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Responses to Common Misconceptions

Misconception 1: Custom tone curves result in inconsistent exposures. Response: Custom tone curves are a consistent adjustment to the normal tone. If you are getting inconsistent results, your metering technique is most likely the cause. Most people with inconsistent exposures simply don't know when to rely on Nikon's Matrix Meter and when not to. While the matrix meter is smart enough to figure out the proper exposure in a wide range of lighting situations, it can be fooled.

Misconception 2: While custom tone curves may work in some lighting situations, they will not work in others, which makes a general use custom tone curve impossible. Response: This misconception arises from unrealistic expectations. Light comes in an infinite variety of contrasts. Although there are no rules to art, just guidelines, to compensate for low contrast lighting, you shoud use a high contrast curve, and to compensate for high contrast lighting, you should use a low contrast curve. The best you can do to create a general use curve is to compromise between the two extremes and create a tone curve with medium contrast. Furthermore, a good general use curve should have a linear response from the shadows up through the midtones so that the resulting image will have a similar contrast over a longer range of tonalities. This will allow you to take both high key and low key images with the same contrast. Tone curves that are not linear in the shadows and midtones, on the other hand, require you to exposure such that the resulting tonality is within a specific range for best results. This makes such curves inadequate for general use. The custom tone curves available here are all intended for general use.

Misconception 3: Custom tone curves limit the camera's capabilities. Response: Custom tone curves take up memory space that would otherwise be wasted. You are actually limiting the capabilities of the camera if you do not have a custom tone curve loaded. If you ever choose not to use the custom tone curve, you can always use the factory settings.

Misconception 4: Custom tone curves alter color too much to be of use. Response: Not all custom tone curves alter color. It is possible to create a custom tone curve that does not alter color by maintaining linearity from the shadows up through the midtones. The reason for this is that the RGB color channels are individually altered through a "neutralizing coefficient" that is optimized for the default normal tone. Maintaining linearity with the normal tone thus allows the custom tone curve to use the same coefficients without any shifts in color. The custom tone curves available here are linear in those regions.

Misconception 5: Custom tone curves blow highlights. Response: It all depends on how the custom tone curve is designed. The formula used for the custom tone curves developed here are a linear portion from the shadows through the midtones followed by a low contrast s-curve in the highlights. As a result, while adding 1/2 of a stop in brightness to midtones, they only add about 1/5th of a stop of brightness to the highlights. In most cases, if highlights are blown with the custom tone curve developed here, they would've been blown even without them. Thus, blown highlights, just like inconsistent exposures, are the result of poor metering technique.

Misconception 6: You can compare the effects of custom tone curves by using the image preview in the Nikon Capture Camera Control dialog box or by plotting the same curve in Nikon Capture or Photoshop. Response: This is completely false. Unfortunately, many people have concluded that custom tone curves result in "washed out" images because they attempted to compare the results of custom tone curves by methods other than actually taking photographs with the curves loaded in the camera. The reason why this does not work is that the custom tone curves are applied in the camera on a logarithmic scale while the same curves are applied to the preview image in the Edit Camera Curves dialog box, Nikon Capture (NC), and Photoshop (PS) on a linear scale. The differences in results can be significant. To test custom tone curves, you have to actually use them in the camera.

Misconception 7: Many people seem to be using custom tone curves, so I should use them too. Response: The custom tone curves available here are not for everyone. If you are comfortable with the default tonality of the D100, there's no need to change a thing.

Misconception 8: Custom tone curves are for amateurs. Skilled photographers don't need them. Response: While it is possible to control many things simply by manipulating shutter speed and aperture, digital photography adds several new dimensions to the reportoire of traditional film techniques. Custom tone curves are just another tool in the bag. In addition, the custom tone curves available here do something that no combination of camera settings can do. Both amateurs and skilled photographers can benefit from the use of these curves.

