Thursday, 17 January 2008

Reason to visit Cambridge

Now there is a reason to visit Cambridge. If you can resist on how lovely this old city looks, then you must be abnormal. All of this pictures here are indeed taken in Cambridge (I've been passing thru most of them when I had my driving lesson). So, book a date and start planning NOW!

All images are taken by Sean T McHugh, you can find his website here.








1. DYNAMIC RANGE

These picture are produced by combining 3 image exposure.
In photography, exposure range is one of several types of dynamic range:
The Light sensitivity range of photographic film, paper, or digital camera sensors.
The luminosity range of a scene being photographed.
The opacity range of developed film images
The reflectance range of images on photographic papers.
A graduated neutral density filter can be used to control exposure range.
The exposure range of a device is usually expressed in stops, which are equivalent to log2(c) where c is the medium or device's contrast ratio. For example, average Digital Video (DV) has a contrast ratio of 45:1, so its exposure range is roughly 5.5 stops. Film has an exposure range of 11 stops, currently the highest in motion picture mediums.

As we look around a scene, the irises within our eyes can adjust to changing conditions as we focus on regions of varying brightness—both extending dynamic range where we can discern detail, and improving the local contrast. This is apparent when we stand near a window in a dark room on a sunny day and see not only detail which is indoors and around the window (such as the frame or the pattern on the curtains), but also that which is outside and under the intense lighting (such as the blades in the grass in the yard or the clouds in the sky).
Cameras, on the other hand, cannot always capture such scenes where the brightness varies drastically—at least not with the same contrast as we see it. Traditional landscape photography has practiced a technique to overcome this limitation by using a filter which lets in more light in the darker regions, and less light in the brighter regions, resulting in an evenly exposed image throughout.



2. FIELD OF VIEW

By looking around a scene, we are able to encompass a broader field of view than may be possible with a given lens. To mimic this behaviour, and to enhance image detail, I often point the camera at several different angles to expose adjacent scenes. These are then combined digitally in a way that accounts for lens distortion and perspective—producing a single, seamless image. This is often referred to as photo stitching or a digital panorama.
In the example below, I used a lens with a relatively narrow field of view (just 17° horizontally, or 80mm on a 35mm camera) to create a final image that contains both more detail and a wider field of view than would be possible with a single exposure. As you can see by comparing the upper and lower images, creating a single image from a mosaic of images is more complicated than just aligning the images at the right places; this process has to take into account perspective. Note how the rooftop appears curved in the upper image, whereas in the final print the rooftop is straight.




3. DEPTH OF FIELD

Our eyes can choose to have any particular object in perfect focus, whereas a lens has to choose a specific focal point and what photographers call a “depth of field,” or the range of distance to each side of the focusing plane which still appears to be in sharp focus. This difference presents the photographer with an important interpretive choice: does one wish to portray the scene in a way that draws attention to one aspect by making only the aspect in focus (such as would occur during a fleeting glance), or does one instead wish to portray all elements in the scene as in focus (such as would occur by taking a sweeping look throughout). Until recently, traditional night photography was especially restricted with this choice, because there is always a trade-off between the length of the exposure, the depth of field, and the noise levels (or film grain) for a given photo. Where artistic flexibility is required, I often use a technique which utilises multiple exposures to create a single photo that is composed of several focal points; similar to how our eyes may glance both near and distant in a far-reaching scene.



For tutorial you can view it here. And hopefully, by the time you visiting Cambridge, you are able to take a photograph like this!!!

Warning : I strongly suggest you to bring your tripod because most of this are taken with more than a minute exposure (except you can hold still that long!)

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