Saturday, February 19, 2011

Sony Cybershot DSC-HX100V

About 20 years ago, digital cameras were something that belonged mostly in satellites. Now everyone has at least one. From tiny mobile phone cameras to wallet-busting professional d-SLRs (see our article on available d-SLRs in India), they come in a large number of shapes, sizes and price points. Today we’re going to talk about the basics of digital cameras. While most of the concepts we will be discussing applies to all types of digital cameras, this article is focused mainly at entry level point-and-shoot digital cameras. So without further ado, click that roundish-rectangular button to Read More of our digital photography primer.

The Basics

First let’s have a quick look at how camera work. In simple words, a digital camera is a box with a pinhole on one side and a light sensitive sensor on the other. Depending on the camera, the size of this box will vary. There may be different types of lenses near the pinhole to ensure that the light falls on the sensor as desired. The sensor itself can come in a variety of sizes and specifications. Some cameras can also adjust the size of the pinhole (aperture). For a still-camera (not a video camera), you don’t want a continuous stream of light coming through the hole. So there will be a little door or shutter that opens briefly, just enough to capture the moment.

Illustration - Camera capturing an image

Mega-pixels

When describing a camera, whether to a friend, or even while buying one, the most common and perhaps the only detail we tend to talk about is mega-pixels. The number of mega-pixels (MP) of a camera has to do with the image sensor and the maximum resolution of the image that the camera can capture. A digital camera’s image sensor is basically an array of many many tiny light-sensitive sensors, each corresponding to one pixel. So an 8MP camera has an array of approximately 8,000,000 tiny pixel sensors. In most cameras, this produces a 3264 x 2448 resolution image. So in simple terms, the higher your camera’s mega-pixel value, the larger your image dimensions (resolution) will be.

So how big is big enough? Is the mega-pixel count the most important thing to look for in a camera? Simply put, no! Many digital photo printers and printing services print at only 200dpi (dots per inch). So if you want to get a standard 5” x 4” photo print, you only need an 1000x800, or a mere 0.8MP image. If you like to just view your photos on your computer, most monitors nowadays don’t go beyond 1920x1200. That’s a trifling 2.3MP (Editor’s Note: This is also why it is idiotic and dumb to tout “HD Photo” as a feature of a camera; a photograph with the dimensions of a full HD signal would be around 2.3 MP). So unless you plan on printing posters and billboards, you really don’t need to worry about mega pixels not being enough.

There are a few upsides to higher resolution that cannot be overlooked, though. While it is highly unlikely you will ever use an 8MP 3264x2448 photo at its full resolution, reducing the resolution later on your computer to say 2.3MP (1920x1200) will usually get you a better and sharper image than an image captured by a camera capable of only 2.3MP. Another advantage of have a high resolution image is the ability of crop portions of the image. If you start with a large image, even smaller portions of the image will still have a high enough resolution. View the example below to see what we’re talking about.

Illustration - Cropping a portion of a large image

ISO and Image Noise

So what else should we look for in a camera other than mega-pixels? Lets start with another thing that is to do with the image sensor - ISO and noise levels. The ISO rating of a camera determines the sensitivity of the image sensor to light. Those who have worked with film cameras will be familiar with these values. The higher your ISO, the more sensitive your camera will be to light. A low ISO setting (<200) will be great for shooting outdoors in daylight, but will not work well at night or indoors. That’s when you need to boost your ISO to a higher value (400 or 800). While this sounds all fine and dandy, the downside is that with higher ISO comes more noise in your photos. While there may be no noise at all at ISO80, the photos may look awful at ISO800. Some cheaper cameras will have noticeable noise levels even at a low ISO100, making the camera almost unusable in anything other than broad daylight. Some high end models like the Nikon D3S will have very little noise even at ISO6400, making them more sensitive than the human eye. The best way to figure out if the camera you have in mind has acceptable noise and ISO levels is to look for reviews and tests online. If you can get your hands on the camera, test it out yourself and then have a look at the photos on a larger computer screen. Please do not think that a high ISO rating for the camera automatically provides great images; it doesn’t. If you are curious to know what exactly is “image noise”, the grainy image below should satisfy your thirst for knowledge.

