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09-13-2014, 06:34 AM   #1
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Focus Points?

[disclaimer: complete beginner]

I have a K-50 and up to now I have obviously been using Auto Focus and when the AF does not focus what I want, I give it my best try by adjusting it manually (18-135 WR so it has the Quick Shift thing).

Now my question is: where do the focus points come into play? Where and when would I make use of them? Does focus points work with auto focus or with manual focus? As you can tell I'm kind of lost to this.

Thanks

09-13-2014, 06:41 AM   #2
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Focus points are just areas where the camera can measure the focus and potentially lock focus. If you're in 11 point af mode, the camera tries to guess where your subject is, and focuses accordingly. The denser the points, the more accurate this can become.

Most advanced users stick to single point af or select mode so you can tell the camera where to focus.

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09-13-2014, 07:18 AM   #3
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I usually leave my camera either on the center AF focus point (focus and then compose) or select the focus point that I want (in that case I move the AF point to where the subject is in the frame).

The only time I use the "AUTO" AF mode (where the camera selects from multiple AF points on its own) is if I'm using continuous AF and shooting birds in flight or airplanes in flight at an airshow. Birds and planes move so quickly that it usually helps to let the camera pick the focus point when you're shooting against the empty sky.
09-13-2014, 07:19 AM   #4
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Original Poster
I'm currently using the default 5 points. Should I change it to 11 points to make it denser as you mentioned?

Also, up to now I have never had to tell the camera "focus on this area point". I guess as you mentioned that's the purpose of the focus points. Is it recommended for me (beginner) to start doing that or just continue what I have been doing?

Today I'm shooting a little girl's birthday party (and before you gasp, it's family, I'm not charging, just taking it as practice and their other alternative was to use cell phone cameras so they are glad I'm bringing my camera which they see as professional).

As I mentioned, although rarely, sometimes the AF does not focus what I want, could I use the focus points to "tell the camera" where I want it to focus? Is that the purpose?

Thanks.

09-13-2014, 07:28 AM   #5
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Hey, welcome!
I would suggest you try using the select point. That way you choose where you want to focus, and the camera won't make a guess that might or might not be the same as you wish.
The other thing to keep in mind is that the AF overlays (little red squares in the viewfinder) are much smaller than actual AF points. The Centre AF point is as big as the ( ) so it might lock focus correctly, but not on the subject that you wanted, because there are two or more in the same focus point. And finally, the AF overlays merely indicate which AF point is in use. The real focus confirm is the hexagon beneath the viewfinder.

Another thing you can use with fast lenses is live view and focus peaking. But this is usually a little slower. But the live view AF is Contrast Detect, using computer algorithms. It is different from the usual Phase Detect AF in non-live view. The CD AF can be more accurate as it doesn't need to be calibrated, but it is slower and focuses on the highest contrast, which can be deceiving.
Finally, the PD AF can be adjusted. Pretty much all modern digital cameras expect that the lens and camera might be at opposite ends of factory tolerances, which would cause consistent front or back focusing. There are many threads about AF calibation (micro adjust or something) using focus charts and other tools. This can be helpful if you notice a consistent AF error with some lenses. (some cameras only have a global AF adjust, while others remember the adjustment for specific lenses)

Edit: Or use Center point, to be safe. Most people like photos with subject in centre anyway

Last edited by Na Horuk; 09-13-2014 at 10:02 AM.
09-13-2014, 10:44 AM   #6
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Using 11 point will not make the AF points more dense.
The system does not fit 11 points into the area where only 5 were used before...

So, 11 point covers most of the viewfinder.
9 in the middle (3x3 square) plus two on either side (at far right/left of viewfinder)

5 point AF: the center point and four around it (above/below/right/left) in a diamond are used... What 5 point does is restrict the number of points Auto AF has to work with from 11 to 5.
As pointed out, 11 point Auto and the camera can choose any point in the viewfinder...
5 point Auto is basically telling the camera to ignore some points and concentrate on the center...

For manual point selection. You choose the focus point but that point still does the AF thing. The camera is still in AF. The only 'manual' thing is you picking the point to use. When you manually select the center point you are telling the camera to only use that point. You can also manually select any of the other points, of course.

I tend to manually select my points and often use just center point. I think 5 point auto select is not bad for subjects in the center. Using either manual point selection or 5 point might be best. The camera might get distracted if it has too many points to choose from.

Maybe don't experiment too much today...
Use your five point as it seems to work most of the time. If you do want to try a different thing, try manual point selection (but camera still in AF) and use center point. Have fun.
09-16-2014, 09:59 AM   #7
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The choice of focusing point depends on your subject and your shooting style. Most people (beginners to pros) it seems prefers to set the camera for only the center focusing point.
This allows you to know and pick exactly what will be in focus.
If you're shooting something like birds in flight or breaching whales where the subject could be anywhere in the frame and at a moments notice, then a multi-spot setting would be beneficial.
09-16-2014, 10:48 AM   #8
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All the above replies from other members are valid... in essence, if you want to have higher percentage of your photos in focus, it is better to select your focus point then letting the camera select it for you.

The only time I let my camera select focus points are:
1) when the object is not still (birds in flight, air plane etc.) as already mentioned by other poster
2) when I have someone else using my camera to take photo; as you don't want to confuse a stranger holding your camera

Some people get accustomed to selecting the center focus point and recompose to make the short. This method is good most of the time, but sometimes, it is better to select the correct focus point rather than moving the camera to recompose as it may result in changing perspective.

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