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Get the best out of your black and white images with basic optimisation techniques

By October 13, 2014 Photography No Comments

When you convert an image from colour to black-and-white, it’s important to set some basic parameters that will bring out the best in the photo before you go on to fine-tune it. Whether you use a Raw converter or post-production software, you can use the basic optimisation process outlined here to bring out the three key qualities in a black-and-white image: tonal range, brightness, and contrast.

Although the specific tools and methodology may vary depending on the particular Raw converter you choose, start the optimization process by maximizing the tonal range of the image. Use the highlight and shadow warning option (shown here in red and blue respectively) to indicate the point at which each end of the histogram is getting clipped. There may be a key option that shows a clipping preview screen.

Although the specific tools and methodology may vary depending on the particular Raw converter you choose, start the optimization process by maximizing the tonal range of the image. Use the highlight and shadow warning option (shown here in red and blue respectively) to indicate the point at which each end of the histogram is getting clipped. There may be a key option that shows a clipping preview screen.

Tonal range

The first step is to ensure the image contains the complete range of tones from white to black—this is the mainstay of optimisation. How you achieve this will depend on the software you’re working with.

If you’re using Raw-conversion software work through the basic sliders—exposure, highlights, shadows, and recovery for example—before you convert to black-and-white, ensuring that they are all set to their optimum points. Your aim is to fill the entire width of the histogram.

Should you be working on an already processed TIFF using post-production software such as Photoshop or Paint Shop Pro, for example, use the Levels command to set the black (shadow) and white (highlight) points.

Clipping

As well as having a histogram to guide you, most software will feature some form of clipping warning that shows you at what point the black and white tones are clipping, or where they are so dark or so light that they no longer reveal any detail. It’s worth enabling the clipping warning and using it to assist you in adjusting the image until you’re satisfied that the highlights and shadows are accurately set.

BW optimise ii b

To set the black and white points in a processed TIFF, call up the Levels command and drag the black-point slider to align with the left of the histogram. Repeat the same process with the white-point slider, but be careful not to clip any highlight detail.

To set the black and white points in a processed TIFF, call up the Levels command and drag the black-point slider to align with the left of the histogram. Repeat the same process with the white-point slider, but be careful not to clip any highlight detail. In Photoshop, holding down the Option/Alt key provides a preview of the clipped areas.

In Photoshop, holding down the Option/Alt key provides a preview of the clipped areas.

When setting the white point it’s important to make the distinction between specular and nonspecular highlights. Examples of specular highlights include the reflection of sunlight off water or the shiny surface of a car. Specular highlights don’t contain any detail and ideally should be clipped, if not the final result may look flat. Nonspecular, or nonreflective, highlights on the other hand, are the brightest parts of the image that retain detail, and should definitely not be clipped or you’ll lose important highlight detail.

Brightness

While tonal range is, to a certain extent, measurable and determined by setting the black and white points, brightness is far more subjective and should be set according to what complements the image and to your taste. Consequently, it’s recommended that you adjust the brightness when you’ve converted the image to its monochromatic state.

Again, how you adjust overall brightness levels depends on your particular software, but a Curves adjustment layer in post-production software offers a good level of control without affecting the black or white points. While for those using a Raw editor, the Brightness slider (or if that is not available, the Exposure slider) is the traditional route, using additional controls if necessary to ensure highlights (or shadows) don’t clip.

Contrast

Finally, assess the image for contrast. Essentially, contrast is the relationship between the brightest and darkest tones; however, it is generally accepted that you exclude the very brightest (specular) and very darkest tones, as taking these into account will usually give an extreme result.

Both brightness and contrast can be adequately covered using the same tools in most Raw converters and post-production image editors. In the case of the former, the Exposure and Contrast (or Brightness) sliders are effective at adjusting the mid-tones, but can force the highlights to clip. So turn to other sliders such as Highlights or Recovery to bring them back. In post-production software the Curves.

Both brightness and contrast can be adequately covered using the same tools in most Raw converters and post-production image editors. In the case of the former, the Exposure and Contrast (or Brightness) sliders are effective at adjusting the mid-tones, but can force the highlights to clip. So turn to other sliders such as Highlights or Recovery to bring them back. In post-production software the Curves.

With the sophisticated algorithms found in today’s software, it’s possible to make localised contrast adjustment in which adjustments are made depending on the value of neighbouring pixels (e.g. Lightroom’s Clarity slider). However, don’t be tempted to go over the top with these extra levels of control. If you push these sliders too far, you can find yourself looking at an unrealistic image.

Adjust and re-adjust

While this process is set out as a linear workflow, it’s important to remember that as you make one adjustment, it will have an impact on how the others are perceived. Therefore you might find that after you’ve adjusted the brightness levels you need to return to the tonal range and re-assess it. Likewise, don’t be afraid to tweak tones and brightness when you’ve adjusted the contrast, either.

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