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12-14-2013, 01:24 PM   #1
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Help on Da 12-24

Hi just got a DA 12-24 this BF from B&H. I notice sometimes the bottom left is out of focus,& sometimes the bottom right or right side? Sometimes the focus is not where I want it(use spot center single focus point mostly),and at infinity or close to the AF motor is very clunky?
Also there seems to be alot of noise in the shots at 800-1600,which I don't get on my other lenses? I am probably doing something wrong or maybe need to calibrate it on the K5II...any help or suggestions are greatly appreciated. Can post some photos on dropbox soon.
Thanks

12-14-2013, 01:27 PM   #2
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Hi. Many ways to check focus - do a search on this site. Post a few photos too please, it would be good to see what you see!
12-14-2013, 01:41 PM   #3
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QuoteOriginally posted by Shanti Quote
Hi just got a DA 12-24 this BF from B&H. I notice sometimes the bottom left is out of focus,& sometimes the bottom right or right side? Sometimes the focus is not where I want it(use spot center single focus point mostly),and at infinity or close to the AF motor is very clunky?
Also there seems to be alot of noise in the shots at 800-1600,which I don't get on my other lenses? I am probably doing something wrong or maybe need to calibrate it on the K5II...any help or suggestions are greatly appreciated. Can post some photos on dropbox soon.
Thanks
The focal plane isn't flat, so what's in focus in the center isn't necessarily going to be in focus in the corners. Plus, at wide focal lengths sharpness generally takes a hit because of distortion.

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12-14-2013, 02:05 PM   #4
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The AF motor is in the camera body as the 12-24 AF is screw drive and not a SDM. The screwdrive motor is not as quite as an in lens drive motor.



12-14-2013, 06:02 PM   #5
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here are some samples..sky is blown but was more interested to get grass in focus & trees

https://dl.dropboxusercontent.com/u/4825774/12mmF5Iso400S1-100.JPG

https://dl.dropboxusercontent.com/u/4825774/12mmF8Iso400S1-30.JPG

https://dl.dropboxusercontent.com/u/4825774/14mmF5Iso400%20s1-80.JPG

https://dl.dropboxusercontent.com/u/4825774/18mmF8%20Iso400s1-25.JPG
12-14-2013, 09:37 PM   #6
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I see nothing caused by the lens or the camera body on the four images you posted. I believe you are up against two phenomena. The first is that the foreground is not quite in focus because of the depth of the the photograph. Look up Depth of Field on WIKI and you can find some information that might give you an idea. The second is that with an ultrawide lens such as 12mm there is a distortion where the sides of the image appear stretched compared to the centre. This can appear to, and does, affect focus under certain circumstances.

To make sure that there is nothing wrong with the lens, you need to do one of those horribly boring brick wall test shots. Set up the camera in front of a flat subject. The camera sensor (the back will do) must be absolutely parallel to the flat subject. This will tell you if any of the corners are different in focus from other corners.

And lastly, yeah, the focus motor is noisy.
12-15-2013, 08:31 PM   #7
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QuoteOriginally posted by Canada_Rockies Quote
I see nothing caused by the lens or the camera body on the four images you posted. I believe you are up against two phenomena. The first is that the foreground is not quite in focus because of the depth of the the photograph. Look up Depth of Field on WIKI and you can find some information that might give you an idea. The second is that with an ultrawide lens such as 12mm there is a distortion where the sides of the image appear stretched compared to the centre. This can appear to, and does, affect focus under certain circumstances.

To make sure that there is nothing wrong with the lens, you need to do one of those horribly boring brick wall test shots. Set up the camera in front of a flat subject. The camera sensor (the back will do) must be absolutely parallel to the flat subject. This will tell you if any of the corners are different in focus from other corners.

And lastly, yeah, the focus motor is noisy.
Hi I have few more to upload,including a brick wall so you can see if it seems ok...
I found that lens comp. in Lightroom can help a bit,but still grass is hard to get in focus? from what I remember from my film 24mm 2.8,I had from a few feet to infinity in focus at F8 or F11..maybe APS digital is different
12-15-2013, 09:27 PM   #8
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The other thing that happens with digital is that we look at the pictures much more closely, and then wonder why we see things that we never saw before. The grass is hard to get into focus because it is so close to your camera, and you are focused (probably) on the trees, because that is where the AF module would find the most contrast.

I suggest you have another go at the pictures themselves, rather than using ones you have already shot. Here is the sequence I suggest you try for your scenic.

  1. Put your camera on your tripod.
  2. Set it to manual focus
  3. Set the lens to 16mm
  4. Set the aperture to f/8
  5. Set the mode to Av
  6. Using the focus confirmation, focus carefully on something 5.3 feet away. Put your camera bag there and use that, or anything else.
  7. Recompose and take your picture.
Now use your software and have a look.


