Noob here and questions

[tsw910]

Hi everyone,

i just recently purchased the Rebel XT 350D with 18-55mm Lens .. i've always been in love with photography but never took it seriously. the camera's i've owned are all Canon from S320 - G6 - XT 350D. well, i have been reading around and looking at atleast one extra lens to get, and of course i get all confused about the #s that are written and what does it mean. please help !:o

f/3.5-5.6 = ?

USM = US market ?

and if anyone recommands a lens, please explain why .. thanks guys in advance !

[Jon]

Welcome to POTN.
f/3.5-5.6 = The lens (a zoom lens) has an "aperture" (opening) of f/3.5 at it's shortest end and f/5.6 when it's at its longest zoom.
USM - UltraSonic Motor
We have lens recommendations for all needs collected here (http://photography-on-the.net/forum/showthread.php?t=56752) for your viewing (and spending) pleasure. So limber up that credit card and post some pictures!

[tsw910]

thanks JON ...

so the F/3.5-5.6 is aperture opening .. would it be best for the #s to be low or high ? or it doesn't matter unless for certain typ of photos ?

[Jon]

Low is generally better. Smaller numbers mean the lens lets more light in, so you can photograph in darker areas. Some zooms will only have one number - that isn't a mistake, they're designed to maintain a "constant aperture" throughout their range. They're also more expensive.

[tsw910]

thanks JON .. you've been a great help !

[aam1234]

Welcome tsw910,

If you like to get your feet wet in photography have a look at this site (http://www.shortcourses.com). It's a great place to start things off.

[robertwgross]

If a lens aperture number is very low, then it is called a "fast lens." Actually, the lens is neither fast or slow, but it allows the shutter to go faster or slower depending on how much light the lens can collect. The number is the wide open aperture.

If a lens aperture number is extremely low, like f/1.4 or f/1.2, it is generally used only by experienced photographers who know what they are doing. Why? Because if you use the lens fully wide open, like f/1.4 or f/1.2, then your image will have a very narrow depth of field (think of it as a narrow depth of focus). In some cases, you shoot a portrait shot and you get the nose and eyes in focus and the ears will be out of focus. That's probably not what you want.

As a result, most consumer-oriented lenses have aperture numbers more like f/2.8 or f/3.5 or f/4. You can't intentionally narrow the depth of field quite as tight, but they are a little more foolproof.

If you extend the discussion, you end up with ordinary point-and-shoot lenses. Due to the lens and the sensor, the effective aperture is more like f/8, so they are even more foolproof yet.

If you use a super fast lens, you might be able to get a photo of a black cat eating licorice in a coal bin at midnight. But, do you really need that, and do you want to spend the cash for a lens like that?

So, it just depends on what you are trying to do.

---Bob Gross---

[tsw910]

If you use a super fast lens, you might be able to get a photo of a black cat eating licorice in a coal bin at midnight.
---Bob Gross---

that was great response .. love that !


and thanks for everyone being so helpful ! this site is great ! .. i can' seem to leave this site ...