Misconception 9: I don't need custom tone curves becaue I like to post-process every image. Response: You are a sado-masochistic, self-flagellant individual with highly developed computer skills. Seriously, the custom tone curves available here do not claim to eliminate post-processing for ALL images. I make a distinction between the types of photographs I take and the amount of post-processing I spend on them. For my landscapes, portraits, abstracts and B&W photographs, I often use post-processing techniques to blend exposures or emphasize things. This is a necessity because these photographs are intended as art. Also, these photographs are typically low in volume. As for my action, event, candid, travel, nature, and snapshot photographs, I use little to no post-processing at all since these photographs are more journalistic in nature and typically much higher in volume. The results I achieve through the use of custom tone curves are most often adequate for these purposes. If I do any post-processing on these photographs, it is usually confined to minor rotations, cropping, white balance adjustments, or white and black slider adjustments. I avoid complicated midpoint slider or curves adjustments because they alter saturation and contrast in such a way as to reduce the natural look of the image. I try to use as much automation as possible such as Digital DEE or the Photoshop actions available here.

Creating Your Own Custom Tone Curves

     If you would like to create your own custom tone curve, there are several important rules you should be aware of:

1. Where there is an increase in slope, there will be an increase in contrast. Conversely, where there is a decrease in slope, there will be a decrease in contrast. 
2. Where there is an increase in contrast, reds and yellows saturate more quickly than greens and blues.
3. Where there is a decrease in contrast, all colors become less saturated.
4. Also, keep in mind that image detail is closely related to contrast.

     As you can see, there are restrictions in how much you alter the default tone curve. In general, you should try to avoid excessively altering linearity from the shadows up through the midtones because it is easier to notice contrast changes in this range of tones and images may appear unnatural.  I would not recommend any custom tone curve that has more than 2 or 3 anchor points or is overly curvaceous in the left half of the curve (the portion affecting shadows and midtones). However, the right half of the curve (the portion affecting highlights) is much more forgiving. The reason for this is that the scale used to apply the custom tone curve in the camera is not linear. The first half of the custom tone curve affects approximately the first three-quarters of the original image's tonality (shadows AND midtones) while the second half only affects the last quarter of the original image's tonality (higlights ONLY). This is based on personal observation after working with hundreds of variations of curves and literally taking thousands of photographs. Apparently, the D100 applies custom tone curves to images on a logarithmic scale as opposed to the linear scale used to represent the curve.

     The above characteristic of custom tone curves also means that applying a curve in Photoshop (PS) or Nikon Capture (NC) with the same shape as a custom tone curve will not yield the same results as applying the custom tone curve in the camera. Conversely, applying a custom tone curve in the camera with the same shape as a PS or NC curve will not yield the same results as applying the curve in PS or NC. The image preview in NC Camera Controls also gives an incorrect representation of the effect the custom tone curve would have on actual photographs.

     The latest custom tone curves I created are available here for download. They were originally designed for the Nikon D100, however, I have received several emails from D70 users claiming they work exactly the same in the D70. All the custom tone curves I've ever created have the common theme of adding the precise equivalent of +0.3 EV or +0.5 EV to the default "normal" tone. I test all my curves with literally hundreds, sometimes thousands, of photographs, tweaking them until I observe histograms that match peak for peak the histograms of images taken with a setting of +0.3 or +0.5 EV. The only difference I allow for is in the highlights where tones are typically compressed to retain as much detail as possible. This has the additional benefit of making images appear more film-like by softening the transition to pure white. I also design all my tone curves to avoid unecessarily altering the linearity of shadows and midtones, which makes my curves good for general use since the contrast remains relatively the same whether you are shooting a low key or high key image.

     As mentioned before, I only recommend using simple curves such as the ones I’ve provided here.  Ironically, a tone curve with too many bends can shift hues and alter color saturation. Furthermore, such a curve cannot be for general use since it assumes a specific a distribution of tonalities. The best tone curves are nearly linear.  Another simple yet effective curve is the one created by Neil van Neikerk available at http://www.planetneil.com/nikon/d100-customcurves.html.

     As a final word of advice, remember that no matter what custom tone curve you use, if your metering technique is poor, no custom tone curve will help you.

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