Lenses, Sensitivity / ISO, Shutter speed, Aperture, ND Filters, Reflectors and added Lights
These are the core physical variables in a camera. Everything else revolves around, and supports these values.
Lenses take the light that comes into them and focus’s it on the camera sensor, either film or digital. Moving light in a way that keeps its integrity is difficult. Remember optics have only been able to be produced somewhat recently, we’ve had relatively inexpensive glass for thousands of years, but useable optics are much more difficult to make, and when it was finally figured out, it transformed all of society. Science in a very real way, depended on the telescope for its proliferation and to our starting to claw our way out of the superstitious age of antiquity. Unfortunately, we still have a long way to go…
Good lenses are expensive, because the tolerances involved are small. Any deviation of one light band over another make chromatic aberrations that simply look bad. Often producing colored banding effects around high contrast parts of an image where the light diverged. Any deviation from perfect warps the light in unintended ways causing distortion as well, but for the most part it’s the chromatic aberration and softness that affects most obviously modern low quality lenses.
You also need big lenses if you need lots of light which is even more expensive, which is why those telephoto lenses cost more than the camera that mounts to them. To get a decent field of view out of a long tube one needs a wide tube which results in large, heavy glass, there’s simply no way around it. If you need the light, you need the glass to go with it.
The lens is also what controls the focus, either manually, or automatically controlled with a tiny motor. There is always only one thin focal plane that can ever be truly in focus, the focal distance controls where in the scene that plane is, and the aperture size controls how quickly that focus becomes blurry, and will be discussed later.
Sensitivity / ISO
This is the overall base sensitivity of the light capturing media, whether that be film, or more commonly now, the digital sensor of the camera. Either way, all the variables in the chain eventually lead to ISO. More sensitivity leads to more noise, in again either film or digital, physics is physics…
Higher ISO values represent more sensitivity, with a base usually of 100, but some cameras inexplicably use 200 as a base. These are usually represented with exponentially increasing numbers, so 100, 200, 400, 800 etc. There is no reason either in film or digital for this to be the case other than convenience. For film it is simply cost prohibitive to manufacture film in 100’s of different sensitivities. For digital it seems to be much more a matter of tradition, as there is no technical reason that I am aware of to prevent using an infinite gradation of values.
Again in digital and film both, 100-400 ISO is considered clean, and reasonably free of noise, meaning fully usable in most all instances. Above that and you will be able to start seeing at least some amount of random dots of noise either from the grains of chemicals in the film, or in the digital world, random flips of the sensor bits will produce a similar, albeit more disconcerting noise.
By the way, this same phenomenon is present in the human eye as well. Close your eyes and ‘look’. Do you see pure flat complete blackness without texture, or can you actually see a random noise that your brain ‘sees’ as black. This is due to the rods and cones of the eye firing off, or the mind falsely interpreting different signals, just like they had been stimulated by light. Twitches in muscle fibers, static on a screen, a hiss in audio equipment, and noise from your camera sensor all share similar causes. The key takeaway here is that noise is always present, and can only be mitigated, so don’t get overly hung up on it.
This is how long the sensor is exposed to light. Longer open times equals more light in a linear relationship to the open time. This is based on fractions of a second. So a shutter speed of 1/60 (or sometimes just 60) is 1/60th of a second that light is hitting the sensor before going into darkness again and stopping the exposure.
This entire time that the sensor is being exposed to light the world is still moving along. People walking, the camera shaking slightly from your breathing, a slight breeze moving the leaves. All of these things reflecting light is what makes it into the camera lens and produces a picture. If they’re moving while you are exposing the photo then the light is moving on the sensor as well. So the shorter the duration of exposure, (ie a faster shutter speed), the less blurring you will have.
Just like noise you will always have some amount of blurring, it’s just a matter of if you can see it, and it you can, if it’s detrimental to the frame.
So if you want the frame to freeze the scene you will need to increase the shutter speed as either the subject or the camera movement increases. 1/60th is a good general guideline to being able to hand hold a camera with a moderate lens, while getting a crisp image without noticeable blur in a still image. For video work you have more leeway in slow shutter speeds as the constant motion prevents us from examining each and every frame and they all just run together due to ‘persistence of vision’. I.e it takes a tremendous amount of processing power to intake and process all of the data coming in to the human brain, and it can only deal with it so quickly, it is not even close to ‘instant’.
But past the above digression, here is the skinny:
- Less than 1/20 is for dark scenes where you may need even multiple minutes of exposure time to gather enough light, or where you want lots of motion blur.1
- 180° is also a term you might find relating to motion pictures. This equates to double your recorded frame rate as your fraction of a second. So if you are recording at 24fps then a 180° shutter would be 1/48th of a second shutter speed. Faster than this will start to make the effect of individual frames of the movie become perceptible due to the lack of blurring. If shooting at faster fps, then faster than 180° shutter speeds have less of an impact, again due to POV.
- 1/60 and slower may get you a little blur unless managed in some way. In-lens or in-body stabilization, tripod, etc.
- 1/60 to 1/250 or so is good for most general circumstances.
- Wildlife may need 2000 or more.
- Action sports may need even faster speeds depending on the desired amount of blur.
Again, just as ISO settings shutter speeds are based in a doubling for ease of manual lighting calculations more than anything else, modern cameras can easily have the shutter speed at any arbitrary amount.
