LESSON 2 - Camera Tutorial, Part 2
(Zooming, Focusing, Macro, Camera Body, CCD/CMOS Sensor, Megapixels and Resolution)
Article by Stephen J. Kristof
© 2010, all rights reserved
In the previous tutorial, you learned about focal length and how it affects the apparent size and closeness of an object. You also learned about the importance of wide lenses with wide apertures (holes) in order to compensate for the necessary loss of light as focal length increases. Next, you'll learn about clarity as it relates to zooming.
2.2.1 Zooming and Clarity
Limit your use of zoom to circumstances when you cannot get the lens close enough to your subject because of physical restrictions. For instance, you cannot run out onto a baseball diamond to get a close shot during a game, but you can zoom-in. Getting closer to a human subject is always a better idea than zooming-in from a distance.
Heavy use of zooming (ie. long focal length) usually increases image blur. Average DSLR lenses have a certain degree of barrel distortion, which essentially means that the image will begin to stretch at the edges. Zooming with an average priced camera or inexpensive-to-average priced DSLR lens may give your human subject the classic but unflattering "adding ten pounds" effect. Barrel distortion is less of a problem or may even be eliminated in more expensive lenses that retail out for more than $1,500, but this level of optics is out of reach for most camera users.
Using Long focal length also comes with the disadvantage of decreasing the amount of light that enters the lens, which may cause an underexposure problem. WHY does this happen? Put very simply, consider that when you reduce a scene of a certain size into a frame that is far smaller, less of the subject matter - and less of the light - gets into the camera.
Notwithstanding all of the above, remember that FACES are much more interesting than are full-body shots. As you learned in our Quick Tips #1, the best portrait advice is to, "Get closer. Then get closer. Then get closer again." At that point, you may be ready to press the shutter. Practise by shooting ‘faces’, head and shoulder ‘portraits’ and longer shots of the same person/people, rather than shooting only one and hoping it looks OK.
Having said this, try to get closer using your physical proximity rather than letting the lens do all of the work for you. As mentioned, a little zoom is OK for human subjects, but not a lot. Get closer by getting the lens closer!
Pro Secret You Need to Know:
What About Cropping? If you're thinking that you can crop on photo editing software down the road, yes, you can use Photoshop and a multitude of other software programs to zoom-in after the fact, but this also comes with a cost; the photo will not be nearly as sharp as it otherwise could have been if the subject’s face had taken up the entire frame in the first place. Put it this way; if your camera is capable to producing images of 18 megapixels, those roughly 18 million dots that comprise the image run across the entire frame.
When an image is cropped, a portion of those cutting-out dots (pixels) are eliminated. If that image was cropped in to 1/4 of the original frame in order to get a closer view of a subject's face, this also means that the resulting image will be comprised of only 1/4 of the camera's optimal pixel depth. Your are then using an 18 megapixel camera to shoot images with a mere 4.5 megapixel resolution. In short, not good practice if you want sharp images.
