Photography 101 – Everything You Wanted to Know!

Advanced Terminology

Stabilization

Each manufacturer likes to call it differently, you will find lenses (and some camera bodies that have built-in stabilization on the sensor) with remarks such as “Vibration Reduction” (VR on the name, for Nikon lenses), “Image Stabilization” (IS on the name, for Canon lenses), “Vibration Control” (VC on the name, for Tamron lenses), “Optical Stabilizer” (OS on the name, for Sigma lenses), etc etc.

What’s Stabilization / Vibration Reduction?

When handholding a usually normal to super telephoto lens our hands can’t keep the lens/camera perfectly steady, especially for a “lot of time” for a throughout steady exposure, or we could be shooting from a boat or a helicopter (everything’s possible!). Generally when you shoot a lens without having the camera on a tripod, in order to have a camera shake blur-free image, you need to keep your shutter speed at or faster ideally than 1/focal-length*35mm-equiv (what this means is, for example if you are shooting handheld a 35mm lens on a Full Frame [a.k.a. 35mm sensor] camera your shutter speed should be kept at 1/35s or faster to capture shake-free photos, if you are shooting a 35mm lens on an APS-C camera [crop sensor] then you need to multiply your focal length by the crop factor of your sensor [1.5x for Nikon DX cameras, 1.6x for Canon cameras], so in this particular case the minimum shutter speed you should be shooting at would be 1/35 * 1.5 or 1/35 * 1.6).

What VR/IS/OS/VC/etc does is help you shoot at slower shutter speeds without having any camera shake induced blur, how much depends on how good the Vibration control/reduction mechanism is, some lenses can do well even 4 stops of slower shutter speed, others 3, others 2 and others just 1 stop.

the opening in the center is the “aperture” (on the top photo the aperture is fully closed [f/22 for this lens], on the bottom the aperture was set to f/8)

This is a tough one to explain, let me try to make it as simple as possible. If you look into a lens you will notice that somewhere near the rear side there are some blades that open up and close down creating a hole with variable size (depends on the f-number, the aperture that you choose using the camera body’s dials/buttons). It essentially controls how much light is allowed to hit the camera’s sensor during the exposure. Why would you want to allow less light to hit the sensor per a specific amount of time? For its side-effects, either to capture a scene using a longer shutter speed, or to control the Depth of Field.

The aperture is “measured” or should I say expressed, in a f/number format. It’s a ratio of the lens focal length to the pupil’s (the hole created by the aperture’s/diaphragm’s blades) size. Essentially, a “larger” f/number f/11, f/16 means a smaller opening, less light hitting the sensor, while smaller numbers like f/2.8, f/4, f/5.6 give you a bigger opening, allowing more light to hit the sensor.

Minimum Focus Distance (a.k.a. Close Focus distance)

Just like our eyes, optical lenses also have a minimum distance at which they can focus an image properly. Place your subject closer than that distance and you will never be able to get it in focus. Macro lenses like mentioned before, can focus closer than normal lenses.

Please note that the minimum focusing distance is measured from the camera’s sensor plane and not from the lens front or rear element.

Filter Thread / Diameter

For both photography and videography there are a few types of filters (add-on glass/synthetic-material that does something to our incoming light, the most common filter types are Neutral Density, Polarizing and UV filters). The most common way to “mount” a filter on a lens is by screwing it onto the lens via the “filter threads” in the front end of the lens. Each lens has a different body/barrel diameter, thus a different diameter of the filter thread is needed, in the specifications sheet of any lens with a filter thread the value will be listed in millimeters. If you plan on using a filter on more than one of your lenses, you should purchase the filter with the thread equal to your biggest lens filter thread diameter, and use step down rings to attach it to your lenses with a smaller filter thread diameter. That way you save money, and you get better performance out of it because the larger filter will have less or even no vignetting at all on smaller lenses.
There are some lenses out there with no filter thread (usually ultra-wide angle lenses on which the front glass element of the lens is extruding), there are “add-on” off-brand mounting mechanisms/kits (called Filter Holders) that allow you to use a filter on those lenses.

Chromatic Aberration

take a look at the areas where the arrows are pointing, you’ll see purple and green “fringing” (or halos), this is what Chromatic Aberration looks like in actual photos

We’ve all seen photos on the internet where there is some weird colored (usually purple & green, but can be any color) “halos” around the edges of various objects in the scene. Sometimes it’s very noticeable even zoomed out, other times it’s visible only when you zoom in. That’s a “defect” of the lens, it happens because the inner optical elements of a lens have different refractive indices for different wavelengths of light and as a result some colors do not meet the same convergence point (i.e. we have a defocused part of the image) and these “errors” appear in the photos as colored halos around the objects (actually everywhere where there’s plenty of color/brightness contrast, especially in the little to very out of focus parts of the image it is more evident). It can be corrected (not perfectly every time) in post-processing.
You can also decrease its presence simply by “stopping down” the lens (that’s the technical/geek way of saying “close down your lens aperture” [use a higher f/number, for example a f/2.8 lens usually showcases very good Chromatic Aberration performance  once you close the aperture down to f/4 – f/5.6]).

