Dec 12, 2013

Jugaad Security System

I own a book shop in Nainital and I live in a house just behind (attached to) the shop. As you enter my house there is a cupboard that we use to keep any spare cash (Small amounts that would be sent to the bank the next day) we might have form the day's sale. About 4 months back my mother started to notice money disappearing form the cupboard. First time my mum told me about the issue, I brushed it aside thinking it might have been a calculation error from our side. Then the same thing happened again another 2-3 times. This was more than a coincidence so we stopped using the cupboard for the purpose of keeping any sort of cash but we still did not know who was taking the money. We have a few staff members at our place (all of them had been with us for a considerable amount of time - some of whom had been working at our place for more than 20 years). Since the only people who had any access to the cupboard apart form the family were the staff member we suspected that one of them was up-to something.

We have a CCTV system installed in our shop and we could have easily installed another camera in the house to find out the culprit. This had 2 issues - 1) Who would actually sit down and go through the whole footage? Big waste of time 2) Who would want a surveillance camera inside the house?.

I had recently got 2 DSLRs for a workshop that I will be taking on DIY film-making and since I was currently only using one of them  I decided to put up the second one for finding out who the culprit was. I had a magnetic switch lying around and had a spare 2.5mm cable (from my experiments using an arduino as an intervellometer to capture time-lapse videos). Using just the cable, the magnetic switch attached to the cupboard and some duct tape I rigged up a camera trigger that would click a picture of the cupboard the moment someone opened or closed it. I set the Camera on a table (Nothing too obvious). Manual Focus. High ISO - 12800 (Because the room could get quite dark say when there is no-one there and the lights are turned off). The camera (Canon 600D) batteries last a long time when the LCD is turned off - about 2 days so that was not a problem.

Magnetic Switch

On the third day of the experiment there was a slight rush in the shop and I was busy at the Til. One of the staff members went inside taking advantage of the fact that I was distracted, opened the cupboard hoping to find some money (which was not there as we were not using that system anymore) and the camera got him. I went in for lunch and checked if any pictures was taken since morning and there he was caught in the act. We called the police. Got whatever money he had stolen form us back and fired the guy. Might not have been the most elegant security system but it got the job done. The local police kind of liked the whole idea because it reduced the amount of work they had to do.

Anyway here are the pics for the thief caught in action

DIY Polariscope

A few days ago I was stuck in one of those YouTube loops (happens once a month) and I came across this awesome video on the Prince Rupert's Drop by SmarterEveryDay (Excellent channel BTW). About 3:00 minutes into the video they use something called a Polariscope to check out the stresses built up inside the Prince Rupert's Drop. Watching that I realized that I had all the things needed to build this at home.

You need the following things for creating a Polariscope :

1) A polarized light source (White in color preferably) - Since almost all LCD's use polarized light to display images you could use your iPad or Laptop screen displaying a white image. I went for my 22" monitor as I needed a bigger surface.

2) A transparent object - Not all objects work well for this as some don't really have that much stress. 
          - Things that work well - Glass statues, use and throw forks and knives, glue sticks, etc.
          - Things that don't work well - Soda bottles, plastic OHP sheets, Tupperware, etc.

3) A polarizer - A CPL (Circularly Polarizing) filter works best but you could also use those Throw-away 3D glasses you get at movies or your even your sunglasses. 

4) A camera - DSLR works best but even a phone cam should work I guess.

Setup the items as in the diagram and move around (rotate) the polarizer till the white light from the LCD becomes almost black. and you will see the stresses in the transparent object.

I tried out a few objects I had lying around and here are my results

Photoshop - Human Cloning Project

A few days ago I posted this picture of myself on facebook

Loads of people asked me how I did this so I decided to make step-by-step a tutorial. It is ridiculously easy. I was going to do a video on this but then decided against it as it would have taken a lot longer and currently I don't have that much time at hand. I'm quite busy with the work @ Mistri Labs

Step 1:

Setup your camera. You will need camera where you can set exposure manually (Aperture Priority and Shutter Priority will not work too well in this case as the light will vary was the subject moves in the frame). Most P&S and DSLRs have this feature. Even a decent phone camera should work (You might need to download an extra app to set the manual exposure on your phone). You will need a tripod (or any surface that you can place your cam on if you don't have a tripod).

- Setup the ISO - Don't use auto because the light changes as you move around the room.
- Setup the aperture - For all the people using DSLRs don't go all f/1.8 because you need most of the shot to be in focus. I suggest start at f/7.1 and work around that area.
- Setup the shutter speed that you think gives you the correct exposure.

Now you need to take 3-4  shots (maybe even more depending on what you are creating) of your subject (In my case that was me) from the same vantage point. You camera should not move between shots. I used a timer to shoot these but if you have a friend behind the camera you can ask them to do it - depends on you.

