What's the relationship between between ISO, Shutter speed, Aperture and Light in photography?

Photography is a word having Greek roots, which basically means "drawing with light". When I started doing digital photography few years ago, this did not make sense to me at all. How can you make a picture just using light? Only light matters? My pictures were blue, black, red and washed out all the time, but I didn't feel like giving up. It took me a fair amount of time to understand controls such as shutter speed, aperture and ISO which was the outcome of non stop reading and a lot of mistakes.
Coming back to the concept of light, it started to make sense when I attended a film photography workshop couple of years ago. The dark room with very dim or near to zero red lights was a whole new point of interest for me. My partner and I made a pin hole camera out of Pumpkin. Here is an image of our pinhole camera, sorry for making my pumpkin look upset. ;)

Picture from photography workshop
Pin hole camera photography workshop

This workshop made me understand how important light is when taking pictures, and the rules apply to both film and digital photography. Basically the value of ISO, Shutter speed and Aperture directly affect the amount of light hitting the sensor. This light gets transformed into an image by sensor circuitry. A short and crisp way of explaining the light variation whenever one of these values is changed is shown in the image below.

ISO, Shutter speed and Aperture in photography
Relation between ISO, Aperture and Shutter speed in terms of light. 
The tricky part here to understand here is how to vary each of the above three things simultaneously. A couple of quick examples:
1) Sunset landscape shot: Low shutter speed for more light, high f stop for more details. Yes, high f stop would minimize the light, but shutter speed would cover up for it.
2) Bike racer daytime action: Fast shutter speed to freeze action. F stop as low as possible to make background out of focus. But if image is too white, then only solution is to increase f stop so as to control the incoming light.
Quick tip: When to vary ISO? Well, depends on the situation. Example: A dancer inside a low light room. If the amount of lowest feasible shutter speed (to freeze action) and lowest f stop are not able to provide properly exposed shot (hard to see dancer's face), then ISO becomes a life saver.

Hope this post would help you to fiddle around with these 3 main settings. The variation style mentioned in this post is applicable for Manual mode shooting.

Be a DSLR Ninja.

How to make your own product photography light tent for cheap?

Have you ever bought a product from eBay or any other online store? Notice how the images are so crisp, sharp and properly lit. Well, the magic wand behind those professionally looking photos is a soft box, light box or simply a light tent. The whole purpose of having a light tent is to spread the light evenly in every direction. Why? Photography is all about light. A light box minimizes issues such as shadows, harsh blown out edges (from flash or direct light) and faded color. 
Now the difficult part, spending money. You can buy a professionally built light tent online around 70-100 bucks. More cheap? Buy used. More cheap? Do it yourself. Yes, that's the best way. Only thing required from you is a visit to your local market and a couple of hours. Here is a list of things you will need:

1) Old used cardboard box or moving box. Any color would do. Preferably 18x18x16 inches. 
2) Cello tape or any other kind of tape. Duct tape would also work, I believe it works for everything.  
3) Tissue paper or a white muslin fabric/cloth. 
4) Cutter. 
5) Three table lamps. 
6) Three 80W or 100W fluorescent or daylight bulbs. 
7) A pen or pencil for marking. 
8) White poster board. 

Before we start, I request you not to scream with joy ( I did) looking at your product pictures after finishing the light box set up. Let's do it:

Step 1: A cardboard box has 6 sides, out of which one is already opened in order to take out whatever product was in it. This would be the entry for placing the product. Also, do not touch the exact opposite side to this opening. 
 Step 2: You have 4 sides remaining now. Choose any 3 sides of your choice and make square shaped gaps by using cutter. 
a) If you are using a tissue paper like me, take a pen to mark the gap size required for a tissue paper to fit. This cut would be smaller as tissue paper has a limited and fixed size.  
b) If using a white muslin cloth, you can cut as much big as you want leaving some space on the edges for cello tape to sit on. 

Step 3: After finishing the cuts an any three sides, all you have is a box with three sides wide open. You can put your hand or arm or even face through that gap into the box, just to have some fun. Place the tissue paper on top of gap, hold it firmly. Grab the tape and apply on all 4 sides. Do similar thing for remaining 2 sides as well. 
If you were using a white muslin cloth, cover up the whole gap and fix using tape on all four sides of cloth. Do similar step for remaining 2 sides. 

Step 4: Did you notice you still have 2 sides intact out of total 6? One would be your product background and other one as the box base. Tilt the box and place it in such a way that you will have gaps on top, left and right side. Take the white poster board and place it inside the box in a sliding motion. It needs to form a curve. Fix with tape. See picture below:

Product photography light tent
Light Tent or Light Box ( Not finished yet)

Step 5: Bring all three of your table lamps containing day light bulbs close to left, right and top gap. Turn on the power. Voila! 

Place any suitable sized object inside your light box and take brilliant quality product pictures using your DSLR or smartphone camera. 

Here is a sample shot:

Sample Product Photography Image

Be a DSLR Ninja.