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
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.
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.
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
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.
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
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
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