Basics of Photography 1

8/2/2019 Basics of Photography 1

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BASICS OF PHOTOGRAPHY

Focal Length

When parallel rays of light strike a lens focused at infinity, they converge to a point

called the focal point. The focal length of the lens is then defined as the distance

from the middle of the lens to its focal point.

The focal length of a lens is usually displayed on the lens barrel. Below is a picture

of a Canon lens with a focal length of 50mm. The maximum aperture is f/1.8.

Lenses are usually categorized as having a wide-angle, normal or telephoto focal

length. A normal SLR lens covers a 24x36mm film frame with a field of view that

corresponds approximately to our normal vision; a lens with a focal length of 50mm

(55mm is also popular) is considered as normal.

Any lens with a focal length less than 50mm (or 55mm) can be considered as wide-

angle; any lens with a focal length greater than 50mm (or 55mm) can be considered

a telephoto. A zoom lens offers a range of focal lengths. This table lists some of themore popular focal lengths:

Lens Popular Focal Lengt hs for 35m m c am er as

Wide-angle 18mm, 20mm, 28mm, 35mm

Normal 50mm, 55mm

Telephoto 90mm, 135mm, 200mm, 300mm

Take a look at the two Nikon lenses below; the lens on the left is an SLR camerazoom lens with a focal length of 28-105mm. This is a popular zoom lens because it

provides a good wide-angle (28mm) as well as enough telephoto reach for a good

portrait (with 105mm, you can fill the screen with a face without getting in your

subject's face, so to speak).

The lens on the right comes with the Nikon Coolpix 5400 digital camera and has

zoom focal lengths of 5.8-24mm. Believe it or not, this is the equivalent of 28-

116mm zoom lens on a 35mm SLR camera! (The Coolpix 5400 no longer seems to


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be available although accessories for it are, but you might track one down for a good

price on eBay.)

N i k on 28 - 105m mf / 3 .5 -4 .5D AF-Zoom N ikkor

Nikon Coo lp ix 5400: 5 .8 -24 mm( 28 - 116m m , 35m m equ i v al en t )

f / 2 . 8 - 4 .6 Z oom N i k k o r ED

Because the image sensor size used in digital cameras are of different sizes, the same

focal lengths may be expressed using different numeric values. Smaller image

sensors require smaller lenses; larger image sensors require larger lenses to ensure all

the surface of the image sensor is covered. Other factors, such as the amount of

optical zoom provided, may further affect the distance between lens and the image

sensor.

It's more convenient to use the SLR equivalent as a handy reference point. Most, if

not all, camera manufacturers will list the 35mm SLR equivalent in the

specifications of a digital camera. Interestingly, some digital cameras are now even

engraved with the 35mm equivalent on the lens barrel to express the focal length of

the lens. It makes more sense in a way, though it is important to bear in mind that

35mm equivalent does not mean 100% compatibility with the real SLR lens. This is

especially true in the area of depth of field.

If you use a digital SLR (dSLR) that uses lenses made for 35mm film cameras, you

need to be aware that the focal lengths expressed on the lenses must be multiplied by

a factor. That factor, the Focal Length Multiplier, depends on the image sensor size

used (that will be in the Specifications section of your camera manual).

Of course, if the image sensor is full-frame, i.e. it is the same size as 35mm film,

then the multiplier is 1, and the focal length of the lens is accurate.


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However, only a few dSLRs use a full-frame image sensor (such cameras are beyond

the budget of hobbyist photographers, being in the range of several thousands of

dollars), with most using a smaller image sensor, usually APS size (or roughly half-

frame). That's why you'll read that a focal length multiplier of, say, 1.6 needs to be

applied to the focal length of the lens to obtain the true focal length.

So, suppose your dSLR has a Focal Length Multiplier of 1.6 and you use a 50mm

lens with it, the actual focal length of the lens when used with your dSLR is 1.6 x

50mm = 80mm. This is both good and bad. The good news is that you can now get

super telephoto focal lengths on your dSLR without buying costly and unwieldly

dedicated lenses. For example, a 100-300mm zoom lens, with a focal length

multiplier of 1.6, becomes approx. 160-480mm. The bad news is, of course, that

super wide-angle lenses are equally affected and a 28mm lens becomes a 45mm lens.

