Threshold Adjustments and Screen Blending Mode

Apply a psychedelic effect to any image with the threshold adjustment and the screen blending mode. Amaze your friends! Impress your parents!

1. Open an image in photoshop – one with a clear definition between tonal information is best.
2. At the bottom of the layers panel, click the adjustment layer icon (what one of my student’s charmingly referred to as the “black and white cookie”) and select Threshold. Threshold converts your image into a pure black and white image with no in between tones. Double click the Threshold thumbnail in the layers panel and adjust the slider to bring out as much detail as you wish – because this is an adjustment layer, you can always go back and tweak it further.
2. Go back to the “black and white cookie” icon and select gradient, at the top of the window are the thumbnails, click on the drop down and then click on the gear icon to load some gradients, the more colorful ones work best for this effect – for my example I chose noise samples.
Change the style to whatever you prefer and as well as the angle and the scale. What’s best about this effect is that everything is set up as an adjustment layer and can be modified later.
3. Magic Time! Change the blending mode of the gradient fill layer to Screen. With Screen, anything black will accept the color but white will reject it.
4. If you want to selectively edit the image – to erase content that you don’t want to accept color, make a new layer in between the threshold adjustment and the gradient fill layer, select the brush tool and use white as the foreground color, paint out the unwanted areas. To fill in areas, change the foreground color to black. Because this is on its own layer it is completely editable.
5. You’re done!
6. You can take this idea even further and use a screened gradient over top an image you have made into a halftoned bitmap like in this tutorial (you will have to convert it back into RGB by going to IMAGE>MODE>GRAYSCALE and then IMAGE>MODE>RGB)
7. Or even try it over a black and white graphic including text.
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