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03-07-2007, 07:51 AM   #1
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K100D link/lock of AE-L and AF

I'm a new owner of the K100D so am still learning as quickly as I can. I would be interested in hearing what folks see as the advantages & disadvantages of fixing the exposure when focus is locked (AE-L with AF locked setting) and linking AE-L and AF so exposure is set with the AF (Link AF point and AE). I understand the latter applies to multisegment metering only.
Thanks for any thoughts you may have to offer.
SB

03-07-2007, 07:41 PM   #2
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QuoteOriginally posted by atnbirdie Quote
I'm a new owner of the K100D so am still learning as quickly as I can. I would be interested in hearing what folks see as the advantages & disadvantages of fixing the exposure when focus is locked (AE-L with AF locked setting) and linking AE-L and AF so exposure is set with the AF (Link AF point and AE). I understand the latter applies to multisegment metering only.
Thanks for any thoughts you may have to offer.
SB
The "link AF to AE" function only affects the multi-segment metering. I suggest this should be only enabled when one used auto multi-point AF and does not recompose. By enable this function, the camera will put more weighs on the metering segment that are in focus as measured by the AF point(s).

The "link AE-L to AF" functions means that everytime the focus is achieved by the AF system, the AE value will be locked altogether. I enable this function by default now as I use central single point AF only. And for CW and spot metering used, I need to lock the AE anyway except in M mode. Even for evalutive metering, Pentax actually puts much weight in the central (spot) metering cell indeed, so it would be no harm to lock to the centre, again.

Just in case if you do not want to lock AE with the framing when you do the AF, press the AE-L for what you want to meter before hand, do the AF and then recompose.
03-08-2007, 02:04 AM   #3
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QuoteOriginally posted by RiceHigh Quote
do the AF and then recompose.
Sorry I have to mention this as I prefer not to see people taught bad habits that results in focus problems..

Why focus recompose sucks.

This is why having 9 cross sensor points is such a great feature in the Pentax DSLRs...

Last edited by joele; 03-08-2007 at 02:27 AM.
03-08-2007, 04:09 AM   #4
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QuoteOriginally posted by joele Quote
Sorry I have to mention this as I prefer not to see people taught bad habits that results in focus problems..

Why focus recompose sucks.

This is why having 9 cross sensor points is such a great feature in the Pentax DSLRs...
I had seen this article years ago but I'm afraid the difference and amount of error involved is indeed *very small* than they are actually visible, even for my FA*85/1.4 opened fully wide at 1.4.

When compared with the AF errors by the AF system itself, it is nothing at all.

If anyone don't believe, try it yourself with your *own* camera and lens.

Do note that the *assumption* in the above article for a perfectly flat in-focus plane is non-existent for even perfect glass like my Pentax FA*85/1.4!

03-08-2007, 04:13 AM   #5
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QuoteOriginally posted by joele Quote
Sorry I have to mention this as I prefer not to see people taught bad habits that results in focus problems..

Why focus recompose sucks.

This is why having 9 cross sensor points is such a great feature in the Pentax DSLRs...
I must also point out that the central AF point of any Pentax AFSLRs are far more accurate than the surrounding ones, even for my MZ-S, which is the most accurate Pentax AFSLR ever.

So, practically, you'll probably get more AF errors in the end!

p.s. I have some very good evidence on how the surrounding AF points suck in accuracy, just that I have not yet written an article to tell the case yet!
03-08-2007, 06:03 AM   #6
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I personally "trying for myself with my own camera and lenses" got far more focus errors as a result of my bad habit of focus recompose than the AF system gives me due to not using the center focus point.. Unfortunately (make that fortunately) I have too many other things to do in my life than write a 200 page speculative thesis on the subject ;-)

Last edited by joele; 03-08-2007 at 06:18 AM.
03-08-2007, 06:20 AM   #7
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The 9 focus point sensor is a very useful feature. The buttons make AF so much easier especially when it comes to bright lenses like fa77 or fa31

The ease to select focusing point through the buttons really make the camera dear to my heart. This feature enables quick focus and less likely to create out of focus shots when DOF is very narrow.

If Joel had not shown me this, I would still do the "focus and recompose" kind of clumsy approach to take photos.
03-08-2007, 06:22 AM   #8
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For example, the focusing point was on this lady's face - sharp as razor!



03-08-2007, 06:26 AM   #9
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This shot has a focusing point at lower part of the image in low light situation

03-12-2007, 06:24 AM   #10
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RiceHigh: Thanks for the clear explanation of the AF-AE link/lock relationships.

joele: Great article on focusing. I'll do some experimenting tonight to get the feel for the issues discussed with my own system, but it makes perfect sense to me. Thanks.
03-12-2007, 06:44 AM   #11
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Thanks for photo examples.
So I assume then you have your focusing mode set to "Select" rather than "Auto"? You then compose your frame as you want it to look, then select the focus point you want with the buttons on back of the camera, then shoot without recomposing. I'll give that a try rather than the "Auto" mode I've been using.
Under what conditions, if ever, do you link or lock your AE-AF points?
Thanks
03-12-2007, 03:15 PM   #12
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Oh my! I'm going to have to read my manual again. I've had my K100 for almost 3 months. After reading this thread I am TOTALLY lost. I have no idea what you're talking about!!!
Should I be concerned that I don't what all this means?
03-12-2007, 09:47 PM   #13
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QuoteQuote:
Sorry I have to mention this as I prefer not to see people taught bad habits that results in focus problems..
...
Though possibly otherwise of some use, amazingly enough, the article suggests focusing on the bridge of the nose instead of nearest eye in portraits.
03-13-2007, 12:12 AM   #14
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I wish to remark that if the camera is set to "linked AF to AE" but the user has set the multi-AF point manually, I don't know if the manually selected (single) AF point is counted or the AF measurement works as it was in "auto 11 points". So, this would be something that unknown, unless someone tests it clearly. Anyone? Or, anyone has already known the answer?

QuoteOriginally posted by RiceHigh Quote
The "link AF to AE" function only affects the multi-segment metering. I suggest this should be only enabled when one used auto multi-point AF and does not recompose. By enable this function, the camera will put more weighs on the metering segment that are in focus as measured by the AF point(s).

The "link AE-L to AF" functions means that everytime the focus is achieved by the AF system, the AE value will be locked altogether. I enable this function by default now as I use central single point AF only. And for CW and spot metering used, I need to lock the AE anyway except in M mode. Even for evalutive metering, Pentax actually puts much weight in the central (spot) metering cell indeed, so it would be no harm to lock to the centre, again.

Just in case if you do not want to lock AE with the framing when you do the AF, press the AE-L for what you want to meter before hand, do the AF and then recompose.
03-13-2007, 12:14 AM   #15
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QuoteOriginally posted by SpecialK Quote
Though possibly otherwise of some use, amazingly enough, the article suggests focusing on the bridge of the nose instead of nearest eye in portraits.
I do both, or even sometimes I focused on the "farther away" eye of the model, I think that depends on what the photographer wants and on the DoF control..
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