If it says 17mm, it's fixed at that...you can't zoom in or out. Advantages: cheaper.
If it says 18mm - 55mm, that means you can zoom in to 55mm. Advantages: more range.
fisheye = 8mm wide-angle = 14 - 17mm regular = 18 - 55mm telephoto = 85mm+
fisheye = you get everything. This is why peepholes and security cameras are fisheye: you want to see as much as possible. Disadvantage: things are super distorted...this effect will rarely look good with every photo and it's terrible for portrait photos b/c people's noses will look enormous. fish-eyes exaggerate depth of field a lot (your nose is right in my face but your ears are super far away)
wide-angle = not as severe as fish-eye but you still get more stuff. But again things will look a little distorted.
regular = great for portrait photos, tries to mirror reality as closely as possible.
zoom lens = depth of field gets flattened a lot, so things can look super flat. On the other hand you can take a photo with this and it will blur out the background a lot...a very pretty effect. This is also the lens you want if you're in the back of a concert but still want a photo of the singer...or if you want a photo of the moon. Another way to blur the background a lot: use a larger aperture.
Smaller number = larger aperture So f/2.8 = larger aperture than f/22.
Here's an image that illustrates that.
So more light gets in at f/2.8
Larger aperture = smaller depth of field.
Examples:
f/22 == smaller aperture == larger depth of field == more things in focus f/2.8 == larger aperture == shorter depth of field == less things in focus
Lenses with larger apertures are also described as being "faster" because you get more light so they need to stay open for less time. So if you're shooting a hummingbird for example, you probably want a lens with a larger aperture.
The rebel: $450 60D: $1000 Mark II: $3,500
What's the difference?
- Bigger sensor size. This makes a big difference: http://www.cambridgeincolour.com/tutorials/digital-camera-sensor-size.htm Basically your Rebel is cropping your pictures for you :( It also means that that wide-angle lens you rented is useless. For example, I rented a wide angle lens which is 17mm. The standard lens which I got with my Rebel is 18mm - 55mm (a zoom lens). So I get just 1mm with my wide angle lens. BUT the Rebel has a 1.6X crop factor, so that lens is actually a 17x1.6 = 27mm lens :(. Larger sensors also have larger pixels(?). Basically each pixel gets a bigger square so you get more light. i.e. you can take your ISO waaay up (6400 ISO) and while on a rebel this would give you a super noisy photo, on a Mark II it will still be quite smooth. So basically, lots more ISO without adding image noise. You also get a higher dynamic range...i.e instead of getting blown out whites and pools of black, you get more subtle gradations. This is always a good thing.
Reference: http://www.cambridgeincolour.com/tutorials/digital-camera-sensor-size.htm
My lens is an 18 - 55mm, and you can buy a 17 - 40mm canon lens for $900. I asked why someone would pay $900 for what sounds like essentially the same lens.
Key points:
- the 17-40 lens has a constant aperture f/4 vs the 18-55 which has a variable aperture f/3.5-5.6. That means for the standard one you can't shoot with the same aperture across all zoom lengths.
- L lenses (it's an f/4L) tend to have better optics -- sharper focus and fewer optical flaws such as chromatic aberration (See this answer on what kind of distortions lens can introduce. Basically, every lens will add some kind of distortion, but the goal of every lens is to try to capture reality as accurately as possible).
- the 17-40 lens is built to work with larger sensors, which as I pointed out above, require larger components, and that's why this lens is expensive. But again larger sensor = better photo.
- finally, build quality should be better for the 17-40mm i.e. more weather resistant, better optics.
Now you can understand what it takes to produce an image like this one: http://www.flickr.com/photos/43894176@N07/5338151979/
- Long exposure (54 sec) so you need a tripod for sure
- Focal length 50mm i.e. regular size, not wide angle
- ISO speed 5000! Must be a camera with a large sensor, because that would lead to a lot of distortion with a smaller sensor. It's a 5D Mark II...a $3500 camera.
Another one: http://www.flickr.com/photos/chrisk1982/8191471358/
- Wide angle: 17mm
- 2 sec exposure
- 100 ISO
- small aperture (f/10) for larger depth of field
This is an absolute must-read for getting gorgeous photos: http://www.cambridgeincolour.com/tutorials/high-dynamic-range.htm
HDR is something you do by combining multiple images in photoshop.
Look at this image without HDR vs this one with HDR!
An alternative is GND filters, you can try this in photoshop with RAW images.