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Week 3 Lens And Focal Lenghts
1. Week 3 Lens and Focal Lengths Joel Kinison “ If I saw something in my viewfinder that looked familiar to me, I would do something to shake it up. – Garry Winogrand Check out more of Hákon’s work at PhotoQuotes.com and www.Imageree.com .
14. Lens Focal Length The focal length of a lens determines its angle of view, and thus also how much the subject will be magnified for a given photographic position. Wide angle lenses have small focal lengths, while telephoto lenses have larger focal lengths.
42. Meter Measures Light Subject Overexposed Automatic – average scene Subject Exposed properly Fooled by reducing the exposure 1 stop
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Notes de l'éditeur
How often have you seen a photo that is missing something, thinking, “This is a good photo but I’d make it different somehow.”? Sometimes small things make a big difference. Don’t be afraid to shake things up.
The smaller the aperture, the deeper the depth of field (the other two factors remaining the same). For example, if the lens focal length and the shooting distance stay the same, the depth of field is much deeper at f/16 than at f/1.4. Definition : Depth of field is the range of distance within the subject that is acceptably sharp. The depth of field varies depending on camera type, aperture and focusing distance.
The shutter-speed selector controls the length of time that the shutter remains open. The shorter that time is, the less likely a moving object will appear blurred.
Slower films are less sensitive and generally require longer exposures / more light. Faster films react rapidly, and can be used in low light situations. Film speed ratings double each time the sensitivity of the film doubles. An ISO 100 film is one stop slower than an ISO 200 film. It needs twice as much light as the ISO 200 film for correct exposure. The more sensitive the film, the more “grainy” it is.
Basic Zone (Pre-Sets) Portrait Mode – icon- a head in profile. Use this mode when you want a subject in the foreground in sharp focus. Landscape Mode - Icon = mountains. Use this mode when you want a wide-angle shot with the background in focus. Night Scene (portrait) Mode - Icon = starry field. Use this mode when you're shooting a subject at night. Illuminates the subject with the flash, while keeping the shutter open longer to provide more light for the background. Creates a balance. Black and White Mode - Icon = a figure in contrast. Use this mode to take pictures in black and white Macro (close up ) Mode - Icon = a flower. Use this mode for extreme close-ups. Blurs the background, narrow DPF. Sports Mode - Icon = a running figure. For shooting scenes with lots of motion, which you want to capture without blurring .
Pin hole camera Compound lens
The smaller the aperture, the deeper the depth of field (the other two factors remaining the same). For example, if the lens focal length and the shooting distance stay the same, the depth of field is much deeper at f/16 than at f/1.4. The shorter the lens focal length, the deeper the depth of field (the other two factors remaining the same). For example, comparing a 28mm lens with a 50mm lens at the same aperture and shooting distance, depth of field is deeper with the 28mm lens.. The greater the shooting distance, the deeper the depth of field. i.e. other two factors remaining the same). For example, if the subject is photographed from three and then from seven meters away, the zone of sharpness in the foreground and background is greater at seven meters.
The focal length of a lens determines its angle of view, and thus also how much the subject will be magnified for a given photographic position. Wide angle lenses have small focal lengths, while telephoto lenses have larger focal lengths.
While normal film cameras take 35mm film (it is a standard for the industry) there is much variety between manufacturers on image sensor sizes. The main reference point that people therefore use is the 35mm one which is considered ‘full frame’ size. If you compare the size of the film in a normal SLR (film is 35mm) to the image sensor in most DSLRs you’ll find that the size of the DSLRs sensor is generally smaller (unless you get what’s called a ‘full frame’ DSLR). Until recently ‘full frame’ cameras were largely in the realm of professional DSLRs and all lower end cameras had smaller sensors.
This is very useful for times when it's not feasable to use a tripod. For exampe, sporting events, museums or photographing moving animals like birds or fish. Those who have tried to photograph a flying bird while their camera sits on a tripod will understand the frustration. This is when you'll want to turn on vibration reduction and image stabalization, then hand hold your digital SLR camera. When to turn off VR and IS? When you are shooting with a tripod and remote release (landscapes for example), you should turn off the lens VR and IS settings to acheive sharper images. Otherwise, when your camera goes looking for a vibration and doesn't find one, it will continue to look for one, which can cause a slighly shaky result. However, make it a habit to turn it back on again when your done photographing landscapes. I've been caught many times with it turned off, when I actually needed it on.
One of the first lens purchases aspiring landscape photographers typically made is a wide or super-wide lens, anything (in full-frame 35mm terms) from 24mm on down, and with good reason, wides offer photographers the ability to capture the sweeping vistas of the natural landscape. But they can also be a challenge to use effectively, it’s all to easy to end up with a wide-angle shot that lacks the power and grandeur we felt when we were shooting.
