How to Convert Pictures to Grayscale in Photoshop CS6
Most people use Adobe Photoshop Creative Suite 6 to enhance an image. This may not happen by adding distracting colors. Sometimes, grayscale is the answer instead. You can convert a color image to grayscale in a multitude of ways. Here are a few that you may want to try.
Choose Image→Mode→Grayscale. Photoshop then asks you whether you want to discard color information. Click Discard. If your image contains multiple layers, Photoshop first asks whether you want to merge your layers. If you want to keep your layers, click the Don’t Merge button.
Although this method does the job in stripping color from your image, you may be left with an image that’s flat and lacking contrast. You can apply a Levels adjustment (choose Image→Adjustments→Levels) to boost the contrast, or you can try one of the other conversion methods.
Be aware that you can no longer apply color to your image after you convert it. If you choose a color in the Color panel, the color appears gray in the foreground and background color icons. If you want to apply color to your grayscale image, convert it back to RGB or CMYK mode.
Lab Color mode method
This method most likely provides a better grayscale image than the quick-and-dirty method. Make sure that you finish all your edits that require layers before you follow these steps:
Choose Image→Mode→Lab Color.
Converting to Lab Color mode converts the channels into a lightness channel and a and b channels containing ranges of color. If you have layers, you’re prompted for whether you want to merge your layers. You can choose either option because, in Step 2, you have to flatten the image if you want to proceed with the operation.
Choose Window→Channels. Delete the a channel by dragging it to the trash can icon at the bottom of the panel.
Again, if you have layers, click OK to flatten your layers. If you select Cancel, you abort the operation.
If you delete the a channel, the b channel then changes its name to Alpha 2.
Delete the Alpha 2 channel.
That leaves you with the lightness channel, which is now named Alpha 1.
Your color image is now a grayscale one.
Best channel method
If you look at the individual channels in the image, one often stands out as being a very good grayscale image by itself.
You may find that the Red channel provides a good grayscale image when the subject is people because humans have a lot of red in their skin. Or you may find that the Green channel looks good in a scenic shot. The Blue channel rarely yields a nice image. Most of the crud picked up in a digital image finds its way into the Blue channel.
In the Channels panel, select each channel and view its contents. Find the channel that looks the best, select it, and then choose Image→Mode→Grayscale. If you have layers, Photoshop asks whether you want to flatten your layers. Click OK. Photoshop then asks whether you want to discard all the other channels. Click OK.
You can also use the Channel Mixer to create custom grayscale images.
Finally, you have yet one more way to convert to grayscale, via the Black & White feature in the Image→Adjustments submenu.