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04-05-2010, 08:45 AM   #1
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Slap or Focus issue or just a Newb?

Hi all,

I've been noticing this on about 30-40% of my shots with the k-x. I've been experimenting with the different modes, but I get far too many shots that aren't sharp.

K-x
Sigma 17-70 4.5
Energizer Lith AAs

all shots handheld, and only resized for web viewing.

I've tried SR on and off, forced higher shutter speeds to eliminate blur, waited for focus confirmation.

Haven't tried all the scientific processes of putting it on a tripod, and taking multiple exposures with all sorts of settings on and off. Should I try the focus calibration in debug mode? Is it mirror slap? Or am I just a newb (I expect that I am, but 30-40% of my shots are pretty unusable, that's really discouraging)?

see the following examples, and thanks for any suggestions:
http://picasaweb.google.com/lh/photo/asWtvTeOU9YLSMGh1QAl_w?feat=directlink

http://picasaweb.google.com/lh/photo/gtCS8A6uLU5yYvrfH1YcuQ?feat=directlink

http://picasaweb.google.com/lh/photo/5upUz3rr3gwxKe53aLzjPw?feat=directlink


Last edited by thetruthkc; 04-05-2010 at 08:46 AM. Reason: trying to get photos to show up
04-05-2010, 08:54 AM   #2
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Looks like you're shooting wide open at 70mm. Before messing with debug modes and all that, I would try stopping the lens down to about f8. I would also make sure I have the latest firmware.. That's just me though. What do I know, never even held a Kx......

04-05-2010, 09:12 AM   #3
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The first picture, the camers focused on the bushes behind the girl . The third picture, the camera focused on the bubble in front of the girl .

It seems like you didn't select to use the center focus point .
04-05-2010, 09:22 AM   #4
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I agree - the camera cannot read your mind regarding where you want it to focus. In auto select mode, sometimes it guesses right, sometimes it does not. You're almost always better of selecting the focus point yourself - either using the mode where you do that shot-by-shot using the LCD, or just by leaving it in center point mode.

04-05-2010, 10:28 AM   #5
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Original Poster
Thanks for the tips!

I'm still learning, coming off of my P&S (auto).

I've decided to choose the "center point" focus. So i guess at this point it doesn't matter if I choose 5 or 11 points?

I have the latest firmware, I'll be experimenting with "stopping down". However, it is hard to adjust so many settings while trying to 'catch' the kids in their moments.
04-05-2010, 10:44 AM   #6
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Try using the Program mode (P mode), that lets you adjust the aperture and ISO, while the shutter speed is automatically determined. I would stop it down to about f8, ISO 200-400 for a sunny day and that'll give you a fast enough shutter speed to catch kids in action. Once you set the aperture and ISO, you're free to shoot as long as you're in the same lighting condition since only the shutter speed changes in each shot. I would not go below 1/100 for kids running/moving around.

If you're having issues with the auto focus picking the wrong target you can try center focus only. It's odd because the girl is at the center of all those pics and she's not in focus, so you must have used auto selection points. You can try the focus and recompose method. Select center focus, focus on the girl and then recompose the shot, it's not the fastest way but it's the surest way of having the chosen subject in focus.

The K-x has breathtaking noise suppression at high ISOs, I've routinely shot at ISO 1600, not because I needed to but because I can. With the noise suppression available in LR3 Beta, I would seriously consider shooting ISO 1600 and f8-f11 and a high shutter speed for the sharpest portraits.
04-05-2010, 10:54 AM   #7
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Thanks again!

I can't wait to go home and shoot some more now.

I looked up some more tips and found some good ones here:
Overcoming Depth of Field Problems in Portraits

How to Identify Your Lens’ Sweet Spot

Thanks guys!

(sorry about the false mirror-slap alert)
04-05-2010, 07:05 PM   #8
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I feel your pain. I have the same combination, and was getting similar results.

On page 194 of the manual - footnote number 2 mentions something called "fine sharpness" - Turn it on (and use centre point focus and keep the shutter speeds high) and you will start getting "crisper" results. Note the purists may not like this option - you will see some sharpening artefacts if you really pixel peep.

04-06-2010, 07:02 AM   #9
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Thanks Harold, I'll check it out tonight.

I switched to center focus only.

I did a very 'informal' test last night and used Av mode (with varying ISO ranges). I've found that the Sigma is sharper at smaller apetures. At 70mm f/4.5 I noticed the blur that I was getting with my previous captures, as I moved down towards f/8 then the photos looked much sharper (at the expense of shutter speed).

However, i was very happy with the ISO 6400 performance. here is a link to the album:
Picasa Web Albums - Karl - temp_kx_prob

Excuse the 'creepy' doll, I did this test late last night and the kids were sleeping (and I probably couldn't keep them still enough for those shutter speeds anyway).

Next newbie question: If lenses need to be stopped down to get sharp results, why are they advertised at those apetures? If most or all of your photos will lack sharpness, why even advertise it? Is it 'just' acceptable?

thanks all for your help!
04-06-2010, 11:56 AM   #10
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"Sharp" is a relative term. The kit lens is still perfectly usable wide open; it's just that it - like almost all lenses - gets noticeably *sharper* when stopped down. So you use it wide open when necessry to get a faster enough shutter speed or want the shallow DOF that results, or stop down when you have enough light to make that viable and prefer the deeper DOF that results.
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