Illustration - Image noise and distortion

Zooming In

Another thing to look for, which most folks are aware of, is the zoom level. While not much explanation is required here, we would like to warn you to beware of digital zoom. Optical zoom is what you want; at least, it’s what really makes a difference. Optical zoom involves your camera actually moving its lenses to zoom into the scene you want. Digital zoom merely crops the captured image and shows you just a portion of the image, thereby giving you the illusion of zooming in.

Optical Zoom in a point and shoot digital camera

Stabilization

A feature that we recommend you look for in a camera is optical stabilization. Whenever you take a picture, during the short period the shutter opens, light enters your camera’s small pinhole and enough of it needs to reach the image sensor in order to form an impression. This is often hard to accomplish in low-light conditions. The three ways to possibly fix this are (1) increase the image sensor’s sensitivity (ISO), which has its limits and causes a lot of image noise (2) increase the size of the pinhole (aperture), which is a very limited feature in point and shoot cameras, if at all present (3) increase the time that the shutter is open; the longer the shutter stays open, more light can reach the image sensor. However to get a sharp image, both the camera and the subject need to be perfectly stationary. While holding a camera steady for 1/2000th of a second is easy, it isn’t easy for 1/20th of a second. Ideally, a tripod or a stand can hold the camera stationary. But how many of us actually walk around with tripods?! This is where optical stabilization comes in. The camera detects the movements and vibrations in your hands and accordingly moves lens elements actively to compensate the movement. A good optically stabilized (not digitally stabilized) camera can get you excellent photos in low light conditions. Canon calls it IS (Image Stabilization) and Nikon calls it VR (Vibration Reduction).

Few other things to look for

Lens quality: You will have to do your research online for this. Some cheaper cameras have poor quality lenses that suffer from chromatic aberration. Poor quality lenses cause different coloured light waves (different wavelengths) to be focused at different points. This produces an image that’s out of focus with fringes of different colours visible. We’ve provided an example shot exhibiting chromatic aberration below.

Illustration - Result of poor lens quality

Size and aesthetics: Not much explanation is required here. Find something that meets your size and weight requirement. An aesthetically pleasing camera will make you happy every time you look at it! Sometimes you may have to sacrifice certain functions for extreme looks, like the slim cameras with touchscreen capabilities that every digital camera manufacturer from Sony to Nikon is releasing. These are way too slim to include anything other than a 4x-5x optical zoom lens, and they cost as much as some high-zoom, high-end point and shoot cameras; but if you like their form factor (an example from Sony is pictured below) then you could go in for the compromise of functions for the looks.

Sony Cybershot DSC-TX10

Camera mode dial in a point and shoot digital cameraManual settings: We’ve gone through a few of the settings and features of digital cameras in this article. Most (if not all) of today’s point-and-shoot pocket cameras and many d-SLR cameras adjust all of them automatically. If you are the adventurous type and want more control over their camera, you might be happier with a camera that lets you adjust each setting individually. While SLR cameras and other high end models allow complete control, there are a few cheaper point and shoot cameras that let you switch to manual mode. They might be a good place to start if you like photography, and would like to explore the possibilities of digital photography before deciding if a high-end d-SLR would be worth the extra cash, for your use.

Storage Media: The most common storage media are SD cards (SDHC if >4GB). However some manufacturers and models use different types (Compact Flash card and Sony’s Memory Sticks). So if you have a collection of one type, you might want a camera that can use them. A few digital cameras come with built-in storage, but generally, most don’t. So make sure you are aware of the cost and availability of the storage media that your camera can accommodate.

In this primer to digital photography and digital cameras, we have laid out the basics. In our next article, we will try to look a little bit deeper into actual picture taking. As usual, the comments form below awaits your thoughts, opinions and suggestions.

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