Anything Photoshop or Photography

JUST WHAT DOES A LAB INVERSION DO?

Image of a purple wildflower on a black backgroundThis week I have been reading a book, The Way of the Digital Photographer, from one of my favorite photographers and Photoshop people, Harold Davis.  As always, I love reading his books because they are not over-complicated, but have a fresh approach to post-processing your images. The above is the first time I have used his LAB inversion technique and I really liked the results. Harold has a nice website article called Using LAB Color Adjustments that goes into a lot more details on how to get this effect and even more creative results than what is shown in this blog. He has a great tutorial in one of his older books called The Photoshop Darkroom if you really want to understand it. The bottom line is that by switching LAB mode and inverting the LAB Channel at the top of the Channels panel, all color values in the image will be swapped with their opposites, and Harold says it can create electric blues. With just the L (Lightness) channel selected, the grayscale information is reversed so that the black becomes white and white becomes black – this is great when the image is on a white background and you want it on black as shown above. With the “a” channel inverted, the magenta pixels become green pixels and the green become magenta. Same with the “b” channel when it is inverted – blue pixels become yellow and yellow pixels become blue. Once this is done, he likes to adjust the blend modes and layer opacities for more effects and to use layer masks to apply some of the results to localized areas of the image. Pretty creative process here!

The above image is of a little tiny wild flower plant growing on my porch – just hanging in there. I had to lie down flat to get the picture since the plant is no more than 2 inches tall with a white cardboard background set behind it. The original image from Lightroom is shown at the bottom of the blog so you can get a feel for how this technique can really change up an image.

After the doing the basic Lightroom adjustments which included sharpening the main flowers, the image was brought into Photoshop where the image was changed to LAB mode first. To do this, go to Image -> Mode -> LAB. This needs to be done on a flattened layer since the LAB mode does not read all Photoshop layers info like masks and adjustment layers correctly. Therefore you may want to duplicate your image at this point and use it in LAB mode. Once in LAB mode, duplicate your layer (CTRL+J). Go to the Channels panel where you can now invert the whole LAB image, or the individual channels, especially the L channel where only the luminance info resides. Just do a CTRL+I if using all the layers, or highlight the individual channel and with all the eyeballs on, CTRL+I to invert just the one channel. For the above just the L layer was inverted, but I tried them all. Very interesting results with each. Instantly this beautiful black background showed up with the soft colors in the background objects. At this point you can try localizing the effect with a layer mask, or changing the blend mode of the inverted layer. The image now needs to be flattened again so that the colors do not change when converted back to RGB. Go back to Image -> Mode -> RGB to continue the processing. The steps are listed more clearly further down in the blog. In this image a little more sharpening was done and Melissa Gallo’s Painted Textures Taupe Canvas was applied.

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Image of a display of Margaritaville mixers that have been inverted in LAB modeAbove is another example of what a LAB inversion effect does to the L channel. This image was a lot of fun to do, but it did take a lot clean up – I basically wanted the colors to stand on there own – an image of mixers at Margaritaville in Orlando just happened to have the elements I wanted to show. The original image I posted on my Mixers for Margaritas! Tidbits Blog. (Here are the details on what was done to get the above image using the image from the blog: This blogimage was flattened. The layer was taken into LAB mode where the layer was duplicated, then in Channels panel, the L channel was inverted. Back in Layers panel the blend mode was changed to Linear Burn, then flattened before returning to RGB color mode. The layer was duplicated and taken into Topaz Simplify 4 where only black lines were applied – only Edges section is used. Once out of Simplify, went to Select -> Color Range where the Highlights were selected with Fuzz 1, Range 255, and Inverted checked. A layer mask was added and the selection applies. To get a little more black line emphasis, PS Ink Outline filter was applied using Harold Davis settings of 11/5/19. The Color Range line layer was set to 59% and the original Simplify layer was deleted. Some clean up was done to finish up.)>

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Image of the Incredible Hulk Coaster done with a LAB inversion effect
This image of the Incredible Hulk Coaster (to see a video from the front seat of the ride, click here) at Universal Studios in Orlando, Florida, is a good example of what an image will look like with the “a” channel inverted in LAB Mode along with the L Channel. In this case the L channel caused the background to turn to a nice dark color since it was originally light, and the “a” Channel conversion caused the roller coaster to become a red-orange color from the original green-yellow. To help you follow along, here are the LAB steps that are basically the same for  each image:

1. Opened image in LAB by going to Image -> Mode -> LAB.
2. Duplicated layer and highlight it.
3. Go to Channels Panel and select “a” channel – invert (CTRL+I) the channel.
4. Highlight the L Channel and invert it also.
5. Click LAB Channel eyeball so all channels are turned on.
5. In Layers Panel, changed blend mode to Linear Light. (Could add a black layer mask at point and add only parts of the effect into the image.)
6. Go to Image -> Mode -> RGB and choose Flatten Image.

Pretty dramatic change but I like the results. To make the reds and blues really vibrant, just before converting back to RGB Mode, the LAB layer with the inverted channel changes was changed to a Linear Light blend mode. Then, once back in Photoshop, the layer was duplicated and set to Multiply blend mode at 52% layer opacity just to make it more vivid. The Lightroom original for this image is shown below.
Image of original photos of purple wild flowers and roller coasterAs you can see, this LAB conversion technique does have some possibilities. It tends to give a graphic feel to your image. It can pick up a little noise and I had to run Topaz DeNoise 5 at an overall setting of .39 to the coaster image – then added a black mask and painted in areas that looked too noisy – surprisingly it was not the dark background (since it came from a light sky) but the reds and blues. This LAB Inversion effect is definitely something to remember when you want to do something very different to an image – pretty easy technique to follow and some really interesting results can be obtained. Hope you will give it a try!…..Digital Lady Syd

Digital Lady Syd Related Blogs:
Unsharp Mask Filter In LAB Mode

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One response

  1. Pingback: TRY A LITTLE INVERSION FOR A CREATIVE CHOICE | Digital Lady Syd's Fun Photoshop Blog

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