AF-L and metering relationship???

Trailbandit · Jul 4, 2015

So I'm having this weird problem:

I'm using SEPARATE af lock and ae lock. It doesn't matter what I assign to what but let's say I have the back button on af-L and set my shutter button on half press ae-L.

If I focus on a dark place, LOCK FOCUS ONLY by keeping af-L pressed, RELEASE SHUTTER COMPLETELY and recomposed to a brighter place then press the shutter and take the picture it comes up overexposed!

BUT: If I ALSO lock exposure on the dark spot, then the bright spot comes up HUGELY overexposed!!

What is up with that??? It seems after locking focus the metering system meters somewhere in between the focus lock metering and the proper metering.

Is that normal? Am I missing a setting I should change??

Mako2011 · Jul 4, 2015

Trailbandit said:
So I'm having this weird problem:

I'm using SEPARATE af lock and ae lock. It doesn't matter what I assign to what but let's say I have the back button on af-L and set my shutter button on half press ae-L.

If I focus on a dark place, LOCK FOCUS ONLY by keeping af-L pressed, RELEASE SHUTTER COMPLETELY and recomposed to a brighter place then press the shutter and take the picture it comes up overexposed!

Are you sure AE-L/AF-L button is set to "AF-Lock only"? Are you using spot metering or center-weighted metering? Note that Auto-exposure lock doesn't necessarily work with Matrix metering per page 69 in the manual.

Trailbandit said:
BUT: If I ALSO lock exposure on the dark spot, then the bright spot comes up HUGELY overexposed!!

That would seem right (unless I'm reading wrong). You tell the camera to meter for a dark scene then recompose to a bright scene.....then the result should be a very overexposed looking scene.

Trailbandit said:
What is up with that??? It seems after locking focus the metering system meters somewhere in between the focus lock metering and the proper metering.
Is that normal? Am I missing a setting I should change??

What metering mode are you using? What exposure mode? What is your menu c1 set to? What is your menu f2 set to?

Trailbandit · Jul 4, 2015

Mako2011 said:
Trailbandit said:

So I'm having this weird problem:

I'm using SEPARATE af lock and ae lock. It doesn't matter what I assign to what but let's say I have the back button on af-L and set my shutter button on half press ae-L.

If I focus on a dark place, LOCK FOCUS ONLY by keeping af-L pressed, RELEASE SHUTTER COMPLETELY and recomposed to a brighter place then press the shutter and take the picture it comes up overexposed!

Click to expand...

Are you sure AE-L/AF-L button is set to "AF-Lock only"? Are you using spot metering or center-weighted metering? Note that Auto-exposure lock doesn't necessarily work with Matrix metering per page 69 in the manual.

///////// Absolutely positive, it's set to AF-L only, but also irrelevant (as I explain below it does this regardless of using AE-L/AF-L or half press) Also page 69 refers to a problem regarding AE lock which I am not using ///////////

Mako2011 said:

BUT: If I ALSO lock exposure on the dark spot, then the bright spot comes up HUGELY overexposed!!

Click to expand...

That would seem right (unless I'm reading wrong). You tell the camera to meter for a dark scene then recompose to a bright scene.....then the result should be a very overexposed looking scene.

/////////// Yes, absolutely. I'm just pointing out that this really isn't an AE lock problem as actual AE lock is evidently very different. Sorry for not being clearer /////////////

Mako2011 said:

What is up with that??? It seems after locking focus the metering system meters somewhere in between the focus lock metering and the proper metering.
Is that normal? Am I missing a setting I should change??

Click to expand...

What metering mode are you using? What exposure mode? What is your menu c1 set to? What is your menu f2 set to?

/////////// metering mode is indeed matrix
exposure mode is aperture priority
C1 is ON but I state again that I RELEASE the shutter button when recomposing and press it again when taking the shot so it's not. I think, relevant /////////

f2 is OK button mode (which I don't think is relevant) and is set to RESET

f5 (wich is AE-L/AF-L setting) is in this instance set to AF-L only but this also happens without using the back-button at all!

