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08-11-2015, 06:19 PM   #1
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Link AE and AF point

If I have this off (so metering is not linked to focus point), does it take the meter reading at the center? Also if I switch the lens to manual focus, then the meter reading will be in the center and whatever I have it set to will make no difference?

08-11-2015, 06:53 PM   #2
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QuoteOriginally posted by Murfy Quote
does it take the meter reading at the center?
Not unless you set it to centre-weighted average or spot.

Matrix metering (the default) effectively uses 86000 metering points across the whole frame. Pic related:



Unless you have linked AE to AF point, if you switch an AF lens (eg the 18-135 kit lens) to manual, metering will just work however you set the metering to work - whether it be spot, centre-weighted, or matrix.

Last edited by rawr; 08-11-2015 at 06:57 PM. Reason: Added pic
08-11-2015, 08:42 PM   #3
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QuoteOriginally posted by rawr Quote
Not unless you set it to centre-weighted average or spot.
Or mount a non-A contact lens...

...in that case it defaults to center-weighted.


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08-11-2015, 09:03 PM   #4
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QuoteOriginally posted by stevebrot Quote
Or mount a non-A contact lens...
...in that case it defaults to center-weighted.
True. But OP did mention '...if I switch the lens to manual focus', and not many AF Pentax lenses out there are non-A, I think.


Last edited by rawr; 08-11-2015 at 09:08 PM.
08-11-2015, 09:19 PM   #5
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QuoteOriginally posted by rawr Quote
Not unless you set it to centre-weighted average or spot.

Matrix metering (the default) effectively uses 86000 metering points across the whole frame. Pic related:



Unless you have linked AE to AF point, if you switch an AF lens (eg the 18-135 kit lens) to manual, metering will just work however you set the metering to work - whether it be spot, centre-weighted, or matrix.
so if I have spot metering on a manual lens, it uses the center to get the spot meter reading, so the link ae to af point option is basically null? if I use spot metering on af lens but have the link ae to af point off, it spot meters in the center, no matter where I set the focus? I mostly use spot metering, sometimes, center weighted, and some old manual lens. if I use matrix metering and link ae to af point (on af lens) then it doesnt really matter either? if I reiterate what you just said, I apologize, I am just making sure I understand this setting. I normally set link ae to af point on with spot metering but I was trying to understand if I would ever need to have it set to off. I am trying to see if I understand the setting correctly.
08-11-2015, 10:48 PM   #6
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QuoteOriginally posted by Murfy Quote
so if I have spot metering on a manual lens, it uses the center to get the spot meter reading, so the link ae to af point option is basically null?
Yes.
QuoteOriginally posted by Murfy Quote
if I use spot metering on af lens but have the link ae to af point off, it spot meters in the center, no matter where I set the focus?
Yes. By default, spot AE metering meters a tiny 5% of the scene dead-centre in the frame. And according to the manual, it's fixed there. If you have 'Link AE to AF point' turned off, the camera will have no reason to do anything different.
QuoteOriginally posted by Murfy Quote
I mostly use spot metering, sometimes, center weighted, and some old manual lens. if I use matrix metering and link ae to af point (on af lens) then it doesnt really matter either?
If you manually choose spot metering as the AE mode, then 'Link AE to AF point', it would be logical for that 5% metering spot to follow around your AF point (within the coverage area of your 27 AF points). Ditto for if you selected centre-weighted metering together with 'Link AE to AF'. And in multi-segment metering mode, when setting 'Link AE to AF Point', it would be logical for the camera to bias the exposure reading towards wherever the AF goes, rather than meter across the whole scene.

So sure, with AF lenses, sometimes using 'Link AE and AF point' might make manually selecting spot metering or centre-weighted metering redundant. With the 'Link AE and AF' option, you can just leave the metering mode at the default 'Multi-segment' setting, do your AF and rely on the 86k metering sensor to follow where you focus.

But it is also possible that the metering mode you select first (Multi-segment/ Centre-weighted, or Spot) may override or limit the scope of operation of 'Link AE and AF Point'.

This is one of those areas (like AF-C) where the K-3 has a ton of advanced features, but unfortunately there isn't a lof of detailed information about how they work in the manual. So I am just taking educated guesses here.
08-12-2015, 04:03 AM   #7
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My understanding is that linking AF and AE only works in multisegment mode with AF lenses - and means a spot meter readout at the selected AF point. Switching to centreweighted or spot metering means standard centreweighted and spot metering, not linked to the AF point. I agree with that the manual is unclear here.
08-12-2015, 06:22 AM   #8
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QuoteOriginally posted by rawr Quote
This is one of those areas (like AF-C) where the K-3 has a ton of advanced features, but unfortunately there isn't a lof of detailed information about how they work in the manual. So I am just taking educated guesses here.
Is there any other more in depth book? I am just getting back into photography after a long absence, so I only had a Nikon d200 (and k1000 before that) but the manual was much more extensive and I also got cd and field guide by other authors. I know Pentax is not a huge share of the market, but I wish there was something more detailed out there.

08-12-2015, 06:38 AM - 1 Like   #9
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QuoteOriginally posted by Murfy Quote
but I wish there was something more detailed out there.
Don't we all.

Go to your local university and visit the engineering or CS faculty, and suggest that someone do a PhD on Pentax K-3 advanced features. PhD students are always searching for new and un-explored topics (terra incognita).
08-12-2015, 07:26 AM   #10
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QuoteOriginally posted by rawr Quote
Don't we all.

Go to your local university and visit the engineering or CS faculty, and suggest that someone do a PhD on Pentax K-3 advanced features. PhD students are always searching for new and un-explored topics (terra incognita).

hmmm...my niece is actually a mechanical engineer...maybe I will bug her. I will just causally ask if she wants to borrow my camera and then ask her questions about it...LOL
08-12-2015, 07:37 AM   #11
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QuoteOriginally posted by Murfy Quote
Is there any other more in depth book? I am just getting back into photography after a long absence, so I only had a Nikon d200 (and k1000 before that) but the manual was much more extensive and I also got cd and field guide by other authors. I know Pentax is not a huge share of the market, but I wish there was something more detailed out there.
#pentaxebook

Fantastic model-specific books written by a Pentax user. I love mine, and others do too.
08-12-2015, 06:27 PM - 1 Like   #12
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I did a quick test on how the camera meters when set to link AE with AF point. I set the camera on a tripod facing a cluttered corner of my room and framed it so there would be a range of values so I could see changes in settings as I move the AF points.

Linking AE to AF point only seems to have an effect with using matrix metering + 3x3 zone AF select or single point AF select and spot metering + single point AF select.

There is no effect with using spot metering + 3x3 zone AF select, center weighted metering, or 27 point auto AF.

From what I can tell setting matrix metering + 3x3 zone AF select or single point AF select the camera meters weighted towards or in favour of where you place your AF points while still considering other areas in the frame.

Spot metering + single point AF select seems to meter fully off where you place the AF point. The same effect as spot metering from the center, locking the AE, then recomposing.

When using spot metering + 3x3 zone AF select, metering is off the center point of the sensor regardless of where you move the 3x3 grid.

When using 3x3 zone AF select, it seems to either using the center of the 3x3 grid or averages values from all 9 points.

Didn't test in live view but would imagine would be similar. Probably not the most controlled or ideal way of testing, should probably frame a giant greyscale value chart to get a better measure.
08-13-2015, 08:05 PM   #13
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QuoteOriginally posted by Fat Albert Quote
#pentaxebook

Fantastic model-specific books written by a Pentax user. I love mine, and others do too.
thanks, I checked out the samples and will probably buy. I read a few things in the sample that looked pretty good
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