpg

thanks for all the advice in thats been given i really appreciate it
 
Go back and take a photo of the brick wall again but make sure your facing the wall straight on. The idea is to get something the same distance from the camera across the frame so it shows flaws in the focus from one side to the other with something that is the same distance from the lens/camera. Depth of field on an angle will make items further away or closer out of focus anyway so you need to remove that from the equation.

Where did you buy the lens and how long have you had it, if its less than 12 months then return it to where you bought it from let them sort it either with a repair or replacement, if you have photos from when you got it showing the fault then take them so they can see the exif data to prove it was faulty when new not developed over time due to damage. Even if its older than 12 months old and you have the photos to show it was faulty when purchased take it back to the shop with the proof and they should replace/repair it.
 
You need to be careful about field curvature. When you are flat onto a brick wall, and particularly if you are relatively close with a wideish lens, the edges of the field are a lot further away from you than the centre. If you are wide open, this could put the edges of the image out of focus because of the distance and nothing to do with the lens. What is true is that both sides of the image should be even (i.e. the in/out of focusness should be the same on both sides).
 
thanks for the replys, i bought the camera off a friend (the one who introduced mr=e to the site), i have asked him to check his photos, and this thread to see if we can see when the problem occurred, if it is a focus problem, is it worth getting repaired considering they want at least £86?
heres some more pics, sorry the wall isnt big enough but hopefully will help you guide me.
ist 17mm at f5
IMG_4189.jpg

second 70mm at f4.5
IMG_4190.jpg

3rd 70mm at f22
IMG_4191.jpg
 
These definately look softer on the RHS - less obvious on the one at f/22 - but that will be with increased DoF. I'd say the lens needs looked at by Sigma - I've no idea what the lens is worth or whether the repair is worth it - only you can decide - but I wouldn't use it as it is.
 
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