Photography Basics - Putting It All Together: The Exposure - Episode 6

     So we have discussed, in nauseating detail, each of the three main light controls that exist on most digital SLR cameras. How does all this come together to help you control image exposure? I will relate my usual techniques for photography to help explain! 

     When you shoot an image, the first thing that you should be thinking about is what you "expect" the final image to look like. In most cases, you will just be looking for a normal, nicely exposed image of a subject and/or scene. I typically shoot in Program Priority or "P" mode on my camera. The camera can handle a good normal exposure in most "normal" light situations. I also typically shoot at somewhere around a 200 ISO to get the best image quality.

     Let's take what might be an average daylight scene outdoors. If we're shooting at 200 ISO, with a 24-105mm lens I might get a shutter speed of about 1/500th of a second at f/11. (I'm making these numbers up as I go so don't hold me to them).

     What if I want to shoot a portrait and I want the background to be completely out of focus? I'd be looking for a small f-stop number, maybe f/4. Hmmm... well, that means that I'll have a lot more light entering the camera because f/4 would represent a bigger aperture opening than f/11. So I'll need a faster shutter speed. I might have to go up to 1/4000th of a second. 

     What if I want to shoot a landscape and I want everything in focus? Well , then I would take my aperture to f/32. That's a much smaller opening so I'd have to slow down my shutter speed to let in more light. I might and up at 1/30th of a second for my shutter speed.  

     So we did a couple of portraits and a couple of landscape shots. Now, lets do a portrait of a couple walking at sunset on the beach!? Well, this offers a bit of a challenge because now you might want the entire scene in focus (a small aperture) but still want the faster shutter speed because your subject will be in motion. But the high f-stop number would render a very slow shutter speed because it's such a small opening. It would be hard to get the subject to stay still enough to avoid blurring so I'd need a faster shutter speed. A shot taken at sunset ar ISO 200 and f/32 would require a shutter speed of about 1/8th of a second. That's too slow to hand hold and too slow to even do a moving subject. If I took my ISO up to 1600, I could get about 1/60th of a second which is much better and perhaps very manageable but I'd like a faster shutter speed for a moving subject in low light. So I'd probably close my aperture (or stop down as the real pros say.. I guess) one or two f-stops to f/22, which would give me 1/125th of a second shutter speed, or f/16 which would give me about 1/250th of a second. That would be much easier to hand hold and get very sharp images.

     Did you notice the relationship in the numbers for the scenarios above? Each time I opened the aperture up 1 stop (smaller f-stop number), the shutter speed increased to the next faster speed. Each time I closed the aperture down one f-stop (bigger f-stop number), the shutter speed went to the next slower speed, in order to keep the same exposure at the same ISO. The same  is true of the relationship with the ISO. If you go to higher ISO number, you need less light. You can either close the aperture down (bigger f-stop number) or speed up the shutter (sensor is exposed for less time) to get the same exposure. If you go to a lower ISO number, you need more light. You can open up your aperture (smaller f-stop number), or slow down your shutter speed to let more light in and keep the same exposure. 

     That relationship, in summary, looks like this:

        To let more light in: smaller f-stop number, slower shutter, or high ISO.
        To let less light in: bigger f-stop number, faster shutter, or lower ISO.

     I hope this all makes at least some sense. There are many different situations that require you to think about how the camera will react to the light it sees and how it will affect your image. Then you have to know how to override the camera to get the image you want. 

      So that wraps it up for the discussion about what you can do with the camera to control the brightness of your image. Next we'll start talking about the mode dial and other camera settings you can use to make it easier to get the images you want!

Photography Basics - The Medium: A Discussion about ISO - Episode 5

     What is the "medium"? In photography, it's the part of the camera that is actually capturing the image. On older 35mm film cameras, it was the film. On todays digital cameras, it's the digital sensor. So what does the medium have to do with light control? Well, lets step back in time a bit. 

