简单分享DSLR相机

简单分享DSLR相机。。。

其实在相机里要拍一张照片，它有分几个部分Aperture，Sutter，and ISO。这是最重要的部分~接下来就要看你的技术了~

好想捕抓所有美好回忆的成长过程~

Aperture 是 光圈，在canon相机里的function “AV”Aperture Value。就是 当它的f value 越少， 它的光圈就越大，当光圈越大就吸收光度很快，当一有充足的光度Sutter speed就越快，当Sutter 快时，有速度的motion就它的效果就会拍的很准，精致，漂亮。它的Focus point一focus后，它的背景会是模糊，这是我最喜欢玩的比如这张照片是最好的例子~
这架相机我用的是canon EOS 450D它的镜头很特别，专门拍效果~

Sutter speed 是 快门~是可以setting 要拍摄的速度，如果把它的value放到最快1/4000秒， 比如拍一个在移动的动作，它的动作将会捕抓的很准~不过这当时aperture 也会放得很低~因为它要吸收很多光。

Learn :Aperture

Aperture refers to the size of the opening in the lens that determines the amount of light falling onto the film or sensor. The size of the opening is controlled by an adjustable diaphragm of overlapping blades similar to the pupils of our eyes. Aperture affects exposure and depth of field.
Just like successive shutterspeeds, successive apertures halve the amount of incoming light. To achieve this, the diaphragm reduces the aperture diameter by a factor 1.4 (square root of 2) so that the aperture surface is halved each successive step as shown on this diagram.

Because of basic optical principles, the absolute aperture sizes and diameters depend on the focal length. For instance, a 25mm aperture diameter on a 100mm lens has the same effect as a 50mm aperture diameter on a 200mm lens. If you divide the aperture diameter by the focal length, you will arrive at 1/4 in both cases, independent of the focal length. Expressing apertures as fractions of the focal length is more practical for photographers than using absolute aperture sizes. These "relative apertures" are called f-numbers or f-stops. On the lens barrel, the above 1/4 is written as f/4 or F4 or 1:4.

We just learned that the next aperture will have a diameter which is 1.4 times smaller, so the f-stop after f/4 will be f/4 x 1/1.4 or f/5.6. "Stopping down" the lens from f/4 to f/5.6 will halve the amount of incoming light, regardless of the focal length. You now understand the meaning of the f/numbers found on lenses:
Because f-numbers are fractions of the focal length, "higher" f-numbers represent smaller apertures.
Maximum Aperture or Lens Speed
The "maximum aperture" of a lens is also called its "lens speed". Aperture and shutterspeed are interrelated via exposure. A lens with a large maximum aperture (e.g. f/2) is called a "fast" lens because the large aperture allows you to use high (fast) shutterspeeds and still receive sufficient exposure. Such lenses are ideal to shoot moving subjects in low light conditions.

Shutterspeed

The shutterspeed determines how long the film or sensor is exposed to light. Normally this is achieved by a mechanical shutter between the lens and the film or sensor which opens and closes for a time period determined by the shutterspeed. For instance, a shutter speed of 1/125s will expose the sensor for 1/125th of a second. Electronic shutters act in a similar way by switching on the light sensitive photodiodes of the sensor for as long as is required by the shutterspeed. Some digital cameras feature both electronic and mechanical shutters. Shutterspeeds are expressed in fractions of seconds, typically as (approximate) multiples of 1/2, so that each higher shutterspeed halves the exposure by halving the exposure time: 1/2s, 1/4s, 1/8s, 1/15s, 1/30s, 1/60s, 1/125s, 1/250s, 1/500s, 1/1000s, 1/2000s, 1/4000s, 1/8000s, etc. Long exposure shutterspeeds are expressed in seconds, e.g. 8s, 4s, 2s, 1s.The optimal shutterspeed depends on the situation. A useful rule of thumb is to shoot with a shutterspeed above 1/(focal length) to avoid blurring due to camera shake. Below that speed a tripod or image stabilization is needed. If you want to "freeze" action, e.g. in sports photography, you will typically need shutterspeeds of 1/250s or more. But not all action shots need high shutterspeeds. For instance, keeping a moving car in the center of the viewfinder by panning your camera at the same speed of the car allows for lower shutterspeeds and has the benefit of creating a background with a motion blur.

This image was shot at 1/500s, freezing the splashing of the waves.
Motion blur created by tracking the car with the camera and shooting at 1/125s. The motion blur and speed effects were further enhanced using techniques described in my interactive e-book.

Prosumer and professional cameras provide shutter priority exposure mode, allowing you to vary the shutterspeed while keeping exposure constant.
Zoom lenses specify the maximum aperture at both the wide angle and tele ends, e.g. 28-100mm f/3.5-5.6. A specification like 28-100mm f/2.8 implies that the maximum aperture is f/2.8 throughout the zoom range. Such zoom lenses are more expensive and heavy.

Sensitivity (ISO)

Conventional film comes in different sensitivities (ASAs) for different purposes. The lower the sensitivity, the finer the grain, but more light is needed. This is excellent for outdoor photography, but for low-light conditions or action photography (where fast shutterspeeds are needed), more sensitive or "fast" film is used which is more "grainy".Likewise, digital cameras have an ISO rating indicating their level of sensitivity to light. ISO 100 is the "normal" setting for most cameras, although some go as low as ISO 50. The sensitivities can be increased to 200, 400, 800, or even 3,200 on high-end digital SLRs. When increasing the sensitivity, the output of the sensor is amplified, so less light is needed. Unfortunately that also amplifies the undesired noise. Incidentally, this creates more grainy pictures, just like in conventional photography, but because of different reasons. It is similar to turning up the volume of a radio with poor reception. Doing so will not only amplify the (desired) music but also the (undesired) hiss and crackle or "noise". Improvements in sensor technology are steadily reducing the noise levels at higher ISOs, especially on higher-end cameras. And unlike conventional film cameras which require a change of film roll or the use of multiple bodies, digital cameras allow you to instantly and conveniently change the sensitivity depending on the circumstances.

ISO 100
ISO 800
ISO 100 - Red Channel
ISO 800 - Red Channel

The above unmagnified crops of prosumer digital camera images show high levels of color noise at higher sensitivities. Noise is usually most visible in the red and blue channels.