Tuesday, August 10, 2004

Quality is all in the lens

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,
 

8 comments:

Jack said...

Hey Mark,
Thanks for the post. Since I'm not a pro photoJ, but I work closely with them, it's always helpful for me to learn basic stuff like this lens lesson.
Hope you're well. I'm headed East at the end of the week, but I assume we will keep in touch via blog.

Mark M. Hancock said...

Yup, I'll be watching and wishing you well. Take care in the land of snakes. You gotta come back this way after your soiree in the capital. Plus there is always the intra-media paintball game down the road. ;-}

Tomas Stargardter said...

"What's the most important part of a camera system?"

The photographer of course.

TS

XTL said...

The f/2 lens is three stops faster (allows three times the amount of light to pass through the lens in the same amount of time).

This sounds odd to me. I mean logarithmic scales are funky, but if you put those three stops to shutter speed, for example -- and why not? -- you get 2^3 = 8 times faster shutter and the same amount of light in 1/8 of the time. Presuming light flows in evenly I would say it's now coming in "eight times faster", not three.

Mark M. Hancock said...

Light is squared. Lenses are not. You're welcome to try eight stops instead of three, but you'll be five stops off the correct exposure. Try it during a $5K commercial gig, and tell me how well it works. ;-}

XTL said...

My points is exactly that three STOPS is 2^3=8 TIMES the light. And like I said, I can see how you can interpret it the other way.
And you had to answer with an insult and appeal to authority. Shame to see something like that in something that is otherwise full of sensible text.

Jan Fredrik said...

XTL is entirely correct. At 3 stops faster means 8 times the amount of light. Or said in a different way; each stop means twice (or half, if you're stopping down) the amount of light compared to the previous stop. No amount of high paying gigs are going to change this fact.

Mark M. Hancock said...

True and corrected. Three stops is eight times the amount of light. This is determined by the inverse square law of light rather than the shutter speed.
BTW, what xtl viewed as an "insult" is my "sense of humor" (note the emoticon).