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What is an SLR?

From: Shooting with the Canon 5D Mark III

Video: What is an SLR?

All cameras have at least one thing in common; they have a lens that sits in front of a focal plane. On that focal plane is a recording medium; either a piece of light sensitive film, or paper, or a digital image sensor. The focal plane needs to sit directly behind the lens, because the lens is used to focus light onto that recording medium. Another way to think of it is that the recording medium looks through the lens. What's tricky about camera design is that if the recording medium is sitting there looking through the lens, how is there room for you to look through the lens to frame your shot? Camera designers have wrestled with this problem since the beginning of photography, and they have come up with lots of solutions.

What is an SLR?

All cameras have at least one thing in common; they have a lens that sits in front of a focal plane. On that focal plane is a recording medium; either a piece of light sensitive film, or paper, or a digital image sensor. The focal plane needs to sit directly behind the lens, because the lens is used to focus light onto that recording medium. Another way to think of it is that the recording medium looks through the lens. What's tricky about camera design is that if the recording medium is sitting there looking through the lens, how is there room for you to look through the lens to frame your shot? Camera designers have wrestled with this problem since the beginning of photography, and they have come up with lots of solutions.

For example, with a view camera, you actually take the recording medium off, so that you can look through your lens to line up the shot, and then you put the recording medium back on. Needless to say, this doesn't make for a particularly speedy shooting. In a twin lens reflex camera, you look through one lens, and a second lens exposes the film. However, if I am shooting up close, my framing might be off, due to the parallax shift between the two lenses. Similarly, in a rangefinder camera, I look through this viewfinder, while the camera looks through this lens.

I still might have parallax issues, but with a camera like this, I can actually change lenses, and still have a viewfinder that works. The SLR, or single-lens reflex, solves all of the issues with these other designs. With an SLR, there is just one lens, a single lens, and both you and the recording medium look through that same lens. To make that happen, there is a mirror inside your camera. Now, here is how this works. Normally, light comes through the lens, it enters the body, and it bumps into a mirror that's sitting right here at 45 degrees.

The mirror bounces light up into this thing, which is called a pentaprism. Inside this part of your camera, there is a five-sided prism that knocks the light around until it comes out the viewfinder here. So when you look through the viewfinder, thanks to this series of prisms and mirrors, you're looking through this lens right here; this single lens on the camera. When you press the shutter button, the mirror that sits right here flips up. When that happens, light can pass into the camera body, and instead of bouncing up here, it just keeps going straight.

The shutter opens, it passes through the shutter, and hits the image sensor. When the shutter -- when the exposure is done, the shutter closes, and the mirror comes down. When that happens, light goes back to being bounced up here. This is why, when you press the shutter button, your viewfinder goes dark for a moment, because when this mirror pops up, the viewfinder basically goes blind. So with this single lens, I can, thanks to the mirror, get light out the viewfinder, and get light back to the sensor. That's the SL part of SLR.

The reflex part is referring to the fact that the mirror moves; that it goes up and down. You can actually see the mirror in your camera. I am going to turn the camera around to the front, so that we can look inside the mirror chamber itself. Now, if I take the lens off the camera --I'm just going to take it off, just like I normally would here. This is the mirror chamber. So you can see the mirror right there. It is, in fact, sitting at a 45° angle.

Your lens sticks into this chamber as far back as these metal contacts here. Sitting behind the mirror is the shutter, which is closed right now, and then behind that is the image sensor, obscured by the shutter. I have got the camera in a mode where if I press and hold the shutter button down, the mirror will stay up, and the shutter will stay open for as long as I hold the button. So I am going to do that right now. I am going to pop the shutter open, and that mysterious glowing thing back there is your image sensor. Now, your image sensor doesn't actually glow, but you can think of it that way.

What's going on here is every pixel on the surface of the sensor has a little lens over it. It's part of how light gets focused properly onto the sensor, and those mirrors are tiny microscopic things, and they're all reflecting and refracting light in this weird way that's giving us this cool rainbow effect back there. I am going to let go of the button now, and the shutter and mirror are going to come down. Here is a slow-motion movie of this whole thing happening on a different camera. You can see the mirror flip up, the shutter open and close, and the mirror come back down.

So what's the downside? Well, SLRs are larger than a typical rangefinder camera, which makes them a little less convenient. They can't have the giant media sizes of a big view camera. They have got a lot of mechanical parts that break down, and they can be noisy, but overall, today's SLRs, is particularly digital SLRs, offer the best all-around camera design, allowing for incredible flexibility of lens choice, shooting options, portability, and ease of use, while all giving you a nice big bright viewfinder. While there are a lot of great point-and-shoots on the market -- and a point-and-shoot is often the best camera choice, depending on the shooting situation -- SLRs score over their smaller point-and-shoot counterparts both in terms of image quality, and shooting flexibility. With their larger sensor size, they provide quality, better lowlight performance, and the ability to shoot with shallower depths of field. With their interchangeable lenses, fast burst rates, and advanced features, you can shoot just about any subject with an SLR.

Now you just have to learn how to use it, and that's what you are going to do in this course.

