Elk Cow Running - Jasper National Park, Alberta
I just published an article about composition and how it relates to photography. Another subject area and perhaps more confusing and therefore more critical to proper understanding is exposure. Some say that photography is all about light. As in, without light you can’t have photography. Without good light, you can’t have good photography. When the light is just right, then your photography has a chance to be just right. Those that say photography is all about light have a really good argument.
The thing we’re talking about here is exposure. We’re talking about how to get your light just right to make your photographic images look right. Unfortunately, exposure seems to be a confusing and complicating topic. In fact, camera makers seems to invest zillions in the marketing on their new technologies to make good exposure simple and easier to capture. To remove all your angst about getting exposure right, the manufacturers have invested tons supposedly making determining exposure simple and accurate. Personally, I think the whole process completely over-done. In fact, the more complicated names camera companies apply to camera metering systems only seems to make getting a good exposure the thing of complex equations and really smart people. It’s not. Honest...
When you get down to the basics, exposure is really not that complicated. To avoid most of the high tech talk associated with camera metering systems, I’ll mostly stay with the basics. We’ll talk about how exposure is determined and then how it relates to photographic situations. I’m doing a couple of articles to describe all this. These articles will be less about what your camera does and more about the simple matters of exposure. The first portion of these articles will be able exposure in general. I’ll follow this with articles that talk about changing aperture and how that affects exposure and your images. Then I’ll talk about changing shutter speeds.
Let’s get down to it.
The basics of exposure is all about capturing light. Dependent on the sensitivity of your image capturing device--i.e. your camera--the amount of light that’s hitting your subject, and the tonal characteristics of your subject, the mood you’re trying to impart to your audience, you’ll be adjusting your exposure settings to get the right exposure. Without getting into the artistic qualities of exposure, let’s just say for now all exposure is created equal. In other words, for a certain amount of light that’s falling on a subject, and the subject looks kind of like some sort of “normal” thing, the exposure will have a certain basic value. From that, if the “normal” changes the exposure will change.
The Sunny-16 Rule
The most basic statement about the relationship of exposure and it’s many parts is the Sunny-16 rule of thumb. For those that don’t know, the Sunny-16 rule here’s the run down.
In broad daylight in the middle of the day--when the sun is as bright as it can be, i.e. high noon--you get proper exposure by using the following camera settings. When your camera’s ISO is set to 100, and your aperture is set to f/16--hence the 16 part of the Sunny-16 moniker--the camera’s shutter speed will be 1/100th sec. Since all of these settings are related, when you change any one of them, you’ll have to change another to compensate. For example, this means if you increase the aperture size to f/11, 1-stop increase in light, the proper shutter setting is now 1/200th sec when the ISO is still 100. It also means if you increase the ISO to 200, the aperture or shutter speed to compensate for the increased sensitivity of the sensor setting.
What does this mean? It means proper exposure is completely based on the light falling on your subject. Regardless of the physical characteristics of your subject, if it’s in this standard light, the Sunny-16 rule of thumb will tell you how to set your camera to get proper exposure. It’s that simple.
What happens when you have a really dark subject with a really light background? What’s the right exposure? It’s based on the Sunny-16 rule of thumb--i.e. 1/100 sec at f/16, at ISO 100. Subject characteristics simply do not matter right now. We’ll talk about compensation later.
Incident Meter Readings
Of course, all light is not standard or high-noon sun. What do you do then? The perfect answer is to use what’s not in your camera, an incident meter. All camera’s use reflective meters. This means, these meters measure the light reflecting off the subject. As a result the light reflecting off the subject and coming to your camera is completely dependent on the subject. A really dark subject won’t reflect much light. A really light subject will reflect lots of light. The result is lots of changing exposure settings based on the subject characteristics and a reflective meter reading. When you use an incident meter, the light is measured as it falls on the subject instead of as it’s reflected. When using an incident meter, you can completely disregard what the subject looks like because we’re only interested in how the light falls on the subject.
So, when the light is less than the Sunny-16 standard, you can pull out a handheld incident meter to measure the light that falls on your subject. Of course, when you use an incident meter, you have to make sure the light you’re measuring is the same as what’s falling on your subject. In a wide open area with no trees or other things obstructing you or your subject from the light source, taking an incident meter reading is as simple as holding up the meter into the air and pointing its little white dome behind you. Armed with this meter reading, you can put the settings into your camera set to Manual mode fully confident the subject and background will be properly exposed as long as they’re in the measured light. The subject can change all day long--turn light or turn dark--without affecting your meter reading as long as the incident light that’s falling on your subject doesn’t change.
