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01-02-2010, 07:53 PM   #1
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how to focus?

I have a quick, major beginner question about focusing pictures. I just got a K-x and I've been reading about the different ways to focus pictures in the manual (full auto focus, manual focus, center point and recompose, and selecting the focus point .... ?!) and I'm really unclear about which method I should be using, and when to use which one. If someone could give me a bit of help, I would be really appreciative ...

Thank You!

01-02-2010, 07:58 PM   #2
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I understand that you are a new user. This is a common question. Try searching the forum for 'focus' in the thread titles, and you should find the answer you are searching for.
01-03-2010, 12:44 AM   #3
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It's a very personal decision. See the "how do you focus?" poll and thread in the General Photography forum (I think) for lots of different viewpoints. Me, I either use center with focus/recompose or I focus manually (the latter with my manual lenses, of course, but also when experiences tells me AF will have a hard time).
01-03-2010, 11:26 AM   #4
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Auto focus is reliable enough most of the time. You just need to know when it needs help, then choose the help method that works best for you. A list of times when AF might need help:
  • Subject is not in the center of the frame. AF won't necessarily choose your subject to focus on.
  • Depth of field is narrow. That will happen if the f number is small, or at close distances. AF will focus on something, but the subject may not be entirely covered by the depth of field.
  • Fast-moving subjects. AF takes time, and it may be too slow.
  • Subject has low contrast. The AF sensors look for edges and contrast. If they can't "see" any contrast, they will not lock on anything. Point the camera at a blue sky to see. Or, the sensors will lock on a high-contrast area that's not your subject.
  • Low light, and/or limited-spectrum light. The classic situation is a single tungsten bulb. Low light often means you're using large apertures and therefore limited depth of field, and contrast is limited. That's where AF will be taxed.
The above situations might require different methods to solve. For example, a photo of a flower at very close distances in the daytime - choose a smaller aperture (larger number) like f11 or f16, and maybe use the flash, to get a larger depth of field. With a person in a chair reading by one 60w bulb, a flash would ruin the ambiance. I would use manual focus here, but AF might work if you select a focus point.

Manual focus is not easy, otherwise AF wouldn't exist. But it is usually an option. You can get better with practice. Confidence in manual focus can improve your photos a lot, even if you only improve your ability to see focus in the viewfinder.

Last edited by Just1MoreDave; 01-03-2010 at 01:16 PM.

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