Albert

12-16-2013, 01:59 AM   #9
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QuoteOriginally posted by Canada_Rockies Quote
I see nothing caused by the lens or the camera body on the four images you posted. I believe you are up against two phenomena. The first is that the foreground is not quite in focus because of the depth of the the photograph. Look up Depth of Field on WIKI and you can find some information that might give you an idea. The second is that with an ultrawide lens such as 12mm there is a distortion where the sides of the image appear stretched compared to the centre. This can appear to, and does, affect focus under certain circumstances.

To make sure that there is nothing wrong with the lens, you need to do one of those horribly boring brick wall test shots. Set up the camera in front of a flat subject. The camera sensor (the back will do) must be absolutely parallel to the flat subject. This will tell you if any of the corners are different in focus from other corners.

And lastly, yeah, the focus motor is noisy.
I Agree.
12-16-2013, 11:42 AM   #10
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QuoteOriginally posted by Canada_Rockies Quote
The other thing that happens with digital is that we look at the pictures much more closely, and then wonder why we see things that we never saw before. The grass is hard to get into focus because it is so close to your camera, and you are focused (probably) on the trees, because that is where the AF module would find the most contrast.

I suggest you have another go at the pictures themselves, rather than using ones you have already shot. Here is the sequence I suggest you try for your scenic.

  1. Put your camera on your tripod.
  2. Set it to manual focus
  3. Set the lens to 16mm
  4. Set the aperture to f/8
  5. Set the mode to Av
  6. Using the focus confirmation, focus carefully on something 5.3 feet away. Put your camera bag there and use that, or anything else.
  7. Recompose and take your picture.
Now use your software and have a look.


Albert
Hi will try that tonight..thanks
12-16-2013, 07:14 PM   #11
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Here are some test shots..on tripod,level both directions,remote release others are brick wall & sewer pipe..FF jpegs No PP,just reduced in size on dropbox files,RAW shots were the same in corners as well,even with sharpening/clarity applied
Just want to know that it is how this lens is supposed to be,most seems sharp but corners are difficult
can't uplaod to pentax forums?




https://dl.dropboxusercontent.com/u/4825774/DA12-24%20test%20shots/1224test1w.jpg

https://dl.dropboxusercontent.com/u/4825774/DA12-24%20test%20shots/1224test5w.jpg

https://dl.dropboxusercontent.com/u/4825774/DA12-24%20test%20shots/1224testlastw.jpg

https://dl.dropboxusercontent.com/u/4825774/DA12-24%20test%20shots/24mmF8%20iso400%20S-160.JPG

https://dl.dropboxusercontent.com/u/4825774/DA12-24%20test%20shots/24mmF6.3Iso400S-60.JPG
12-17-2013, 10:17 AM   #12
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The indoor shots look as if the camera is tilted every so slightly downward. I'm going by the perspective distortion by the window. The brick wall looks perfect. You might be a little bit thrown off by the ultra wide distortion that is stretching the bricks in the corners. This is a characteristic caused by optics when three dimensional scenes are projected onto a flat surface.

From those five images, your lens is working as well as any 12mm lens out there, much like mine. Now you need to stop worrying and just enjoy the lens. Too much pixel peeping ruins the fun, I find when I start doing it (and we all do, mostly).

To upload to the forums as an attachment, click the [go advanced] button and upload from your computer. You can upload to the user gallery on Pentax Forums, too, and then use the shown below the image, like this below. Scroll down when you get to the gallery, and you will find a block of code bracketed by the IMG tags. To upload to the user gallery here on the top bar of the forum view, click "Photos", then "User Photo Gallery", then "Upload Photo". If you right click the image below and select "View Image Info" you can see the code you are looking for on your own photos.

12-17-2013, 09:25 PM   #13
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QuoteOriginally posted by Canada_Rockies Quote
The indoor shots look as if the camera is tilted every so slightly downward. I'm going by the perspective distortion by the window. The brick wall looks perfect. You might be a little bit thrown off by the ultra wide distortion that is stretching the bricks in the corners. This is a characteristic caused by optics when three dimensional scenes are projected onto a flat surface.

From those five images, your lens is working as well as any 12mm lens out there, much like mine. Now you need to stop worrying and just enjoy the lens. Too much pixel peeping ruins the fun, I find when I start doing it (and we all do, mostly).

To upload to the forums as an attachment, click the [go advanced] button and upload from your computer. You can upload to the user gallery on Pentax Forums, too, and then use the shown below the image, like this below. Scroll down when you get to the gallery, and you will find a block of code bracketed by the IMG tags. To upload to the user gallery here on the top bar of the forum view, click "Photos", then "User Photo Gallery", then "Upload Photo". If you right click the image below and select "View Image Info" you can see the code you are looking for on your own photos.
Hi on the indoor the level was centered both ways? the Pentax one,but good to know the lens is ok just read some people saying they returned 3 to find a good one..problem here NO one has Pentax so must trust what I read here & online
I try that way to upload,as went direct to message attach.not through gallery
Thanks for your help
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