[amaze8]

Am using D700 and just bought a Sigma 50mm 1.4. Tried shooting but in all cases, I can only get some part of the object in focus, and other parts blur. Following is an example (using F2.0, s 1/60). I can only get 1-2 pieces of the steck in focus, and others were out of focus a lot. Can any ching help? Same for portrait, when using F1.8 or 2.0, I can only get the eyes in focus, but other parts of the face are already blur.

[tungch8899]

colors are excellent. just the focus problem you mentioned.

[pigpig2000]

<<<I can only get the eyes in focus, but other parts of the face are already blur.

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what you need to know is DOF, read the entire page below ^_^
http://en.wikipedia.org/wiki/Depth_of_field

[snoopybee]

pigpig2000, I think this must be the lens' problem ......... as I could not believe someone using such a professional kit would not know what is DOF ??? ;-)

[amaze8]

Thanks. I understand DOF and its relationship with aperture. Just that I saw many pics taken by others using S50.4 (particularly portraits) have sharp focus for the whole face, but for those I took I got it sharp for only a portion of the face. It could be because the face was facing me with an angle so the distances to the lens are slightly different, and it was too close to me.

[amaze8]

Thanks Snoopybee Ching. Yesterday I took the lens to Sigma to cal. They checked and told me no need to cal because it works very well with my D700. So I think the problem is with me, rather than the lens. Just that when taking a close up picture on a dish, I got 2 pieces of steak out of focus.....may be I have to push up the ISO and use F8 or 11.....

Will keep on trying.

[pigpig2000]

<<<pigpig2000, I think this must be the lens' problem ......... as I could not believe someone using such a professional kit would not know what is DOF ??? ;-)

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^_^!........

[pigpig2000]

<<< I got 2 pieces of <<<steak>>> out of focus.....may be I have to push up the ISO and use F8 or 11.....

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let me help you to make those to become one before you try ^o^

set the iso as auto and test with different aperture.
the size of the subject also playing a very important matter here. enjoy testing and dont get fat ^_^

[amaze8]

pigpig2000 ching, thanks a lot for the help. In the past all my lenses did not have apenture bigger than 2.8 so I guess I have to adjust to this lens. Will test it out. Thx.

[FreeMiLk]

I have exactly the same combination that you have. D700 + S50.4. And i have find the same problem too. But after i read your comment that you had bring the lens to Sigma CS and they said you lens is fine. I think it is normal for f1.4 aperture lens. Cause when i enlarge the focus point of the photo (using f1.4), it looks normal to me. As you said, see what is going to happen if you using f8+
Please let me know what you think too after test ^^

[amaze8]

FreeMiLk Ching,

Cause when i enlarge the focus point of the photo (using f1.4), it looks normal to me.
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How to enlarge the focal point?

Good that you shared your experience as we have the same set of camera/lens. I am also using 24-70. The reason I bought S50.4 was I wanted to get an even sharper picture given it is fixed focal length. So far I didn't get it yet, and I found the 24-70 better. So I am quite puzzled.....

I hope it is only because I don't know how to make the best use of the S50.4. If I still can not use it to get better PQ than the 24-70, I will consider selling it because 24-70 is much more convenient.

[FreeMiLk]

How to enlarge the focal point?
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Sorry for confusion, i meant to put the image into the computer and enlarge it.

I think we should run some test. Set the tripod, using the same focus length on 24-70 ( which is 50) and same aperture which is (start from f2.8) to see the different between 2 lens. I dont have 24-70 but i do have 28-70. I knew 28-70 is an old lens and the sharpness just cant compare with the 24-70. But still worth to try the different.

[tungch8899]

I think we should run some test. Set the tripod, using the same focus length on 24-70 ( which is 50) and same aperture which is (start from f2.8) to see the different between 2 lens. I dont have 24-70 but i do have 28-70. I knew 28-70 is an old lens and the sharpness just cant compare with the 24-70. But still worth to try the different.
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yes will try testing this weekend.

[amaze8]

I will test my lenses too. Good to have more people testing and compare results.

[amaze8]

Here is the test:

F1.4 S50.4
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F2.0 S50.4
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F2.8 S50.4
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F2.8 24-70:
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F5.6 S50.4:
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F5.6 24-70:
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F8.0 S50.4:
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F8.0 24-70
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