Local Light: Sketch-o-graphs

Fishhook barrel cactuses live up to their name. The spines look like fishhooks and are just as sharp. These, along with the hair-like structures, create an almost abstract covering for this common cactus. Looking closely at the edges, you can see the fine black lines that the sketch actions add.

An earlier post on local light discussed how photographing nearby subjects provides an opportunity to see them in new ways using different techniques, either during the capture phase with the camera or in post-processing. This past summer I decide to more fully explore this approach. My daily walk on the neighborhood streets offers plenty of interesting subjects in the form of Sonoran desert cactuses and other succulents. But I also wanted to do something different photographically with them and had my eye on the sketch technique I learned from Steve Dell. His photos using this technique along with those of Bob Hills made me want to explore this technique to see what works for me. These “sketch-o-graphs” can still look photographic, but they usually have enhanced edges and color. I was also planning to include the sketch action in the TK8 plugin and wanted to gain additional experience using it to insure the plugin included the best practices for getting good results. NOTE: The sketch actions in the TK8 plugin are accessed via the Workflow Extras button on the main interface of the Multi-Mask module (green outline, left image), and this opens a new interface where the Color Sketch and B&W Sketch actions are located.

Choosing the subject

Based on what I saw in Steve’s and Bob’s photos, images with lots of detail and texture seem to be the best candidates for sketches. Things like clouds, moving water, and out-of-focus elements are less affected by this technique. The sketch action finds edges in the image, and the stronger the edge contrast, the more prominent it will appear in the sketched version. My local subjects, the succulents along my street, were ideal for this as they had excellent texture and well-defined edges. However, I actually took it a step further and focus-blended most of the the images. Since many of the images were shot with a macro lens, focus-blending eliminated most out-of-focus areas and helped insure the entire image would convert well as a sketch.

The converted RAW file is on the left and the finished sketch is on the right. The sketch technique enhances both color and edges. Color sketches often soften fine textures in the image, which makes the resulting image look more sketch-like. The strong edges, though, become more prominent and make this an ideal image for sketching. Agaves create some of the most beautiful patterns in the Sonoran desert. There is a welcoming softness in the flower-like shape of their leaves, but the sharp tips are a reminder to not get too close.

RAW file conversion and initial sketch

The sketch actions can have quite an impact on the image, though it’s not easy to predict what the image will look like once it’s been converted to a sketch based on the initial RAW fie conversion. As such, I’m not necessarily looking to make a perfect image in Lightroom or Camera Raw. Instead, what I want from RAW conversion is an image that converts well to a sketch, and that usually means a little experimentation. In Camera Raw, I apply a linear profile, click Auto, and then make a few adjustments to balance brightness, color, and saturation. Images that have slightly under-saturated colors tend to work better as sketches since the sketch action usually bumps up saturation. The image is opened as a smart object in Photoshop, and a sketch action is immediately run on it. If it looks good, I’ll work with that sketch from then on. However, if I don’t like it, I’ll delete the group containing the sketch layers and tweak the RAW file by double-clicking on the smart object’s thumbnail to do additional processing in Camera Raw. I go back and forth this way, creating a new sketch after each RAW file adjustment, until I get a sketch I like. In this way, RAW file conversion and making the initial sketch are essentially one step. This initial sketch, created immediately after RAW file conversion, becomes the base image for additional development in Photoshop. Running sketch actions on different RAW conversions lets me zero in on the best starting point for developing the sketch in Photoshop.

These images demonstrate the enhanced color and edges that come from running the Color Sketch action. The image can look quite photographic still, but often much improved compared to the RAW conversion. These are cereus cactus flowers that bloom for just one night each year.

Color Sketch or B&W Sketch?

There are two sketch actions: Color Sketch and B&W Sketch. Which to use is often a matter of personal preference, and I’ll sometimes try both to see if I prefer one over the other. The actions make it easy to try both, and there’s no easy way to predict which will look best. One thing to keep in mind is that the Color Sketch sometimes pulls unexpected colors out of the deep-shadow areas or adds excessive color saturation to some areas, like blue skies, and if these don’t look right with the image, then the B&W Sketch might be the preferred alternative. However, even with the Color Sketch, overly colorful shadow areas revert back to being quite dark and less colorful after the initial sketch adjustments. Occasionally, over-saturated colors require a little extra effort to control later on, and it’s sometimes better to pull back their saturation in the RAW file before running the Color Sketch action (and is another reason to coordinate RAW file conversion with making the initial sketch).

A black and white sketch-o-graph of an agave clearly shows how the edges of the leaves have been enhanced with a black line, which looks quite natural in this monochrome rendition.