For example C1 set to OFF , no back button focusing, and just half pressing and recomposing. Does EXACTLY the same thing.

Mako2011 · Jul 4, 2015

Trailbandit said:
Mako2011 said:

Trailbandit said:

So I'm having this weird problem:

I'm using SEPARATE af lock and ae lock. It doesn't matter what I assign to what but let's say I have the back button on af-L and set my shutter button on half press ae-L.

If I focus on a dark place, LOCK FOCUS ONLY by keeping af-L pressed, RELEASE SHUTTER COMPLETELY and recomposed to a brighter place then press the shutter and take the picture it comes up overexposed!

Click to expand...

Are you sure AE-L/AF-L button is set to "AF-Lock only"? Are you using spot metering or center-weighted metering? Note that Auto-exposure lock doesn't necessarily work with Matrix metering per page 69 in the manual.
///////// Absolutely positive, it's set to AF-L only, but also irrelevant (as I explain below it does this regardless of using AE-L/AF-L or half press) Also page 69 refers to a problem regarding AE lock which I am not using ///////////

Trailbandit said:

BUT: If I ALSO lock exposure on the dark spot, then the bright spot comes up HUGELY overexposed!!

Click to expand...

That would seem right (unless I'm reading wrong). You tell the camera to meter for a dark scene then recompose to a bright scene.....then the result should be a very overexposed looking scene.
/////////// Yes, absolutely. I'm just pointing out that this really isn't an AE lock problem as actual AE lock is evidently very different. Sorry for not being clearer /////////////

Trailbandit said:

What is up with that??? It seems after locking focus the metering system meters somewhere in between the focus lock metering and the proper metering.
Is that normal? Am I missing a setting I should change??

Click to expand...

What metering mode are you using? What exposure mode? What is your menu c1 set to? What is your menu f2 set to?
/////////// metering mode is indeed matrix
exposure mode is aperture priority

Click to expand...

Trailbandit said:
Trailbandit said:

C1 is ON but I state again that I RELEASE the shutter button when recomposing and press it again when taking the shot so it's not. I think, relevant /////////

Click to expand...

I got you....are you by chance seeing a AE-L indicator in the viewfinder?

Trailbandit said:
Trailbandit said:

f2 is OK button mode (which I don't think is relevant) and is set to RESET

Click to expand...

What camera?

Trailbandit said:
Trailbandit said:

f5 (wich is AE-L/AF-L setting) is in this instance set to AF-L only but this also happens without using the back-button at all!
For example C1 set to OFF , no back button focusing, and just half pressing and recomposing. Does EXACTLY the same thing.

Click to expand...

If c1 is set to "off" and you are in matrix metering....don't forget that there is a Focus-point bias. Matrix metering will bias the exposure based on the focus point. I wonder if that might be at play.

Trailbandit said:
HOWEVER:
Your point that matrix metering is to blame is INDEED the culprit! setting exposure to spot and center weighted eliminates the problem!
However this seems completely counter intuitive because I still re-meter the exposure when pressing the shutter after recomposing... no??
This is confusing!!

Agreed. I'm still trying to get a handle on what your seeing and why

mrbr · Jul 4, 2015

Trailbandit said:
So I'm having this weird problem:

I'm using SEPARATE af lock and ae lock. It doesn't matter what I assign to what but let's say I have the back button on af-L and set my shutter button on half press ae-L.

If I focus on a dark place, LOCK FOCUS ONLY by keeping af-L pressed, RELEASE SHUTTER COMPLETELY and recomposed to a brighter place then press the shutter and take the picture it comes up overexposed!

BUT: If I ALSO lock exposure on the dark spot, then the bright spot comes up HUGELY overexposed!!
What is up with that??? It seems after locking focus the metering system meters somewhere in between the focus lock metering and the proper metering.
Is that normal? Am I missing a setting I should change??