     In the days of film photography, film came in different "speeds". These speeds were referred to by ASA number. With digital cameras we use ISO numbers. The lower the ISO number, the less sensitive the film is to light, the more light it needs to get a good exposure. The higher the ISO number, the more sensitive the film is to light, the less light it needs for a good exposure. The purpose behind the different speeds is to allow photographers to shoot in different light conditions. If a photojournalist is going to be shooting a night event or indoor event with little light, he would shoot a higher ISO to be able to get faster shutter speeds.

     But, as it seems with everything in photography, ISO had a side effect. Photographic film is actually created by mixing small solid particles of crystals (typically silver halide) into a gel mixture and coating a plastic film with the mixture. When you expose the film with the mixture on it to light, it records an image on the film. A small ISO number means the particles are very small but not as sensitive to light. The smaller particles mean a finer grain to the film and therefor, good detail is recorded. Larger particles mean better sensitivity to light but also larger grain, so you could lose some detail in the image and you would actually see the film grain in the final image. 

     Oddly enough, the same effect carries over to digital sensors but not for the same reason. A digital sensor consists of millions of tiny pixels, or picture elements. Each pixel is an electronic device that reads an analog signal (in this case, light) and coverts it to a digital value. As is true of all electronic sensors, there is always some background noise that it picks up. Think back to the days when you had televisions that got their signal off antennas. A nice strong signal produced a good picture. There was background noise there but the station signal was strong enough to override that background noise. As the signal got weaker from the TV station, the background noise would "bleed" through and show up as what we called "snow" on the TV screen. The same is true of a weak radio station where static starts to be heard. That static is the background noise. 

     The pixels of a digital camera sensor work much the same way. Power applied to each pixel renders a certain amount of background noise. But a good strong light signal would overpower the background noise and give you a usable light value for that pixel. This would represent a low ISO value such as 100 ISO. Increasing the ISO value on a digital camera actually just increases the amount of power to the pixels so they become more sensitive to the light signal. The side effect (yes, yet another side effect) is that the greater amount of power increases the background noise. On images that are very dark or have large, dark, uniform areas, the background noise can bleed through and creates "snow" or spots on the final image. We usually use software yo try to clean up as much as possible but often, a high ISO can render an image that looks grainy, like old film images. 

     On newer digital SLRs, the sensors and image processor chips have gotten quite good at producing cleaner images allowing you to get very usable images even at very high ISO values. So ISO can be used to take images in low light conditions so that you can use higher shutter speeds.  

Photography Basics - The Aperture - Episode 4

     The aperture of a camera is a fairly simple device but is often a point of confusion for new photographers. The aperture is simply the size of the hole that the light travels through to get to your sensor. The smaller the hole, the less light. The bigger the hole, the more light. Simple, right? Right! But not really!

     Where the confusion comes in for new photographers is in dealing with the way in which the aperture is represented. We call it an f-stop. The different sizes of the aperture are referred to as a fraction such as f/4, f/11, and f/22. I think some people think that the "f" means f-stop. But it doesn't. The "f" is a variable that represents the focal length of the lens. Yes, I know. No one told you that you'd have to do math for photography. And really you don't. But you do have to remember that the bigger the number on the bottom of a fraction, the smaller the number the fraction represents. So even though 22 is a bigger number than 4, f/22 is a smaller fraction than f/4, so it represents a smaller aperture. If you really wanted to get technical, you could plug in the focal length of your lens into that fraction and figure out exactly how big an opening you'll have. So if you have your 50mm lens attached and are shooting an f-stop of f/4, then your aperture will be 50/4 or 12.5mm. If you set your f-stop at f/22, then your aperture opening is 50/22 or 2.27mm. That's a pretty small opening. 

     So the size of the aperture controls the amount of light entering your camera. But, like shutter speed, there is a side effect. The size of the aperture also determines how much of your scene is in sharp, or what we call "acceptable", focus. The term for the amount of the scene that is in acceptable focus is "depth of field". The depth of field is easier to relate to the f-stop number. The higher the f-stop, the greater the depth of field. So, for example, f/22 would give you a much deeper depth of field than f/4. The best way to understand this is if you were shooting a flower up close and wanted to make sure that the background was out of focus, you would shoot at a low f-stop number such as f/2. If you were shooting a mountain landscape and wanted everything in focus, you would shoot at a high f-stop number such as f/32.

