20 Sep 08 The Magic Behind Digital Camera
Author: Harry Rockwell
A digital camera, as opposed to a film or videotape camera, uses an electronic sensor to transform images (or video) into electronic data. Modern digital cameras are typically multifunctional and the same device can take photographs, video, and/or sound.
In 2005, digital cameras are starting to push traditional film cameras out of many markets. Shrinking device sizes have recently allowed miniaturized digital cameras to be included in multifunctional devices, such as cell phones and PDAs.
Classification
Digital cameras can be classified into several groups:
* Professional video cameras such as those used in television and movie production. These typically have multiple images sensors (one per color) to enhance resolution and color gamut. Professional video cameras usually do not have a built-in VCR or microphone.
* Camcorders used by amateurs. These are a combination of camera and VCR to create an all-in-one production unit. They generally include a microphone to record sound, and feature a small LCD to watch the video during filming and playback.
Still cameras
Digital still cameras are generally characterized by the use of flash memory and USB or Fire Wire for storage and transfer.
Most have a rear LCD for reviewing photographs. They are rated in mega pixels; that is, the product of their maximum resolution dimensions. The actual transfers to a host computer are commonly carried out using the USB mass storage device class (so that the camera appear as a drive) or using the Picture Transfer Protocol and its derivatives.
All use a CCD (for Charged Coupled Device) which is a chip comprised of a grid of phototransistors to sense the light intensities across the plane of focus of the camera lens.
There has recently been some application of a second kind of chip, called a CMOS (Complementary Metal-Oxide Semiconductor) sensor, and this chip is often differentiated from a CCD proper in that it uses less power and a different kind of light sensing material, however the differences are highly technical and many manufacturers still consider the CMOS chip a charged coupled device. For our purposes, a chip sensor is a CCD.
* Standard Digital Cameras: This encompasses most digital cameras. They are characterized by great ease in operation and easy focusing; this design allows for limited motion picture capability. They have an extended depth of field.
This allows objects at multiple depths to be in focus simultaneously, which accounts for much of their ease of focusing. It is also part of the reason professional photographers find their images flat or artificial-looking. They excel in landscape photography and casual use.
* Digital SLRs typically have a sensor nine times larger than that of a standard digital camera, and are targeted at professional photographers and enthusiasts. They resemble ordinary professional cameras in most ways, with replaceable flash and lens components, which give the user maximum control over light, focus and depth of field.
They are also bulkier and more expensive than their casual-use oriented counterparts. They are superb for portraiture and artistic photography because they can be customized for various applications with a comprehensive range of exchangeable lenses.
Professional modular digital camera systems
High-end digital camera backs used by professionals are usually separate devices from the camera bodies which they are used with. (This is because most of the large- and medium-format camera systems in professional use at the time that digital capture overtook film as the professional’s medium of choice were modular in nature, i.e. the camera body had multiple lenses, viewfinders, winders and backs available for use with it to fit different needs.)
Since the first backs were introduced there have been three main methods of “capturing” the image, each based on the hardware configuration of the particular back.
The first method is often called “Single Shot,” in reference to the number of times the camera’s sensor is exposed to the light passing through the camera lens.
Single Shot capture systems use either one CCD with a Bayer filter stamped onto it or three separate CCDs (one each for the primary additive colors Red, Green and Blue) which are exposed to the same image via a beam splitter.
The second method is referred to as “Multi-Shot” because the sensor is exposed to the image in a sequence of three or more openings of the lens aperture. There are several methods of application of the multi-shot technique.
The most common originally was to use a single CCD with three filters (once again red, green and blue) passed in front of the sensor in sequence to obtain the additive color information.
Another multiple shot method utilized a single CCD with a Bayer filter but actually moved the physical location of the sensor chip on the focus plane of the lens to “stitch” together a higher resolution image than the CCD would allow otherwise. A third version combined the two methods without stamping a Bayer filter onto the chip.
The third method is called “Scan” because the sensor moves across the focus plane much like the sensor of a desktop scanner.
These CCDs are usually referred to as “sticks” rather than “chips” because they utilize only a single row of pixels (more properly “photosites”) which are again “stamped” with the Bayer filter.
