With advancement in technology and arrival of digital sensors came an unprecedented flexibility to the photographers to manipulate light and capture photographs which weren’t possible in film era. A modern DSLR camera provides various ways to manipulate light and capture images to tell their stories. A photographer from 1950s would have to depend on his expert judgment of ambient light, understanding of shutter-speed, aperture and film ISO. Modern Digital cameras are equipped with internal light meters and powerful computing chips that can suggest a user about ISO, shutter speed and aperture settings. With data storage getting faster and cheaper every day, one needs not to worry about 35 images only in a film and this opened a world of opportunity to experiment and easy to learn this craft.
In this section we will look at what controls your camera provides you, how these controls work and how can you use them to produce stunning images.
A modern camera has following five major elements that are responsible for a great image:
1. Lens – responsible for sharpness, accurate colors.
2. Camera sensor – responsible for recording images with color details onto a digital storage medium.
3. Camera Processor – responsible for conversion of pixel current data into colors for each pixel.
4. Camera Metering system – Measures ambient light and helps a photographer to ensure proper exposure.
5. Camera auto-focus system – This system calculates distance between the subject and the sensor and then moves the lens elements to form a sharp image at the sensor. Another system adjusts the lens elements and detects maximum contrast to find the correct focus.
When it comes to camera sensor we can agree with the age old saying, ‘Size Matters’.
You may be puzzled to see that physical size of a camera sensor is much more important than number of pixels. Which means a camera with 6MP resolution with a bigger sensor will produce better images than an 18MP camera with a smaller sensor. To understand why it is so let’s look at the digital sensor in detail.
A digital sensor is an array of photosites arranged in rows and columns on a rectangular chip. Each photosite records light corresponding to one pixel of an image. This implies a 5 MP sensor will have 5 million photo-sites!
Light is a wave made up of photons. Each photo-site collect photons that fall into it like a bucket collects water. After it collects photons it generates an electric current corresponding to quantity of photons (light) collected. Using camera algorithms this current is stored in binary format which represents a brightness value. So note here that there is a minimum light needed for a photo-site to be able to generate a signal. In the same way depending on the size of the photo-site there is also a maximum amount of light that it can collect and produce a signal. More water will just overflow from the bucket and affect neighbouring buckets.
The above method will produce greyscale images. To get colour images sensors employ Red, Green and blue filters. 1/4th sites get red filter, 1/4th get blue filter and 2/4th get green filter. Note that green filters are twice the each red or blue photosites. It is so because human eyes are more sensitive to green colour.
Each photosite has some distance between the next photosite, so there is chances of few photons falling in between these gaps. To take care of this issue sensors employ micro lenses that divert more light into the photosite and thus reduce noise and increase resolution.
Now coming back to number of pixels and sensor size, let’s consider this, if a 2x3cm chip contains 2 million pixels compared to 2x3cm chip containing 5 million pixels, what will happen to pixel size? It is obvious that the pixels shall be of smaller size in the second chip. It was understood earlier that smaller size photo-site can record lesser amount of light. Which means if one such photo-site has a capacity of 5 light units then two such photo-sites cannot resolve between 5 unit pixel and a 7 unit pixel because both pixel will record 5 units light. Google Pixel phone has a camera with 1.4 µm pixel size, Huawei P9 has 1.25 µm pixel size. Nikon D5 has a sensor pixel size of 6.45µm!
Pixel size is the primary reason why high end DSLRs have such vibrant colors and tonal gradations. It is also the reason why high end DSLRs costs so much. It is difficult to manufacture bigger sensor chips and requires great amount of research to develop sensor technology.
The sensor basically converts light data into current data which then is converted into binary data after compression, if necessary is stored onto a digital storage media. Even camera RAW is not 100% raw it also has some processing which enables us to make sense of what camera has recorded.
One thing that matters is how fast a processor can do its task. We often see different manufacturers marketing their cameras flaunting EXPREED-II, EXPEED – III, DIGIC -2, DIGIC-3, 4, 5, etc. Be it computer processors Intel chips, snapdragon processors or camera processors they all are evolving based on developments in semiconductor materials.
Faster a processor can do its task more will be Frames per second that camera can capture, more will be the resolution of the video that it can record.
Camera records light that falls on the lens after reflecting from the object that we are trying to capture in our frame. It is crucial to know how much light is falling on the lens so that settings can be manipulated accordingly to get a proper light in our pictures.
Metering simply means measuring light. Some photographers use external light meters that measure the ambient light falling on the subject. Such meters are also helpful when working with multiple light sources in studio setup. Inbuilt metering systems in the camera meters the reflected light from the subject.
Most cameras let the user to select whether light is to be measured from single central spot, center of the frame or the whole frame. More on this can be found at Use your Camera section of the website.