     But you have to remember the main purpose of the aperture, controlling the size of the opening and therefor the amount of light entering the camera. So shooting that flower at f/2 will mean a shallow depth of field with everything in the background out of focus, but it'll also mean a bigger opening and therefor more light entering the camera. So.... you will have to shoot at a faster shutter speed to get the right exposure. Likewise, that mountain landscape that you shot at f/32 will mean a very small aperture opening, and so a lot less light entering the camera, so you'll have to slow down your shutter speed to get a good exposure. 

Photography Basics - The Shutter - Episode 3

     The shutter is probably one of the simplest aspects of the camera to understand. The earliest cameras consisted of little more than a big box with a small hole in the front of it and plate at the back covered with light sensitive material. The photographer would insert the plate into the back and remove a protective cover over the plate that prevented inadvertant exposure to light. When he was ready to make a picture, he removed a cover over the hole in the front, allowing light into the camera to strike the plate. The light sensitive material on the plate recorded areas of varying intensities of light to render a black and white image. In those days, the light sensitive material used on the plates wasn't really terribly sensitive so the exposure time was often measured in hours. That meant that you had to be doing a still life image or your subject had to remain perfectly still for long periods of time. 

     Over the last 200 years, we've gotten a little more sophisticated with the shutter. On film cameras, the shutter is usually a two-curtain mechanical device. One curtain overlaps the other. When the shutter button is pressed, the first curtain begins to slide out of the way of the film, going from one side to the other or top to bottom. Then the second curtain begins to follow the first curtain, covering the film up again. The time between the two the curtains determines the exposure time.

     So why have two curtains? Why not simply have one curtain that opens, exposes the film, then closes again? Well, the main reason is that todays medium used for exposing images is MUCH more light sensitive than those first cameras. Instead of exposures being measured in hours, they are typically measured in fractions of a second. Today's cameras can capture images as fast as 1/8000th of a second. The fact of the matter is that the physical mechanism that moves the curtain can't move that fast. What happens with a really fast shutter speed is that the second curtain begins closing at nearly the same instant that the first curtain begins opening, exposing a very tiny sliver of the film as the two curtains chase each other across the film plane. So the image doesn't get recorded all at one time but rather one column of light at a time. 

     Today's digital imaging sensors render the physical shutter nearly obsolete. With most point-and-shoot digital cameras, the exposure time is actually determined by the length of time that the sensor pixels (or picture elements) are actually turned "on", capturing light. Since it is an electronic on/off sequence, it can be done pretty much instantly for all the pixels on the sensor at one time. In most digital cameras today, there actually isn't a physical shutter. However, digital SLRs still use the mechanical shutter or a combination of mechanical and digital shutter to control exposure. 

     So, how does shutter speed affect your image? The bottom line is that the longer the shutter speed is, the more light you are gathering, the brighter the image. A "proper" exposure is determined by other factors such as the amount of light available and the size of the opening through which the light reaches the sensor (also known as the aperture, which we'll cover next) and the sensitivity of the sensor (also known as ISO, which we'll cover later as well), as well as shutter speed. But the shutter is literally the last light control in the path the light takes on its way to the sensor.

     There are some side effects to shutter speed that can affect your image. Shooting with a very fast shutter speed has the affect of stopping the action in a scene. That might be what you want if you are shooting a moving subject. Maybe your trying to capture a baseball player swinging the bat and you want to freeze the action. Or maybe you are shooting a hummingbird at a feeder and want to freeze the fast wing beat. 

    On the other side of the coin is a slow shutter speed. Shooting with a slow shutter speed will cause anything moving to be blurred. That might be good if you are trying to get the silky look of a water fall, but it might not be so good for that 3rd grade school play your trying to photograph. 

Photography Basics - Introduction Episode 2

     The word photograph comes from the Greek meaning "to write with light". So photography is the act of writing with light. And in truth, that is really a very good description of what it is we do with photography. Photography is all about light.

