How To Create Grayscale Images in Photoshop

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How To Create Grayscale Images In Photoshop

A colour image is converted to grayscale in Adobe Photoshop
Creating a grayscale image in Photoshop.

A few weeks ago a photographer friend of mine invited to join what he called, “The Black and White Five Day Challenge”. This was a loose challenge floating around Twitter and all I had to do was produce a different grayscale image and post it to Twitter over the next five days. This immediately caught my attention for a couple of reasons.

First, I had simply forgotten that Black and White imaging could be so much fun because most of my efforts were around working with color. Second, a lot of Black and White images were showing up as full-page background images on the web as designers looked for ways to reduce the file size hit on the processor and download times, especially in the mobile space.

What I decided to do, to rise to the challenge, was to not to just use Photoshop but to also use a variety of imaging applications and apps to create the images I posted to Twitter. Naturally, I started with Photoshop so let’s get started. 

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How To Get Started With Grayscale In Photoshop

The RGB version of the image to be converted to greyscale showing the Photoshop Info palette.
We start with an RGB image.

When Photoshop opens an image you are actually looking at a series of pixels with Red,Green and Blue color values that range from 0 to 255.  You can see these color values when you open the Info palette- Window>Info – and run your cursor over an image. The numbers change. Each color can have one of 256 possible values with 0 being no color and 255 being pure color.  For example an image with 0 for all three values is black and if the values are 255 it is pure white because all of the color combined result in that color.

Another area where you can get a great idea of how colors combine to make an image is in the Channels palette. If you open the Channels palette – Window> Channels – you will see the image is composed of what looks like three grayscale layers. These channels act like filters, mixing the various amounts of Red, Green and Blue to create the colors in the photo.

What you can gather from this is the number of colors in the image, when the image changes to black and white, will reduce to 256 and the channels will reduce to one channel. The result is a serious reduction in the color information contained in the photo and a corresponding reduction in file size.

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How To Use The Photoshop Adjustment Panel

The Black and White Adjustment Layer panel is shown.
The Photoshop Adjustment panel.

The first step in the process is not to select Image>Mode>Grayscale. Do that and Photoshop is going to steer you away from this with an alert suggesting you use a Black and White Adjustment. To do this you select Image> Adjustments> Black and White and when you release the mouse the image becomes grayscale and the Adjustments panel opens. From here you can “tweak” the Red, Green and Blue sliders to adjust to contrast in the image. Once you are satisfied, click OK to accept the change.

Another approach is to avoid the menu and, instead, open the Layers panel and add an Adjustment layer. This ,in fact, is a generally  accepted standard workflow. When the Adjustment layer is selected, choose Black and White from the pop up menu and make your changes to the channels in the Properties panel. The advantage here is if you make a mistake or change you mind you don’t have to start over with a new copy of the image. You simply delete the Adjustment layer and the image returns to its original RGB state.

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How To Convert A Photoshop Image To Grayscale

The greyscal image with the Gray panel is shown.
Always change the Image Mode to Grayscale after conversion. to see if you have a Gray channel.

Though you may be tempted to head for Image>Mode>Grayscale you would be making a huge error. Instead save the image as a .psd to preserve the adjustment layer. This way, can return to the original image if you need to make further changes.

Once you have saved the image select . You are going to get a lot of warnings telling you this could be a mistake. Ignore them if you have saved the .psd.If you open the Channels palette you will see there is only a grayscale channel. I made one final change to image before saving. Seeing as how it was destined for a screen I reduced the DPI value from 300 to 100. The really neat thing about that is the files size drop was pretty significant. The original RGB image weighed in at 2 mb. The grayscale image came in at 346 K.

In the next instalment of this series we'll use Lightroom from Adobe to create the grayscale image.