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2.2.2 - Auto-Focus Feature and Procedure Do you know how to focus your camera? Believe it or not, most digital camera owners have no idea that they need to follow a specific procedure in order for their "auto focus" camera to - well - focus!. All automatic focusing systems need the photographer's intervention in order to get a clear image. Below you will find the basic procedure involved with focusing. (If you want a more detailed, explanation, click HERE, as this is covered in our Quick Tip #5) HERE'S HOW TO FOCUS USING TODAY'S AUTO-FOCUS CAMS: 1. Center your subject (or subject’s face) in the middle rectangle. (See RIGHT for an illustration of how a single area, center-weighted auto focus icon appears in a digital point and shoot camera.) 2. Push the shutter button half way until the camera indicates that the subject is in focus by changing the colour of the middle 3. CONTINUE PUSHING HALF WAY as you reposition the framing and then push the shutter all the way when you are ready to snap the photo. *If you focus and then take your finger off the shutter button, the lens will lose its focus and you’ll still get blurry shots. If you are using a more expensive DSLR ("Digital Single Lens Reflex") camera, that has interchangable lenses, you should try to focus the image manually rather than automatically. Therefore, you control the focus on exactly what and where you want to focus rather than the camera doing it for you (perhaps unsuccessfully). Pro Secret You Need to Know... If you are photographing fast moving subjects, particularly when they are constantly changing their distance from you, you will likely have to use automatic focusing. A good example of this would be trying to photograph a sporting event such as a football game. There's nothing wrong with using the "Auto Focus" feature on a DSLR; in fact, these more advanced cameras (and many of the top-shelf point-and-shoot cameras) have multi-point auto focus and metering (exposure) features that do an outstanding job. (see image to the right for an illustration of a multi-point auto focus viewfinder indicator). However, all serious photographers should learn how to focus manually as it is an essential skill that will routinely come in handy; particularly when working on a tripod for long exposures, when using the self-timer or when you need to pre-focus on a fixed distance prior to capturing some action. |
 Note the blue rectangle in the middle of the frame above. This is what a single-area, center-weighted focus icon looks like. This rectangle will change color when the focus is locked.  This is a representation of a multi-point focus indicator. The black rectangles represent areas that the camera has decided should not be focal points. The blue areas have been locked for focus. |
2.2.3 - Macro Mode
You may be wondering, "How do the pro's get images like the ones below? I've tried making these super-close-up images by either getting the lens very close to the subject or by zooming in all the way... Either way, my images look blurry, too bright or too dark! What gives!!??"
The answer is - You need a macro lens or a camera with a macro setting. Macro mode is for photographing objects at close proximity to the lens. Most point-and-shoot digital cameras have a macro mode that may be adequate for basic close-up photos. However, when you look at interchangeable lenses that are available for DSLR cameras, options and flexibility expands dramatically. Expensive 'dedicated' macro lenses allow for extremely close photography with outstanding depth and clarity. Macro options for DSLR lenses also include zoom models that very often also have a macro range.
Below, you will find some examples of very small subjects captured using a macro lens. Click on any image to see a larger version in a slideshow format: (More information about using Macro Mode or Macro Lenses is found further down the page below the images.)
In general, an inexpensive camera without a macro function will have limited flexibility when it comes to photographing objects from a close proximity. These cameras generally have a minimum focus distance of about 1 or 2 feet (1/3 to 1/2 meter). Anything closer than that will look blurry without a macro function. If your camera has a macro feature, it will have a button or menu-based setting with an icon of a tulip. (see icon below)
HOW TO USE MACRO INDOORS WITH LOW LIGHT
Novice photographers who have tried using macro indoors in low light conditions share a common and frustrating experience. If using the automatic exposure mode on the camera, the flash will engage and at such close distances, you might as well be using an arc welder for light. At macro proximity, the flash will result in extreme overexposure, with your object appearing way to bright or completely white.
Pro Secrets You Need to Know:
(1) When shooting in macro, try taping a small piece of white paper over the flash. This will
will both diffuse and reduce the light. Of course, if you have a flash diffuser, try this
first.
(2) Set the camera to "No Flash" and, instead, illuminate your object with a desk lamp,
flashlight or daylight from a window. This will look better and will allow you to take
advantage of shadows and increased texture (depending on the angle of your added
light).
(3) Your background is very important in all photography, but particularly so in macro
photography! Pay attention to what lies beyond your object or to what your object is
lying on top of. Texture, patterns, shapes, colors and detail can easily take the
limelight and take over. Your best bet is to try solid white or black paper or cloth.
Alternatively, shoot outdoors with very short depth of field so that the background's
detail does not show.
2.2.4 The CCD or CMOS Image Sensor
The body of the camera is, basically, a light-tight BOX that holds the all-too-precious light-sensitive chip, the shutter, a viewfinder and other electronics. The inside of a camera is always black and matte (so it is non-reflective).
