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Image adjusted selectively with a gradient
Warm exposure
Cool exposure
Two exposures blended with a gradient mask
Smooth transitions. They’re the essence of continuous tone images. In most cases, you want to preserve them. On occasion, you want to modify them. Sometimes, you want to create them.
While gradients can be used as image layers, they are more frequently used as layer masks. Gradient masks can be used in two central ways, ways that differ from one another significantly. First, gradient masks can be used to selectively reduce the effects of any correction made as an adjustment layer. Second, gradient masks can be used to selectively reduce the opacity of any image layer.
Digital correction with gradient mask techniques replace and surpass using traditional graduated filters. Not only can you make more precise corrections digitally, with gradients you can control the placement of the gradient and transitions within it more precisely. The gradient is uncoupled from the exposure and is indefinitely and infinitely modifiable.
You can do much, much more with gradients. Here are a few of the things you can accomplish using gradient masks.
Transition between stronger and weaker settings of a correction – enhance contrast and color balance selectively, reduce fall off, neutral density filtration, color filtration, add or remove vignetting, etc.
Transition between dark and light exposures – extending dynamic range.
Apply filtration selectively – sharpening, blurring, noise, etc.
Transition between exposures with different points of focus – increasing depth of field.
Transition between adjacent exposures of the same subject – increasing format.
Transition between more saturated and less saturated renditions of an image – accentuating atmospheric perspective.
Transition between the same image with two different white point settings – accentuating or creating the appearance of mixed light sources.
Believe it or not, this is only the beginning of the possibilities gradients offer. Mastering gradients is an essential digital skill.
Although gradients can be extremely complex and can yield extremely sophisticated results, once the basic principle behind them is firmly grasped, they are actually quite simple to create and use.
Gradients are easy to create. You’ll find the Gradient tool (essentially a brush) midway down the Toolbar, below the Eraser and above the Blur tool. With the Gradient tool active click hold and drag a vector across an image, either on a layer mask or less frequently on a new blank layer. A gradient will be created between the start (where you click first) and endpoints (where you drag to). The start and endpoints may be placed anywhere on the canvas. Gradients can be drawn for any length at any angle. The shorter the distance between the two points, the tighter the gradient will be with more abrupt tonal transitions. The longer the distance between the points the softer the gradient will be with smoother tonal transitions. Favor longer gradients with smoother transitions. They can always be tightened and repositioned by adjusting contrast. (Reducing contrast will not produce the opposite effect; it will posterize the gradient.) There may be times when you want to place a start or endpoint outside the border of an image. You can do this by expanding the window around the image. Click and drag on the lower right-hand corner of the window. Gray will be seen surrounding the image but inside the window. A start point, endpoint, or both may be placed anywhere within the window.
Linear gradient
Reflected gradient
Radial gradient
Star gradient
Angle gradient
There are five types of gradients to choose from. Two, Angle and Diamond are of limited use. Three, Linear, Radial, and Reflected are very useful. Linear uses the start and endpoints to define a gradient along a line. Radial uses the start and endpoints to define the radius of a circle. Reflected uses the start and endpoints to define the center (foreground color) and outsides (background color).
Of the sixty-six gradient presets you can choose from, the first two serve most purposes – Foreground to Background and Foreground to Transparent. (Most people can pretty much forget about the other sixty-four presets.) Classically, black and white or shades of gray are most frequently used.
Curves gives you more control
Gradients can be extraordinarily flexible. You can alter the characteristics of a gradient by checking the Edit button under the gradient Options palette. If you don’t get precisely the effect you’re looking for, you can try again. Or, if you’re fine-tuning a monochromatic gradient there’s an easier way. After creating a gradient, slightly longer than you think you need, apply a Curves adjustment to the gradient (Image > Adjustments > Curves). Move the midtones; shift the midpoint. Move the highlights left and/or shadows right; shift the endpoints – quickening the transitions in between. Move the white point down and/or the black point up; change the endpoints to gray. Move the white point down to the black point and the black point up to the white point; invert the gradient. That’s control!
Linear and Reflected gradients combined
You can combine multiple gradients with one another in a variety of ways. Here are two. One, start with one gradient and use the Foreground to Transparent option to add a second. Two, start with one gradient and change the Gradient Tool’s blend mode to Darken or Lighten to add a second. The two methods sometimes yield different results.
Blend modes can be used to modify how a gradient interacts with the image it is drawn on in a variety of ways. For the most control, don’t use the blend mode with the brush; instead, draw the gradient on a separate layer and use the blend mode of the layer to achieve the same effect with more flexibility and control.