BTW, what is an incident meter? It’s one of those contraptions that have a little white dome with a light meter sensor underneath. How it’s used is you face the white dome towards where the light is coming from or directly away from the subject and press the memory button. What you have now is a stored reading of the light falling on the little white dome. If your incident meter is in the same light as your subject, you don’t have to be next to your subject to get a good reading. Surprisingly in most open air nature photography situations, the light on you is similar to what’s on your subject. Of course, if you’re in the shade or you’re in different light, none of this stuff will work. Then you have to take your meter right up to the subject to take a reading. This is definitely a problem if your subject is uncooperative like a wild predator or something with really sharp teeth and claws.
Dealing With Your Gear
Okay, this all makes sense to you I’m sure. But there are some things to worry about because of limitations with camera sensors and such. For example, when properly exposed, really bright white will likely exceed the capture capability of your image sensor. What happens is you won’t have any detail and things will look completely saturated with no info or texture. Clearly, that’s not what you want if your subject is predominately white like a Great Egret. To fix this, you manually reduce the exposure to compensate for the limitations of your equipment. In a perfect world you wouldn’t have to do this. Since it’s not a perfect world and image sensors are less than perfect, you have to take action like this. This process is called “protecting the whites” because you’re reducing the exposure to allow the bright whites to be recorded instead of being “clipped” by the sensor.
Note, I’m not talking about changing things for the proper exposure. That’s already perfectly set using an incident meter or the Sunny-16 rule-of-thumb as noted before. I’m talking about dealing with the limitations of your gear and applying a compensation which is not the same thing as determining proper exposure.
The converse is true as well. If your subject is black like a Black Bear, you may have to increase the exposure a bit, allow more light to hit the sensor, to compensate for the inadequate capture capability of your image sensor. Once again you’re dealing with the adequacy of your camera gear when doing this compensation. This process is called “exposing to the right”. I’ll get into where this name comes from in another article.
Whether increasing or decreasing the exposure because of the camera limitations, this does not change the “proper” exposure. The proper exposure was determined earlier as I noted before. Doing this compensation is completely not related to the light falling on the subject or reflecting off it. It’s completely related to inadequacies with your gear. If your gear was more capable you wouldn’t have to do this compensation. Specifically, the limitation of your gear is its got less dynamic range than your eye. You eye can see so much more than your camera from the light to the dark areas of the scene. While you can see the detail of a black bear on a snowy scene in broad daylight--as if that could happen--your camera can’t. So, that’s why we apply these corrections or compensation.
Of course, the situation where you have a very dark/black subject with a very light/white background will be extremely difficult to deal with. Under those situations you have to make compromises to pick which tonal quality--black or white--you want to emphasize. Unless you use other techniques like fill flash or some sort of post processing technique, you as the photographer will have to make conscious choices of how to adjust your exposure.
Working With Your Camera
As I noted before, your camera does not have an incident meter in it. No camera has one. It has what’s called a reflective meter. Unlike an incident meter that measures the light that “falls” on the subject, a reflective meter measures the light “coming off” the subject. As a result, the characteristics of the subject will significantly affect how this meter reads. A really light/white subject will reflect a lot of light. Conversely, a really dark/black subject will soak up a lot of light. Even though the incident light, the light falling on the subject, doesn’t change, each situation will result in significantly different meter reading with your camera’s reflective meter. This is definitely a challenge to deal with.
What do you do? First thing, you have to have a basic understanding of what the exposure should be. To be able to do that effectively, you’ll already understand the incident meter discussion we had previously. With that you’ll have to get how your subject or background will affect the reflective meter reading. A really light/white subject will make your meter show an artificially fast shutter speed or small aperture to deal with the bright light coming in. A really dark/black subject will do just the opposite. How much will it change? That’s a good question. It completely depends on so many things like the background, the size of the subject... Honestly I don’t care very much. I know it’s something and I know it changes the meter reading. I also know which direction the change is. But, how much... I don’t care all that much and it really doesn’t matter in today’s day of digital photography and instant feedback.