The choice of method for a given capture is of course determined largely by the subject matter. It is usually inappropriate to attempt to capture a subject which moves (like people or objects in motion) with anything but a single shot system.
However, the higher color fidelity and larger file sizes and resolutions available with multi-shot and scan-backs make them attractive for commercial photographers working with stationary subjects and large-format photographs.
Webcams
* Webcams are digital cameras attached to computers, used for video conferencing or other purposes. Webcams can capture full-motion video as well, and some models include microphones or zoom ability.
These devices range in price from very inexpensive to expensive higher-end models; many complex webcams have a servo-controlled base capable of tracking facial motion with the help of software.
Interpolation
Image color or resolution interpolation is used unless the camera uses a beam splitter single-shot approach, three-filter multi-shot approach, or Foveon X3 sensor.
The software specific to the camera interprets the information from the sensor to obtain a full color image. This is because in digital images, each pixel must have three values for luminous intensity, one each for the red, green, and blue channels. A normal sensor element cannot simultaneously record these three values.
The Bayer filter pattern is typically used. A Bayer filter pattern is a 2×2 pattern of light filters, with green ones at opposite corners and red and blue elsewhere.
The high proportion of green takes advantage of properties of the human visual system, which is determines brightness mostly from green and is far more sensitive to brightness than to hue or saturation.
Sometimes a 4-color filter pattern is used, often involving 2 different hues of green. This provides a wider color gamut, but requires a slightly more complicated interpolation process.
The luminous intensity color values not captured for each pixel can be interpolated (or guessed at) from the values of adjacent pixels which represent the color being calculated.
In some cases, extra resolution is interpolated into the image by shifting photosites off of a standard grid pattern so that photosites are adjacent to each other at 45 degree angles, and all three values are interpolated for “virtual” photosites which fall into the spaces at 90 degree angles from the actual photosites.
Connectivity
Many digital cameras can connect directly to a computer to transfer data. USB is the most widely used method, though some have a Fire wire port.
Integration
Some devices, like mobile phones integrates digital cameras. Mobile phone cameras are much more sold than standalone digital ones.
Digital cameras need memory to store data. The higher one goes in pixel size, the more memory will be needed. Cameras use a removable memory card to store data, but the cheapest and smallest cameras may simply use fixed internal memory instead. Some cameras come with inbuilt memory as well.
Autonomous devices
An autonomous device, such as a PictBridge printer, operates without need of a computer. The camera connects to the printer, which then downloads and prints its images. Some DVD recorders and television sets can read memory cards too.
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18 Sep 08 Top 20 Questions to Consider When Buying a Digital Camera
Author: aldrin garcia
My top 20 key questions to ask yourself when buying a digital camera.
1. How many “megapixels” /resolution?
Once and for all, at least to me, you have to get the highest resolution your money can buy at the time you buy. Period.
2. Who made the lens?
Most cameras will give you an idea where the lens was made just by looking at the front of the lens. Know if the lens of your camera came from a reputable company like Leica, Zeiss, Canon, Etc… Lens quality is one of the most important factors you should consider especially if you’re going to use it for commercial, technical or scientific purposes.
3. Will I need interchangeable lenses? How many are available for my specific camera in mind?
Having the option of interchangeable lenses gives you the freedom to experiment with different kinds of focal lengths. Although some P&S (point and shoot) cameras can rival DSLR’s with a generous zoom range for a non interchangeable lens system.
Also note the number of lenses available for use with your specific camera because of flexibility reasons. You can practically cover the entire “zoom range” with interchangeable lenses versus modest zoom ranges on non interchangeable lens systems or P&S cameras.
4. Does it have a zoom capability? What’s the range?
Almost all applications that I listed above will need some form of zooming in (telephoto) or out (wide angle), especially if you don’t have the space to move around the object you are shooting.
For Landscape shots, wide angle shots are very common and appealing while zooming in on the details serves as a break and complements the wide angle shots.
For weddings and events, you need a zoom because there will be times where you are limited by the shooting space and you will have a difficult time moving around. Its a good thing to know that you can do all sorts of framing without even moving from your position.
A nice zoom will give you the efficiency and versatility in your photography, so my suggestion is to go for the longest range you can get (usually from a 7X to a 10X for Point and Shoots).