Hi ,

What you describe resembles strong what is written in KR's D70 review (http://www.kenrockwell.com/nikon/d70perf.htm#performance) :

QUOTE :

OBSERVATION: The meter has an odd and clever bit of programming. In normal operation (not setting AE lock to ON for the shutter button) the AE is still half locked when you press the shutter halfway! What does this mean? It means if you lock the focus by holding the shutter button halfway that the exposure only moves half as many stops as it has to when you recompose. You'll only notice this if you recompose to something many stops different. If you do you'll see the meter change its reading as you recompose, but now if you take your finger off the button you'll see the reading jump the rest of the way to the exposure at your final composition. This is also what you might call "sticky" exposure: it sort of partially sticks to where you locked focus, even when you have not intended to lock exposure.

UNQUOTE

But if you use AE-lock, the choosen setting should be froozen ... that is my experience anyway with my D5100.

Greetings,
Marc

Trailbandit · Jul 4, 2015

@Mako: Camera is a D7000 (sorry for not mentioning)

No AE-L indicator. I made sure to check

Focus point bias is a good point but since I do re-meter by releasing and repressing the shutter it "should" just meter the focus point from scratch as well. (or so I thought :\ )

Actually, mrbr, what you say is indeed exactly what I feel is happening. I did not make a note of the f-stops but I would say it is about half way! The shots (dark, bright(AE-L) and "problematic" look very much like they were bracketed intentionally)
I also crossed referenced this with my D5100 (back-up body) and it also does the exact same thing
AE-lock works very much as expected and completely freezes exposure metering.
I guess that figured it out then.
Thanks a lot guys!
I'm OK as long as this is not a problem
I also checked and observed that this also happens with AF-L even if you actually use manual focus!! As long as you press the AF-L (only) button sticky-exposure engages! And only in matrix metering.
Weird.... Can't figure out WHY this is useful ??

Mako2011 · Jul 4, 2015

Trailbandit said:
@Mako: Camera is a D7000 (sorry for not mentioning)

Thanks...I was thinking D5100 so wrong pages in manual. When I can (may take a bit) I'll set my D7000 up like yours and check...PM me if I forget.

Trailbandit said:
No AE-L indicator. I made sure to check

Focus point bias is a good point but since I do re-meter by releasing and repressing the shutter it "should" just meter the focus point from scratch as well. (or so I thought :\ )

I think so too...but haven't set mine like yours.

Trailbandit said:
Actually, mrbr, what you say is indeed exactly what I feel is happening. I did not make a note of the f-stops but I would say it is about half way! The shots (dark, bright(AE-L) and "problematic" look very much like they were bracketed intentionally)
I also crossed referenced this with my D5100 (back-up body) and it also does the exact same thing
AE-lock works very much as expected and completely freezes exposure metering.
I guess that figured it out then.
Thanks a lot guys!
I'm OK as long as this is not a problem

Good Luck friend!

Trailbandit said:
I also checked and observed that this also happens with AF-L even if you actually use manual focus!! As long as you press the AF-L (only) button sticky-exposure engages! And only in matrix metering.
Weird.... Can't figure out WHY this is useful ??

Maybe the engineers at Nikon think they know what's best for us

mrbr · Jul 5, 2015

Trailbandit said:
@Mako: Camera is a D7000 (sorry for not mentioning)

No AE-L indicator. I made sure to check

Focus point bias is a good point but since I do re-meter by releasing and repressing the shutter it "should" just meter the focus point from scratch as well. (or so I thought :\ )

Actually, mrbr, what you say is indeed exactly what I feel is happening. I did not make a note of the f-stops but I would say it is about half way! The shots (dark, bright(AE-L) and "problematic" look very much like they were bracketed intentionally)
I also crossed referenced this with my D5100 (back-up body) and it also does the exact same thing
AE-lock works very much as expected and completely freezes exposure metering.
I guess that figured it out then.
Thanks a lot guys!
I'm OK as long as this is not a problem
I also checked and observed that this also happens with AF-L even if you actually use manual focus!! As long as you press the AF-L (only) button sticky-exposure engages! And only in matrix metering.
Weird.... Can't figure out WHY this is useful ??