One solution is to buy a 16mm fisheye lens which, when factored up by 1.6,

becomes a 26mm lens.

To confuse matters even more, 'digital' lenses are appearing (or sold along with

digital camera bodies) which show the digital focal length range rather than the SLR

equivalent. Canon provide an 18-55mm lens with their EOS digital range of cameras.

While this is equivalent to a 35mm SLR range of 29mm-56mm, that equivalent

range isn't printed on the lens. A little experience will let you identify 35mm SLR

lenses from lenses specifically designed for use with dSLRs.

Lens Terminology

EF - The EF lens mount allows all the Canon EF lenses to be used on any of theCanon EOS. EF stands for Electro-Focus: automatic focusing on EF lenses ishandled by a dedicated electric motor built into the lens. All communication

between camera and lens takes place through electrical contacts; there are no

mechanical levers or plungers.

USM - Ultrasonic motor drive - EF lenses equipped with USM drives have fast,silent and precise auto focus operations, and consume less power compared to

other AF drive motors. There are two types of USMs, the ring-type USM and the

micromotor USM. Ring-type USM is always preferred because of its superiorperformance and efficiency, and it allows for full-time manual focus operations

without switching out of AF mode.

IS - Image stabilizer - the Image Stabilizer (IS) counters camera movements andshakes by optically correcting such shakes with accelerometers and lens groups

that move in relation to the shakes, thus minimizing or even eliminating minute

vibrations from the image. A general rule-of-thumb to overcome such vibrations

would be to set the shutter speed equal to or faster than the reciprocal of the lens


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focal length (e.g. 1/125s for a 100 mm lens). IS lenses can improve on this rule by

up to three stops. That is, the same 100 mm lens could be used at 1/30s.

L - series lenses - top of the line Canon EF lenses are designated as L-series. L-series lenses have superior optical performance and are typically built with a solid

construction to withstand constant use and harsh conditions. They can be

recognized by a red ring around the front part of the lens. Most recent L lenses

have sealing to help resist dust and water. L-series lenses are more frequently

used by professionals and serious amateurs due to their high price and large mass.

EF-S - The lens mount is a derivative of the EF lens mount created for a subsetof Canon digital single-lens reflex cameras with APS-C sized image sensors.

The three basic lens types, determined by the focal length (measured in millimeters)

of the lenses, are the following:

Normal - A normal lens shows mostaccurately what a normal human eye

will see. 50mm is a typical normal

focal length. The 50mm is the most

popular and versatile lens. The quality

is excellent while also being

inexpensive. It is smaller and lighter,

and the aperture allows photographs to

be taken in low-light situations.

Telephoto - A telephone lens brings the

background closer. Longer-than-normal

focal lengths such as 70mm and

300mm are typical for a telephoto lens.

Since a telephoto lens will bring the

subject up close, it is popular for sportsphotography.


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Lenses come in either prime or zoom. Prime lenses have a fixed focal length. In

order to fit more or less into the viewfinder, the photographer must physically move

forward or backward. Focal length in a zoom lens can be changed by turning the

zoom ring on the lens. A zoom will have a variable focal length such as 28mm-

105mm. While zoom lenses are more convenient for storage and versatility, prime

lenses often have a sharper lens and work better in low-light situations.

In addition to focal length, consider the lens speed and its focusing distance. The lens

speed is determined by the f-stop setting. A faster lens will be heavier and more

expensive. The focusing distance is the distance from the lens to the subject needed

to achieve a focused photograph.

Other special lenses to consider include the following:

Macro. A macro lens's focus is closer to the subject and is used for close-upphotography.

Fisheye. A fisheye lens uses an angle of view up to 180 degrees. The angledistorts the photograph so the four sides appear to be farther away.

Teleconverter. A teleconverter attaches between the camera and another lens.It increases the focal length of your lens. Although teleconverters will bring

the subject closer, they do not allow as much light through the lens. Thus, they

need slower shutter speeds and/or a fast ISO.