Distortion (a.k.a. Optical Distortion)

there’s nothing wrong with the grid, and of course the boxes and the color bars on the wall are perfectly vertical in reality, this is the distortion caused by the 18mm ultra-wide angle lens

Every lens out there has some sort of optical distortion, it is a matter of physical design, design limitations and physics. Some lenses have a low distortion rating, others a lot, and some a whole lot, enough to make it impossible to correct it perfectly. Depending on the “kind” of distortion “pattern” a lens has, you can stumble upon the following terms:

• Barrel distortion
• Pincushion distortion
• Mustache distortion

If you shoot a grid with your lenses you will notice some lines bending and deforming, that’s the result of optical distortion.

Coma

make no mistake, this is the same LED photographed at the same distance just in various positions around the frame, the deformation is the result of th Coma(tic) aberration

Coma is another defect of optical lenses, it makes off-axis point sources (e.g. stars, distant light bulbs, etc) appear distorted, almost looking like a comet, having a “tail”. Usually coma gets worse as you get closer to the edge/corners of your frame. Just like with the other aberration we talked about, Chromatic Aberration, stopping down the lens usually helps lessen the “coma” aberration.

Vignetting

notice the decrease in luminosity (brightness) as you leave the center of the frame and move towards the corners, this is what we call “Vignetting”

Vignetting is the term used to describe another fault/aberration of optics (lenses), due to the complex lens design some front elements cast a shadow on the elements behind them, resulting in a loss of light near the surroundings/corners and near corner (off-center) parts of the image. Just like with the other two aberrations (Chromatic Aberration & Coma[tic] Aberration), Vignetting aberration also gets better as you stop down your aperture. It can be fixed in post-processing as well, unless your lens has a very extreme vignetting (like 5 or more stops of light loss). Vignetting can also be used as an artistic element, an “effect” to help the viewer focus on the area of interest of an image by intentionally darkening the peripheral parts of the image which are deemed “unnecessary or uninteresting” according to the artist (photographer).

Lens Flare & Ghosting

loss of contrast, orbs and other artifacts caused by the bright light source, this is Lens Flare & Ghosting

here’s how our box and scene looks without the effects of Lens Flaring & Ghosting

These two are essentially the same thing, although they appear in our photos in a different way. They both happen (together or just one of the two) when you have light rays from bright sources of light hitting your lens directly. Lens flare usually occurs when you have a light source inside your frame that is much brighter than the rest of the scene (it can also happen with the light source being outside your frame, it just needs to hit your lens front element) and it results in a lot of haze/lack of contrast, and various optical artifacts like orbs & polygons “overlaying” or completely covering parts of your image.

Ghosting appears in your image as visible artifacts like circular/semi-circular/polygonal shapes of varying color and size throughout your image, usually in a direct line starting from the bright light source’s position.

The orbs and polygonal shapes amount depends on lens design, specifically they are equal to the number of your lens elements.
Each lens has its own “performance” and behavior regarding Lens Flare & Ghosting, some do very well, some terrible.

Underexposed/Overexposed

top: an under-exposed photo, it is generally dark across the frame and there’s loss of detail in the dark shadows

middle: a properly exposed photo

bottom: an over-exposed photo, we have lost the sky details, and there are no deep shadows to create contrast within the frame

Under (dark) or Over (bright) is used to express an error regarding the “illumination” of a photograph. Underexposure & Overexposure is considered an error unless the artist did it on purpose in order to achieve a dark (moody) or very bright (usually for simplicity in long exposure shots) image.

Exposure

In layman’s terms the term Exposure in photography has two meanings or uses. One meaning & use is to describe a photo taken using a single shutter actuation, instead of saying “nice photo” one might say “nice exposure”. Although the most common usage is for expressing a correctly or incorrectly exposed (“lit”) photograph. Purely technical and theoretically, the exposure is simply the outcome of the “play”/relation of three variables of our photographic equipment:

The Shutter Speed (which is for how long our sensor/film is allowed to receive photons [light])
The lens Aperture (how big or small the opening of our lens diaphragm is, controlling how much light enters the sensor/film per time unit/during the exposure time [i.e. shutter speed])
The ISO/ASA sensitivity value of our sensor/film

This is usually referred to as “the exposure triangle” simply because these three variables (Shutter Speed, Aperture, ISO) control how much “light” is “depicted” in our photo, they essentially control how bright or dark our photo is (regardless of the available light in the scene).

Here’s a graphical illustration of the Exposure Triangle (showing its variables/dependencies and their effect on the final image)

Depth of Field

By Depth of Field photographers refer to the “acceptable sharpness” region of a photo. Not everything that our lens can see/cram into our photo is in sharp focus or in focus at all. The Depth of Field essentially is an expression of the minimum and maximum distance from the camera’s sensor plane or film within which the “contents” are in decent focus. The Depth of Field depends on many factors including the focal length of your lens, the aperture used and the distance to your subject/focus point. You can use a Depth of Field calculator to see how each value alters your DoF (see dofmaster.com for example).