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04-02-2012, 12:40 PM   #1
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K5 Segment Metering with AE-L with AF Locked set ON, AE linked to AF Point set ON

Image you are photograghing flowers with say 2 or 3 blooms off centre. You position the Focus Point to one of the flowers to ensure that one flower will be correctly focused & the exposure is linked to that flower to set the correct exposure. The viewfinder shows 1/30S, F16, ISO 200, you press the shutter button half way to focus & the exposure changes 1/25S, F16, ISO 200. Not a great change in exposure but it set me thinking back to AE-L related problems that I had previously experienced.

I checked the following modes to see how they compared with surprising results:

Av Mode
Looking through the viewfinder, the exposure is as follows: 1/30S, F16, ISO 200
Press shutter button half way, the exposure changes to: 1/25S, F16, ISO 200
Release shutter, press AE-L, the exposure is: 1/30S, F16, ISO 200
Press shutter button half way, the exposure changes to: 1/25S, F16, ISO 200

TAv Mode
Looking through the viewfinder, the exposure is as follows: 1/160S, F16, ISO 1250
Press shutter button half way, the exposure changes to: 1/160S, F16, ISO 1600
Release shutter, press AE-L, the exposure is: 1/160S, F16, ISO 1250
Press shutter button half way, the exposure STAYS THE SAME: 1/160S, F16, ISO 1250

From a quick look at other modes, they appear to behave the same as Av.
i.e. exposure changes when shutter button is pressed half way with both no AE-L & with AE-L.

TAv Mode appears to be the only mode that works correctly with AE-L.

Having used a *istDS/K10 for 7 years which held the same exposure when the shutter button was half pressed and when AE-L was pressed, this behaviour appears inconsistent to me.

I would have thought that in the example above, the exposure would have been taken with regard to focus point before the shutter button was pressed half way. If we assume that the exposure is 'finalised' when the shutter button is half pressed to read information from the focus point, then how is AE-L supposed to work.

Is segment metering actually working as it should on the K5?

04-02-2012, 01:37 PM   #2
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What happens if you press AE-L before the shutter release?
04-02-2012, 02:07 PM   #3
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Its because you have set exposure linked to the focus spot. It will be reading an average exposur until you half press the shutter then it will
change and give you a reading as a spot focus on your focus zone is my guess. Or have i missunderstood something here.
04-03-2012, 08:46 AM   #4
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QuoteOriginally posted by jbinpg Quote
What happens if you press AE-L before the shutter release?
Pressing the shutter half way locks the exposure so pressing AE-L will cancel AE-L - you have to press AE-L twice to set AE-L to on.

04-03-2012, 08:51 AM   #5
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QuoteOriginally posted by westmill Quote
Its because you have set exposure linked to the focus spot. It will be reading an average exposur until you half press the shutter then it will
change and give you a reading as a spot focus on your focus zone is my guess. Or have i missunderstood something here.
This was my interpretation of what was happening (despite the *istDS/K10 not performing this way) but it means that you can't use AE-L to lock the exposure if it's going to change when to press the shutter half way.

And TAv behaves differently to Av (and potentially all other modes) - if this interpretation was what is happening, it should be consistent for all modes.

I should point out that this does not happen every time, it seems to occur when the exposure is hovering between 2 settings.
04-03-2012, 09:05 AM   #6
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Ok Ive just grabbed my K5 and tried mine. Camera was on AV, spot focus attached to focus point. Mine held the exposure perfectly. I even refocussed a couple of times and still no problem. My guess is its as you say... hovering between two points but its got to pick one. My Cameras are set to one third increments ! If you have yours on full or half stops.... that wouldnt help. Just a thought !
04-03-2012, 09:14 AM   #7
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The camera gives more priority to the zone the focus is in.
04-03-2012, 09:14 AM   #8
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QuoteOriginally posted by WightWalker Quote
Pressing the shutter half way locks the exposure so pressing AE-L will cancel AE-L - you have to press AE-L twice to set AE-L to on.
Interesting discussion.

How about this option: Keep AEL locked to the focus, but focus with the AF button. disable the half shutter focus action

04-03-2012, 10:50 AM   #9
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QuoteOriginally posted by westmill Quote
Ok Ive just grabbed my K5 and tried mine. Camera was on AV, spot focus attached to focus point. Mine held the exposure perfectly. I even refocussed a couple of times and still no problem. My guess is its as you say... hovering between two points but its got to pick one. My Cameras are set to one third increments ! If you have yours on full or half stops.... that wouldnt help. Just a thought !
Both Spot & Centre Weighted work fine with none of these these problems as AE can't be linked to AF.

I also have 1/3rd increments which probably exasperates the problem, but then that was also the default setting on my *istDS/K10.

To me, there's some minor difference in the firmware which makes the K5 more susceptible.

I'm in discussion with Pentax & hope that they recognise the problem to provide a simple fix.
04-09-2012, 11:35 AM   #10
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QuoteOriginally posted by philbaum Quote
Interesting discussion.

How about this option: Keep AEL locked to the focus, but focus with the AF button. disable the half shutter focus action
I've struggled, myself, in getting things to behave as I want and found the solution above to be the only way to really get a consistent result with my camera for focus and exposure. I typically like this route when I want the AEL anyway as it usually occurs when I am trying to seperate the focal point from the exposure.

Then again, I find myself often moving to Manual mode because that has just become a normal for me... I screw up too many photos in the auto-exposure or semi-autoexposure modes with my K5... mostly because I don't pay attention to shutter speed and ISO as much as I should from shot to shot. M mode, I am forced to.
04-09-2012, 12:18 PM   #11
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Instead of EAL why not use the manual mode with the green button.

You can change the green button function to act like Sv, Tv or Av on demand.
04-13-2012, 11:52 AM   #12
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QuoteOriginally posted by Anvh Quote
Instead of EAL why not use the manual mode with the green button.

You can change the green button function to act like Sv, Tv or Av on demand.
In Manual Mode, pressing the Green Button gives you a correct exposure BUT it chooses a weird shutter/aperture combination which doesn't seem to relate to the Program Line. I have to press the Green Button, then AE-L so as to adjust the shutter/aperture values to suit my set up.

If only the K5s AE-L fuctioned correctly, then we wouldn't be forced to find work arounds!

I've moved across to TAv Mode as this is the only mode where the AE-L button works correctly - fortuneately, the K5s IQ isn't too compromised at high ISO values!
04-15-2012, 05:19 PM   #13
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It's related to a program line but it has his own options in the Custom menu, so take a look there and set it like you want.
I'm sure you can have it act like Av or Tv on command the other mode is like Sv on command so it changes the shutter and aperture to MTF line i believe.
I've never used the last option so...
12-05-2012, 07:33 AM   #14
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I have the same problem on my K5 as you do. Only in Tv does the camera do what it is supposed to do and stops changing the values by itself.
12-05-2012, 10:30 AM   #15
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QuoteOriginally posted by westmill Quote
Its because you have set exposure linked to the focus spot. It will be reading an average exposur until you half press the shutter then it will
change and give you a reading as a spot focus on your focus zone is my guess. Or have i missunderstood something here.
I think that westmill has a good theory.

You could probably test this indoors with a single light source. Hold the camera with the light source off center, select the AF point that would include the light source, and then half press the shutter to engage the metering and AEL. You should see a dramatic difference in metering at that point.

If this is indeed the case, the difference might be the newer metering system that is more discreet with 77 metering segments as opposed to 16 (starting with the K7).

Scott
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