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D800 metering system quirks

geneluck

Reading, UK
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geneluck Silver Member Nikonian since 16th Oct 2004
Mon 04-Mar-13 06:53 PM | edited Mon 04-Mar-13 07:00 PM by geneluck

I continued to test my D800 today and tried with some testing condition of bright light and shadow. To my great surprise,one of the pictures looked really overexposed. I fired a second shot just to confirm:exactly same result. I then set the exposure compensation to a whole -1 stop and that seems to be at the limit before blowing highlights. I then reset the exposure compensation to 0 , moved a bit bakcwards and shot again: this time the exposure looked good to me.
So what could have caused the D800 to overexpose the first 2 pictures?
the camera setting was the same for all 4 pictures :

taken with 70-200 VRII at 70mm f4 ISO 100 in Aperture mode matrix metering so
for all 4 , the camera determined the shutter speed:

#1 and #2 (overexposed) where shot at 1/160s
#3 (exposure compensation set to -1) was shot at 1/320s (which you would expect)
#4 (taken from a bit further back)was shot at 1/800s


All pictures where shot in jpeg, and simply resized in CS6
Jean-luc






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Jean-luc

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RiverWader

Gardner, US
80 posts

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#1. "RE: D800 metering system quirks" | In response to Reply # 0

RiverWader Silver Member Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014 Nikonian since 14th May 2010
Mon 04-Mar-13 06:07 PM



Looks like you could be using spot metering. The camera will expose for the focus point in this mode. If it was metered using the part inside the tunnel, that would yield overexposed areas that are hit by the sun, In the latter 2, the point would have metered on the sunny portions.

Just a guess.

-Pat

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JPJ

Toronto, CA
1327 posts

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#2. "RE: D800 metering system quirks" | In response to Reply # 0

JPJ Silver Member Nikonian since 19th Aug 2009
Mon 04-Mar-13 06:08 PM

I have not tested this myself, but Thom Hogan reported that the D800 does that weighted focus point matrix metering that first appeared in the D80 (my experience was the d7000 also did this which caused people to believe it overexposed).

Basically it exposes with an emphasis for what the focus point is on in matrix metering.

In your case I would hazard a guess that in your first two photos the focus point was in the dark tunnel as it is well exposed in there causing the rest of the photo (which is in direct sunlight) to be overexposed.

I would then guess that when you backed up the focus point was on something outside the dark tunnel, thus you have exposed photo except the tunnel which is very dark.

Jason

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geneluck

Reading, UK
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#3. "RE: D800 metering system quirks" | In response to Reply # 1

geneluck Silver Member Nikonian since 16th Oct 2004
Mon 04-Mar-13 06:27 PM

Thanks Pat. As I wrote it in my post, I was using matrix metering.
Jean-luc

Jean-luc

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geneluck

Reading, UK
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#4. "RE: D800 metering system quirks" | In response to Reply # 2

geneluck Silver Member Nikonian since 16th Oct 2004
Mon 04-Mar-13 06:32 PM

Thank you Jason. That could certainly explain this over-exposure, but then this can hardly be called matrix metering any longer.
At least, it should not cause a clipping of the highlights. I would have thought this behaviour would be achieved with either center weighted or spot metering.
Jean-luc

Jean-luc

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Testing123

Southern California, US
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#5. "RE: D800 metering system quirks" | In response to Reply # 0

Testing123 Silver Member Nikonian since 25th Jan 2009
Tue 05-Mar-13 02:05 AM

Hi Jean-luc,
Have a look at a Youtube video Jason Odell did that explains and shows matrix metering bias with the focus point:
http://www.youtube.com/watch?v=Mi_klUkJByw

Hope that helps...

Allen

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JPJ

Toronto, CA
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#6. "RE: D800 metering system quirks" | In response to Reply # 4

JPJ Silver Member Nikonian since 19th Aug 2009
Tue 05-Mar-13 03:13 AM

What is a greater mystery is why Nikon appears to keep changing their minds. Some models use this focus point weighted model of matrix metering and others don't. A consistent model would allow us to adjust once and for all.

Jason

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geneluck

Reading, UK
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#7. "RE: D800 metering system quirks" | In response to Reply # 6

geneluck Silver Member Nikonian since 16th Oct 2004
Tue 05-Mar-13 06:22 AM | edited Tue 05-Mar-13 06:22 AM by geneluck

Agreed. Or at least there could have been an a option for matrix metering to behave without bias.
Jean-luc

Jean-luc

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geneluck

Reading, UK
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#8. "RE: D800 metering system quirks" | In response to Reply # 5

geneluck Silver Member Nikonian since 16th Oct 2004
Tue 05-Mar-13 06:39 AM | edited Tue 05-Mar-13 06:40 AM by geneluck

Thanks a lot Allen. The statement was not very clear to me in the video and only after the first question and answer, I think I got what he says.
I will test now it if this works
with the D800 in AF-C focusing mode with AF-ON only focus activation.

1- choose my point of focus , press AF-ON ,release AF-ON(this should acquire and lock focus)

2- recompose and at the same time move the focus point with the thumb wheel to the area from where I want the camera to compute and bias the exposure from.

3- take the picture by pressing the shutter release hoping that the focus stays on the first point of focus and that the metering is done based on the point of focus chosen in (2-)
Jean-luc

Jean-luc

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km6xz

St Petersburg, RU
3577 posts

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#9. "RE: D800 metering system quirks" | In response to Reply # 8

km6xz Moderator Awarded for his in-depth knowledge in various areas, including Portraits and Urban Photography Nikonian since 22nd Jan 2009
Tue 05-Mar-13 01:51 PM

Why not just use the AE-L button to lock metering before recomposing?

Overall, even with the tremendous DR of the D800, a scene like the posted images can exceed the range of a camera, any camera but less so with the D800. Each scene's best exposure is based on intent, not just light levels. What tone levels do you want most to preserve and which can be lost is a decision every photographer deals with. Some make the decision to let the very smart camera make that choice, others want to control it personally, most do a combination of the two.
Matrix bias on the focus point is a good choice by Nikon, they know most photographers are interested in capturing the most detail of the subject under the active focus point in which case, Matrix works very well. If there is a desire to let some other portion of the scene become the mid point in zone, the photographer has the tools to achive that also.
Stan
St Petersburg Russia

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geneluck

Reading, UK
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#10. "RE: D800 metering system quirks" | In response to Reply # 9

geneluck Silver Member Nikonian since 16th Oct 2004
Tue 05-Mar-13 08:16 PM

Thank you Stan.
"Matrix bias on the focus point is a good choice by Nikon". I would think that it depends what you are shooting : if you are in portrait and wedding photography this is most certainly true. For landscape which is most of my work, I tend to agree with Jason Odell who recommends the method listed above.
Jean-luc

Jean-luc

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liamtoh1ps

US
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#11. "RE: D800 metering system quirks" | In response to Reply # 8

liamtoh1ps Registered since 17th Apr 2012
Tue 05-Mar-13 09:21 PM

This is also another good reason to decouple the auto-focus from the shutter button and use the AF-ON button.

And as Stan pointed out AE-L button is another option when you have AF and AE coupled to your shutter button.

Pravin.

G