You can reposition any gradient using the Move tool. Moving a gradient mask on an adjustment layer presents few problems. You can easily tell if you are working on the image or the mask – its icon will be highlighted. Because and image layer and its mask are linked, to move a mask separately you must first unlink the two by checking off the link icon between them and then targeting the mask to move it separately. It’s likely you will want to relink the two when you are done.
Gradients can be transformed substantially (Edit > Free Transform).
Gradients can be created within active selections to affect only selected areas.
Some gradients suffer from banding. To reduce the effects of banding, add a small amount of noise (Filter > Noise > Add Noise); this will often break up the effect of banding. Be careful not to overdo it or you’ll simply trade one distracting artifact (lines) for another (dots).
But wait, there’s more! Here are three more ways to create extremely useful gradients.
Use a soft-edged brush to create a gradient
One, use a soft-edged brush; the feathered edge automatically creates a gradient.
Two, make a selection, then make an adjustment layer, double click on the mask to activate it’s properties, and use the Feather slider. I don’t like automatically feathering selections. I prefer this method over automatically feathering selections: you get a better preview; you get more precision; and you can modify the gradient by reactivating a masks’ properties.
Blur a shape to create a gradient
Three, blur a hard-edged shape and you can create a gradient. By the same token, if a gradient does not have sufficiently smooth transitions it may be blurred, in whole or in part; watch for posterization if you do this.
Remember, masks are black and white images. Anything you can do to a Grayscale image you can do to a mask – adjust its contrast, filter it, transform it, Liquify it, clone it, paint it, etc.
Learning to make good gradient masks is an indispensable skill for adjusting digital images. Their power and versatility are simply unrivaled.
Read more about Selections & Masks.
Learn more in my digital photography and digital printing workshops.
A complex contour mask – made one minute.
Digital imaging offers the ability to define complex contours efficiently and precisely, enabling users to affect an image in very specific areas. What was once extremely tedious and challenging is now quick and easy. Once you learn a few essential selection and masking techniques, few contours will elude your grasp.
Before I continue, let me caution you against always defining contours precisely. Remember, contours in continuous tone images are often quite soft. What’s more, many times, photographers simply need to define broad areas to work in with smooth transitions into surrounding areas. Just because you can define contours precisely, doesn’t mean you should. But it’s highly advantageous to have the option of doing so when you need to.
Besides defining an area by hand, either with a selection or brush tool, there are a number of more efficient and precise ways to isolate contours; the Magic Wand Tool, the Magnetic Lasso Tool, the Color Range feature, and deriving a contour mask from a contrast mask. Try these first.
Keep in mind that all of these techniques use contrast within an image to isolate a contour. Contrast in any one component of color can be used – luminosity (light and dark), hue (warm and cool), or saturation (intense or desaturated). If contrast helps define a contour then you can accentuate the contrast of any one component of color within an image to make it easier to define a contour, using an adjustment layer. Once the contour has been defined, you can throw away the adjustment layer that was only intended to be used to make selection easier.
The Magic Wand, found in the Tool Bar, is ideal for selections of broad areas of color. Two check boxes give you control over how the Magic Wand tool behaves; Tolerance (which defines the range of related values away from the sampled color that will be included in the selection – based on 256 levels) and Contiguous (which limits a selection to areas of similar color that abut one another). In the same location in Tools, the Quick Selection Tool offers fewer controls but does an even more intelligent job. Try it before you move on to other options. Many times it does a surprisingly quick good job with little or no fuss.
The Magnetic Lasso, also found in the Tool Bar, tool can be used for slightly more difficult contours. Using it, you can add an extra degree of discrimination manually. The tool will define the majority of the contour for you, if there is adequate contrast between it and surrounding areas. While the default settings often provide excellent results, Width (the distance from the path drawn where contours will be detected), Edge Contrast (the amount of contrast required for a contour to be detected), and Frequency (the number of points placed while defining the contour) can be used to modify the sensitivity of the tool. Drawing a contour too quickly will reduce the accuracy of the tool. While defining the contour, if points are placed that are undesirable you can hit the Delete key to eliminate previously placed points, one at a time. When using Lasso and Marquee tools, practice drawing selections in closed loops. If you define only part of a contour and then let go, a straight line will snap between your start and finish points. All selection tools can be used multiple times to define a selection and can be used in combination with one another; hold the Shift key to add to and the Option/Alt key to subtract from an existing selection.
The Color Range feature, found under the Select menu, is very useful for defining complex contours involving multiple areas. Color Range has predefined settings to automatically detect Reds, Greens, Blues, Cyans, Magentas, Yellows, Highlights, Midtones, and Shadows. In addition, it has a Sampled Colors feature that can be used to define a custom range of colors that can be increased or decreased by using the Add to Sample (+) and Subtract from Sample (-) droppers. Selections can be expanded and contracted using the Fuzziness and Range sliders –for Sampled Colors, Shadows, Midtones, and Highlights but not predefined hues. The selections Color Range makes are often more sophisticated than the previous tools mentioned, defining areas not just with black and white but also shades of gray.
