I've Got the Blinkies - Is My Display Broken?
Back in the dark ages of film, there were really only two ways to set your exposure. Either you let your camera do it on automatic exposure (program mode) or you took control of it yourself and checked out the meter before pressing the shutter release. As good as automatic program mode may be, it can really only guess as to what you want an image to appear. If you were shooting an average scene, program mode may well nail the exposure to create a great looking image. But personally I've never gone out of my way to shoot average images. That has long made me a huge fan of manual exposure and checking the meter reading myself.
Of course the difficulty in this approach is that an exposure meter can read what you aim it at. Matrix metering attempts to factor in the entire scene, but this leaves you at the mercy of how smart (or not) your camera may be. Most of the time, you'll end up with average images once again, and I've already told you my feelings on average images. Center weighted metering asks you to help in the decision of what really matters in your image, weighting the central portion of the metering pattern more heavily than the remainder. But a weighted average image isn't much better than any other form of average, so you'll rarely find my meter set on center weighted. No, the only way to retain full control yourself is with spot metering.
But there are a lot of potential spots you might meter on in any given scene. Back in the film days, most shooters found something medium toned and centered their meter reading so that this spot read on the zero mark, trusting that by doing so everything else would fall where it should. Those of us intent on getting the best images we could under tricky lighting conditions would meter on multiple points and use graduated neutral density filters to modify the lighting enough to avoid burned out highlights or large portions of impenetrably black shadows.
In this era of digital photography, this strategy of spot metering still holds valid, but we have some new tools at our disposal, and some new concerns to contend with.
First, there's a difference between the way film handled overexposure and the way a digital sensor does. Neither one likes it very much, but their tolerance differs nonetheless. The responsiveness of film fell off gradually as highlights approached burned out white whereas highlights on digital pretty much fall off the cliff when you hit the limit. Each photosite counts up exposure and when that bucket is full, it's full. Everything records just fine until you hit that point, and then that's it, you're done. Ugly, burned out white highlight spots can ruin an image.
At the same time, the linear gamma of a raw capture means that recorded values will be more accurate at brighter exposures. With every stop of brightness added, you have twice as many possible values that can be recorded. Human vision responds to successive doubling and halving of brightness as if they were all equal changes, but your camera doesn't see that way. It sees every progressive addition of brightness for what it actually is, basically just counting how many photons of light fall on it during the period the shutter is open and the exposure is in progress. This means you'll get better results if you expose your images as bright as possible and then adjust them to suit in Lightroom or other conversion software later, so long as you don't burn out the highlights at the time you shoot. This is the theory of "expose to the right."
So today we're faced with competing objectives. Expose things too bright and you'll burn out the highlights and create unsightly white spots where none should exist. Expose things too dark and you're wasting a portion of the accuracy your camera is capable of due to the linear gamma issue.
I've written before that many shooters who espouse "shoot to the right" may well be wrong since by doing so they are risking burned out highlights and other problems. Most users are better off not risking this problem and will get more consistently usable exposures by staying more in the middle than by risking falling off the cliff edge.
Your best weapon in exposure dilemma is the blinkies. Nikon technically refers to this by the somewhat boring name of Highlight display in the Playback Options. But "blinkies" more accurately describes the feature. When enabled, your camera LCD display will present you the image with blinking white spots where the burned out highlights are, if there are any. If you've turned this feature on and don't see any change in the image display, congratulations, you must not have any burned out highlights. But those of you who shoot in contrasty lighting are no doubt well familiar with the phenomenon.
But not everyone who has seen blinky highlights on their images fully understands what use this tool for. It's not uncommon to look at the blinky display merely as a curiosity, but even those who know better tend to check them out only occasionally. And so long as there are no blinking highlights staring back at them, believe that all is well.
But if you want to expose to the right as much as you can without burning out the highlights, the blinky highlight playback display is your friend and guide.
In this digital age of HDR image capture, not everything needs to shot as multiple captures and blended together later to yield a good result in challenging light. Many images can be shot just fine by pushing the exposure right up to the point where blinky highlights start to show up, but without pushing things over the cliff. Bump up the exposure until you see blinky highlights start to show up, and then back off the exposure just enough to make them go away. Especially on modern cameras that have improved noise characteristics and 14-bit RAW capability, it can be surprising how much detail you have available to work with in a single capture.
Don't just check that you don't have any blinkies. Go ahead and push your exposure right up to the cliff edge if you need to. The blinkies don't mean your display is broken. They mean your display is helping you make better images.