Using Your Dslr Camera Beyond the P Mode
First of all, what is the P mode? Your camera is blind to the world and has to make a lot of assumptions about it including how much light is out there, where to focus, how fast your field is absorbing and the ideal depth of field (or how much in front and behind your field should be in focus e.g. 2 metres in front and behind the field or. As much as possible). Switching your camera to P mode means the camera has to make the best 'guestimate' it can for all these unknowns.
Why does the amount of light matter to your camera? Think of your own eyelids and how each of your eyes has an iris. When it's a very sunny day you tend to squint and your irises strengthen to safe your retinas. Conversely, in a gloomy room, you open your eyelids as wide as potential and your irises contract.
Your eyes irises and eyelids vary the amount of light because your retinas like a safe bet amount of light to register facts - too microscopic light and your eyes only see microscopic information, too much light and your retinas are overloaded and you see nothing. Your camera's sensor is the monocular equivalent of your retinas - the place where facts about light is registered, and just like your retinas, the Dslr's sensor likes an ideal quantity of light. Unlike your eyes, your camera has no eyelid or iris to regulate the quantity of light. Instead the camera controls light by varying the shutter speed and aperture.
Two new terms, shutter speed and aperture, deserve an explanation. Think of a shutter as a primitive eyelid for your camera, primitive in that the shutter is whether open or done and cannot be anything in-between. When you take a photo, the shutter temporarily retracts so light can come straight through the lens and register on your camera's sensor. The longer the shutter retracts, the more light hits the sensor. In a absorbing room, you only want the shutter to retract for a short time or the sensor will be overloaded. In a dark room, you want the shutter to retract for much longer to give your camera's sensor sufficient time to register the far dimmer light. The typical shutter speed is 1/125th sec which means the shutter temporarily retracts for a tiny fraction of a second but most Dslrs' shutter speed ranges from 30 seconds to 1/4000th of a second. A later narrative in this series will later account for why you would want to vary shutter speed.
Now you know what a shutter does, where does gap ,break fit in? The gap ,break is the iris of your camera. It is physically part of your camera's lens, it is ordinarily octagonal and it restricts light by increasing and contracting.
Unlike an iris, an gap ,break has a ratings law e.g. F5.6, f8, f11. What does this mean? The 'f stop' rating plainly explains how much light is let in by the gap ,break using a scale where f2 lets twice as much light as f4 as f5.6 lets twice as much light as f8 which lets in twice as much light as f11.... This is a confusing scale - just remember, the smaller the gap ,break (e.g. F4 instead of f 11), the more light is let in.
In summary, a Dslr controls how much light registers on the camera's sensor by varying the size of the gap ,break and by varying the time the shutter retracts. It stands to infer that different combinations of shutter speed and gap ,break will corollary in the same amount of light reaching the sensor.
For example, if your sensor needs a shutter speed of 2 seconds and an gap ,break of f8, if you duplicate the shutter speed to 4 seconds (which will let twice as much light in), then you need to change the gap ,break from f8 to f11 in order to halve the amount of light let in by the shutter.
Before you worry about what composition of shutter and gap ,break to use, you need to work out how much light is required by your Dslr's sensor. Cameras have built in light meters to quantum the prevailing light condition but they have to make an assumption about how much light is being reflected from the objects you want to photograph. Why? The camera's light meter measures light that is being reflected from your option of field and the normal environment nearby your subject. However, the camera's light meter cannot know the reflectivity of your field matter so it has to assume that overall, your field reflects as much light as a light grey (known as "18% gray") piece of paper and this assumption works for the majority of subjects.
To understand why this assumption isn't always appropriate, imagine three tennis balls, one is white, one is grey and one is black.
Let's assume the white ball is three times as absorbing as the black ball. In other words, the white tennis ball reflects three times as much light as the black ball. Now let's imagine what your Dslr assumes when you aim your camera at the white tennis ball. Does your camera assume it is a black tennis ball in a very absorbing room, a white tennis ball in a very dark room or a light grey tennis ball in median lighting.? Faced with these three options, your camera assumes the tennis ball is light grey, whether it is in fact white, black or grey.
In order to make a white tennis ball a grey tennis ball photo, your camera will underexpose the photo i.e. It will speed up the shutter speed from say 2 seconds, to 1 second so that the sensor is only exposed for half the time it should be.
In order to make a black tennis ball a grey tennis ball photo, your camera will overexpose the photo i.e. It will slow down the shutter speed from say 2 seconds, to 4 seconds so that the sensor is exposed for twice the time it should be.
If this is all a bit too theoretical, think about photos you have taken that were incorrectly exposed. A first-rate example is snow - instead of pristine white landscapes, your pictures have dull 'sooty' snow because your camera didn't know that the scene's full, reflectivity wasn't light grey but much brighter so it exposed the focus to make your snow light grey!
Tags : DSLR Camera
Nikon D90 12.3MP DX-Format CMOS Digital SLR Camera with 18-105mm f/3.5-5.6G ED AF-S VR DX Nikkor Zoom Lens
Fusing 12.3-megapixel image quality inherited from the award-winning D300 with groundbreaking features, the D90's breathtaking, low-noise image quality is further advanced with EXPEED image processing. Split-second shutter response and continuous shooting at up to 4.5 frames-per-second provide the power to capture fast action and precise moments perfectly, while Nikon's exclusive Scene Recognition System contributes to faster 11-area autofocus performance, finer white balance detection and more. The D90 delivers the control passionate photographers demand, utilizing comprehensive exposure functions and the intelligence of 3D Color Matrix Metering II. Stunning results come to life on a 3-inch 920,000-dot color LCD monitor, providing accurate image review, Live View composition and brilliant playback of the D90's cinematic-quality 24-fps HD D-Movie mode.Made in Thailand.
## View More Images ##
Product Brand :Nikon
Product Rating :
Price : Too Low to Display! Check Price Now!!
Let's have a look at our Nikon D90 12.3MP DX-Format CMOS Digital SLR Camera with 18-105mm f/3.5-5.6G ED AF-S VR DX Nikkor Zoom Lens Features
- 12.3-megapixel DX-format CMOS imaging sensor
- 5.8x AF-S DX Nikkor 18-105mm f/3.5-5.6G ED VR lens included
- D-Movie Mode; Cinematic 24fps HD with sound
- 3-inch super-density 920,000-dot color LCD monitor
- Capture images to SD/SDHC memory cards (not included)
Compare Nikon D90 12.3MP DX-Format CMOS Digital SLR Camera with 18-105mm f/3.5-5.6G ED AF-S VR DX Nikkor Zoom Lens Price
|
Related Products
### Product Information and Prices Stored : Feb 18, 2011 14:39:07 ###
If this Information is Not Updated, Please Check!!!
See Also : Nikon Coolpix Wildgame Innovations Game Camera Buy Nintendo 3DS Games
Tidak ada komentar:
Posting Komentar