Turn any photo into a dot grid artwork with these Photoshop actions. You'll get great results with dots that change size. They get larger in brighter areas and smaller in darker areas. Free download available.
Now double click on your flattened layer to open up the layer styles, and jump down to gradient. We're going to do a rainbow gradient so create something similar by just choosing basic a basic red, orange, yellow, green, blue, and purple and place them however you choose.
As soon as your satisfied with your gradient, duplicate the layer with all the styles and simply drag it downwards a tad.
Duplicate the layer you just moved down (total of 3 "V" shape layers now) and on this duplicate, set the blending mode to "soft light" Now you'll start to see some highlighed areas.
Duplicate the top layer that you just put in screen mode. Remove the layer styles, we just want it to be white. Now set the layer blending mode to "Linear Dodge" or "Add". Now you should see major highlights like below.
The highlighting is very intense though, so we need to take it down a notch. We'll do this by making a layer mask on the layer set to "Add" mode. Create a mask by clicking the mask button in the layers menu and using a large soft brush with a lowered opacity, perhaps somewhere around 25%, paint blotches here and there similar to this pattern below. This just makes the light look more random.
Now that the highlighting from the "Add" layer has been taken down a peg, you should see something like this. With bits and pieces of highlighting here and there. We want something kinda random so it looks like it's shiny and reflecting light. The shininess is a typical retro style effect.
Duplicate the "Add" V-shape layer and set it's blending mode to "Overlay". Now invert the color from white to black. We're starting to give the shape a color contrast in the shadows now instead of the highlights.
Duplicate the top "V" layer once more and set the blending mode to "normal". Then set the opacity down to 50% or so.
Duplicate the top layer once more keeping the blending mode at "normal" and set the opacity at 100%. Don't be alarmed if a lot of the image has been blacked out at this point, we'll bring back some of it in the next steps. BUT: if it is completely black right now, we have problems, you'll need to play with your black "V" shape layers so that you see some color "V" layers underneath them.
Now it's time for the lens flares... another trademark look of the retro style. Create a new layer on top of everything else, and fill it completely with black. Then take your lens flare brush and get it to an appropriate size and place a lens flare on the canvas where it will be overtop of the "V" shape. You only want to be placing flares on your shape, but you'll be able to move them around later.
Now create a new layer and taking your marque tool, select a rectangular area on the top or bottom half (it doesn't matter which) of your flare. We're going to make a flare "burst".
Taking a large soft brush, but not too large that it's bigger than your rectangular selection, create a white half circle like so.