- Credit due to Darrell Young for f/1.8, f/8 and f/22 selected images and creative content examples
Wednesday, May 7, 2014
Essentials of Photography — Part Two, The Eye of the Photographer:
Last month we discussed such basic concepts at how to fill the frame, using horizontal as well as vertical format for framing scenes, rule of thirds, and some other compositional principles. This month we will talk about some other composition tools that are essential to achieving images that are sharp, clear and well crafted.
Using a tripod allows the photographer to use low ISO, full range of shutter speeds and apertures. It is always a way to slow down and craft an image the best way. Tripods offer a wide range of possibilities for creating the best angle of view while maintaining a secured platform for the camera. Frequently photographers use the tripod in its upright with all legs extended so that they can shot standing up at almost eye level. Remember, tripods are designed to have the legs spread out and even telescoped to various distances so that an image can be captured very low to the ground or way off in the distance creating spectacular angles of view (see Fig. 1 and Fig. 2 below).
Also, make sure your tripod is sturdy. There are many tripods on the market that are at best flimsy. Be sure to get one that can carry the load of camera(s) and lens(es) and stay rigid.
Tripod Heads -
It is important to evaluate and decide on the type of Tripod head that works best for what you want to do. There are Ball & Socket Head with single and multiple knob controls. Some have level indicators and most have rotation markings for when there is a need to evaluate the turn of the platform. There are pan-tilt-swig heads with multiple locking levels.
Other Things to consider -
Shutter release controls such as cable release (either manual or electronic or even infrared allow the photographer to reduce even more any vibration caused by pressing the shutter release on the camera. Such remote release ensure that the tripod and head combination continues to be super stable.
Additionally, if your camera is an SLR use the mirror up feature that allows you to capture the image with the movement of the reflex mirror. This is very important with long lenses that allow for significant magnification. There is nothing worse then a fine image whose resolution ends up being not as sharp as desired when full zoomed or when the image is cropped. See your camera manual on how this feature works.
One of the most common preconceptions held by many less experienced
photographers is that certain focal lengths must be used for particular subjects.
The notion that you should always use a short focal length (wide-angle) lens to
shoot the sweeping vista of a landscape, or that a long focal length (telephoto)
lens must be used for getting in close by magnifying the subject in sports, or
wildlife photography, is misleading and could potentially stifle creativity.
There are no hard and fast rules when it comes to choosing a focal length, but
in order for you to make an informed decision, it is important to understand
the effect that each type of lens has on the way the picture is recorded, and
why these effects are so important when composing a picture.
Normal (Standard) Focal Length Lenses:
The type of lens is determined by the relationship between its focal length of
the film or digital sensor that records the image. For example, a standard lens
has a focal length equivalent, approximately to the diagonal measurement of
the format, for example on 35mm film it is around 45mm to 50mm. If you use
a digital SLR with a sensor that has the same dimensions as 35mm film then a
standard lens has the same focal length. If you use a D-SLR with a sensor
smaller than a 35mm film frame (i.e. less than 36 x 24mm) the standard lens
for this format of sensor will be shorter than 45mm to 50mm. For example, for
a D-SLR camera that has a sensor with the APS-C format (i.e. 24 x 16mm) the
focal length of a standard lens is about 30mm to 35mm.
Short (Wide-angle) Focal Length Lenses:
Short (Wide-angle) focal length lenses are arguably the most exciting to use because of their extended angle of view, which takes in more than our eye, and the standard lens, is able to see normally. They have tremendous depth of field, even at relatively large aperture values, providing sharpness from front to back, together with the ability to exaggerate perspective when an object is placed close to the lens, as it appears to loom large in the frame against a distant background. It is important to use wide-angle lenses with care. All too often, the subject can appear too small in the frame surrounded by a large area of dead space. The key is to consider your composition carefully and move in close to fill the frame. If it is necessary to tilt a wide-angle lens be careful, as straight lines, particularly those close the edge of the frame will become distorted, appearing to either lean inwards, or outwards depending on whether the lens is tilted up, or down respectively.
