What if cavemen had not chronicled their journey by painting pictures of their prey or carving things into stone? Would we have understood their general way of life just by inspecting the bones we found years later? Chronicling lives, journeys, and experiences is a precious tradition of human beings, both for the richness of information it provides and its ability to help us relive memories. The invention of cameras made documenting events even more effortless and today’s technological inventions have made cameras even more accurate and aesthetically valuable.
The advent of Single Lens Reflex cameras (SLR) gave the realm of photography the precision it yearned for, and Digital Single Lens Reflex cameras (DSLR) brought that technology and precision to all novice photography enthusiasts. The question is, what was so amazing about SLRs and DSLRs that earlier cameras lacked?
Getting an Image
Any camera, from the most basic to the extreme high-end, uses the same basic principle – it captures light bouncing off subjects to create an image. There are three critical components to any camera; its lens, shutter, and film or image sensor. Much like the human eye, cameras also have an adjustable lens that helps to converge light at the point where either the camera film or image sensors reside. This focal place for them is usually behind the shutter. When the shutter opens, the camera film or image sensors are exposed to the incoming photons from the lens to form an image. The exact mechanism of how they are converted into an image that we see will be discussed a bit later.
Inside an SLR
The most basic and irreplaceable step before taking a picture of anything is to look at it through the viewfinder. In older cameras, the light striking the viewfinder, which gave you a preview of how your picture would look) and the actual light entering the lens of the camera were at slightly different angles. This meant that you thought you were clicking a very good frame, but sometimes due to the slight angular difference, the actual picture turned out to be slightly different. For hobby photographers, this did not matter much, but for professional photographers, it was a huge deal. The SLR took care of this major flaw.
In an SLR, a slanted mirror called a reflex mirror sits in front of the closed shutter with a translucent glass and prism positioned above it. The mirror redirects the incoming light from the lens onto the translucent glass, which serves as a projection screen. The prism’s job is to flip the image right side up so that it can be correctly viewed from the viewfinder. When the button is pressed to take an image, the mirror folds up and the shutter opens up, which frees the path of light striking the image film residing behind the shutter.
The superiority of DSLR
A DSLR camera has a very similar mechanism to SLR cameras, but there are some key differences in the hardware and storing of image data. In terms of hardware, the light from the mirror is focused vertically onto a pentaprism, which converts the vertical light to horizontal light by passing it between two separate mirrors directly onto the viewfinder. Also, in a DSLR camera, there is an image sensor behind the shutter, instead of traditional film, which records and sends the data to a memory card for storage. The digital aspect saves time and effort, since the end product is ready and able to be viewed immediately. However, the question arises of how image sensors that only record the light can convert it into a finished image of a scene?
Converting Light into a Digital File
Whenever we think about buying a digital camera, the first thing we look at is the megapixel value of the camera, typically following the principle that more is better. However, do we actually know what that value means? Let’s take a closer look at that cryptic number and where it actually comes from.
A megapixel is simply one million pixels, and the number of pixels on the image sensor of a camera determines its megapixel value. The sensor is made up of many tiny pixels called photosites. The sensor is not actually flat, but contains very tiny wells that trap light particles (photons) and allow them to be measured. The photosites generate an electrical signal depending on the intensity or luminance of the light trapped fwithin each site. Hence, a sensor alone can only record the light and dark areas of an image. In order to obtain color data, each photosite employs a filter that is either red, green or blue. If a photosite had a green filter, for example, then it would only record green color data from the portion of that image.
Well, in that case, wouldn’t we get an end product (image) that looks more like tiny patches of red, green and blue? How do we end up with such life-like images? Well, those pixels with a filter of a single color also take information about other colors from the neighboring pixels. In a complex process called ‘demosaicing’, the interpolation process makes an informed guess about the color of each pixel that makes up the whole image.
The storing of this data then happens by converting these measurements into bits of data that can be stored on the memory card. A single pixel can register up to 8 bits of data. Voila! The end product we have is a JPEG image stored on your memory card that can be instantly viewed, transferred to another device, manipulated using software and shared with all your friends on social media!
Except for the initial investment in a DSLR, the rest of your photo-documenting journey is relatively hassle-free, while still giving you professional-quality images. Now, get out there and unleash your inner shutterbug!