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11-03-2007, 03:18 AM   #16
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Will,I agree with you,why using selective auto focus if you always use center point,I have no idea,but what I do,I use selective auto focus all the times because I change the auto focus point a lot when I shoot wedding because I shoot horizontal and vertical so I change my auto focus point for different situation but if I want to use only center point why put to selective.

11-03-2007, 07:42 AM   #17
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Terminology

"Selective Focus" usually means the technique of a narrow depth of field to draw attention to specific (sharp) elements in your photograph.

This thread isn't about that -- it's about selecting the autofocus point manually.
11-03-2007, 09:18 AM   #18
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I too use it when the subject is near. Try it and you will see that recomposing doesn't work at short distances, say one meter or so.
11-03-2007, 03:20 PM   #19
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QuoteOriginally posted by WMBP Quote
snip
Selective focus is achieved by using the AF point switching dial that encircles the four-way controller. Turn the AF point switching dial to SEL, and you're using selective focus, whether you use the center point or one of the other ten points.

But I asked you, if you ONLY AND ALWAYS use the center point in SEL focus, then what is the difference between using selective focus and using center-spot focus -- one of the other three auto-focus options? I don't think you answered this question.

Will
Now that we know what you really mean when using the term selective focus here is your answer.

I do not use selective focus as you have defined it - nor do I let the camera pick which focus point is used. I use the center focus point exclusively - that's just what I do and your mileage will vary.

The difference is that I can rapidly decide object is to be in focus - set that object to the center of the frame - push the AF button (remember the shutter button does not activate AF on my cameras - it is de-coupled). I can then point the camera at the object that I want to meter off of (if using spot metering) - hit the ael button - then ------ compose ------ and press the shutter button. If I release the shutter button - to modify the exposure or recompose - the focus does not change - I do not have to let the camera hunt - or move the focus point with the 4-way switch to get the "point" in use on the subject again.

Your technique and workflow will be different than mine - but I just use the center because I have 30+ years of experience doing it and while I have tried other methods I find them limiting. To answer directly - selective focus, as you defined it, is a waste on my machines.

OT a little: Now just be glad that you are not using the N*kon D3 - with 51 focus points, ironically all more or less concentrated around the center of the frame. Just how many wheels would you need to use that? How many shots have you lost - while trying to choose what focus point is best?

The Elitist - Formerly known as PDL

11-03-2007, 05:46 PM   #20
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There was a thread on dpreview recently which contains links to a couple interesting articles on this topic.

Don't recompose!: Pentax SLR Talk Forum: Digital Photography Review
11-04-2007, 10:54 AM   #21
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corrected subject: why use the SEL focus point option?

QuoteOriginally posted by mattdm Quote
"Selective Focus" usually means the technique of a narrow depth of field to draw attention to specific (sharp) elements in your photograph.

This thread isn't about that -- it's about selecting the autofocus point manually.
Matt,

Thanks for correcting me on that and I apologize for confusing my own question by using the wrong term. One of the reasons that I try to be fairly complete in the things that I write is that it minimizes the chance of my being misunderstood due simply to a mistake on my part OR my reader's about the meaning of a single word or two. Notwithstanding my misuse of the term "selective focus," the point of my question was clear to those who read more than the subject line, since the first several responses spoke directly to the issue I was trying to raise.

I'm not sure what to call this option on the camera. Painted on the camera are the letters "SEL". Presumably this means "select," and what you're selecting is, um, the focus point. I guess the best one can do is speak awkwardly of the "SEL focus point option."

Will
11-04-2007, 11:09 AM   #22
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QuoteOriginally posted by PDL Quote
I do not use selective focus as you have defined it - nor do I let the camera pick which focus point is used. I use the center focus point exclusively

PDL,

My apologies for confusing the issue with the wrong term.

I take it now that I misunderstood you earlier, but I would like to confirm this. I take it now that you do NOT use the SEL (select) option on the AF point switching dial, but that you use exclusively the "." (center) option on that dial. Is that right? (NOTE: Terminology as employed in the Pentax operating manual, p. 18 and p. 132.)

If so, that eliminates the question I was asking earlier (why use the SEL option if you always select the center point of the 11 points available).

Will
11-04-2007, 12:45 PM   #23
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Will,

Yes I have the focus point switch shifted to the right most "." point. This feature is also set via the menu on my *ist Ds when I use it. Also - as I have belabored to death - the AF function is decoupled from the shutter button on both cameras. I exclusively use the either the AF button (K10D) or the OK button (*ist Ds) to focus on either camera. However, when I give the camera to my better half (I have finally taught my son "my" method) I set everything back to "default out of the box". To do this is much easier on the K10D than the *ist Ds.

I apologize for high jacking the thread - thinking that you were originally talking about using focus selectively to isolate the subject.

The Elitist - formerly known as PDL

11-04-2007, 12:53 PM   #24
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QuoteOriginally posted by PDL Quote
Yes I have the focus point switch shifted to the right most "." point. This feature is also set via the menu on my *ist Ds when I use it. Also - as I have belabored to death - the AF function is decoupled from the shutter button on both cameras. I exclusively use the either the AF button (K10D) or the OK button (*ist Ds) to focus on either camera. However, when I give the camera to my better half (I have finally taught my son "my" method) I set everything back to "default out of the box". To do this is much easier on the K10D than the *ist Ds.

