Week 3
Assignment
The Lens
Intro to Photography with Denni Russel
DIGITAL PHOTO I
The LENS is the eye of your camera. How did you find last week's assignment?
Without a lens your sensor will simply react to the light without producing a recognizable image.
The Lens
The Lens
The Lens Filters Composition
The Lens
A lens is a tube with special glass, or sometimes with crystal, 'elements' inside it. The lens bends the light that passes through it in such a way that it will create a focused image at the point where we place the sensor. This is called the focal point. The sensor lies along the focal plane.
There is no special lens for every situation. Different lenses let you make all different kinds of photographs.
These elements are shaped and polished to do very specific jobs. They take the light and focus it on what we call the focal point.
To understand why that is, let's look at what goes into your lens: lens elements
The Lens
The Lens
By changing the length of the tube, and the shape and magnification qualities of the 'elements' within it, you change the way the light is bent and focused.
Not all lenses are created equal.
These changes give us different focal lengths.
focal point this is where we put the sensor
Focal Length
There is no such thing as a perfect lens.
But how do we know what kind of lens will work best for any given situation?
To correct for minor flaws we place a number of elements in a lens.
We have to become familiar with focal lengths.
High quality lenses have many elements in them.
50 mm Focal Length
100 mm Focal Length
Focal Length Every lens has a focal length.
'Reading' Your Lens
The focal length tells you what you can see with it.
Your focal length is written on your lens.
There are 3 main types of lenses:
a normal lens a wide angle lens a telephoto lens
Wide Vs. Long
Wide Vs. Long Wide Angle lenses give you a wide angle of view. Far away objects will appear small.
If you have a lens with more than one focal length, its range will be written like this. If it has one focal length only it will have only one number.
Prime Lenses
Zoom Lenses Zoom lenses have more than one focal length.
A prime lens has only one focal length. These are often called fixed focal length lenses. These are usually high quality lenses.
Telephoto lenses give you a narrow angle of view. Objects far away will appear closer.
You can change the focal length by turning part of your lens, or sometimes by pushing and pulling the lens telescopically. Zoom lenses have two sets of numbers: 18-55mm, 24-70mm 24-300mm Notice the 'mm'. This stands for millimetre. What are your focal lengths?
Focal Length
Focal Length
What you See
Focal lengths range from 10mm - 1200mm! Here are some focal lengths: 10mm, 12mm, 14mm, 15mm, 16mm, 17mm, 20mm, 24mm, 28mm, 35mm, 70mm, 80mm, 105mm, 135mm, 200mm, 300mm, 400mm, 500mm, 600mm, 1200mm.
10mm
10mm 16mm 24mm 33mm 70mm 130mm 200mm
Digital vs. Film Lenses
Digital vs. Film Lenses
Digital vs. Film Lenses
Digital SLRs have complicated our understanding of lenses. We've became used to the angle of view lenses give us with 35mm film cameras. That angle of view, the width of a scene captured, is actually going to be different using the same lens on different types of cameras.
Digital vs. Film Lenses
We call sensors that are the same size as 35mm film full frame sensors.
Most digital cameras have smaller recording chips than 35mm film.
We call sensors that are smaller than 35mm film cropped frame sensors. 36mm wide 24 mm wide
35mm film
APS-H
APS-C
36mm x 24mm
28.7mm x 19mm aprox.
24mm x 16mm aprox.
Digital vs. Film Lenses
24mm tall
16 mm tall
Full Frame
Cropped Frame
Digital vs. Film Lenses When printed at the same size (4x6 inches, for example), the smaller chips seem to magnify the scene, when in actuality they are simply showing us less of the scene.
A smaller recording sensor will see less of a scene than a larger sensor. It dose not see as much of the top, bottom, or sides. This is why we say it is cropped.
APS-C - 24mm x 16mm APS-H - 28.7mm x 19mm Full Frame
Full Frame - 36mm x 24mm
APS-H
APS-C
Canon 1Ds Mark II, full frame sensor, 70-200mm lens, set at 73mm.
This is why you might hear the term 'digital magnification factor'.
Digital vs. Film Lenses
Digital vs. Film Lenses
Digital vs. Film Lenses
There are other issues associated with digital vs. film lenses.
Full frame lenses are designed to spread the light over the entire area of the film or sensor.
Many digital lenses are designed to spread their light only over the smaller area of the smaller chip.
Those issues deal with how the light is spread over the recording sensor.
36mm wide 16 mm tall 24 mm wide 24mm tall
Nikon has their DX series while Canon calls their cropped frame products EF-S lenses.
Digital vs. Film Lenses This causes problems when switching certain lenses between digital cameras with differently sized sensors.
Digital vs. Film Lenses
Auto Focus
Benefit of Digital Lenses:
There are two main types of auto focus your camera might have both options, or maybe even more!
Because these lenses cover a small area they can be made smaller than their film counterparts. This results in lighter, easier to carry lenses.
Lenses optimized for cropped frames don't spread their light over the larger area. This can cause vignetting.
Digital Cameras are more sensitive to detail than film. Digital lenses are usually sharper than equivalent film lenses.
For still subjects For moving subjects A third option lets the camera switch back and forth between the two depending on what your subject is doing.
