Question about Sigma 30mm f/1.4 EX DC HSM for Sigma

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Front/Back Focus Problem at Sigma 30mm F1.4 Lens

I just bought my Sigma Lens 30mm f1.4, i just realised that it has minor focusing problem. With apperture open wide (that's f1.4) and my subject distance is around 2 feets 6 inches, i focus at one point but the result is the sharp image is slightly at the back of my focus point (my original focus point is blur). I dont know whether this is front focus problem or back focus. I use Sony Alpha A100 DSLR. Please help me.

Regards,

Abdul Malik

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  • cottage4 Mar 19, 2009

    i was focusing at 2 persons a meter away. when the photo was developed, it was the wall behind my subjects that was clear. my subjects were slightly blurred.

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Hello Abdul!
I recommend that you print this test chart: http://www.photo.net/learn/focustest/scale45.jpg
Just print it on an ordinary paper, then put it on a table, and take a picture at it from a 45 degree angle, using the center focusing point only, aimed at the thicker line in the middle. The numers are centimeters. Take the test picture at f/1.4. Make sure you have good light so you get a fast shutter time. If you have a tripod, mount the camera on the tripod prior to taking the test picture.
Then examine the picture in your computer, zoomed to 100%. Now it should be clear wheter you got back- or front focus, and how large the problem is.
Unfortunately, there is no way for you to adjust the camera and lens combination yourself, you will have to send/bring the camera to an autorized camera workshop. This is covered by the warranty.
Hope this helps!
Regards, 
/Chris

Posted on Jan 19, 2009

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Posted on Jan 02, 2017

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