Contrast masks can be turned into contrast masks, for the most challenging selections with very fine detail and/or transparency. Based on the luminance values of individual channels (R,G, or B), a contrast mask can be used to define a contour by accentuating it’s contrast so dramatically that all shades of gray are eliminated leaving only black and white values. Duplicate the channel with the best contrast in the area you wish to isolate. Or, load it as a selection by dragging it to the selection icon in the Channels palette and then create a layer mask. Then, accentuate the contrast of the alphachannel or layer mask, using Curves. When accentuating contrast, pay particular attention to using increased contrast to define the contour you are concerned with. Avoid the temptation to use contrast to drive broad areas to white or black, if doing so will adversely affect defining the contour precisely. On occasion, you may want to select a specific area of an alphachannel or layer mask to accentuate contrast locally. Where unwanted values remain, select and fill or use a brush to paint an area with the appropriate value (black or white).
Using these tools and strategies few contours will elude your definition. You’ll be able to define very complex contours efficiently and precisely.
Read more about Selections & Masks.
Learn more in my digital photography and digital printing workshops.
RGB image
Red Channel
Green channel
Blue channel
The relationship between highlights and shadows is a critical aspect of any image. Photographers have been trained to become highly sensitized to these relationships. Today, photographers have more control and greater precision than ever before over these key visual elements, using the digital darkroom. In Photoshop, the type of adjustment chosen will provide very specific control. The specificity of an adjustment can be further refined by using a mask. One type of mask yields extreme precision and is derived directly from the light and dark relationships within an image, a luminance or contrast mask.
A contrast mask will allow you to target a specific range of tones without affecting the others; highlights, shadows, and even midtones. In the analog darkroom it’s quite challenging and time consuming to make contrast masks; in the digital darkroom it’s quite easy to quickly make contrast masks. And, you can refine or modify them infinitely and indefinitely.
Here’s how to do it.
Load a channel as a selection and with that selection still active create a layer mask. The quickest way to do this is to go to the Channels palette and while holding the Command key click on a channel – R, G, B or RGB. This will create a selection based on the luminance (light and dark) values of the channel you choose.
With so many choices before you, which channel should you choose? Choose the channel that is light in the areas you want to adjust and dark in the areas you don’t want affected. When in doubt, load the RGB master channel as this will give you a selection based on luminance. If you choose an individual channel (R, G, or B) related hues will become lighter than others and complementary hues darker than others – i.e. in the red channel reds will be very light while cyans will be very dark.
The active selection outline will appear complex; a dotted line will appear at all 50% gray values, but the whole image will be affected to varying degrees based on the density of the values used to make the selection. As values grow darker the affect reduces; as values grow lighter the affect increases. Remember this mantra, “Black conceals; white reveals.” You can turn a selection into a mask in one of two ways, make an adjustment layer (Layer: New Adjustment Layer)(the selection automatically becomes an adjustment layer mask) or make a layer mask (Layer: Layer Mask: Reveal Selection).
As a mask is comprised of shades of gray its lightness and contrast can be adjusted. Very often, contrast masks can be improved by having their contrast adjusted. Use Curves for the greatest precision in contrast adjustment. Here are a few strategies for doing this. Increase the contrast of a mask and its lightest areas will allow more of an effect to show through while its darkest areas will allow less of an effect to show through. Darken the mask and it will allow less of a correction through. Lighten the mask and it will allow more of an effect through. In special cases, you may want to raise the black point when applying Curves to a mask; this will allow some adjustment to be applied to the deepest values with increasing intensity in the highlights. Conversely, you could lower the white point to reduce the effect in highlights or you could simply reduce the opacity of the adjustment layer.
Would you like to target the shadows instead of the highlights? Invert the mask (Image > Adjustments > Invert or Command I) to reverse the relationship between highlights and shadows; black becomes white and white becomes black.
Mask inverted
Contrast masks add the ability to target highlights and shadows to any color adjustment tool that does not already provide this function and to all filters.
Question whether you need a contrast mask when making image adjustments with Curves, which provides the ability to target specific ranges of tone without the use of a mask. If the adjustment you want to make to a specific region of tones in an image is extreme and you want to substantially reduce the affect on adjacent tones, then, and only then consider using a contrast mask in combination with Curves. Guard against introducing posterization when doing this.
