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01-07-2009, 08:29 AM   #1
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K100D Super focus issues

Yesterday was my first day in the forum. I hope someone can help me. I am shooting with the Pentax K100D Super. However, I am experiencing some focusing issues. It seems that my background is in focus and my subjects are blurry. I think I am taking a great shot and then when I look at it at 100% on my laptop, I see that my subject is blurred but the background is clear. Please help - I am up for any suggestions. If you know of any debugging software/firmware please let me know.

01-07-2009, 08:33 AM   #2
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could you post an example with in-tact exif data, this will help us to diagnose the problems you are experiencing...
01-07-2009, 08:38 AM   #3
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Pictures would help in this case. I have a K100D Super as well and I find that most of my focus issues come from either 1. Me moving slightly to cause AF-C to shift focus slightly or 2. My subjects moving. Here is something for you to try. Link AF to the "OK" button and use that to AF and then use the shutter button for shutter control only. AF once then take the picture and see what happens.
01-07-2009, 11:16 AM   #4
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It would be nice from you to provide full details (shooting mode, camera configuration, focus mode. shake reduction state, tripod/handheld etc). So we could directly go on trying to figure out what the problem might be, and skip the part where questions are asked for every detail.
Btw, i had similar problem https://www.pentaxforums.com/forums/pentax-dslr-discussion/45604-k100ds-focus...naccuracy.html (you might look, what details are asked and what tests recommended by others) , but more, i think specific, and got very helpful feedback from forum members.
Another very similar: https://www.pentaxforums.com/forums/pentax-dslr-discussion/46023-k100d-super-...s-problem.html

01-08-2009, 09:49 AM   #5
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I apologize for not responding sooner - I travel a lot and will not be back home unitl this afternoon. I will post a few examples then. Thank you so much for helping.
01-08-2009, 09:00 PM   #6
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My Example

Here is one example -I shot with my K100D Super ISO 200 50MM F2.8 1/1600 SEC - the corn stalks around her are clear , at least the ones to the left and right but her face looks flat and blurred a bit. In the second example the folks in front are clearer than those in the back. I believe I took that one with my sigma 24-135MM 2.8 - 4.5
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01-08-2009, 10:07 PM   #7
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QuoteOriginally posted by shesweet59 Quote
Here is one example -I shot with my K100D Super ISO 200 50MM F2.8 1/1600 SEC - the corn stalks around her are clear , at least the ones to the left and right but her face looks flat and blurred a bit. In the second example the folks in front are clearer than those in the back. I believe I took that one with my sigma 24-135MM 2.8 - 4.5
These seem like classic examples of the camera simply having chosen to focus on something other than you intended. It can't read you mind to realize you were more interested in the woman's face than the corn stalks (or the part of her that was dead center in the photo), or more interested in the back row of people than the front. And if you had wanted both front and back rows to be in focus, you would probably have had to picked a smaller aperture for more DOF.
01-09-2009, 01:00 AM   #8
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QuoteOriginally posted by shesweet59 Quote
the corn stalks around her are clear
Which AF point did you use for this shot?
You can check even after the fact using PhotoME, which can show you which AF point has been used.
If it was the centre one (default) the focus seems to be spot on. I suggest to put the AF point selection from Auto to manual and use the cursor keys at the back of the camera to select the one AF point that matches your main interest in the subject.

QuoteOriginally posted by shesweet59 Quote
In the second example the folks in front are clearer than those in the back.
Presumably the f-ratio was too low. Use a higher f-ratio (smaller aperture) to gain more depth of field.

01-09-2009, 04:18 AM   #9
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I think everyone here may have hit the issues already. Here is a link to PhotoME:

PhotoME - Exif, IPTC & ICC Metadata Editor

Download it and use it to extract the EXIF data for the original copies of the above photos. Then post the EXIF here for us to see and also tell us which AF points the camera used for each photo.
01-09-2009, 12:35 PM   #10
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You guys are awesome - I try all suggestions and let you know how it all works out :-)
01-10-2009, 02:59 PM   #11
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In addition to all comments which are absolutely valid,

Specifically for the lady in front of the corn stalks;

A combination of f/2.8 and shutter speed= 1/1600 sec is not necessarily the best solution if you want everything on the photograph to appear sharp. Depth-of-field at that aperture is pretty tiny and it may even cause your model's ears appear blurred even if you have sharp focus on the eyes.

You might have tried another combination like f/4 and 1/800 sec or even f/5.6 and 1/400 sec (Again, if you want everything on that picture to appear sharp)

Actually this very comment is valid for the other photograph as well (Which marc Sabatella has already commented on). However, you could have avoided this problem by positioning yourself better (At a point where you can see all of your subjects - the people - at the same virtual plane)

Remember, keeping everyone at a virtual plane is much more effective than forming a semi-circle while taking "Group" photographs. This might seem odd, though, as you might think (And you are right if you do) you will be equidistant to everyone if you form a semi-circle. Yes you will be equidistant, but focusing of lenses do not work that way
01-10-2009, 03:06 PM   #12
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QuoteOriginally posted by oguzgel Quote
Specifically for the lady in front of the corn stalks;

A combination of f/2.8 and shutter speed= 1/1600 sec is not necessarily the best solution if you want everything on the photograph to appear sharp. Depth-of-field at that aperture is pretty tiny and it may even cause your model's ears appear blurred even if you have sharp focus on the eyes.

You might have tried another combination like f/4 and 1/800 sec or even f/5.6 and 1/400 sec (Again, if you want everything on that picture to appear sharp)
Excellent point. And of course, that's a perfectly viable option in that picture, since there was more than enough to stop down and still get a fast enough shutter speed. The second picture, however, is going to be problematic, because there wasn't nearly as much light. Stop down enough to get more DOF, and you'll be dealing with shutter speeds that are difficult to hand-hold even with SR, and also may show subject motion even when they are *trying* to hold still.

QuoteQuote:
Remember, keeping everyone at a virtual plane is much more effective than forming a semi-circle while taking "Group" photographs. This might seem odd, though, as you might think (And you are right if you do) you will be equidistant to everyone if you form a semi-circle. Yes you will be equidistant, but focusing of lenses do not work that way
My understanding is that this is lens-specific. Macro lenses are specially designed to have flat planes of focus, but other lenses may be more curved. Maybe not to the extent of a all points being equidistant, but it's worth experimenting with any given lens to discover how it works in that regard if you're going to do that sort of photography.
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