Long (Narrow-angle) Focal Length Lenses:
A lens with a long focal length (i.e. greater than a standard lens) is often referred to as a long, or telephoto lens. These are essential for some subjects; particularly those that are difficult to approach such as timid animals, or players on a sports field, because they magnify the subject enabling you fill the frame with it at longer distances compared with standard or wide-angle lenses. Lenses with a long focal length are also perfect for isolating a subject from its surroundings, for example, a detail, or pattern within a landscape. Just as perspective can be exaggerated by moving in close with a wide-angle lens, a lens with a long focal length has the opposite effect and can flatten perspective, making objects appear closer to each other than they are in reality.
To control the amount of light that passes through a camera lens it has a device
known as the iris; a series of interlaced blades that form a near circular hole, or
"aperture", at their center. By adjusting the diameter of this hole, or "aperture",
a photographer is able to adjust, with precision the amount of light that reaches
the film of digital sensor in the camera. The size of the aperture is usually
expressed as a numerical value prefixed with the letter "f" in the following
form: f/8. The lower the f-/number the larger the hole in the iris, so more light
can pass through the lens; hence these values are often referred to as wide apertures.Conversely, the higher the f-/number the smaller the hole in the iris,
so less light can pass through the lens; hence these values are often referred to
as narrow-apertures. The range of aperture values available on any particular
lens will vary from lens model to lens model, dependent of the design of the
specific lens; however, regardless of whether the aperture value is set by
adjusting a ring on the lens, or turning a dial on the camera it follows a sequence, so that f/8 lets through twice as much light as f/11 but only half as much as f/5.6. The size of the step between f/5.6 to f/8 is often referred to as 1- stop (1EV). Many cameras allow the setting of intermediate values, for example in steps of 1/3-stop (1/3EV) in which case the sequence of aperture values goes as follows: f5/6, f/6.3, f/7.1, and f/8.
Depth of Field —
For Depth of Field (DOF), I have elected to include not only some text material, herein, but also some specific links from some fine sources that offer wonderful examples that I believe will appeal to most everyone to get a better understanding of how to create the most suitable DOF for each image you take. Sometimes you may want to focus at one item and blur all around it, another time you may want full, clear detail from the foreground all the way through the entire image to the farthest point in the image, and other times you may want what is called shallow depth of field where the item in the foreground such a person in portrait is clear and sharp with the background blurred.
You may have wondered "How do pros make those wonderful landscapes where everything seems to be in focus?" Well, it is not merely by closing down the aperture of superb wide angle lenses. They maximize DOF(depth of field), the region of acceptable sharpness, by focusing at the hyperfocal distance. A simple function of lens focal length, aperture and the diameter of the Circle of Confusion.
The wider the angle of a lens, the shorter its focal length and deeper depth of field. So, as an example, an 18mm lens will have deeper (longer) depth of field than a 105mm. Also, the smaller the aperture you use the bigger the depth of field; i.e. in any given focal length lens, one gets more depth of field with it at f/16 than at f/4, for example.
The Circle of Confusion (CoC) has nothing to do with other camera brand users. It is the largest on-film or on sensor circle that you can see as a well defined point on an 8 x 10 print at arms length; that is, when viewed at from a "normal" viewing distance of 2 to 3 feet. Anything larger is seen as a small circle, not a point and is therefore perceived as out of focus. Using Nikon cameras, which I am most familiar with, here are some examples. For 35mm film and FX format the diameter of such circle is 0.025mm. Often rounded to 0.03, the exact number used here is 0.02501. For the Nikon DX (APS-C) digital sensor format, the
number used here is 0.0200.
These two sample images were shot at f/16. The one on top was made focusing at infinity, the image below was produced with the lens focused at its Hyperfocal Distance.
Now on in the image on the next page, take notice of the sharpness of the bush on the right hand side of the frame and the expanded DOF all the way to the horizon when using Hyperfocal Distance. Compare the two images.
Here is some more examples and comments focused on aperture setting and shutter speed relationships:
Depth-of-field (DOF) is one of those things that can confuse a lot of new camera users. Yet, it is very important!
Choosing the right combination of apertures and shutter speeds is initially hard to comprehend. This article is written to help you understand those relationships to help you control your image's look, while maintaining correct exposure.
I'm going to attempt to explain these concepts with pictures.
Lets say you are taking a picture of a friend, who is standing 2 meters (~6.6 feet) away from you. About 2 meters behind your friend is another person. There is also a third person standing about 2 meters behind the second person. Three people total — each about 2 meters apart — with your friend in front.
