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Thread: My new lens

  1. 21st March 2012, 07:25 PM #1
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    Default My new lens

    I recently bought a new lens from DigitalRev and was happy with both price and delivery time, ordered on Wednesday, delivered on Tuesday (it would have been Monday, but it was a public holiday). However I was a bit disappointed with the images I was getting off the lens, they seemed a bit "soft" compared to the images from my other lenses. I did a bit of reading up on autofocus issues and discovered that sometimes a lens can backfocus/foward focus so I downloaded a focus test chart

    Attachment 202203

    and made a box to fix it to.

    Attachment 202200

    Using some tungsten/halogen worklights for decent lighting I took a series of photos to check the autofocus of the lens.
    Obvoiusly the lens is foward focusing, it is focussed about 12 - 14mm in front of where it should be.

    Attachment 202197

    I made an initial adjustment of -5 in the Micro Focus setting on the camera, however I adjusted the wrong way and made it worse .

    Attachment 202198

    After a bit of to and fro-ing from the "studio" (family room) to the computer to check the results of my adjustments I finally achieved a reasonable focus. Lucky too because I had to dial the compensation all the way to +20, which is as far as it goes.

    Attachment 202199

    I'm wondering if I should ring the Australiian agents for Sigma as I'm still not 100% happy with the focus. I've heard that they will adjust the lens free of charge, even if the lens was purchased o/s.
    Attachment 202204
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  3. 22nd March 2012, 11:44 AM #2
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    Interesting GJ. I also was advised that Sigma(Aust) do honour warranty etc on overseas purchased lenses. Will be interested to hear how you fare with them. It looks a great lens.
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  4. 22nd March 2012, 02:33 PM #3
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    I just got off the phone with C.R. Kennedy (the importer) and was told that as I purchased the lens on the internet I am the importer and have to carry the warranty costs. Maybe I'll give it a couple of weeks and see how my calibrations work out, and try again. This time I'll tell them that I purchased the lens while I was o/s.
    The tech guy did say that it was more common for the lens to foward/back focus on a Canon body.
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  5. 22nd March 2012, 05:32 PM #4
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    Interesting

    So what body do you have? And what is the lens actually calibrated on in the factory?
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  6. 22nd March 2012, 06:11 PM #5
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    Canon 7D. When I asked the guy at Kennnedy's if I needed to bring the body in when/if I get the lens calibrated he said not to worry as they have a 7D body there. I would have thought that they would tune the lens to an individual body . He did say that they have more issues with Canon bodies than Nikon.
    Funny thing is I've always thought my other Sigma lens (17-70 f2.8) was razor sharp. I'm going to have to take some shots of the test chart with my other lenses and see how they come up.
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  7. 22nd March 2012, 06:12 PM #6
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    Quote Originally Posted by Grumpy John View Post
    Funny thing is I've always thought my other Sigma lens (17-70 f2.8) was razor sharp. I'm going to have to take some shots of the test chart with my other lenses and see how they come up.
    Might be a good exercise!
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  8. 22nd March 2012, 06:46 PM #7
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    Are you saying that I need exercise .
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  9. 29th March 2012, 06:30 PM #8
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    I've tested my other two lenses and the results are below.
    I took 3 shots manually refocussing the lens to infinity between each shot.

    Sigma 17-70 f2.8. No adjustment required .
    Attachment 203201 Attachment 203202 Attachment 203203

    Tamron 70-200 f2.8. Slight foward focussing.
    Attachment 203204 Attachment 203205 Attachment 203206

    After correction.
    Attachment 203207 Attachment 203208 Attachment 203209

    All in all this was an interesting exercise and worth the effort. I'd be interested to know the results if any one else does the exercise.
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  10. 29th March 2012, 07:34 PM #9
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    What did you photograph the platter with?
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  11. 29th March 2012, 08:58 PM #10
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    Quote Originally Posted by tea lady View Post
    What did you photograph the platter with?
    Sigma 17-70 @23mm f3.1 1/200 sec . Link
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