     The light we see with our eyes and with our camera falls into one of two categories. It's either emitted light (such as from a light source of one sort or another like a light bulb or the sun) or it's reflected light. Most of what we see on a day to day basis is reflected light. So, to really blow your mind, when you really think about it, except for emitted light, you're not really seeing anything around you. What you are seeing is the light reflect off of things around you. In much the same way that you might not think of looking at a reflection in a mirror as actually looking AT something, looking AT something is really nothing more than seeing reflected light. Kinda mind boggling isn't it? And perhaps to some, it seems like semantics. But to a camera, it's really a very important concept. Your camera sensor records the light that reflects off your subject. Period. Therefor, in reality, that light is the most important aspect of your photograph.

     The camera's job is to capture the light in such a way as to render an image that is representative of what we see when we took the picture. All cameras, from the first camera made in the 1820's to the most sophisticated imaging device made today, capture images in pretty much the same way, by allowing a certain amount of light for a certain period of time to strike a medium of some sort that records the light. The job of the photographer is to see, understand, and, to the degree possible, control the light the camera sees in such a way as to get the image the photographer wants to capture. In order to do that, you have to understand the way the camera sees the light. 

     In the following blogs, we'll first talk about the three major controls a camera has for controlling light: the shutter, the aperture, and the medium. While there are certainly other aspects of the camera that control the appearance of the image, these are the three controls that affect the exposure itself.  

Photography Basics - Motivation - Episode 1

     I've been a photographer, in one form or another, since about 1984, when I bought my first real camera, a Pentax K1000 35mm completely manual camera with a 50mm manual focus lens. No auto settings and, at that time, no internet to search for how-to videos on YouTube! And to make matters worse, trial and error learning was a slow process. I had to take the pictures, filling a whole roll of film so I don't waste it, then drop the film off to be developed, wait for the pictures, then look and see what I got. If I needed to change something, then I started the whole process over again. And of course, I had to remember to write down my settings so I knew what to change. Film didn't have EXIF information! 

     My point is I learned photography one picture at a time. It was a slow but rewarding process. I have never been a professional photographer (meaning I have never made a living at it) so at different times of my life, the learning process, as well as photography itself, had varying priorities in my life. Sometimes I didn't shoot at all for months, sometimes I did. But it was never a high priority. I always treated it as a hobby I did in whatever time I had to myself when I had done everything else I thought I needd to do with my spare time, when I had any. In other words, I didn't nurture it. Often it was just to take pictures of family events or vacations. 

      That all changed when I met and married Ronda!!! She has been my encouragement and inspiration. She loves my photography and helps me to nurture and feed the desire to do more and get better. In the process, she has developed an interest in photography as well. So I have tried to teach her what I know about photography. I love to teach! But I have discovered that it is different when I teach her. She is an artist. She paints, mostly on canvas with oil. And she is very good at it. As an artist, she has the advantage of already being very good at what I consider to be the hardest part of photography: composition. Anyone can learn how to use a camera. Even point-and-shoot cameras and phone cameras can take very good pictures. But, for the most part, the camera you're using isn't what makes a shot good. It is the composition that makes the difference. If you buy someone who does not have an eye for composition a camera bag with $10,000 of some of the best gear in it, you're still not likely to get a great picture from them. But I have given Ronda my hand-me-down cameras (which she has graciously not complained about) and she has made many amazing images with them. I believe she is better at the "art" of photography than I am. But I know the camera pretty much inside and out. So I had set out to try to teach her. I have discovered that the nature of our personal relationship has had an impact on my teaching. I have always viewed her as a contemporary in everything, including photography. So when I try to teach her something, I use terms and concepts that seem very basic to me and assume they are to her too. But she is soon lost in the information overload I give her. I often have people asking for advice about what kind of camera to get or how to take pictures. I've always answered them with what I thought was basic information. Now I wonder how many people I've talked to politely shake their heads yes and nod and look like they are getting what I'm saying but leave the conversation more confused than when they asked! :-) 

     That long winded story is the background for this blog. My goal is to teach the art and science of photography in such a way as to make it useful and understandable to everyone, including Ronda. :-)