Canon user: exposure on selected AF point

Hello nikon owners.

I have, after many years of doing photography learned that nikon users can actually exposure on their selected AF point. So i am wondering if any of you could please give me some in-depth user review of this feature.
I am a wedding photographer. And i always focus with a single af point. And there is nothing id love more than to be able to expose on that af point aswell. Soooo.. Pessimist as i am, i cant believe this will work as a reliable expsoure source. (If it is i will buy a nikon and use this for every shot ill ever take) .

In the canon camp you have to lock expsoure then compose/focus. Sometimes i dont have time for that during a wedding. If i can put my focus point on someones face and just "click" and get perfect expsoure ill be very happy.

sooo. Please, does it work? Some real world examples would be nice.
Could it correctly expose a backlit bride walking up the isle if i put a single af point on her face 15m away?

Nikon offers Matrix, Center Weighted, or Spot metering (a user switch).

Matrix is "affected by" the focus spot, but there are many other factors over the full frame, and is much closer to full frame than to spot.

Frame sizes vary, DX and FX. Speaking of the D7100 DX model:

Center Weighted is an adjustable area, the DX 7100 offers 6, 8, 10, or 13 mm diameter (center weighted) in the 24x16mm frame.

Spot metering is a 3.5mm spot (DX frame, about 2.5% of the frame) at the moveable focus point.


The D800 FX frame says spot is 4 mm diameter (1.5% of 36x24mm frame) at the moveable focus point,
and Center Weighted is 8, 12, 15, or 20 mm diameter.

Camera metering (including Spot metering) is ambient only, TTL flash uses its own version of center weighted. My notion is a slightly smaller center area. And in many cases, flash is subject to a minimum shutter speed, which is not about ambient either.


You are aware that Spot metering just makes the spot come out middle gray? Not "correct", but middle tone, regardless. If on a human face, you will likely need about +1 EV compensation.

I ETTR so thats not a problem. But how well does this expose on focus point feature work in practice?
A wedding photographer's view would be nice

Betebete said:

I ETTR so thats not a problem. But how well does this expose on focus point feature work in practice?
A wedding photographer's view would be nice

Click to expand...

Sorry, I really don't use Spot metering, and don't have wedding pictures.

I can offer this: Details about Metering Principles (moving the single focus point)

and down lower, about Flash not using Spot: Details about Metering Principles

Never thought of this option as I use centre weighed metering.

For D3300 the manual states 3.5mm circle centered on selected focus point. Just checked it. Framed a scene with graded light - extreme left dark wall, extreme right bright sunlight with brightness dropping from right to left. In aperture priority with ISO 100 and F11 selected, the speed varied from 1/100 to 1/15 as I kept moving the AF point from right to left.

So if you use spot metering option it will meter at the selected spot, but you have to select single point AF and AF-S modes.

here are the shots










Stiched image