Auto Focus
Auto Focus
Long Lens Shake
Not all auto focus systems are created equal. Some lenses have much faster motors and computers for auto focus than others. USM lenses (ultra sonic motors) are faster, quieter, and more expensive. Auto focus for relatively stationary subjects.
Auto focus for moving subjects.
Lens Stabilization
Lens Choice
Long focal lengths require fast shutter speeds. A small shake at your end = a big shake at the far end of the lens!
The general rule is that you want to choose a shutter speed faster than the focal length of your lens. This means that if you're using a focal length of 100mm you might want to use a shutter speed of at least 1/125th. 1/60th or slower might cause camera shake.
Lens Choice
Many companies now offer mechanical ways to help you make a steady image. Some are built into the camera, while others are built into the lenses.
So, how do you decide what focal length to use in each situation?
In camera stabilization is good for 2 stops. Full frame : Cropped frame (approximately) 24mm = 16mm 50mm = 33mm 105 = 70mm
In lens stabilization is good for 3 stops.
Lens Choice I used a 50mm lens to capture this landscape. (equivalent to 33mm)
Perspective
Perspective
Ever notice that your buildings tend to warp when you shoot up? This is because of perspective.
When you tilt your lens you create a distorted image. This happens because you are moving part of the film plane farther away from the subject than another part of the plane.
I used a 400mm lens to capture this lioness. (equivalent to 266mm)
Perspective
Think of when you look down a road. Objects in the distance are smaller than those up close. When you tilt the camera up you are creating the same effect.
Tilt-Shift Lenses
Macro Most lenses don't let you get up close to a subject. To get really close you need to go 'macro'.
building
film
tilt
normal
The front of the lens bends so the film plane can remain parallel to the scene. The architectural photographer's best friend. Also great for landscape photographers.
Macro
Macro
Macro
Your lens might have a macro ratio written on it.. Lens Reproduction Rations
This will tell you the maximum magnification of a scene that it can produce. It will look like this - 1:6 1:6 means that a 1 cm object will measure 1.66 mm on the sensor (it's 6 times smaller). 1:1 means that a 1 cm object will measure 1 cm on the sensor. I used a 100mm macro for this image.
1:16
1:8
1:4 1:2
1:1
2:1
4:1
Fish Eye Lenses
Teleconverters
Teleconverters
Sometimes it's either too expensive or impractical to have an extremely long telephoto lens... and yet you still want to shoot something that is far away. There is a cheaper and lighter alternative...
teleconverters. A teleconverter multiplies the focal length of your lens by either 1.4 or 2 times.
Teleconverters
Filters
Filters
There are downsides, however... 1) Teleconverters reduce the amount of light coming into the camera. This means that they will change your maximum aperture and make it smaller. If your maximum aperture was f4, with the 1.4 x converter it will become an f5.6 (+1 stop). A 2x converter will make your lens an f8 (+2 stops).
A filter is a piece of glass, or plastic that alters the light before it travels through the lens. Filters are used to change colours, textures, amount, feel, etc. of light entering the camera.
Screw in filters attach to your lens by the 'thread' on the front element.
2) They make auto focus slower.
'Reading' Your Lens This thread has a particular circumference. This is written in "mm". What are the sizes of your lenses?
Polarizing Filter
Filters
Polarizing Filter
Drop in filters, usually made of plastic, slide into a holder which screws into the front of your lens. These filters are easier to stack and manipulate than screw on filters. Cokin makes the majority of these filters that you'll find.
Polarizing Filter
Blocking Light Sometimes you will want to use a longer shutter speed than the ambient light will allow.
A simple turn of the front element will allow you to remove reflection from glass!
Blocking Light A Neutral Density filter (ND) will do the same thing. They are gray and they come in a variety of densities. They do not change the colour of the scene.
Don't 'fix it in Photoshop'... Use a filter for better photos. These are the filters used to make Caribbean water so blue!
To do this you can use a filter to block some of the light. A polarizer will block 2 stops of light.
Bracketing
Composition
Bracketing your shots allows you to capture a number of images of the same scene at different exposures.
Let's talk a little about composition.
Take a light meter reading. Adjust your shutter and aperture until it shows a proper exposure.
We're going to keep it simple for now... The first thing to keep in mind is that a good photograph is always going to include an engaging subject.
Now overexpose by one stop. Now underexpose by one stop. That is bracketing.
Don't waste your shots... Try to find something worthwhile before making the image.
Composition
Composition
Try to Simplify
Examine every corner of the view finder. Visualize the final image. How do you want it to look? What emotion, or feeling are you trying to capture?
Is this photo too busy? Is there something in the frame that you won't be happy with? Try to simplify the image. Are you cutting off the top of someone's head, or the edge of a sign?
Many photos have so much going on that you don't know where to look...
Make sure things are the way you want them to be.
Leading Lines
Framing
Foreground Objects
What are the lines doing in the shot. Do they confuse things? Do they lead your eye to the subject? or away from the subject?
Horizontal Framing
You can frame your scene to give a sense of 'packaging'. This tree helps us understand the scale of the scene.
Angles
Try not to shoot head on... Horizontal subjects tend to look best framed horizontally.
Composition
Is this photo telling a story?
Rule of Thirds
When the subject - or its most important element - is placed near one of the intersecting points of an imaginary grid, the viewer's eye is led through the frame. The result is an aesthetically strong image.