I do not believe that the direction that this thread has gone is very helpful, so I thought I may add some useful content. A lot of this should be covered in the photography book you ordered, but hopefully it is still useful. Warning: this is going to be a bit of an essay.
Camera Settings
Arguably, the most important camera settings to understand are the f-number, shutter speed, and ISO.
- F-number: The f-number essentially a ratio between the focal length of the lens and the diameter of the aperture (or entrance pupil) of the lens. Low f-numbers mean that the lens is letting in more light and smaller f-numbers mean that the lens is letting in less light. There was a nice diagram of this posted earlier. small f-numbers will also result in small depth of field, which could be good or bad depending on your objectives. It can give a blurry background which one method of highlighting a subject, but it can also lead to instances where items you want to be in focus are not (e.g, a dogs eyes in focus but its nose out of focus). Smaller f-number will give greater depth of field, which can be useful for landscape shots or environmental portraits.
- Shutter Speed: The shutter speed is the length of time the shutter remains open to let light in. Keeping the shutter speed open longer lets more light in. There are two items to be concerned with when selecting shutter speed: blurry subjects due to subject movement or blurry photos due to cameras shake. If a subject is moving fast, you need a fast shutter speed to get a sharp shot. A good guideline is to use ~1/1000 second for faster motion (e.g., sports), and 1/200 seconds for portraits (you can go less, but 1/200 is pretty safe). In order to make sure that camera shake is not an issue, a good guideline is to set the shutter at 1/[the lens focal length]. So, a 70 mm lens should have a minimum of a 1/70 shutter speed. This is just a guideline, so feel free to experiment.
As previously mentioned, f-number, shutter speed, and scene luminance define the mathematical definition of exposure. However, it gets confusing because raw editors like Lightroom and Capture One typically have an exposure slider, which do not really change the exposure (it cannot go back in time and change the camera setup), but does change the brightness or lightness of the image. All the bickering about exposure is about this confusion.
- ISO: ISO is essentially a parameter that translates the light captured by the camera to the brightness of the image you want. For example, if you take a picture in a dark room (low exposure) and want the picture to look bright, you may use a high ISO. Alternatively, you could shoot outside on a bright day but set a very shot shutter speed (e.g., 1/8000) and large f-number (e.g., f22) (low exposure), and use a high ISO setting to get a bright image. The downside to using a low exposure is that the camera is capturing less light, which results in noise .
It is typically best practice to try and meet your artistic intent and try and optimize exposure. However, I wouldn't worry about this too much about this. A little noise never ruined an image.
Composition
There are several useful techniques to highlight a subject in a photo. In general, photographers will often try focus an image on a single subject or story and avoid elements that don't help tell that story. Below are some helpful techniques:
- Sharpness: Using depth of field (often a low f-number) to make your subject sharp and the background less share is one way to highlight your subject. This method is very useful, but is only one technique out of many (and one that is sometimes overused in my opinion). An example is a portrait where the face is sharp, but the background is recognizable, but blurry. One may also include techniques such as panning (e.g., picture of a racecar) and using low shutter speeds to show water in motion (e.g., a picture of a waterfall) under this concept.
- Scale: The size of the subject in the image in comparison to other objects can help emphasize the subject. For instance making the subject larger than other objects will help direct the eye to the subject. However, scale can also be used in other ways. For example, one may shoot a small person in a vast landscape to make that landscape seem large and impressive.
- Color: Color can be used to emphasize a subject. If you have ever watched interior design shows, you have probably seen them use bright color throw pillows or curtains that "pop" against the other colors in the room. The same concept can be used in photography. One may have a bright subject against a natural landscape or use complementary colors. Colors can also convey a mood. For instance, we tend to think of colors with a blue tint as being "cold" and a yellow tint as being "warm." You can use color to help tell the story.
- Light: You may use light to help emphasize your subject. For instance consider a picture where the subject is luminated, but he background is darker. Your eye will naturally focus on the light part of the image.
- Leading Lines: Leading lines can be used to help lead a viewer through the image and provide a sense of depth. An example is a road that curves through a landscape, leading the viewers eye from the foreground to the background.
- Negative Space: One can use negative space to emphasize a subject. For example street photography photos of a small person walking with a large wall as the background (uses both negative space and scale to emphasize the subject).
- Balance: Balancing objects in the frame can make a picture more visually pleasing. For example, placing all of the objects on one side of the frame can make the picture seem unbalanced. The rule of thirds is a guideline that can be used to help balance objects in a photo (but it is a guideline that may be broken).
- Texture or Patterns: Texture may be used to emphasize a subject. For example, a photo may be of a series of windows in a skyscraper with a single window lit, showing someone working late. The one window that brakes from the pattern of dark windows tells a story and makes the photo compelling.
- Decisive moment: Not really a composition technique, but capturing a unique moment such as an embrace, smile, reaction, etc. can be the difference between an average and excellent photo. One should look for those moments. An example is that I managed to catch a huge hug between my wife and one year old daughter after she kame home from work (still wearing her business suit). The photo tells a story and makes me happy.
I may have missed some elements of composition, but hopefully this is a good start and gets you thinking about how you may apply some of these techniques. The goal is to tell a story and create a visually pleasing image.
One last note is to try and avoid distracting elements, such as a light pole sticking our of someone head, or a bright light that is not part of the composition.
Lighting
I am not going to go into a lot of detail here, but lighting is extremally important to photography. Light can have different characteristics that impact the final photograph. Two of those characteristics are hard light and soft light.
- Hard light: Hard light occurs when the light source is small in comparison to an object. The reason is the angle of the light from the small light source (recommend looking up a diagram). Think of the sun on a bright cloudless day (even thought the sun is big, it is very far away, which makes it seem small). The sun will give very "hard" distinct shadows. These shadows are often challenging to deal with since they can cause shadows under eyes and make it hard to balance light and dark portions of the scene. However, the hard shadows may be used artistically in come cases. You can also create hard light with a flash by or light bulb.
- Soft light: A large light source in comparison to the subject creates soft light. A large light source allows the light to approach the subject form many different angles, allowing it to somewhat fill in, or soften, the shadows. This is the reason why portrait photographers use large umbrellas and softboxes. They make the light source large in comparison to the subject, resulting in less harsh shadows. You may also encounter soft light in the natural world. Consider an overcast day where the clouds diffuse the light from the sun. On those days the shadows will be less harsh because the clouds act as a giant light source.
You may also consider the direction of the light. the direction of the light may be used to emphasize features. For instance, have you ever seen pictures of models with well defined abs? It is likely that the direction of the light was set to rake over the abs so that the light and shadow areas helped define them. The same concept can be used in landscape photography. When the sun is setting, it will rake across the landscape which may held define some of the texture present in the landscape.
Closing Remarks
I hope some of this information is useful. I mostly wanted to contradict the implication in this thread that photography is all about knowing the mathematical definition of exposure (and worse yet, whether they human is setting exposure in aperture/shutter priority modes). It is good to understand those concepts, but there is so much more to photography. This is often forgotten during discussions on this forum. Have fun, experiment, and stay safe.
