The Megapixel Myth!!

So you own a 8 mega-pixels or 12 mega-pixels camera phone. Or a digital compact camera of even higher resolution – 18MP, may be even more. Well fine, that’s great. But why is that the 18MP pictures don’t look so great like that of a 12MP DSLR camera, the one you see with professional photographers, even though your camera has higher mega-pixels rating? The reason is, higher mega-pixels doesn’t always mean better picture.

Lets dig a bit deeper..!

LET US START WITH PIXEL

Pix-el, the word means picture (pix) element (el). A pixel is the smallest building block of a digital image in raster format. All the pictures we see are mostly of raster type. The other type is called vector image. You might have observed very small squares in a picture when zoomed in a lot. Those squares are called pixels. A picture is made up of a few to many million pixels depending on its quality and size.

THE IMAGE SENSOR

Well, now we know what a pixel is. Let me ask you, how does your phone or camera captures an image? If it was the old film cameras we would say, the light falls on the film strip and some chemical reactions take place imprinting the picture on to the film. But we don’t load a film in our digital world these days. Still we need something to capture our images. That is called the image sensor – some electronic equipment that detects light falling on it and then converts it to electrical signals. These electrical signals are then Converted to digital format to store or display them as images. It is marvellous. We can use it any number of times, not as the old film.

But this thing – the image sensor – is one factor that defines the quality of an image we snaps. (The other major factors are lighting, lenses and technique we use.) An image sensor is divided in to very small elements just as a picture is. The pixels count the camera mentions is the number of these elements on the sensor. One mega-pixel means one million pixels. Thus a 18MP camera will have 18 million sensor elements or pixels on its sensor. Each element in the sensor can detect the intensity of light falling on it and registers the amount of light in digital form. But actually a sensor element cannot detect all the light that falls on it. Instead it can detect only one colour of light among red, green or blue. The red, green and blue (in short RGB) are called the primary colours. Any colour can be made with different combinations of the primary colours at different intensities. This property of colours is made use of in a digital camera too. Thus, each sensor element detects the intensity of any one of these primary colours in the incoming light falling on it and that value is registered. But this data alone now, cannot generate any viewable image since each sensor element detected only one of the three primary colours. But to make this to a valid viewable image, camera uses some kind of algorithm to generate the true colours that fell on its sensor. Using the data of various primary colour intensities in neighbouring sensor elements, camera software regenerates the original colour and thus the original image. There are various algorithms used to combine these primary colours’ intensity data to generate viewable images. That varies according to different manufacturers. So it is with the primary colours’ intensity data, that a real image was formed. All professional cameras and certain lower end cameras allow users to store images as what a sensor sees. That is as the intensities of primary colours alone. These images are called RAW files. As the name suggests, its raw. To regenerate the original image, the RAW file has to be processed. And according to the various methods implemented for processing, the outcome varies. Thus a RAW file is very flexible to edit. For this reason often RAW files are called digital cameras’ negatives, as of a film camera. Well, so that is how an image is captured.

IMAGE SENSOR AND QUALITY

Wait, we were saying something about quality of image and image sensor. Yeah, the quality does vary depending on this thing. The main difference in the image sensors used in a DSLR camera (professional camera) and a compact camera is that, those big professional ones have very large image sensors. That is the area is larger – bigger dimensions (longer and wider image sensors in professional ones). For comparison, a full frame camera (the professional one like Canon 5D) has a sensor size of 36mm X 24mm and a compact camera on the lower end has a sensor of size 5.27mm X 2.97mm. That is a big difference. What does that mean? It means for the same mega-pixels count, say 1 MP, the size of sensor elements in a DSLR will be very large than that of a compact camera. If one million pixels were to be included on two sensors of different areas, the one with larger area would have pixels with larger dimension than that of the smaller one. A mobile phone is comparable to a compact camera and quite obviously its sensor will be small. The problem here is, on a small sensor the manufacturers are squeezing in more elements to give that large mega-pixel name, like 8MP or more. There is a small exception here though. Nokia N808 Pureview stands out a bit. The 41MP phone has a much much larger sensor compared to other mobile phones and it does show the difference in the captured images. Well, that is a rare case.