Digital camera SLR users need to be aware of the focal length differences in lenses

that are interchangeable for film and digital cameras. All focal lengths listed on

interchangeable lenses are for film cameras. To get the true focal length of a digital

camera the number needs to be multiplied by 1.6. Remember that the lens won't be

as wide on a digital camera as you would get on a film camera using the same lens.

Wide - A wide lens captures a wider

expanse of the background than what

the human eye will see. Shorter-than-

normal focal lengths such as 24mm

and 35 mm are typical for a wide lens.

Wide lenses are popular for landscape

photography and large group shots.


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For example, the standard 50mm lens on a film camera is actually 80mm on a digital

camera.

When purchasing a new lens, first consider your needs. What will you be

photographing? The subjects of your photographs should dictate whether you need a

normal, telephoto or wide lens. Then, consider the trade-off between the optics

quality, the camera's weight, the convenience of a prime vs. a zoom lens, lens speed,

focal distance and price. Often it will be a balance of these considerations that leads

you to a good camera.


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Understanding ISO, Aperture and Shutter Speed

Each of the three aspects of the triangle relate to light and how it enters and interacts

with the camera.

The three elements are:

ISO the measure of a digital camera sensors sensitivity to light

Aperture the size of the opening in the lens when a picture is taken

Shutter Speed the amount of time that the shutter is open

It is at the intersection of these three elements that an images exposure is worked

out.

Most importantly a change in one of the elements will impact the others. This means

that you can never really isolate just one of the elements alone but always need tohave the others in the back of your mind.

The Window

Imagine your camera is like a window with shutters that open and close.

Aperture is the size of the window. If its bigger more light gets through and the

room is brighter.

Shutter Speed is the amount of time that the shutters of the window are open. The

longer you leave them open the more that comes in.

Now imagine that youre inside the room and are wearing sunglasses (hopefully this

isnt too much of a stretch). Your eyes become desensitized to the light that comes in

(its like a low ISO).

There are a number of ways of increasing the amount of light in the room (or at least

how much it seems that there is. You could increase the time that the shutters are

open (decrease shutter speed), you could increase the size of the window (increase

aperture) or you could take off your sunglasses (make the ISO larger).

Ok its not the perfect illustration but you get the idea.

BringingItAllTogetherMastering the art of exposure is something that takes a lot of practice. In many ways

its a juggling act and even the most experienced photographers experiment and

tweak their settings as they go. Keep in mind that changing each element not only

impacts the exposure of the image but each one also has an impact upon other


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aspects of it (i.e. changing aperture changes depth of field, changing ISO changes the

graininess of a shot and changing shutter speed impacts how motion is captured).

The great thing about digital cameras is that they are the ideal testing bed for

learning about exposure. You can take as many shots as you like at no cost and they

not only allow you to shoot in Auto mode and Manual mode but also generally

have semi-automatic modes like aperture priority and shutter priority modes which

allow you to make decisions about one or two elements of the triangle and let the

camera handle the other elements.


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What is ISO?

In traditional (film) photography ISO (or ASA) was the indication of how sensitive a

film was to light. It was measured in numbers (youve probably seen them on films

100, 200, 400, 800 etc). The lower the number the lower the sensitivity of the film

and the finer the grain in the shots youre taking.

In Digital Photography ISO measures the sensitivity of the image sensor. The same

principles apply as in film photography the lower the number the less sensitive

your camera is to light and the finer the grain. Higher ISO settings are generally used

in darker situations to get faster shutter speeds (for example an indoor sports event

when you want to freeze the action in lower light) however the cost is noisier shots.

Ill illustrate this below with two elargements of shots that I just took the one on

the left is taken at 100 ISO and the one of the right at 3200 ISO (click to enlarge to

see the full effect).

100 ISO is generally accepted as normal and will give you lovely crisp shots (littlenoise/grain).

Most people tend to keep their digital cameras in Auto Mode where the camera

selects the appropriate ISO setting depending upon the conditions youre shooting in

(it will try to keep it as low as possible) but most cameras also give you the

opportunity to select your own ISO also.

When you do override your camera and choose a specific ISO youll notice that it

impacts the aperture and shutter speed needed for a well exposed shot. For example


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if you bumped your ISO up from 100 to 400 youll notice that you can shoot at

higher shutter speeds and/or smaller apertures.

