Wireless Networking

Finally I've gone wireless.. given the amount of time I spent on R&D, thought I'll share with others so they don't have to go through all the pain..

So what all do you need to have a wireless network ?
Of course you'll need the device that you wanna connect to wireless network. Lets assume it's your computer. Other common possible candidates are smart phone, music system, PlayStation, XBox, internet phones etc.
Your computer needs to have an adapter that can listen to wireless signals and understand them, this would be your wireless adapter card, this is mostly internal (physically inside the computer CPU).
You'll need an internet connection from some ISP. This could be a broadband (through telephone line) or cable (through a separate cable wire) or satellite (through a satellite!) or... Data transmitted over different medium (telephone line, cable, satellite...) is de/modulated in different way.
So depending on the type of medium you'll need a modem a cable/broadband.. modem.
Now that you have a modem that can send and receive data to/from internet and a wireless adapter in your computer, all you need is to establish a wireless connection between modem and the wireless adapter, this is the work of your WAP (wireless access point). Additionally to handle the networking part (taking care of packet scheduling, DHCP...) you'll need a router.
Most wireless routers sold in Indian market are wireless access points cum routers. So you get both in one.

Here is a diagram that shows the normal connection setup in a home network with a router with in-built access point.


A few other things of interest:
1. Common standard you'll keep hearing about is 802.11a/b/g. These are different wireless standards that these wireless devices conform to. You need ensure that your router and wireless adapter both support same standard (most cases both support multiple standards so nothing to worry about)
Here is a simple nice comparison of standards:
See the table in this link

Throughput: This is the max speed at which data is transfered. Remember that in most cases this would not be a bottleneck, instead it would be the number of devices connected to the network and the speed supported by your internet connection.
Range: Although this column says 100-150 fts, in most cases you'll have a "low" or "very low" signal across 2 rooms or on a different floor. Reason for this in India in particular is that we have brick walls, which are killing for signal strength. (Of course you can spend a fortune and get ones that will transmit in your whole apartment block). What could help here is the placement of your router. So try out different angles and different places in the house. See to it that the router is not too close to the wall.
Frequency: Need to bother/think about this when you have other devices like cordless phones etc that also work in same frequency range. Just ensure that router works in a different range (this is configurable).
Hot-spot access: Don't bother about this for now. :)
Power drain: Indicates the effects on your electricity bill.
Interference risk: This is purely indicative of probability. Wherever it's high/medium it's simply because there are other known devices (like cordless phones etc) that also operate in same range. If you don't have one don't need to bother, if you have one you can always configure your router to use different channel.
Cost: Think this should be very clear..
PS: Dual band means a router that supports multiple standards. In India most support both 802.11b and 802.11g

Camera For Dummies Basics: Shutter Speed

Hope you already had a look at the previous 2 posts:
Camera For Dummies: Basics
Camera For Dummies Basics: Aperture

As we learned earlier a basic requirement of taking a good photo is to ensure correct exposure level. A camera provides you with 2 mechanisms to do this,
1. Change the size of hole/aperture through which the light passes and thus controlling the amount of light OR
2. Change the shutter speed and thus controlling how long you expose the film to light.
We already discussed option 1 "changing aperture" in Camera For Dummies Basics: Aperture.
In this blog we'll talk about the things one can do with shutter speed.
So what can you do with/to the shutter speed of your camera?
Anyone would know the answer to that: "You can increase it or you can decrease it" :)
But what we are here to know is what happens if you increase it or decrease it.
Increasing the shutter speed will make shutter remain open for a shorter time and vise-versa.
Lets see first what happens when you use slow shutter speed.
Lets say on a pleasant evening you are out shopping (I know guys you would rather watch TV) and you hear the sound of a Yamaha engine and just across the road you see a 2012 Chevy Corvette 3ZR waiting for the green. You feel lucky as you have your camera handy. But the speed of your hands is no match for 638hp of it's 7.0L engine. As you fumble to get the camera ready the lights are green and you have just enough time for a quick click before it vanishes from sight. You pray that it was in frame and the "auto" mode your camera did a decent job at deciding the exposure. But you're horrified when you see this in the LCD screen of your camera:

