An attempt to talk about metering

Reed in backlight • January 7th 2009, near Überackern, Austria

This strong backlight scene of the dry leftovers from last years reed was taken close to sunset (3:45pm). The exposure was corrected by something like -1.0 in Lightroom to work out the solar disc a little more. Once more, thanks to the S5pro's excellent dynamic range I didn't have to worry a lot about the exposure - I can use matrix (pattern) metering most of the time. With the D70s, I had to fiddle around with exposure compensation a lot more to avoid blown out highlights, and the above photo would've been a candidate for quite some of it - I'd guess something between -1.33 and -2.0 EV, because of the large amount of darker areas.

I never wrote much about exposure metering before because the web is full of it. But there's one simple rule that I haven't read anywhere (it may well be that I just haven't searched hard enough): you just have to think like the camera's built-in light meter. Or rather, you have to understand what the light meter in the camera thinks.

I don't want to repeat the obvious and explain the "blindness" of light meters in details - they only and always give you an exposure suggestion that is OK for a reflection of 18% grey (which looks more like 50% brightness to us, but thats a different story), because thats all it can see. The two examples where this technique fails are familiar: the bride in her white dress in the snow would end up underexposed, and the black cat in the coal cellar would be overexposed if you'd just follow the exposure suggestion of the light meter in your camera - at least for "standard" metering methods like spot and center weighted (integral) metering.

Whats more problematic is that matrix (or pattern) metering adds some sort of intelligence to it. Problematic in a way that you don't know what will happen. Matrix metering divides a scene into certain key areas, and compares what it sees, luminance-wise, with an enormous amount of similar scenes stored somewhere in the cameras circuits, trying to determine what would be the best exposure. Matrix metering knows that you're taking a photo of a bride in the snow, and adjusts the exposure for you (at least in theory).

Therefore, the camera manual says that matrix metering and exposure compensation don't mix very well, and that you should NOT use exposure compensation with matrix metering because the logic in the camera already KNOWS that an exposure compensation is needed for this and that type of scene - it is already taken care of in the exposure suggestion of the camera. Just like everybody else, after a while I learned where the logic would fail nevertheless, because a lot of factors add to it - the active autofocus area, for example, or the distance to focus (for lenses that supply this information to the camera, marked "D" for "distance" in the Nikon world).

But what will happen when you try to make a photo of a person in a room that stands against a bright window? Who knows what the matrix metering will do? If you point the AF sensor on the person, it will completely blow out the highlights in the windows, but if you don't, the person will be a pitch black silhouette (sidenote: thats a crappy example, because the real solution is to use fill flash). These were the situations where the results of matrix metering always were somewhat puzzling for me.

So, when I'm facing tricky exposures, I'm using spot metering. I meter an area of a scene that is "neutral", exposure wise (18% grey...) and adjust the exposure for that. I found that this works best in manual mode, because framing the scene is an entirely different thing than metering in that case. Another approach is to meter the brightest spot and then overexpose - depending on the camera, more or less is possible here (again, it depends on how bright the brightest spot really is and how bright YOU think it is). I have yet to make my own tests with the Fuji S5pro.

Another quite lengthy article. Damn. I'm writing this as a sort of lesson for myself. Its the classic situation: the moment you explain something to someone else, you understand it perfectly clear for the first time. I hope that moment lasts! :-)