1. Get Close! Because wide-angle lenses take in a bigger angle-of-view than other lenses, using a wide-angle lens at the same distance from your subject will render that subject smaller than it would otherwise. To compensate for this, you’ll have to move closer to your subject. Don’t be bashful about getting close, particularly with super-wides&mash;it’s almost impossible to get “too close” to your subject with a 14mm lens. This emphasis in size that wide-angle lenses give nearby objects means that … 2. It’s All about the Foreground Contrary to what you might expect, this means that the most important element of your wide-angle landscapes is the foreground. While wide-angle lenses do capture the wider landscape, they also (almost inevitably, because of their wide field-of-view) capture quite a bit of foreground as well, and this foreground is emphasized by the wide-angle perspective. As a result, if your foreground isn’t interesting, your photograph won’t be interesting. This leads us naturally to the Josef Muench idea of the near-far composition, an image which uses a wide-angle lens to not only show a broad vista, but also to show one detail of that landscape in an up-close, intimate way. When you’re photographing wide, be sure to spend some time looking for the most interesting foreground available to combine with your grand vista. (If there isn’t an interesting foreground, you might want to consider using a longer lens to leave out that less interesting foreground.) Fallen Redwoods, Stout Grove, Jedediah Smith State Park, California. Image Copyright Joe Decker 3. Watch those Verticals! Wide-angle lenses tend to bend and distort verticals, as you can see in the tree trunks near the top of Fallen Redwoods . Now, you might decide you like that effect, or that you hate it, but it’s important to be aware of it and to make a conscious decision about it. For some images it’s fun to embrace, but more often I find myself having to work to avoid it or correct it later. Avoiding it can be as simple a matter as composing so that there’s only a single obvious vertical (and that that’s vertical), alternatively, using shift movements with a tilt-shift lens can correct some of this distortion in-camera. Post-exposure, Photoshop’s “Lens Distort” filter can also save the day. 4. Leading Lines Compositionally, lines (such as streams or railway tracks) leading from the bottom corners of an image towards the center often have a particular magic for guiding the viewers eye through the picture, making for strong images, and this is particularly the case for wide-angle images. Hot Stream is a great example of this, the viewers eye tends to wander from the corner back through the image along the stream. As the stream moves back into the image, the stream gets smaller (in terms of inches on the printed page) quickly due the wide perspective. This quick fade (in width) into the distance creates a real sense of depth in the image. Hot Stream, Húsavík, Iceland. Image Copyright Joe Decker 5. Filter Woes Shooting wide creates two problems for those of us who use filters. Polarizers are a specific problem, the effect of a polarizer on a blue sky varies across the sky so greatly that wide-angle images including the sky are left horribly unnatural, so leave off the polarizer unless you know there’s no blue sky in your scene. Screw-in filters are a separate problem, it’s all too easy for the filter edges, particularly if you’re stacking more than one filter on the same lens. Filter systems, such Cokin’s P-series filters (with the wide-angle filter holder), can help you avoid these problems if you must use filters. Dwarf Arctic Birch, C. Hofmann Peninusla, Greenland. Image Copyright Joe Decker 6. Focusing One of the things I enjoy most about working with wide-angle lenses is the ease of focusing them. As you move to wider and wider focal lengths, the depth-of-field at a particular aperture gets deeper and deeper. This allows you to make great use of the concept of hyperfocal distance, that is, the nearest distance you can focus a particular lens at a particular aperture and get “good focus”. At 24mm, by focusing about six feet out from the camera you’ll capture everything from about three feet to infinity in focus—even at f/11. At 17mm, focusing at the right point at f/11 will get you everything from infinity down to 17 inches away. Find (using a web site like this or any of a number of other sites, software tools or printed tables) and write down the hyperfocal distance for a couple of your widest lenses at a couple of your favorite apertures, and you’ll have an easy way of bringing the entire scene of near-far compositions into critical focus. Using wide-angle lenses can certainly be tricky, but I love them all the same. Used well they can allow the photographer to create images that immerse us in a world with both small, intimate details and bold, dramatic vistas. Joe Decker is a professional nature photographer and writer for Photocrati’s Photography Blog He also offers nature photography workshops and coaching around the western United States.
Elements – lens have several series of lens. Each glass is an elements, each lens has several elements that are physically glued together Prime lens force you to compose better photos. You just can’t zoom in and out from the safety of your own home.
Zoom lenses can be a better option than prime lenses when photographing in sand or snow. In these conditions, changing lenses can be a real hazard for the inner workings of your camera, so working with one lens is better.
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