Tuesday, October 21, 2008

How to Convert Color Digital Images into Black and White Ones

As part of our series of posts on Black and White Photography the following tip on converting images from color to black and white was submitted by DPS reader - Frank Lazaro. You can see his photography at his Flickr page. Please note that most of the shots in this post can be enlarged by clicking them.



With the proliferation of digital photography, people have now started to look at ways to recreate what film has done for them, including recreating a black and white photo.

There are numerous ways to make a digital black and white, some include:

1. In camera filter - By changing a setting in the camera menu to take a black and white photo. Essentially this is a built-in color de-saturation method that removes the color information after the camera takes the picture. I won’t be covering this method in this article.

Pros: Easy, simple and does not require any knowledge or post processing to create a black and white photo.
Cons: Limits the contrast and dynamic range of the photos. In my personal experience, leaves the photo looking washed out or flat.

2. Post Processing - There are various methods in creating a black and white in a post processing environment.

I’ll cover several here. Please note, when I refer to Photoshop, I am using the generic term to mean using any photo editing tool with similar feature, such as Gimp or Photoshop Elements. There are also numerous plug-ins for Photoshop that will convert to Black and White as well. It is not possible; or rather I do not have the time to go over each one, so I will cover the ones that are the most popular in my opinion.

Using iPhoto or Google’s Picasa or Photoshop Elements. With in several of these tools, and even in the professional Photoshop products, there are built-in black and white filters. The benefits to these are they make creating a black and white photo as simple as one click. Granted some of the filters work better than others, but for the most part do a decent job.

Pros: Simple one step process to create a black and white photo
Cons: Requires the purchase or installing of additional software. Quality is hit or miss

Using Photoshop. Even within Photoshop there are multiple ways to create a black and white photo. I’ll only cover a handful of the popular methods, including my personal preferences.

To quick outline the methods, here is a quick list:

  • Channel Mixer
  • Lab Color Method
  • Gradient Map
  • Desaturation

Channel Mixer

The more popular way to convert a photo into black and white is using the Channel Mixer.

There is a common misconception though with this technique - the RGB percentages must equal 100%. The truth is they do not need to equal 100%, they can actually equal whatever you want them to be, since the main goal is to make sure the photo looks the way you want it to look.

When I have used this method before, I usually start with the following settings:

R: 70% G: 30% B: 5%

From there I adjust the settings until the photo looks the way I want it to.

How to convert using the Channel Mixer
First, open your photo and then add a Channel Mixer adjustment layer.


Select Monochrome and adjust the percentages for RGB. Again, I usually start with 70%, 30%, 5%.


Adjust the percentages until the photo looks good, don’t worry about great, we’ll get to that in a moment. You can also adjust the constant percentage to lighten or darken the photo. In this case I darkened the photo by setting the constant to -2%.

When done, click Ok

Now, duplicate that layer twice. If you flatten the photo, just drag the layer to the Create a New Layer Icon on the Layers window. If you prefer to not flatten, you’ll need to duplicate both the above layers. The easiest way to do this is by selecting both the adjustment layer and the photo and dragging them to the Create a New Layer Icon on the Layers window.


Click on the one of the duplicated photo layers.

Change the Screen Mode to Color Burn and reduce the opacity to something between 5% and 15% (personal preference).


Click on the other duplicated layer

Change the Screen Mode to Soft Light and reduce the opacity to something between 5% and 30% (personal preference).


Now the Photo should have more depth and not look as flat. You can adjust each of these layers based on the photo of your personal taste.

One thing I find useful is at the end to add a contrast layer, this will darken the darks and lighten the white. This is optional step.



Lab Color Method

This process has become a personal favorite of mine. It is rather simple, but does require the use of a robust post-processing application, such as Photoshop CS.

Open the file you want to convert.

Convert to Lab Color by going to Image>Mode>Lab Color


From the channel window (if it is not open, go to Windows>Channels) and select the Lightness Channel.


Select all by either going to the menu Edit>Select All or Ctrl-A or Cmd-A and copy the selection either through the menu or Ctrl-C or Cmd-C. Then convert back to RGB Mode, go to the menu Mode>RGB.


Go back to the Channel Window and select the Red channel. Paste either through the menu or Ctrl-V or Cmd-V.


Select the Green Channel and paste either through the menu or Ctrl-V or Cmd-V.


Select the Blue Channel and paste either through the menu or Ctrl-V or Cmd-V.


Reselect the top channel to make all the color channels visible again and you are done.


If for you feel the photo looks flat, you can use the duplicate layer method mentioned above. Just duplicate the main layer twice and follow these steps above.

If the photo is too dark, add an Levels Adjustment layer and lighten the photo.



To lighten the photo, I adjusted the center value and increased it to 1.20. The original value was 1.0. Too darken the photo, decrease the center number. To lighten, increase the center number.

Gradient Map

I don’t use this method all that much, but it is a pretty simple process.

Open the file you want to convert and add an Adjust layer. Click on Gradient Map. On the Dialog box, click on the pull down menu and select Black and White. Click Ok and you are done.




Desaturation Method

This method, in my opinion, leaves the photo looking flat. This is another simple method. Open the file you want to convert and add an Adjust layer. Click on Hue/Saturation. On the Dialog box, decrease the saturation value to -100%. Click Ok and you are done.





There is absolutely no right way to convert a digital photo to black and white. I have barely touch the surface in terms of how to and what kinds of software allow you to create a black and white photo. There are numerous plug-ins, methods, applications etc not mentioned here - but no one way is perfect. In the end, do what looks and works best for you and your photos. Enjoy.

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