Image 1

Image 2

Image 3

Image 4

Step 2: Open all photos in Photoshop and put them in different layers inside the same composition

Step 3: Select the second layer from the bottom and create a layer mask

Step 4: Keep the second layer from the bottom of the stack selected. Hide all the layers above it using the eye icon. Select brush tool, select the colour black. Paint in the version of your self from the lowest layer in the stack.

Step 5: Repeat Steps 3-4 for each layer and you are done.

Tips :
- Don't do this in areas that change over a short time (Example - in front of a tree as the wind might change the shape of the tree from shot to shot).
- Don't do this in areas that the light changes often (Example at a sunset scene)
- Don't move too much furniture around as you will have to Photoshop those things around. Will waste your own time.
- You could change clothes in between shots to give a more random feel to the image.

Have fun :-)

Nov 8, 2013

DIY MaKey MaKey

I was just browsing around the internet and came across this video which described how to make your own Makey Makey board using an Arduino Leonardo. I had all the components laying around at home so I decided to make my own. Here is a video where i used 4 glasses of water to play some drums from No I can't play music, well not right now anyway :-).

The Makey makey is basically a circuit that converts anything conductive - even slightly conductive (Metal, Coins, Bananas, Humans, Coke Cans, Glass of Water, etc.) into a button on your keyboard. You connect a wire from the circuit to the object you want to make into a button (key). Connect your self to the wire from the circuit labeled "hand". Done. Now the moment you touch the object it will send a key-press (example 'a') to your computer via USB. 

Using the Arduino Leonardo you can convert up-to 6 objects into a key at any given time. Unfortunately i had only 4 crocodile clips at the time with me so I made only 4 keys. You could make 6 if you wanted to.

If you want to build your own check out the video it is quite well made and goes through the whole process step by step. The circuit is ridiculously simple. The way it works is it makes a potential divider circuit between the Resistance (on one side) and your body+object (on the other side) and reads the voltage from the center. Using this voltage it figures out if you have touched the object or not. Because the resistance value is huge (10 mega-ohm and more) even slightly conductive objects can be made into keys.

Red - Connects to the Arduino Board
Blue - Output - Connects to the objects and your hand.
Purple - Resistance (Use 22 Mega-ohm  if possible, I used 10 Mega-ohm)

Once you have made the circuit you can write the code to Arduino (Available in the description at

In my case I modified an Anti-Static strap to use as a connection from the circuit to my hand because i did not want to hold a wire every-time i use the circuit.

Note for people that get scared (to my surprise there were quite a few of them - I don't blame them how should they know) of using this because it might give you a jolt : It is perfectly safe to use (well unless you go Full Retard and do something incredibly stupid like connect this to the mains power in your house.)

If you don't want to build your own version of this and just want to play around. Just order one from the makey makey site and have fun.

Update: Version 2.0 - Better case, A lot more modular.

Nov 7, 2013

Macro Shots with a Canon 600D

I recently bought a a Lens Reversal Ring  for my DSLR. It is a pretty nifty gadget available at dirt cheap prices. The way it works is you screw it on the filter thread of your lens and then mount the whole lens to your camera in a reverse orientation. What this essentially does is it converts your lens into a macro lens lens (You can focus on things that are super close to your lens).

Obviously there are some disadvantages to this approach rather than getting a proper macro lens. Firstly as your lens is mounted in reverse you don't have any control over the electronics (So auto-focus). Secondly, in case of canon lenses (in Nikon it closes down) the lens opens up the widest aperture (with no control) which can be a problem some times as you get a really shallow DOF which causes issues sometimes.

For the second issue there is a workaround and it works (well sort of - alteast on Canon 600D and other similar cameras). Lets say you want to click a pic with an aperture at f/7.1.

Step 1: You do is you put you camera in video mode. Your lens should be mounted normally as it usually is.

Step 2: Set the aperture as needed. In this case f/7.1

Step 3: Now without changing any setting and without turning you camera off remove the lens. The aperture will be stuck at whatever value you set in the video mode. Screw on the reversal ring and mount the lens in reverse.

I shall try to put up a tutorial video in a few days.

For focusing there is not much you can do. The focus ring is pretty much useless (especially if you have an STM lens). In the kit-lens the focus ring is okay but this can only be used for fine-tuning. Almost all the focusing has to be done by moving the lens around (Be careful as you are very close to the subject you might scratch you lens). You will in most cases need a tripod as even a tiny shake is very noticeable in macro shots.

Anyway here are my first few shots. If you need the settings (ISO, Shutter Speed etc) go to

Nov 3, 2013

Guitar 3D

I've been learning how to play the guitar for a few now days. As customary I had to render out a 3D image of one (not the exact guitar I'm learning on)

I downloaded the basic structure of a guitar form some site a few days back (I forgot the link from where). Anyways it was a simple low poly model so I had made a lot of changes to the same. Refined the whole thing. Did the texturing, lighting and camera setup.

After that rendered the whole thing out (took about 20 minutes for each image as 4K). The DOF was added later in Photoshop as rendering it out was too tedious.