Let's talk about something basic today: lens quality.
Lenses are the most important part of a camera system. The most expensive camera in the world is still a light-proof storage box for film. Without a lens to focus the waves of light, the camera is useless. The light focusing quality of a lens directly affects the image.
We want our images to be "sharp" (extremely well focused). PJs pay a lot of money to have the sharpest lenses we can acquire for the camera system we use.
The lens is the single automatic way to improve images. For PJs on a budget, start building your system with a modest camera body, but get the best glass available.
Often, these are used, manual-focus lenses. They aren't as fancy as the ones the pros use, but they aren't as expensive, heavy or fragile (in most cases). Don't get talked into less-expensive auto-everything lenses produced by an off-brand manufacturer. Stick with lenses from the company who manufactured the camera body.
Lenses control light. Light is focused as it passes through the lens. The light then strikes the film or digital sensor (the film plane). This is the critical point in the photographic process. At this point, the circles of confusion are set.
Circles of confusion are points of light, which are focused to strike the film plane. If these circles are broad, they give the image a "fuzzy" look (slightly out of focus). If the circles of confusion are tight, they make a sharp image.
Since light is both a wave and a particle, think of light as water through a sprayer bottle or water pick. There are some lenses which only spray and some which only have a tight stream setting. Get the lens with the tightest circles of confusion to direct the light exactly where it's needed.
The other major consideration with a lens is its "speed." Lens speed is measured in "f-stops." The f-stop is a determination of how much light is allowed through a lens.
A lens with a maximum aperture of f/5.6 is considered "slow." In other words, these lenses are best used outside during the daylight.
A lens with a maximum aperture of f/2 is considered "fast." The f/2 lens is three stops faster (allows eight times the amount of light to pass through the lens in the same amount of time). It can be used in lower light or allows for faster action in moderate light (as in a gym). Costs climbs considerably as lenses become faster.
Enough for now,