Aperture?

Another crucial element in photography, and except for the way it is written down, it is a rather simple concept. Aperture refers to the size of the opening in the lens that is letting the light into the sensor. That's pretty much it. The size of the lens opening. The hole. It has a lot of implications and a great impact on the resulting photograph, but it is still just referring to the size of the opening used to let the light in.

As you might expect, the larger the opening, the more light it lets in. So why would we not always use the largest aperture available and get the most light? Well, there are several reasons, but one obvious one should be that sometimes there is too much light. Outside on a bright sunny day, you may not be able to shoot with a wide open aperture without over exposing your photos. But the amount of light it lets in is not the only thing to consider. The aperture you choose also has a profound effect on the Depth of Field(DOF). And the larger the opening, the shallower/smaller the Depth of Field. This is important for many reasons, as depth of field is crucial to creating desired effects, such as the creamy blurred backgrounds(also called bokeh) many people love. And on the opposite end, you sometimes want everything(or as much as possible) in sharp focus, such as in a landscape photographs. So depending on what you're trying to do, aperture is probably going to play an important part in it. 


Here is a little demo I put together to demonstrate the effect of aperture on DOF(Depth of Field, the section of the image that is in sharp focus).

 
A few guidelines on aperture:

- For bokeh(that creamy blurred background), which helps isolate the subject(great for portraits!), you will want to use a wide aperture, and get up close, so shooting either wide open, or only slightly stepped down should help achieve this. There is a trade off in sharpness when shooting wide open, but it is mostly around the edges, and unless you are planning on making really large prints, it won't really matter all that much. But that's something that is easy to test for yourself and compare the results. Shooting at longer focal lengths helps with this too, so that's another way to get bokeh. Since at wide/large apertures, the DOF is shallow,  you will need to be very accurate with your focus. If it is even slightly off, or focused on the wrong part of the frame, your subject will come out soft.
 
Some things/tips to consider regarding aperture: 

• Most lenses have a "sweet spot" when it comes to sharpness at around f/8 to f/11. So this is a good aperture to use when DOF doesn't matter, such as when shooting a flat subject(everything at the same distance, or focusing at infinity, or pattern shots). So if aperture doesn't matter, and you have enough light(or a tripod), use an aperture between f/8 and f/11 for maximum sharpness.

• When you absolutely want to maximize Depth of Field, then you have to shrink the aperture as much as possible. You lose a little image quality to diffraction. Here again, many times it is negligible, you can test for yourself and see if it is something you can even detect, and find acceptable. This is especially necessary when shooting macro photos, since up close the Depth of Field is very shallow.

• When shooting the night sky, the priority is collecting as much light as possible, so the widest aperture possible is how I shoot those pictures.

• When I shoot landscapes, I go for sharpness, so I stick to f/8 to f/11. As long as  you focus at least a third of the way into the frame(distance wise), that should get all of it in sharp focus(in other words, just don't focus on the foreground). But I am not saying that's the best or only way to do that, just telling you how I do this.

Aperture is a key element of photography. Luckily, it is also not that difficult to understand. Just get out there and practice. One way to learn aperture is to set your camera to Aperture Priority ('Av' on a canon, 'A' on Nikon and most other cameras) mode. In this mode, you can just set the aperture you want, and the camera will pick the rest

Glossary

First, I will define some photography terms that will probably be used often in this blog. Don't worry about memorizing them now, we will mention them so much that it should become second nature to you at some point.

Disclaimer: I am trying to keep things simple, so if you want a more technical definition, this is not the place. I don't think that at this point it really adds to the discussion to get very technical.

Aperture - Basically, the size of the opening in the lens. This can be controlled(up to the lens' maximum and minimum apertures). It is written down as a fraction, such as f/1.4, f/5.6, f/8, f/11, etc. Since it is a division, the larger the f-number, the smaller the aperture(opening) and the less light it lets in(and the more DOF). So try to remember the smaller the f-number, the bigger the aperture. It is an inverse relationship.

Depth of Field(DOF) - In the photograph, the distance range that is in focus. Aperture and focal length have dramatic effects on DOF.

Exposure - A term for the amount of light that you allow to hit the film or sensor of the camera.

ISO - The level of sensitivity to light of the image sensor or the film. The higher the ISO, the more sensitive it is. Fun Fact: The initials come from the International Organization for Standardization, but they aren't really initials, and come from the Greek word for equal.

Focal Length - This has a somewhat complicated technical definition. For our purposes, suffice it to say that it is the number on your lens that is measured in millimeters(mm). Not the filter size, but the main specification of your lens. 18-55mm, or 50mm, or 70-300mm. That would the focal length. The smaller/shorter it is, the wider the angle of view. The longer the focal length, the more "zoomed in" it is. Most dSLRs come with what is known as a "crop sensor", or APS-C size sensor, meaning it is slightly smaller than the 35mm full frame sensors of the higher end "pro" cameras. This means that in some lenses, such as the very common(and awesome) nifty 50, the Canon EF 50mm f/1.8 II are actually about 1.6 times the focal length they say on there. So this lens would be 80mm on these cameras.

Live view - A feature on many dSLRs that allows you to see the image BEFORE you take it on the LCD display. Very useful for certain types of photos. If you had a point and shoot previously, or even saw one, you should be familiar with this as this is the ONLY way you can see what you are taking in most point and shoots, since they don't have an optical viewfinder(some have a digital one, which is kind of strange).

Shutter Speed(exposure time) - The amount of time that you let light hit the sensor or film. Measured in seconds. Usually denoted as a fraction when it is less than 1 second(1/500, 1/50, 1/6, etc.) and with a quotation mark when more than 1 second(1", 10", 30", etc.).

Viewfinder - Where you put your eye to see what the picture will look like. On dSLRs, it is optical, and what you see is what you get(for the most part).

White Balance(Color Temperature) -  Refers to the the adjustment of color mapping in order to render color tones correctly under artificial or different lighting(such as incandescent or fluorescent lighting). It can be done by choosing a preset(such as daylight, cloudy, color temperature, fluorescent, etc.) in camera or in post processing software(such as DPP, Aperture, Lightroom, Photoshop, etc.).

As I remember more terms, I will add them to this entry so you can reference it as needed as well as define them as they come up. Again, don't worry if this seems daunting or overwhelming, it will all fall into place.