I apologize for high jacking the thread - thinking that you were originally talking about using focus selectively to isolate the subject.

No need for you to apologize -- it was my mistake. I try to be careful with words but I threw you off the scent here with the wrong term. Anyway, I'm glad we got cleared up the issue of which option you use on the "AF point selection dial" and I follow you completely now.

As for uncoupling auto-focus from the shutter button, I can respect that -- but I am pretty sure it would not work for me most of the time, as most of the time I'm shooting in a hurry. I can't think of anything that can be done with the AF button that I can't do with the shutter, and I find the AF button a lot less convenient to use. I keep poking myself in the nose when I try to use it. ;-)

Will
11-04-2007, 01:05 PM   #25
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QuoteOriginally posted by gofer Quote
There's also the scenario where the camera's on a tripod, the shot composed and you just need to select a focus point. I shoot miniture scenes frequently and use selective focusing quite often.
Steve,

Yes, as I said in my original post, that's the one thing I could think of for this option.

To sum up the state of my understanding as of 11-4-2007: Reasons to use the "SEL" option on the AF point selection dial include the following:
  1. Camera's on a tripod and you want to control where the focus point is without moving the camera.
  2. You're shooting a scene with a wide-angle lens, with a very wide aperture and you're pretty close to what you want to focus on (so depth of field is very thin), and the subject is off to the side of the photo rather than in the center. Using the center (".") option here and recomposing might risk putting the focus target OUT of focus when you recompose, as the camera-to-subject distance could change enough to cause the thing you want to be in focus to end up out of focus. Not a common situation, I suppose, for most photographers, but if you need this option, good to have it.
  3. Personal preference: Even off a tripod and even with an aperture with decent depth of field, you are carefully composing a shot (say, a head shot) and you just feel like playing with the focus spot while you peer through the viewfinder and you DON'T feel like moving the camera. This strikes me personally as an odd need but I certainly have no quarrel with anybody who does this!
There may be others, too, but those are the ones I can think of now.

What I think is interesting about this thread is that I rather expected somebody to mention reason #3 -- but I don't think anybody really did. Reasons 1 and 2 are good solid technical reasons. Reason #3 seems to me a personal preference. I'm sure there are people who DO use SEL for reason #3 and just haven't read or contributed to this thread.

Anyway, thanks to all for helping me clarify this issue a bit for myself.

Will
11-04-2007, 01:16 PM   #26
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QuoteOriginally posted by WMBP Quote
I'm not sure what to call this option on the camera. Painted on the camera are the letters "SEL". Presumably this means "select," and what you're selecting is, um, the focus point. I guess the best one can do is speak awkwardly of the "SEL focus point option."
Perhaps "Manually selected AF point option"?
11-04-2007, 05:00 PM   #27
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Yes I manually select my focus point. For the majority of shots it's the centre spot used to focus, then recompose. But for closer-up shots where I think the focus may change as I move, I then select the appropriate point to use using the 4 way controller. The OK button for me is then set to return the point to the centre point.
11-04-2007, 07:25 PM   #28
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I always use the "Manually selected AF point option" mode.. never goes off that mode..

I love posting this article, sorry if you have seen before, but saves me typing up a huge explanation here and bloating out the thread...

Why Focus-Recompose Sucks

For very shallow DOF (which I like) a small difference can be very noticable..

As per Arpe, depending on the distance to the subject and the apeture used, recompose would obviously introduce such a tiny error in some situations that it could be used without any problem. I have just got into the habit of not doing it..

Last edited by joele; 11-05-2007 at 02:17 AM.
11-04-2007, 08:03 PM   #29
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QuoteOriginally posted by joele Quote
I love posting this article, sorry if you have seen before, but saves me typing up a huge explanation here and bloating out the thread...

Why Focus-Recompose Sucks

For very shallow DOF (which I like) a small difference can be very noticable..

As per Arpe, depending on the distance to the subject and the apeture used, recompose would obviously introduce such a tiny error in some situations that it could be used without any problem. I have just got into the habit of not doing it..
Thanks for the link. The article says basically the same thing I was saying in message #6 of this thread, where I talked about the geometry of camera-to-subject (or is it subject-to-camera?) distances. Except that the article suggests that you don't have to shooting ultrawide for this to make a difference, which I find doubtful -- but intriguing enough that you've persuaded me to give the "manually selected AF point option" another try. I can't imagine using it for shooting most of what I do, where I have almost no time at all to set up the shot. But I think I'll at least do some tests in the next day or two and see if I can see a difference between focus and recompose, on the one hand, and manually selecting the focus point without moving the camera, on the other. Will try to post back here with my impressions or findings, especially if I come up with anything interesting.

Will
11-04-2007, 08:15 PM   #30
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Heres another point I dont think I mentioned earlier, When using the camera on a tripod I dont like to move the position of the camera just to focus and recompose.
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