Classically, photographers use a contrast mask when darkening very bright highlights or lightening very dark shadows. For these types of corrections, where industrial strength methods are required, consider using the blend modes Multiply (for highlights) or Screen (for shadows) in combination with a contrast mask to reduce the affect on the opposite end of the tonal scale and prevent loss of detail.
Today, photographers have additional opportunities to enhance color images using contrast masks. In addition to affecting the lightness (luminosity) of highlights or shadows, you can affect their hue and/or saturation. Compare these three solutions; an image with lightened highlights; an image with warmed highlights; and an image with saturated highlights. All three versions will appear more luminous or filled with light, but the qualities of light in each one will differ. After you’ve tried this, try making opposite moves in the shadows. Once you’ve done these experiments, you’ll start seeing new potential in every color image.
Highlight lightened
Highlight warmed
Highlight saturated
Never have we had so much control over the quality of light within our images. Imagine the possibilities. Better yet, experience them. A world of possibilities for image enhancement will unfold before you.
Read more about Selections & Masks.
Learn more in my digital photography and digital printing workshops.
High frequency
Medium Frequency
Low Frequency
Frequency is a term that’s being used more and more. That’s because new tools offer you more control over frequency than ever before. Noise reduction, sharpening, and HDR all offer unprecedented control over the look and feel of detail in our images. Frequency is used to describe the amount of detail packed into a given area of an image. This is measured by the amount of tonal variation between rows or columns of pixels. Imagine measuring an image with a line that passes across it (horizontally from left to right or vertically from top to bottom). The mean or average tonal value along lines can be charted and then compared to values from other measurement lines, especially those nearest to each other.
Of the three stages in a sound sharpening workflow – capture sharpening, creative sharpening, and output sharpening – creative sharpening is the stage that has the most impact. The goal of creative sharpening is to give an image a specific look and feel. There are at least three things creative sharpening can do for your images.
One, creative sharpening can prioritize; it can direct attention to specific areas of an image.
Two, creative sharpening can enhance; qualitative aspects of images like texture and line, can be amplified to produce stronger responses.
Three, creative sharpening can be used to accentuate different qualities of light; a great deal of detail is carried by the luminosity component of color and changing it changes the overall appearance of light within the image.
Used consistently creative sharpening can produce a distinctive style that is more easily recognizable to viewers. (Remember, sharpening is a way to enhance details and it may also be used with its counterpart blurring to make effects appear even stronger by comparison.)
Before sharpening
Unsharp Mask only
Unsharp Mask and High Pass filters combined
Different sharpening techniques make the world look different. A world of difference can be seen between the thin hard line of Unsharp Mask and the broad feathered line of High Pass Sharpening.
Can you choose a combination of both? Yes, you can! You can choose the texture of one, the halo of another, and the line of yet another, applying them either globally or selectively. You can customize the look and feel of detail in any image or image area with astonishing precision and flexibility.
Layers have Blend Modes and can be masked
Double click a layer to activate its Blend If sliders
There are many reasons to use layers when sharpening your digital images.
How do you do this? Simply duplicate the Background layer and sharpen the new layer.
Eliminate Saturation Shifts
Layers can be used to eliminate saturation shifts. Change the Blend Mode of a sharpening layer from Normal to Luminosity. Color noise will also be reduced this way.
HDR software is most typically used to render shadow and highlight detail, but it can also be used to enhance tonal separation and detail in any range of tones, even in images with extremely low contrast. The very same tools that are used to compensate for HDR side effects can be used to sharpen any image.
When multiple bracketed exposures are merged into a single processed file, shadows and highlights that exceed the dynamic range of a camera’s sensor are compressed into the dynamic range of a digital file, taking the midtones with them. Depending on the HDR software used, a variety of tools are available to restore contrast and separation in midtones. If used aggressively, these tools produce the tell tale signs of contemporary or grunge HDR artifacts – halos and texture accentuation. These are the very same artifacts that digital sharpening routines use more conservatively to make images appear sharper - only they look different.
Adobe Camera Raw's Detail panel
Optimal image sharpening is best done in three stages – capture (Do it during Raw conversion.), creative (Do it in Photoshop.), and output (Automate it.).
This article covers the first stage of sharpening – capture sharpening.
Capture sharpening benefits all images. Capture sharpening compensates for inherent deficiencies in optical and capture systems. All lenses and sensors have specific characteristics and deficiencies. They do not all have the same characteristics or deficiencies.
To speed your workflow, default settings for the best starting point for capture sharpening can be determined for all images created with the same lens/chip combination and saved for subsequent use. To optimally sharpen an image, you’ll need to modify these settings to factor in additional considerations – variances in noise (ISO, exposure duration, temperature), noise reduction settings, and the frequencies of detail (low/smooth to high/fine texture) in an image.