When choosing the ISO setting I generally ask myself the following four questions:

1. Light Is the subject well lit?2. Grain Do I want a grainy shot or one without noise?3. Tripod Am I using a tripod?4. Moving Subject Is my subject moving or stationary?

If there is plenty of light, I want little grain, Im using a tripod and my subject is

stationary I will generally use a pretty low ISO rating.

However if its dark, I purposely want grain, I dont have a tripod and/or my subject

is moving I might consider increasing the ISO as it will enable me to shoot with a

faster shutter speed and still expose the shot well.

Of course the trade off of this increase in ISO will be noisier shots.

Situations where you might need to push ISO to higher settings include:

Indoor Sports Events where your subject is moving fast yet you may have limited

light available.

Concerts also low in light and often no-flash zones

Art Galleries, Churches etc- many galleries have rules against using a flash and of

course being indoors are not well lit.

Birthday Parties blowing out the candles in a dark room can give you a nice

moody shot which would be ruined by a bright flash. Increasing the ISO can help

capture the scene.

ISO is an important aspect of digital photography to have an understanding of if you

want to gain more control of your digital camera. Experiment with different settings

and how they impact your images today.


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What is Aperture?

Put most simply Aperture is the size of the opening in the lens when a picture is

taken.

When you hit the shutter release button of your camera a hole opens up that allows

your cameras image sensor to catch a glimpse of the scene you want to capture. The

aperture that you set impacts the size of that hole. The larger the hole the more light

that gets in the smaller the hole the less light.

Aperture is measured in f-stops. Youll often see them referred to here at Digital

Photography School as f/number for example f/2.8, f/4, f/5.6,f/8,f/22 etc. Moving

from one f-stop to the next doubles or halves the size of the amount of opening in

your lens (and the amount of light getting through). Keep in mind that a change in

shutter speed from one stop to the next doubles or halves the amount of light that

gets in also this means if you increase one and decrease the other you let the same

amount of light in very handy to keep in mind).

One thing that causes a lot of new photographers confusion is that large apertures

(where lots of light gets through) are given f/stop smaller numbers and smaller

apertures (where less light gets through) have larger f-stop numbers. So f/2.8 is in

fact a much larger aperture than f/22. It seems the wrong way around when you first

hear it but youll get the hang of it.

Depth of Field and Aperture

There are a number of results of changing the aperture of your shots that youll wantto keep in mind as you consider your setting but the most noticeable one will be the

depth of field that your shot will have.

Depth of Field (DOF) is that amount of your shot that will be in focus . Large depth

of field means that most of your image will be in focus whether its close to your

camera or far away (like the picture below where both the foreground and

background are largely in focus taken with an aperture of f/22).


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Small (or shallow) depth of field means that only part of the image will be in focus

and the rest will be fuzzy (like in the flower on top of). Youll see in it that the tip of

the yellow stems are in focus but even though they are only 1cm or so behind them

that the petals are out of focus. This is a very shallow depth of field and was taken

with an aperture of f/4.5).

Aperture has a big impact upon depth of field. Large aperture (remember its a

smaller number) will decrease depth of field while small aperture (larger numbers)

will give you larger depth of field.

It can be a little confusing at first but the way I remember it is that small numbers

mean small DOF and large numbers mean large DOF.


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Let me illustrate this with two pictures I took earlier this week in my garden of two

flowers.

The first picture below (click them to

enlarge) on the left was taken with an

aperture of f/22 and the second one wastaken with an aperture of f/2.8. The

difference is quite obvious. The f/22

picture has both the flower and the bud

in focus and youre able to make out the

shape of the fence and leaves in the

background.

The f/2.8 shot (2nd one) has the left

flower in focus (or parts of it) but the

depth of field is very shallow and the

background is thrown out of focus and

the bud to the right of the flower is also

less in focus due to it being slightly

further away from the camera when the

shot was taken.

The best way to get your head around aperture is to get your camera out and do some

experimenting. Go outside and find a spot where youve got items close to you as

well as far away and take a series of shots with different aperture settings from the

smallest setting to the largest. Youll quickly see the impact that it can have and the

usefulness of being able to control aperture.