The picture below shows various image sensor sizes. It is clearly visible the difference between the size of a full frame sensor and that of compact cameras. The image sensors used in mobile phones are even smaller. Its not shown in the figure. For instance the apple iphone 4S and Galaxy S3 have image sensors of size 1/3.2″. The Nokia Pureview has one quite bigger. Its size is 1/1.2″.

The significance of size of the sensor element is interesting. A bigger element means, there is larger area for the light to fall on. So a larger element will collect more light than those small ones. More light means better detail and so higher quality.Thus if the mega-pixel count is too high and it is a compact camera or mobile phone, the chances are it has a small image sensor which implies smaller sensor element and thus lower light collecting ability and not really stunning images for the reason that in has higher mega-pixels. Quite simple, right?

Final Word: Don’t get carried away by the very huge pixel number manufacturers use to highlight as a great new  feature of their devices. But it would be worth  to consider new technologies they use to better the image outcome like a new image processor, better noise reduction algorithm, newer lenses, image stabilisation methods and so on rather than just the mega-pixels.

∞

The Biggest Tension – Battery

(This is about rechargeable Lithium batteries that are common in portable devices. For a few quick tips on extending the battery life and squeezing the most out of it, scroll to the bottom of this post)

The modern world is said to be squeezed in all kinds of wanted and unwanted tensions. Well, that is true. But its high time we should take a break from all these. May be we should work on the way we deal with different problems and happenings. huh, I deviated..!! While every one has a million reasons to get tensed, there is one common problem that every human fear of. Its the Battery Backup. Almost all people in the modern world use at least one portable device which work on the stored energy in a battery. The most common one being the mobile phone, along with portable music and video players. And there are tablets, palm tops, lap tops, digital cameras, camcorders, navigation devices and many more.. its a big list!!

THE BATTERY

A Battery is a teeny power house. It provides power in the form of electricity that can drive various devices. A powerhouse which actually is a small chemical laboratory where some chemical reactions take place generating electricity. Quite interesting! We carry a chemical laboratory with us wherever we go..! Now the problem is that, there is nothing called as infinite power. When the chemicals that take part in the reaction run out, the battery dies. Another problem – the reactants can’t regenerate all by its own. So now that we used up all the reactants we need to regenerate them and this is what we call charging the battery. All the chemical reactions that took place to give us electrical energy while the battery was discharging are reversed during the charging process. Charging is done by connecting the battery to a controlled electrical supply. So that is the outline of how a battery charges and discharges.

BATTERY LIFE

By saying battery life, it can either mean the complete life span of the cell or the time for which a battery can power a device in one full charge. The complete life span of a battery is defined by the number of times a battery can be recharged. This is called as charge/discharge cycle. One cycle corresponds to charging the battery (to any level; whether full or partial) and then discharging (using) it. Modern batteries (Lithium cells) have large number of charge/discharge cycles (about 400 or 500). It also depends on the charging behaviour (will explain it). The Battery Backup. Now this is really important when you are out travelling and cannot find a source to recharge the cell. Backup is the time for which the charged battery can power the device in which it is used. It strictly depends on the power or current consumption of the device, usage behaviour and environmental parameters like temperature. Everyone wants the backup time to be loooooong. This is much dependent on the battery capacity and other factors just mentioned before.