Hi,

IMO Nikon matrix metering wants a "good" exposure for the point you did lock focus AND wants a "good" exposure for the focuspoint when you press the shutter release button.

In AF-S using single focuspoint ,by keeping focus lock exposure in memory and making a statiscal "average value" for exposure with the actual calculated exposure ( for the choosen focus point when taking the picture ) it tries to balance the exposure in memory and the exposure calculated at moment the picture is taken. This works well if there are no big exposure differences between these 2 points. But if the difference become greater you can end up in the situation you described.

With matrix metering, AF-S single focuspoint , in the situation you describe ( Does not work in AF-C mode, I have no information for other focus area modes regarding this subject. ) :

possibility 1 : set exposure for highlights

Disable ADL.

1) lock exposure on the bright spot ( to save higlights and open up shadows in PP ) ,

2) focus on chosen point half pressing the shutter release button

3) recompose and make the picture.

4) Then check the histogram for blown highlights and if needed use exposure compensation for ETTR exposure.

Matrix metering works a bit like spot metering in this case. This can be helpfull if you dont can or want to change from matrix to spot metering.

possibility 2 : make an exposure average of 2 points

Disable ADL.

1)focus and half press shutter release button ( = first exposure saved in camera memory ).

2)Point with the choosen focus point to a bright point ( eg the sky ) and lock exposure.

3) Recompose again;

4)Take picture.

possibility 3 : ADL

With ADL enabled , highlights should be saved automatically , but I have no experience in this field because I disable ADL ( switched from NX2 to LR5 which does not recognise ADL nor nikon picture controls. I still miss the NX2 control points in PP , but LR5 has a lot of other advantages so that I am happy that I made the switch ).

You can also use ADL bracketing !

Greetings,
Marc

Trailbandit · Jul 5, 2015

Mako2011 said:
Trailbandit said:

@Mako: Camera is a D7000 (sorry for not mentioning)

Click to expand...

Thanks...I was thinking D5100 so wrong pages in manual. When I can (may take a bit) I'll set my D7000 up like yours and check...PM me if I forget.

Mako2011 said:

No AE-L indicator. I made sure to check

Focus point bias is a good point but since I do re-meter by releasing and repressing the shutter it "should" just meter the focus point from scratch as well. (or so I thought :\ )

Click to expand...

I think so too...but haven't set mine like yours.

Mako2011 said:

Actually, mrbr, what you say is indeed exactly what I feel is happening. I did not make a note of the f-stops but I would say it is about half way! The shots (dark, bright(AE-L) and "problematic" look very much like they were bracketed intentionally)
I also crossed referenced this with my D5100 (back-up body) and it also does the exact same thing
AE-lock works very much as expected and completely freezes exposure metering.
I guess that figured it out then.
Thanks a lot guys!
I'm OK as long as this is not a problem

Click to expand...

Good Luck friend!

Mako2011 said:

I also checked and observed that this also happens with AF-L even if you actually use manual focus!! As long as you press the AF-L (only) button sticky-exposure engages! And only in matrix metering.
Weird.... Can't figure out WHY this is useful ??

Click to expand...

Maybe the engineers at Nikon think they know what's best for us

Trailbandit · Jul 5, 2015

Those are fine points you're making. Besides It's not like you are going to actually lock focus in a completely dark area and then recompose to a completely bright area far away from where you locked focus. In extreme testing it seems counter intuitive but in actual situations it might prove usefully. And if it throws you off you just ditch matrix and go for a wide center weighted metering instead. No sticky focus -> no problem

Thanks mate!

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