Some styles of photography require large depths of field (and small Apertures)

For example in most landscape photography youll see small aperture settings (large

numbers) selected by photographers. This ensures that from the foreground to the

horizon is relatively in focus.

On the other hand in portrait photography it can be very handy to have your subject

perfectly in focus but to have a nice blurry background in order to ensure that your

subject is the main focal point and that other elements in the shot are not distracting.


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In this case youd choose a large aperture (small number) to ensure a shallow depth

of field.

Macro photographers tend to be big users of large apertures to ensure that the

element of their subject that they are focusing in on totally captures the attention of

the viewer of their images while the rest of the image is completely thrown out of

focus.


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Shutter Speed

Shutter speed is measured in seconds or in most cases fractions of seconds. The

bigger the denominator the faster the speed (i.e. 1/1000 is much faster than 1/30).

In most cases youll probably be using shutter speeds of 1/60th of a second or

faster. This is because anything slower than this is very difficult to use without

getting camera shake. Camera shake is when your camera is moving while the

shutter is open and results in blur in your photos.

If youre using a slow shutter speed (anything slower than 1/60) you will need to

either use a tripod or some type of image stabilization (more and more cameras are

coming with this built in).

Shutter speeds available to you on your camera will usually double

(approximately) with each setting. As a result youll usually have the options for

the following shutter speeds 1/500, 1/250, 1/125, 1/60, 1/30, 1/15, 1/8 etc. This

doubling is handy to keep in mind as aperture settings also double the amount of

light that is let in as a result increasing shutter speed by one stop and decreasing

aperture by one stop should give you similar exposure levels (but well talk more

about this in a future post).

Some cameras also give you the option for very slow shutter speeds that are not

fractions of seconds but are measured in seconds (for example 1 second, 10 seconds,

30 seconds etc). These are used in very low light situations, when youre going after

special effects and/or when youre trying to capture a lot of movement in a shot).

Some cameras also give you the option to shoot in B (or Bulb) mode. Bulb mode

lets you keep the shutter open for as long as you hold it down.

When considering what shutter speed to use in an image you should always ask

yourself whether anything in your scene is moving and how youd like to capture

that movement. If there is movement in your scene you have the choice of either

freezing the movement (so it looks still) or letting the moving object intentionally

blur (giving it a sense of movement).

To freeze movement in an image (like in the surfing shot above) youll want tochoose a faster shutter speed and to let the movement blur youll want to choose a

slower shutter speed. The actual speeds you should choose will vary depending upon

the speed of the subject in your shot and how much you want it to be blurred.


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Motion is not always bad I spoke to one digital camera owner last week who told

me that he always used fast shutter speeds and couldnt understand why anyone

would want motion in their images. There are times when motion is good. For

example when youre taking a photo of a waterfall and want to show how fast the

water is flowing, or when youre taking a shot of a racing car and want to give it afeeling of speed, or when youre taking a shot of a star scape and want to show how

the stars move over a longer period of time etc. In all of these instances choosing a

longer shutter speed will be the way to go. However in all of these cases you need to

use a tripod or youll run the risk of ruining the shots by adding camera movement (a

different type of blur than motion blur).

Focal Length and Shutter Speed - another thing to consider when choosing shutter

speed is the focal length of the lens youre using. Longer focal lengths will

accentuate the amount of camera shake you have and so youll need to choose afaster shutter speed (unless you have image stabilization in your lens or camera). The

rule of thumb to use with focal length in non image stabilized situations) is to

choose a shutter speed with a denominator that is larger than the focal length of the

lens. For example if you have a lens that is 50mm 1/60th is probably ok but if you

have a 200mm lens youll probably want to shoot at around 1/250.

Shutter Speed Bringing it together

Remember that thinking about Shutter Speed in isolation from the other two

elements of the Exposure Triangle (aperture and ISO) is not really a good idea. As

you change shutter speed youll need to change one or both of the other elements to

compensate for it.

For example if you speed up your shutter speed one stop (for example from 1/125th

to 1/250th) youre effectively letting half as much light into your camera. To

compensate for this youll probably need to increase your aperture one stop (for

example from f16 to f11). The other alternative would be to choose a faster ISO

rating (you might want to move from ISO 100 to ISO 400 for example).

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Basics of Photography 1