BATTERY RATING AND CAPACITY

Every battery has a capacity as we humans do. While some can lift 50 kilograms with real ease some others struggle to do so (just an example). The battery capacity mentions how long the power house will last for a specified amount of current output from it. For example, on the cell phone batteries there will be figures like ‘3.7V, 1500mAh’ or ‘3.7V, 1250mAh’ or the likes. Consider the first one – 3.7V, 1500mAh. 1500 mAh is equivalent to 1.5Ah (mAh is milli ampere-hour and Ah is ampere-hour). The figures mean that the battery’s terminal voltage (or output) is 3.7V and it will last for one hour if current is drawn from it at the rate of 1.5A. That is, after 1 hour of operation the battery dies if it supplies a current of 1.5A for one hour. Now, if the device takes current from battery at the rate of 0.5Ah, the cell will last for 3 hours. Thus backup time = (Battery rating in Ah)/(Device current usage in Ah) From this we can understand that, if we use a battery of larger rating (say 3Ah) the device will last longer. In the above case, 3/0.5 = 6 hrs

STRETCHING THE LIFE

Starting with the life span. The Lithium batteries are a lot different from the old NiCad ones. The charging and usage method are also much different. But unfortunately most of the user manuals of portable devices follow the instructions that are valid with NiCad cells and not true with Lithium ones. One of the biggest blunders is that, they say allow the battery to completely discharge before charging it again so that it helps in improving the cell life. This was true with Ni-Cad cells. In the case of Lithium cells, its better to topup the battery as fast as possible. That is it is better not to allow the battery to run down below 40 percent of the fully charged state. The advantage is that, such frequent top ups will increase the battery life cycles. (But for NiCad cells this was different. Frequent charging reduced their life) For example, consider a battery of life 500 cylces. If this battery is charged when the capacity drops to 50% then it can be used for more than 1200 cycles this way. And if the recharge is done when the capacity drops by 10%, the cycle number increases as high as around 5000 cycles. But occasionally (like once in a month) discharging the batteries completely till the device switches off and then charging it fully is a good process. It helps in calibrating the voltage meter and is termed to be a good thing for the cell.

SQUEEZING THE BEST OUT

The most important thing is, with no doubt, the backup time. By caring a little, the battery backup can be stretched to the maximum.

• Temperature is the biggest enemy of our little power house. If the heat is large, the battery is strained and badly affect the backup time as well as the life span. Its always advised to keep the temperature low. But how? Well, a battery when delivers large power expels a lot of heat. Doing energy hungry activities on the device like hardcore gaming, recording High Definition videos, capturing photos, making a call and the likes draw a lot of power from the battery. Thus elevating the working temperature and this brings an adverse effect on the battery life. But these cant be avoided. It may strictly be taken care of not to use a phone to make a call or attend one, browse the web, record a video and play games while the device is plugged to an energy source for charging. Because that liberates a lot of heat and badly affect the battery life.

• Try to keep the display brightness to the lowest possible level. Display back light eats a lot of power.

• Don’t frequently switch off and on the device. This is an energy hungry activity.

• For laptops, don’t plug in usb devices or other peripherals if not needed. Also keep a larger RAM and lower virtual memory. This helps the hard disc to rest more. The automatic switch off time of display, n/w card and everything else must be set to a lower value
• On a phone, don’t keep the data connection active if not needed.
• Always remember to switch off the blue-tooth after use. This saves power as well as the privacy.
• Automatic wifi scanning may be switched off. Wifi is really hard on the battery.
• Try to use the lowest value of back light time of displays in the devices.
• Screen savers save battery.
• Don’t keep applications open in phones, tablets and laptops in the background unless necessary. More applications means more memory and so more power.
• Understand the capacity of battery and use the devices wisely according to the limits.

• This might sound crazy but, if the device seem to heat up a lot, open the battery cover for better air flow to cool it down fast (strictly not in the case of laptops).
• Do not over charge batteries. Its the worst case that kills a good cell.
• If available and supported, find a power monitor application for the device and monitor power usage of various applications so that those can be killed if needed (A good task manager may be made use of for this process)
• Find updates from the manufacturer’s website. The updates mostly contain tweaks that reduce battery usage.
• New technologies will be more efficient than the existing ones, in most cases. Go for them if needed.
• If the present battery seems to be insufficient, find another one with larger capacity (larger Ah or Wh – Watt hour rating) if available. Or carry a spare one.

FiNaL NoTe: Never Waste Energy