So what happened?!
Well lets talk a li'l math and see what we can figure..
What you realize is that the Corvette with it's 7.0L engine had already hit 60mph by the time your fumbling hands got around to click the photo. So you go back check the shutter speed that your camera had chosen for this photo and you see a figure of 1/100 (seconds). So you do quick math
60mph is ~100 kmph viz ~25 meters or 75 feet per second
That means in a 75th of a second the  Corvette would've traveled 1 feet.
So?! Well, that means when you clicked your camera the shutter opened and by the time it closed the  Corvette was 1 feet away from where it was [1/100 sec before]. And your camera recorded everything that happened between this period. So what you see is just a blur.
Now if that's clear lets see what we can do to avoid this? Given the maths we did it seems pretty obvious that if we can make the shutter speed fast enough so that the  Corvette doesn't move (at least not considerably) while the shutter is open we should have a still photo. Assuming that movement of about 5 centimeter is okay (hell, it might make it look cool actually!) then the shutter speed should be: ( 3600 / (100*1000*100) ) * 5 = 0.0018 = ~1/550 seconds.
So what we learned is that in the moving world if you want to take a still photo you must set your shutter speed fast enough to convert the movement into a still photo.
A few other examples are:
- A mosquito flaps it's wings 300 times a second, so if you want to take a still photo of a mosquito you should set your shutter speed to 1/300 seconds (0r faster)
- A formula 1 Ferrari's top speed is around 320 kmph, so to take a still photo you'll need a shutter speed of at least 1/2000 ! (this is the reason why you don't see many photographs of formula 1 cars taken at their top speed, instead people take a photo when the cars are turning at low speed, hey now you know where to sit in the stadium when watching an F1 race !)

So now you'll ask the obvious question: When we can take a still photo mostly at a fast shutter speed why use slow shutter speed ?!
Well, a fast shutter speed is a necessity (in some particular situations) where as a slow shutter speed is something of a leisure, that adds some interesting details/aspects to your photo.
Here for example is my favorite photo (again courtesy photo.net) that shows the delights of slow shutter speed:

Here the photographer deliberately slowed down the shutter speed so the train and people in the background moved while shutter was open whereas the couple were in lip-lock and did not move. Thus bringing the focus of the photograph onto the kiss.
Here is the textbook example of what happens when you use fast shutter speed (you can see each individual droplet of water), whereas if you take the same photo by slowing down the shutter speed a bit you get a much better photo, where you can see stream of water instead of droplets:

Now a few technical notes:
1. Shutter speed is a specification of camera body (as shutter is part of camera body).
2. Aperture size (min/max) is a specification of a lens (as aperture is part of the lens).
3. As for a good photo one must maintain the correct exposure level, when you slow down your shutter speed you must reduce the aperture size (close it down). At times (given the amount of light around) it's simply not possible slow down the shutter speed if we have reached the minimum aperture supported by the lens. This happens if you have a bright sunny day.
4. The exact opposite of #3, when you fasten up the shutter speed you'll have to make the aperture bigger (open it up). But in low light conditions night/evening/indoors/overcast/cloudy you'll have less light to work with and so you'll soon hit the limit to which you can fasten up the shutter speed at wide open (maximum supported). => This is the reason why you see so many party/night photos where people are blurred.
Here a few more examples of good use of shutter speed.
Fruit in water (fast shutter speed):

Sand Storm (slow shutter speed):

Bubble burst (fast shutter speed):

Waterfall (slow shutter speed):

Finally can you guess what is this photo of?!

It's the sky at night, the shutter speed was about 8-10 hours and photo was taken close the pole (not sure north or south). Basically the shutter of the camera was kept open the whole night ! So the circles you see in the sky are actually the trails of stars. Usually camera bodies would support slowest shutter speeds of up to 30 seconds. Apart from that support something called "Bulb exposure mode", in this mode when you click the button first time, the shutter opens. It closes only when you click it again (which could be after a few hours).
Before we wind up here is some homework. Can you guess how these were taken?!
Mercedes SLS

 2012 Chevy Corvette