Most of the time you should have enough time to shoot more than one image to get the exposure right. After each image, I check the camera’s LCD and its readings to see if the exposure is about right. I check to make sure the color’s aren’t clipped--over exposed and exceeding the sensors data collection ability. If they are, I’ll pull back the exposure--increase the shutter speed, choose a smaller aperture, or lower the ISO setting.
How do I do this? I use the camera’s meter. I look at the subject and background and make a stab at what the meter reading should be relative to what the camera it telling me--it doesn’t have to be that accurate, just a little close--then I shoot the image. Most of the time I don’t do any adjustments to the meter reading unless the subject and background are clearly “off-normal”. Then I check the camera’s LCD and make more precise adjustments from there.
This works 98% of the time and I’m able to get the image I want 98% of the time before I even think about making adjustments through post processing on my computer. This technique has a pretty high success rate in my book.
I just finished listening to a photography podcast that I subscribe to. The subject of the podcast was about a recent trip to Florida to shoot birds. Those that have shot birds know they come in all colors. One of the many informative topics they discussed was the trials and challenges they dealt with when shooting bright white birds against very dark background. They talked about compensation. They talked about the uniqueness of the Nikon Matrix meter system when the focus sensor goes off center. They talked about classic techniques of spot metering the white bird, then setting a manual exposure. All of these suggestions were very well explained and very accurate. What struck me was how complicated all their suggestions were. The talked about adding exposure for the bird but if the bird was too small then you’d apply less compensation. Then they talked about AE-L (auto-exposure lock) and how to use it when you read the meter reading you wanted. All very interesting stuff and all very complicated. This is definitely not what I do.
If they only considered incident meter reading as I have discussed then apply some compensation to protect the whites of the birds, they’d be done. No more talk of spot metering, understanding the size of the subject, how light or dark it is... anything. All this discussion is moot of you know the proper exposure as a start and compensate from there. Exposure can be quite simple and much less complicated than most will make it be.
Does it matter which meter mode the camera is using? It does a bit. The difference between Center-Weighted and a camera’s high tech Matrix or Evaluative meter is pretty much not that important. The difference between these area meter styles and a spot meter might be really important. A spot meter reading of a really bright or dark minor portion of a scene might really throw off a camera’s reading. So, if someone asks me whether it matters which meter mode to use, I’ll say no with qualification that you don’t use the spot meter mode unless you know what it’s doing.
Things To Adjust
I already noted there are three basic things to adjust to get the proper exposure--shutter speed, aperture, and ISO setting. Changing each item will affect how your final image will look like. The importance of shutter speed and aperture are significant and deserve their own articles--soon to follow. Until then, let’s talk about changing ISO and what that might mean to your final image.
Without getting into some sort of artistic characteristic like freeze action, depth of field or something, changing the ISO directly affects the goodness of an image’s quality. Essentially, if you increase the ISO setting--i.e. make the sensor more sensitive--the smooth, grainless quality of your image file begins to disappear. Spots, grain, or noise begins to appear as the ISO increases. For some this is completely unacceptable. For others, this grain adds a film quality to the image we used to see when shooting highly sensitive film like Tri-X. Dependent on what you’re trying to achieve, increasing the ISO might be a problem.
Still, the effects of increasing the ISO, adding noise to your image, might be minimized using post processing tools like Picturecode’s Noise Ninja. This application like others do a wonderful job eliminating noise to a great degree without killing the fine detail we’ve grown accustomed to with digital files. Of course, there’s no free lunch. Eventually, the most sophisticated application can not eliminate noise without affecting the basic image quality (IQ) of the image.
A really neat tool for newer digital camera’s is the auto-ISO setting. Like Aperture Priority or Shutter priority where the shooter sets a shutter or aperture setting and the camera automatically sets the other based on the meter reading, there’s a new dimension with auto-ISO. Then means you can set both the camera’s aperture and shutter speed settings, then the camera adjusts the ISO based on the meter’s reading. What’s cool about this feature is it adds a new dimension of control for the quality of your image. Instead of having to choose between an aperture setting or shutter speed setting for artistic reasons, you can now pick whatever you want and leave the variable parameter be the ISO. The only thing you have to do is make sure the ISO doesn’t get to the point where it affects your digital file beyond what you want.
We’ll talk about shutter speeds and apertures in the near future.
In The End
There you have it. These are the basic considerations related to exposure. You can definitely talk about this subject much more intently. For our purposes, this is a good start.
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