on July 22, 2014

Everything you need to know to become a Master of Controlling Light: Pt.1 Aperture

Controlling light: Aperture vs Shutter Speed vs ISO: or why you need and ND filter

The elements of photography translate roughly to “painting with light”, and that is the most apt description of what you are trying to do with the camera. There’s a sensor in the back of the camera, and if the light doesn’t reach the camera, then it doesn’t count. That’s not to say that everything has to be shown in camera. Telling a story is about how much you don’t show as much as it is what you do. But what reaches the sensor is what we are concerned with. Knowing that, there are limitations to what the sensor can record. Our eyes are capable of a dazzling array of colors and a tremendous amount of dynamic range. The sensors in our dslrs cannot focus on the same spectrum that we see, nor focus as fast, or even make the contextual adjustments that we do when we view a scene. But in that restriction, there is creativity. You have to decide what you want to capture. you have to make decisions. you have to choose what you see and what you don’t. Now we are getting somewhere. The sensor captures light photons, and it captures them in array of colors. Specifically, it is measuring COLOR and BRIGHTNESS, and the format you record will determine how much of this information you choose to capture. Now we know we can’t capture everything. It’s impossible. If we want to capture pitch black, we are going to overexpose a lot of the bright part of the spectrum. if we catch all the highlights, we will lose all details in the shadows. So how do we decide where to focus that sweet spot: By controlling the EXPOSURE. this a term that carried over from the film days. specifically it is about how much light we are exposing the film to. There are three ways we can control this. They are: Aperture Shutter SPeed and ISO In Part One we will cover the aspect of Aperture. Aperture literally just means the opening. Many of us had to make a pinhole camera out of an orange juice box as a kid. That pinhole was the aperture that light passed through. Think of the lens the same way. When you have a larger aperture, you let more light through, smaller aperture, you let less light through. So whatever decision you decide to make on this variable, needs to be balanced out by the other two. As the diaphragm closes down, the aperture blades from a smaller opening and let less light through. These are designated as f-stops or exposure values (ev). F stops are the basic unit used to measure li ght. Each f-stop lets half as much light in as the previous f stop. F stops are listed as a standard geometric sequence that corresponds the sequence of the powers of the square root of 2. Say what? In plain English, it means that the f stops are: f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32, Etc. Yes, there is an algorithm that gives meaning to all of them, but the easiest thing to do is just MEMORIZE them- at least up to f/11. I say memorize them, but what I really mean is KNOW them. For many people, memorization is difficult because fact with context have very little meaning. If I were to ask you memorize a list of food ingredients, some people might remember them all, some might not. But if I were to ask you what your favorite pizza toppings were, there would be very little difficulty in recall. That is what I mean by KNOWING. Obviously, this will take a little more time, but to understand aperture, you have to use each one, and see what it does to the image at each f/stop- especially how it affects depth of field (DOF). Different styles of shots will require different depths of field. It is very easy, early on, to becomes seduced by the bokeh of shallow depth of field. It is the element that your smartphone or point and shoot can’t really get, and it adds depth to your image. The only way to get over this is to shoot through it. Just keep shooting it- get it out of your system. One of the first things that will ease you out of it is that when shooting video, maintaining tack sharp focus at this DOF is exceedingly difficult. You think you got his face in focus? Great- only you just have the tip of his nose, and in post you realize that you are missing his eyes. Shooting like this will also help you develop as a focus puller, so go ahead and experiment. I will admit that still love this look, especially for B-roll with a rack focus. It gives a very kinetic, spontaneous feel, but its not right for many projects. Closeups F/2.8 or lower 20140722-111110-40270049.jpg I like really shallow depth of field here. For a closeup, I want isolation, I want to be specific. I want to show the viewer exactly what I want them to be looking at.  Notice how the cell phone is the only thing really in focus, and both the foreground and the background have been blurred.  There is no mistaking where I want the audience to look.   (If overused, it CAN be a little bullying to the viewer, and they check out. You still want to make them work for it to stay engaged.)   Most Medium Shots f/4-f5.6 20140722-111151-40311117.jpg I like practicality of this DOF, and its also a lot easier to navigate if there are two people you need to have in the shot.  You can see the sunglasses pretty clearly now,and the photos in the foreground are perceptible, although still not the main draw.  Some times I might want JUST a little more DOF.   This is where Cine lenses or declicked still lenses come in: you can choose you’re aperture very precisely without having to settle on one of the predetermined f/stops of most photo lenses. tip: Many of the vintage russian lenses will have dual aperture rings- it’s so you can focus wide open, then slide it back down for the exposure. This is a great way to dial in your aperture. See the upcoming review of the Russian Trio: Mir 37mm, Helios 44, and Jupiter-9 85mm.   f/11 Fashion editorial or landscapes- establishing shots with lots of light. 20140722-111227-40347886.jpg This is the highest that I go for most shooting situations. Great when you want to get the whole picture into focus.  You get the back leg of the mini-easel all the way to the back of the guys chair in the background.  The vintage coffee grinder on the table is perceptible, and if I needed tome contrasting motion from the main scene, it would still read.  I might use this DOF if I have a character moving deeper within the scene and back again and I wanted to keep them in focus, just change their relative size to the other characters. Citizen Kane uses this technique a lot, and it is brilliant. Be careful though, having this much DOF can look like video if used too heavily (see article on The Film Look). You can see how Orson Wells stays within focus for most of the shot, but just changes size relative to the other characters in the scene.  This follows the film theory that the characters importance in the scene should be relative to their size within the frame.  Truly wonderful work by Wells. But back to the stills:  Within these shots, one of the things you’ll notice (or in fact- not notice) is that the relative exposure for all these shots fall within the same values- EVEN THOUGH the aperture to let through light has become smaller. The way that is done is by compensating for this smaller opening by using one of the other variables- namely shutter speed and ISO. In this particular case, I adjusted the shutter speed because I was shooting stills, and it’s a rather simple process. In our next post, we’ll discuss shutter speed, and what that can- and can’t- do to control light in the moving image.  And