You are shooting with a 50mm lens. You focus on your red-shirted friend's face, and take a picture. It looks like this:
Notice in the picture above that your friend (in red) is in good focus. The girl standing behind her, to the right, is not in focus, nor is the young lad even farther away to the left. This is the result of shooting with a big "aperture." The f/1.8 is a big opening in the front of your lens. It also causes the depth-of-field, or "zone of sharp focus" to be shallow.
Only the girl in front is in focus at f/1.8. Not much else is in focus, so there is very little depth-of-field. The depth-of-field in this picture is well less than one meter. Probably more like 1/2 meter. (~1.5 feet) The zone of sharp focus is therefore only about 1/2 meter deep.
The f/1.8 is an "aperture" number. An aperture is simply an opening in the front of your lens controlled by blades. If you divide the focal lenght of the lens into its aperture f-number you get the diameter size of the effective aperture in the lens. In most cameras you should see the f/number somewhere in your viewfinder display but you won't actually see the effects of your aperture setting. This is because your auto single lens reflex (SLR) camera with an auto lens allows you to focus with the aperture blades wide open and out of the way. The aperture closes down to its selected setting when you press the shutter release to take your picture.
Apertures on a typical zoom lens start at about f/3.5 (big aperture), and go to f/22 (small aperture). The bigger the actual size of the aperture can get (the larger the opening) the "faster" the lens is considered. When you hear about a "fast" lens, someone is talking about a lens with a big maximum aperture opening. The 50mm f/1.8 lens I used for our example photos is definitely considered fast!
So what would happen if we closed the aperture down (also referred to as stopped down") to a medium-small aperture like f/8? The picture below shows what that will do to the depth-of-field:
Notice how the girl in front still looks sharp, and the girl to the right is now in focus too. You still focused your camera on the girl in front but now the girl to the right is sharp too (even though you did not change your focus point).
The depth-of-field, or zone of sharp focus, now extends past the girl in front and covers the girl in back. But, also notice that the boy to the left is still not in focus. The background is not in focus either. This image is the result of a medium aperture opening (f/8), not fast (f/1.8), or slow (f/22). Now let's consider what happens if we "stop down" or close the aperture to f/22:
Now Look! Everything in the picture is sharp. The smaller f/22 aperture makes it easier to get sharp focus. Remember, you focused on the front girl's face in all these pictures. At first only she was in focus (f/1.8), and as the aperture got smaller more and more of her surroundings came into sharp focus (f/8 and f/22).
So, Depth-of-Field is simply the zone of sharp focus. It extends in front of and behind your focused subject, and gets deeper in both directions as you “stop down” your lens. If you set your camera to A mode, or Aperture Priority, you can adjust this powerful functionality to control what is in focus in your pictures.
Notice also that the shutter speed changed as you stopped down your lens. At f/1.8 you needed 1/6000th of a second to keep the light from overexposing your image. A large, fast aperture lets in a LOT of light, so you can only let it in for a short time -- by using a fast shutter speed. As you stopped down to f/8, your shutter speed moved to 1/500th of a second.
The aperture opening is smaller at f/8 than at f/1.8 and less light is getting in through a smaller opening, so the light needs to come into the camera for a longer period of time. 1/500th of a second is a much longer time than 1/6000th of a second.
Then, notice how your shutter speed dropped to 1/40th of a second when you stopped down to f/22. At f/22 very little light is coming into the camera, so you have a long shutter speed at 1/40th of a second.
Here are ways to achieve this with examples, explanation and even ways to calculate it from a wide range of resources:
34mm Film Hyperfocal Chart
Digital Camera Hyperfocal Charts
Note: There are apps such as DOF Master that can be downloaded on smart phones and tablets that help calculate DOF. Some of it is basic and easy but other times you might want to get very precise to achieve the most desirable results. My thanks to Phil Waitkus (Fellow Member of Urban Ecology Center Camera Club) for sharing his knowledge of SetMyCameraDF. It seems to be pretty nice addition to the DOF and Hyperfocal app arena. Up to now, I have used DOF Master and one dedicated to my Nikon Camera and Lens. Google for more information and you will be surprised at what is available that you will become comfortable with. However, the bottom line is get accustomed to using these calculations to enhance the quality of you images.
This second in a series of articles on photography composition was compiled for the Urban Ecology Center Photography Club Newsletter.
John D. Roach