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12-24-2011, 09:39 PM   #1
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Question about Focus on a used Sigma 30mm 1.4

Hi, this might be a newbie question for which I apologize in advanced.

There is shop here that sells a very clean used Sigma 30mm 1,4 for what I think is a good price (30.000 yen).
I went to try it with my K5 and found the following:

- Liveview focusing works perfect.
- Centerspot focusing works perfect
- Sidespot focusing gives clear FF problems. <-- here lies the problem.

I've never tried the in-camera focusing adjustment and don't know if it can fix the problem: only adjust when using sidespot focusing.

I am also going back to Spain soon from Japan, and either I buy this lens now or never, cause I doubt they sell it back home. I really want the lens but don't know what to do

Any thoughts and advice are welcome.
Thanks.

12-25-2011, 01:45 AM   #2
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read this, buy it, and enjoy
12-25-2011, 03:53 AM   #3
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My experience with this lens is that the side focus sensors will not work, probably because the edge areas never really get focused while wide open. Means the lens is actually useful just for subjects you want to be somewhere in the center, like in portraits. Not unusual for a 1.4 lens.
12-25-2011, 09:05 AM   #4
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Thanks for the link Adpo, I'll give it a good read.

And Kameratan, i see yours has a similar problem, must mean that it's normal for the lens.

I'll go ahead with the buy, although now I found it new for just a bit more (35.000 yen).

12-25-2011, 09:16 PM   #5
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Might have something to do that the focus field is very curved, it's quite normal for such fast lenses.
12-26-2011, 05:22 AM   #6
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QuoteOriginally posted by Kameraten Quote
My experience with this lens is that the side focus sensors will not work, probably because the edge areas never really get focused while wide open. Means the lens is actually useful just for subjects you want to be somewhere in the center, like in portraits. Not unusual for a 1.4 lens.
Agreed. Center point is the way to go with this lens. There is enough curvature of field too, that things aren't sharp on the edges either. It is still a great lens.
12-26-2011, 07:41 AM   #7
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QuoteOriginally posted by Rondec Quote
Agreed. Center point is the way to go with this lens. There is enough curvature of field too, that things aren't sharp on the edges either. It is still a great lens.
So you center focus on something off to the side the lock autofocus and recompose. Best way to do it in MHO.
12-26-2011, 02:04 PM   #8
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Lock and recompose will work only if the aperture is small enough to provide the depth of field needed. But if you've got a K-5 and the time you would want to use live view and contrast-AF - works perfectly also on the edges. And actually shows that focus on the edges overall isn't that bad (...I must admit).

10-19-2012, 11:13 AM   #9
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I am so thankful to have found this thread. I know it's a year old, but this information just saved my $500 lens purchase! I have had the 30mm for about 6 months now, and still have not been able to use it due to the focus issue. Finally had a minute to search (coupled with a pressing need for the lens in the next couple of weeks) and found this. Still not having much luck with center focus recompose, shooting wide open, due to the slim DOF. BUT, LiveView AF focus is spot on, and amazingly sharp. Thank you to everyone who took the time to post to this thread. You are a Godsend!
10-19-2012, 11:25 AM   #10
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QuoteOriginally posted by kmwsbabe Quote
I am so thankful to have found this thread. I know it's a year old, but this information just saved my $500 lens purchase! I have had the 30mm for about 6 months now, and still have not been able to use it due to the focus issue. Finally had a minute to search (coupled with a pressing need for the lens in the next couple of weeks) and found this. Still not having much luck with center focus recompose, shooting wide open, due to the slim DOF. BUT, LiveView AF focus is spot on, and amazingly sharp. Thank you to everyone who took the time to post to this thread. You are a Godsend!
The problem is that the focus points are huge. People always think it those little red squares. Wrong ! The centre focus spot stretches all the way out to the ( ) spot metering markings in your frame. This is way to big to expect accurate focussing with very fast lenses. Use as you are doing, which is fine, or simply set manual focus
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