Also note the speed of zooming in or out as this will be a factor if you’re shooting events like weddings. You will fail to capture that “decisive moment” on a mediocre zoom speed.
5. Does it have the provision to capture raw images?
Many photographers will say you’ll need this digital camera feature if you want to have big prints from your pictures. Although this is correct, the main reason why you will want this is because of the benefit it will give you…pure total control of your pictures… from exposure, color, metadata, hdr and a lot more.
6. Can I attach an external flash?
Having an external flash capability will give you the power and creative freedom to light your subjects any which way you like.
You can connect your digital camera to all sorts of lighting equipment thus giving you more options and versatility. This comes in the form of a hotshoe or a PC-Sync socket.
If your digital camera doesn’t have this feature, there is still hope because accessories called flash slaves are being sold by third party companies in different flavors that will also do the same job more or less.
7. Does it have a tripod socket?
Some of the most beautiful landscape pictures that I’ve seen are undoubtedly made with a tripod, so this is a must have if you are planning to do this kind of photography.
The “available light shots” in a wedding, still life and product shots, studio and fine art shots … all need a tripod for successful execution… so guess what happens if you don’t have a tripod socket?… You cannot effectively use a tripod!
8. Does it have automatic and manual focusing?
It will not be evident at first why you’ll need this especially if you’re just starting out in photography. But if you’re like me… A total control freak when it comes to cameras… and you really want to express your creative side, this is definitely a must have.
9. Can you attach filters to it? and what filter size?
Creative expression through special effects is just one of the many reasons that makes photography fun and interesting, and experimenting with filters is one creative pursuit you should try with your photography especially if you’re a beginner.
Always remember to ask if the particular digital camera you are eyeing for can handle filters and ask for the filter size. (To save you from buying the right filter with the wrong filter size) Please note that most Digital SLRs should be able to to handle filters as most lenses that come with it have a filter thread built into the lens.
Most P&S (point and shoot) digital cameras normally doesn’t have a filter thread built-in and might need special accessories to accomplish this so you should check to know for sure.
Again, there are many third party accessories that you could buy to adapt filters to your P&S digital cameras that don’t have this provisions. I’ll discuss all about this in a future post so watch for it. (Or subscribe to my announcement list (feed via email) so you’ll know when it’s up.
10. Can I upgrade the firmware?
The good thing about some digital camera manufacturers is that they keep on improving their digital cameras even after they sold it to you… this comes in the form of a firmware upgrade.
Usually this involves an improvement on one or many features of a camera. Be sure that the digital camera you’re planning to buy has an easy way of upgrading its firmware. This comes in the form of either an easy download via the manufacturer’s website (find it and bookmark it now) or a FREE CDROM.
Another caveat - be sure to consider if a downgrade is also possible or available with your digital camera… Why is there a need a downgrade you ask?… Because, you may want to reinstall an earlier firmware… just in case you don’t like the results from a firmware upgrade.
Occasionally there’s a feature that will be removed by the upgrade that you failed to read about and you decided that you just want to keep that feature instead of a bunch of trivial upgrades from the new firmware. (Yes, I personally experienced this.)
11. Are there extra goodies or software that come with it?
Some people ignore the fact that you can save a lot of money just by doing a simple arithmetic. Did you know that you could actually get your digital camera for a lot less if you study the deals and offers on the marketplace?
If you buy a digital camera and it comes with software that you can really use… like photoshop, elements, or any other image editing software for that matter, then you already saved some money you would otherwise spend. Some dealers will throw in lots of extras… If you just simply ask.
Always try to ask for these things that you’ll end up buying anyway if you don’t - like camera bags, extra lenses, extra batteries, memory cards, tripod, lens cleaners etc. Trust me… you will end up buying these things if you don’t ask for it on the deal. What have you got to lose? Simply ASK. Would you believe that I effectively lowered one of my camera purchase cost by as much as 30%? Ask away.
12. Is there Local Support in your area?
Finding the answer to this one will give you a great benefit in the long run. Wouldn’t you sleep better at night because you feel that extra security - that in case there is something wrong with your digital camera, you can bring it in for repair at a moments notice?
Not knowing when your camera will be repaired (or if it even arrived at a distant repair facility) is one of the worst feelings a photographer can have especially if you’re in the middle of a photoshoot or project.
