Optical illusions ............ painted fingernails - identical images !!!

In Daily life, people spend hours on Computers hooked to the web.  There are bloggers and some do post articles on FB …. but, majority post only pictures – the oft repeated cliché ‘picture speaks more than ….. words!’ …. By some accounts, between  Facebook,  Instagram, and Tumblr, consumers share nearly 5,000 images every second of every day. Add in Pinterest’s estimated 40 million users and even SnapChat’s meteoric rise,  the no. of pictures occupying common web simply becomes incalculable.  Read somewhere that ‘Words actually don’t exist’  … to our brains, at any rate. Mind sees words as a series of letters; people see them as pictures.  In our busy image culture, Yahoo has estimated that 880 billion photographs will be taken this year. The ability to capture, experience, share, search, and recall photographic imagery (still and moving), rests in the pocket of anyone with a smartphone.

But …… pictures too can misrepresent or misread, misunderstood or misinterpreted. The legendary Muthiah Muralitharan’s career was blemished when he was called for throwing – no doubt his action is freakish but it has been okayed after tests of bio mechanists. His deformed elbow creates the optical illusion of throwing but the arm bend is well within the ICC’s new 15 degree tolerance limit.  His action was cleared by ICC after biomechanical analysis in non-match conditions but in 2004 he was tormented again with doubts on the legality of his doosra – all at a time when  there were more than a  handful of raw medium pacers chucking with questionable actions.  Almost all of them escaped without being called by Darrell Hair and his fraternity.

An optical illusion is characterized by visually perceived images that differ from objective reality. The information gathered by the eye is processed in the brain to give a perception that does not tally with a physical measurement of the stimulus source. Optical illusions are often classified into categories including the physical and the cognitive or perceptual.

A classic example of ‘optical illusion’ courtesy www.livescience.com – the black dots seem to appear and vanish at the intersections of the gray horizontal and vertical lines. Called the scintillating grid, this illusion was first discovered by E. Lingelbach in 1994 and is a modification of the so-called Hermann grid illusion. 

Searching about Optical illusions, this post in Daily Mail attracted me most.  The pictures more confusing than #TheDress! These two images are the SAME (but appear as light pink or purple when placed in front of different backgrounds). It is the new set of pictures doing the rounds on Twitter that are boggling the mind. They are two identical images featuring painted fingernails held up to a mouth, but they appear in completely different colours - one is pink and the other is maroon.

         

These images are identical, but they appear very different because of the background they have been placed on in Photoshop. The 1^st  picture was placed on a white background, the 2^nd  picture was placed on a black background.  That is the only difference between the photos: one has been put in front of a black background (the maroon picture), while the other (the pink picture) has been placed in front of a white background.

In the original picture,  the lips and nails are pixellated, with some of the small squares appearing as a shade of purple, while others look pink.  These pixels mean that the image is semi-see through, so it can adapt to different colours when they appear behind it in Photoshop.  Which is why you see a pink pair of lips and fingernails on a white background on Twitter, but when you click on the image to reveal a second picture against a back background it looks maroon.

MailOnline's graphics whizz Leo Delauncey explained the science behind the photos... The colour of the nails and lips in the original pre-photoshopped image was a darker shade of pink. There are two main tools in photoshop that make this possible. Firstly the ‘colour selection’ tool was used to select a specific tone within the pink of the nails and lips.  The midtone makes it possible to select the main colour but leave the shadows under the lips and the highlights on the nails.Then the ‘mask’ tool was applied to the selected area. The mask tool allows you to change the opacity of the selected area. By filling the area black you can make the image within the selected area disappear. By filling the area white you can preserve the opacity of the image. By filling the area grey you can essentially dilute the image, much the same way you would dilute paint with water - where paler grey would equal less water and more opacity, darker grey would mean more water and more transparency.

Once the mask has been applied you have an image that is partially transparent, and the colour affected by the background behind. It’s the same as having some clear coloured acetate or tissue paper. If you hold the pink tissue paper to a white light the tissue paper remains pink. If you hold it up to a blue light it becomes purple.

The illusion comes just a month after the internet went into meltdown over a blue and black dress that almost 50 per cent of people saw as white and gold. 

With regards – S. Sampathkumar

20^th Mar 2015.