Show transcript

This video is part of

Image for Shooting with the Canon 5D Mark III
Shooting with the Canon 5D Mark III

108 video lessons · 19982 viewers

Ben Long
Author

 
Expand all | Collapse all
  1. 10m 29s
    1. Welcome
      2m 16s
    2. What is an SLR?
      5m 28s
    3. A note for 5D Mark II users
      50s
    4. Using this course
      1m 55s
  2. 35m 44s
    1. Exploring basic camera anatomy
      5m 28s
    2. Attaching a lens to your camera
      4m 3s
    3. Examining batteries and media cards
      8m 35s
    4. Powering up
      1m 49s
    5. Exploring the menu system
      2m 53s
    6. Clearing all settings
      2m 5s
    7. Setting the date and time
      1m 55s
    8. Setting the language
      1m 42s
    9. Formatting the media card
      3m 4s
    10. Holding the camera
      4m 10s
  3. 25m 6s
    1. Setting Scene Intelligent Auto mode
      1m 28s
    2. Exploring the viewfinder display
      5m 51s
    3. Touring the LCD screen and the status display
      2m 22s
    4. Exploring the top-mounted control buttons
      1m 42s
    5. Autofocus basics
      5m 7s
    6. Metering basics
      1m 42s
    7. Reviewing images
      2m 59s
    8. Working with image playback
      3m 55s
  4. 39m 32s
    1. Exploring Program mode
      41s
    2. Working with exposure compensation
      5m 2s
    3. Using the lock switch
      1m 21s
    4. Revisiting metering
      1m 43s
    5. Changing the ISO
      2m 14s
    6. Looking at ISO speed settings
      4m 36s
    7. Exploring long exposure noise reduction
      2m 53s
    8. Exploring high ISO noise reduction
      1m 40s
    9. Using program shift
      2m 11s
    10. Exploring image format and size
      3m 59s
    11. Using the Info button
      2m 4s
    12. Examining level and grid display
      3m 45s
    13. Using the Quick Control screen
      1m 35s
    14. Setting the color space
      1m 25s
    15. Configuring multiple media cards
      3m 24s
    16. Using the feature guide
      59s
  5. 23m 15s
    1. Exploring focus modes
      2m 25s
    2. Selecting autofocus areas
      3m 54s
    3. Exploring other autofocus options
      3m 44s
    4. Customizing servo auto focus
      4m 49s
    5. Exploring autofocus custom functions
      4m 50s
    6. Using manual focus
      3m 33s
  6. 10m 31s
    1. Using auto white balance
      1m 48s
    2. Exploring white balance presets
      3m 7s
    3. Using manual white balance
      5m 36s
  7. 10m 47s
    1. Exploring Drive mode
      4m 52s
    2. Using the self-timer
      3m 38s
    3. Using remote controls
      2m 17s
  8. 52m 26s
    1. Exploring metering modes
      3m 26s
    2. Using exposure lock
      1m 22s
    3. Working with focus points and metering
      3m 47s
    4. Exploring Aperture Priority mode
      3m 0s
    5. Using the depth of field preview button
      2m 40s
    6. Using Shutter Priority mode
      3m 26s
    7. Using Manual mode
      3m 27s
    8. Using auto exposure bracketing
      6m 3s
    9. Exploring Bulb mode
      2m 34s
    10. Working with the Auto Lighting Optimizer
      1m 40s
    11. Correcting lens aberration
      2m 46s
    12. Exploring Highlight Tone Priority
      2m 25s
    13. Understanding high-dynamic range (HDR)
      7m 5s
    14. Creating multiple exposures
      6m 25s
    15. Using the mirror lockup feature
      2m 20s
  9. 27m 38s
    1. Modifying LCD brightness
      3m 27s
    2. Rotating images
      2m 36s
    3. Using the playback grid
      42s
    4. Enabling AF point display
      1m 18s
    5. Rating images
      3m 4s
    6. Protecting and deleting images
      4m 40s
    7. Using Quick Control during playback
      1m 17s
    8. Exploring file numbering options
      2m 43s
    9. Creating folders
      1m 10s
    10. Changing file names
      3m 12s
    11. Adding copyright information
      3m 29s
  10. 7m 57s
    1. Defining picture styles
      2m 0s
    2. Exploring predefined picture styles
      2m 1s
    3. Adjusting predefined picture styles
      1m 56s
    4. Working with the monochromatic picture style
      2m 0s
  11. 22m 28s
    1. Activating Live View
      7m 16s
    2. Focusing in Live View
      5m 32s
    3. Focus manually in Live View
      1m 25s
    4. Working with aspect ratio
      2m 33s
    5. Exploring other Live View options
      3m 36s
    6. Reviewing the drawbacks to using Live View
      2m 6s
  12. 12m 16s
    1. Shooting video in Auto and Program modes
      6m 39s
    2. Shooting video in Priority or Manual modes
      3m 35s
    3. Exploring movie playback
      2m 2s
  13. 13m 0s
    1. Exploring custom modes
      5m 38s
    2. Using the custom menu
      2m 56s
    3. Exploring custom controls
      4m 26s
  14. 8m 57s
    1. What are custom functions?
      35s
    2. Working with exposure level increments
      1m 34s
    3. Bracketing auto cancel
      53s
    4. Changing the number of bracketed shots
      1m 5s
    5. Changing ISO speed setting increments
      1m 34s
    6. Exploring the Live View shooting area display
      40s
    7. Enabling safety shift
      2m 6s
    8. Clearing all custom functions
      30s
  15. 8m 16s
    1. Camera and sensor cleaning
      3m 12s
    2. Using the Battery Info command
      1m 45s
    3. Looking at operating conditions and temperatures
      2m 3s
    4. Getting firmware updates
      1m 16s
  16. 15m 10s
    1. Exploring focus and composition
      5m 31s
    2. Using an exposure strategy
      5m 11s
    3. Controlling exposure through Program mode
      4m 28s
  17. 23s
    1. Goodbye
      23s

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