The light-sensitive "chip" is called a CMOS or CCD. These are essentially silicon semi-conductor nano-circuit chips that replace the role of film in traditional cameras and work in a non-chemical way to register images created by focused light that falls upon the face of the chip. The CMOS or CCD is responsible for the pixel depth (resolution) or number of mega-pixels a camera is capable of producing.
There is a strong parallel between this light-sensitive, image-rendering chip and the retina at the back of a human eye. The lens in our eye gathers light, focuses an image and projects it onto the retina. The retina ir rather like a network of microscopic nerves or sensors that respond to the tiny bits of light that make up the scene we are looking at. Each of these sensors will create and send an electro-chemical signal along our neural pathways to the occipital lobe of the brain. (It's actually far more complicated than that, being thatdifferent parts of the brain are involved with the overall processing.)
Suffice it to say for the purposes of understanding photography, that the neural pathways from the retina run to the lateral geniculate to visual cortex in the occipital lobe.) Once there, the brain will process, interepret colors and shading, and reassemble an image out of the multitude of individual nerve signals that it received. This is an ongoing and very complex process that suggests most of the work of "seeing" actually takes place in the brain rather than in the eyes.
A CCD or CMOS embedded into a circuit board, ready for installation into a digital camera. The rainbow-colored part will sit precisely in the focus zone of the body of the camera facing the lens.
Therefore, as noted above, the CMOS ("Complimentary Metal Oxide Silicon") or CCD ("Charge Coupled Device") shown above in a digital camera works in a very similar manner in comparison to the human retina, in very general terms. The CMOS and CCD are made of millions of microscopic dots arranged in a silicon substrate. This semi-conductor may also use other elements or chemicals such as germanium, which is sensitive to light. The overall process is such that when a microscopic portion of the chip (for instance, an area represented by only about 100 individual pixels) is exposed to light that is focused from the lens, the sensors in that particular part of the chip create tiny electric charges. Those electric impulses, along with millions of other individual electric charges, are then sent to the camera's processor, much like an eye's retina sends millions of tiny signals to the brain for processing.
Much happens in processing and that is why cameras from two different manufacturers that use the same exact chip and have the same lens properties can produce images that vary significantly in appearance and quality. What the camera's processor does with the multitude of electronic charges, with respect to detecting colors, contrast, shadows, highlights, etc., can be quite different from camera to camera.
2.2.5 "Megapixels" and Resolution
This is a lot of information to digest, but to keep it simple, remember that the CMOS or CCD is responsible for the number of megapixels. The word "megapixel" refers to the overall number of pixels that comprise an image. The more "dots" or pixels it takes to make-up an image, the more pixel depth or resolution the image will have. This means that the higher the megapixel rating, the sharper the photo will be. (Remember that the lens is the first step in creating an image that is sharp and bright; so the CMOS or CCD is only as good as the lens. If the lens is flawed, too tiny to allow adequate light or simply not clear enough, it really doesn't matter how many megapixels a camera is capable of producing.)
1 megapixel = 1 million (1,000,000) pixels (number of dots that create the image).
If you purchase a camera with a 24 megapixel rating, this means that at the highest quality setting, your camera will produce an image that is comprised of around 24 million dots. However, if the lens is incapable of producing a clear image, you will still end-up with a blurry image that is made from 24 million dots!
Pro Secret You Need to Know...
ALWAYS USE THE HIGHEST QUALITY SETTING!
Many amateur camera owners go out of their way to acquire equipment that is capable of producing the highest number of pixels. They then adjust the quality setting in the menu in order to get more images on their photo memory card. Doing so greatly reduces the pixel rating of your images and does not fully take advantage of the camera's pixel depth advantage. For instance, if your camera is rated at 21 megapixel (MP) and you choose to drop the quality from "highest" to the "lowest" setting, your pixel rating has dropped to as low as 8 MP.
CLICK HERE for Camera Tutorial, Part 3
(The Shutter and High Speed Imaging)
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