This is the diameter of the opening to the sensor. Mounted in the lens assembly and usually composed of 7 or more very thin blades, it forms the cameras equivalent to an iris, closing down or opening up to allow in more or less light. This is measured in f-stops, and once again using discrete steps even though it is no longer necessary…
Small f-stop values equate to larger openings, and larger values representing small openings. F-stop settings have two main effects. First is the obvious one is if you let in less light, then at the same ISO, you need a longer shutter open time. But the second effect is not quite so intuitive. The smaller the f-stop value (read larger aperture) the shallower the depth of field will be.
Depth of field, or DOF, is the amount of the depth of view that is in focus within the image. This can be used to great effect to separate the subject from the background in a portrait, or to ill effect for a sweeping panorama or detail shot of the essence of a scene. For an apparent focus across a large quantity of your image you will need to be at f-11 and above for most standard focal length lenses. Wide angle lenses will naturally have a wider focal plane than do ones with a long focal length. The only caveat to this is that smaller apertures will have more diffraction relative to the total amount of light entering the lens, which will paradoxically lead to a softer focus plane. More expensive lenses will get you sharper images throughout more of its aperture range however. With this in mind, you may want to limit the extremes of your lens options to avoid the worst ends of its quality spectrum. Say, limiting your stops to 2 away from either side of its extremes. It may also be worthwhile for you to do a simple test of the same subject with different aperture values on your lenses and see the difference yourself.
The DOF gets smaller as the aperture gets larger for the simple fact that as you widen the area of light that can get to your sensor, then the different angles that can enter increase as well, leading to a smaller range of in-focus light beams. With a small aperture you have a very limited amount of light coming from other angles, so the focus diverges much more slowly from the ideal. Leading to an image that looks in focus across a larger range.
This blurring of the background or foreground, or in some examples even the subject, is a defining characteristic of the scene, and this choice needs to command a large percentage of your attention when composing the shot.
Neutral Density filters are basically sunglasses for your camera. They are almost completely neutral in color and simply block the amount of light entering the lens so you can pick the shutter speed and aperture to fit the situation without getting over or under exposed shots.
Need a higher shutter speed to diminish blurring? Trying to avoid raising your ISO to prevent excessive noise? Does your subject look overly flat or sharp? Light is your answer. Whether natural, reflected, or electric, or whether it comes from a table lamp or a $10,000 lighting setup that takes up half the van, light is what makes the image. And you either have it, or you don’t. This cannot be emphasized enough, so again, light makes the image.
Good lighting can make literally any subject entrancing and memorable. Bad lighting will make literally anything look awful. So again, it’s not the backdrop, it’s not even the subject, it’s light that you are seeing, and it’s light that you need to manipulate. We do this by arranging people and items in a way to get the light to do what we want. Remember, we are not taking pictures of things, but the light that reflects off of those things so we can record the image we want to see. The camera is just a tool that lets us do that. Whether a 20,000 year old cave painting, an oil painting by Tiziano Vecelli (Titian), or a snapshot of your grandma smiling at you taken on your phone.
Make the image you want, in the way you want.
Reflectors move light from outside of the scene into the scene, usually as fill light to help ease shadows, but can be used anywhere you need a little more light and you have some to spare out of frame. Gold, silver, white, or colored commercial reflectors, or a white sheet you have, anything that will move the light is up for grabs.
Electric light can of course come from studio lighting, softboxes, umbrellas, spotlights, etc. Other in-place sources, called practicals, should not be overlooked though, such as headlights, table lamps, monitors, even candles and firelight can add to the character of a shot even if not necessarily adding much to the exposure.
All of the above combined results in the overall final exposure of the image. Too dark and the shadows may be lifeless, but the same values for another might act to promote a stark sense of power. Too bright and your highlights become deer in the headlights with clouds that look like holes in the sky. Never blow out the highlights of any important part of an image by the way, just don’t do it, it looks almost always looks awful unless you know exactly what you want from the image.
Cameras have different ways that they can deal with automatic exposure, but generally they are changing the shutter speed if you’re in aperture priority mode or if your in shutter priority mode, it usually changes the aperture. Some may also change the ISO value, and that’s probably the most sane way to do it. And it will most likely all only be controlled in discrete steps as there was traditionally no way to easily make stepless changes with a manual film camera, and repeat after me children, people don’t change, they only get replaced…
Almost all cameras have an inbuilt light meter that samples the frame in various spots and lets you know what it thinks is the optimal settings to achieve an even exposure. Some are better, some are worse, but all are prone to needing a little nudge from time to time so you can get the shot you need. In comes exposure compensation.
Exposure compensation comes into play when you use one of the automatic options on a camera, often designated by PAS(M) for Program (mostly auto), Aperture (you set the aperture value) and Shutter (you set the shutter value), it does everything else. The camera then changes the other settings until the exposure is to its liking. The exposure compensation adjustment overrides either the shutter, aperture, or ISO depending on what mode you are using.
M, or manual, gives you full control, and you get the image that those settings produce. So if those settings don’t let much light in, your image will reflect that, it just does what you tell it to do, which for many things is what you wan’t, however, people are much slower than cameras at both making decisions, and changing settings, so don’t get overly carried away with feeling like you need to shoot in manual mode to be a “real photographer” that’s nonsense. You just need to get the image you wan’t, it maters not how you get it. And when things get real, time is of the essence.
There is a lot more, but I’m tired, and I have work to do…