13. What type of warranty does it have? Worldwide / Countrywide?
If you travel a lot its good to know that a countrywide or even better - a worldwide warranty can get your camera fixed wherever you are. Always bring the warranty card and glue it on your camera bag.
14. Does it have the ability to take video and audio?
I know, most DSLRs don’t have this function. But some non interchangeable lens DSLRs have it. This is a very useful feature to have if you’re on a project or photoshoot and want to document or record a procedure, a moment, or an idea that you would otherwise have trouble remembering or even writing. It’s always a good idea to bring a P&S camera backup that have this function.
The things that you could do with audio and videoclips on a photoshoot are only limited by your imagination… interviews, documentation, funny quips, training procedures, bloopers, etc..
15. Does it have a manual white balance?
White balance is one of the most interesting aspects of digital cameras. Its fun and fascinating to work with. Having this option puts the photography fun-o-meter way way up. In future posts, I will be discussing white balance in detail so be sure to stay tuned.
16. How sensitive is it to infrared?
If you’re planning to make infrared pictures or enter the exciting world of Infrared fine art photography then you’ll want to know if your digital camera can do it.
TIP: There is a simple way to test how sensitive your digital camera is to infrared using a very common device - a TV remote control. For P&S, you can aim the remote control towards the lens and gauge how bright the LED from remote is. This should give you an idea how sensitive your digital camera is to infrared. For DSLRs you will need to take shots of the LED and experiment a little or you can simply research or google the particular camera model you have in mind for other people’s experiences and thoughts about it.
17. How high is the ISO sensitivity? Is it manually adjustable?
ISO sensitivity is a term referring to the sensitivity of film to light. In the digital camera world, it refers to the sensitivity of the electronic sensor in your digital camera in relation to the ISO standard used for film.
The higher the ISO sensitivity of your camera the faster or better it can record a specific amount of light.
High ISO sensitivity is useful for taking better pictures in dark settings… such as inside a church or at night. The higher the ISO setting, the more details you can capture of a dark scene.
One caveat - take note of the amount of noise a particular camera exhibits at higher ISOs. Some people like it and some don’t. Again, don’t be afraid to ask or do research on the noise characteristics of your camera model in mind to see if this is the right choice for you.
18. How high or low can you set the shutterspeed? What are the minimum and maximum aperture settings?
Shutterspeed and aperture settings are the basic mechanisms that drive your camera and controls the amount of light that is exposed by the film or image sensor.
You use high shutterspeeds in action shots and to prevent camera shake, and you use low shutterspeeds for movement effects and bulb or long exposures. You can check for these figures on the websites that I gave you in part 1. You can see it in the technical specifications for a particular camera.
A bulb or “T” function is a nice feature to have because you can take exposures for virtually very long periods of time. Another feature to have is if your camera has a remote control to use this bulb or “T” mode. This gives you the capability to take pictures without holding your camera and adding to the “camera shake”.
With the subject of apertures, a small one (small aperture opening) lets you have a wider depth of field so your shots are sharp from near to far versus a large aperture (big aperture opening) where your shots have a narrow depth of field and appear “selectively focused”.
19. Does it have some form of an image stabilizer?
New cameras coming out as we speak often have this feature. Simply put, an image stabilizer is some form of a mechanism built into the lens or the camera body (depending on the manufacturer and their implementation) that basically prevents you from getting blurred pictures when taking pictures in low light or you are using a long or telephoto lens. Having this feature can mean the difference between a blurry picture (aka no picture!) to a usable one.
20. How close can it focus? Macro abilities?
The closer your camera can focus… the bigger the picture of an object you can take in relation to the image dimensions of the final photo… and the bigger the picture of the object… the more detail you can get. If you want to take pictures of small objects such as flowers and fine details then this is a must-have.
That’s it. Whew.
Do you really have to go over all these questions?… Of course not, but even if you only study and ponder on half of them…and take the time… I promise you that one thing will surely happen…
You’ll be…
a lot smarter!
than when you first started asking these questions… ergo you’ll be in a better position to decide what digital camera to buy… Because you are now armed with the most powerful tool anybody can have
the power of information!
In any case, I hope you find as much value in these questions as many of my friends have and be able to get the camera of your dreams.
Enjoy!
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