Initial settings

There are two settings needed for making the initial sketch. They’re both easy to set and it’s best to use the same setting on each image, at least to start. The layers produced by the sketch actions mean the initial settings can always be readjusted later.

  • Minimum–The Minimum dialog window opens as the action runs. The default is “4” and it’s best to leave it set to that as it generally produces output that indeed looks like a sketch, at least in the details and textured parts of the image. The Minimum setting creates the black sketch lines that define the sketch look, and the greater the edge contrast, the more prominent the sketch lines. After seeing the initial sketch it’s fine to go back and adjust the Minimum value, but using “4” as the starting point gives a good impression as to how well the image will work as a sketch.
  • Levels adjustment–The final step in the sketch action is the creation of a Levels adjustment layer on top of the other layers in the Sketch group. The Properties panel is opened (if it’s not already open) and the user can then make a Levels adjustment using this layer, and this adjustment is critical in creating the desired look for the sketch. The initial Levels adjustment is also (nearly) the same for every image: Pull the midtones slider to the far right edge of the histogram that’s displayed in the Properties panel. I’m not entirely sure why this works, but it does. This maneuver restores proper global contrast to the image while maintaining its sketch-like quality. Small deviations of where the midtones slider is placed can lead to slightly different (but noticeable) effects, but placing the midtones slider very near the right edge of the histogram is almost always a good starting point.

Adjusting the sketch

Once you’re satisfied with the initial sketch, there are still ways to fine-tune it. The image below shows the Layers panel after running the Sketch action and the main controls for adjusting the sketch after it’s been made.

  1. Minimum–Because a smart object is used to make the sketch, it’s easy to go back and adjust it. The main thing to experiment with is the Minimum setting. Simply double-click the word “Minimum” to open the Minimum dialog widow. Try settings in increments of 2 in order to see an effect. The default is “4” so try “2,” “6,” or even “8.” Higher numbers make the image darker and the black sketch lines more prominent. Lower numbers make the image lighter with less prominent sketch lines.
  2. Sketch group opacity–Lowering the opacity of the sketch group allows more of the original image to show through. This can make the result look more photographic and less sketch-like.
  3. Add a layer mask to the sketch group and paint black to conceal parts of the image–Some elements in an image, like sky and clouds, might not look as good after the sketch action runs while other parts with more texture and detail might look great. Adding a layer mask to the sketch group provides an easy way to conceal elements that don’t sketch well while revealing those that do.
  4. Change the sketch group blend mode–This is particularly useful when making a B&W Sketch. In this case, changing the sketch group layer’s blend mode to Luminosity changes the monochrome sketch into a color sketch, but with added detail compared to what the Color Sketch action provides. The video below by Dave Kelly has a nice demonstration of this.

Finishing the image

While the sketch action provides a significant transformation from the RAW conversion, it doesn’t finish the image. I see the sketch as providing a new base for further development. Burning, dodging, vignettes, adjustment through masks and even creative techniques, like glows, can still be used once a satisfactory sketch is in place. The sketch itself can look quite good sometimes, but that’s partly because it’s such a dramatic shift compared to how the image looked before running the sketch action. It’s fun to see what the sketch can do, but don’t hesitate to push further. Think about and experiment with additional possibilities. The sketch can certainly create a new creative path, but it will be up to you to follow it and see where it leads.

The image on the left is the focus-blended RAW file conversion. The finished image on the right shows the enhanced detail and color that were added with the Color Sketch action plus additional post-processing. This is a Santa Rita cactus that develops this purple/blue color as it dries out. Despite the extremely dry winter, it still managed to produce a large number of buds this spring.

Sketch-o-graph video tutorial

Dave Kelly does a nice job reviewing several of these steps in working with the sketch actions in the video below.

Additional examples

I’ve included some images from Steve Dell and Bob Hills below to show the variety of images possible from using this sketch technique.

The first gallery shows some Steve Dell’s sketch images. They again demonstrate how images with good detail work nicely with the sketch technique. In the image with the clouds, the clouds still pretty much look like un-sketched clouds. This is typical of image elements that lack distinct edges.

Bob Hill’s images below are from his “Sonoran Garden” series. Again, the texture and detail in these subjects create strong sketch images. Worth noting are how the distinct lines between shadow and sunlit areas on the leaves create even stronger lines in the sketched versions. In addition, the shadows are less dark and filled with more color.

I hope you’ll give the sketch actions a try. Sketch-o-graphs are easy to make and can produce some surprisingly unique and attractive images.

7 thoughts on “Local Light: Sketch-o-graphs

  1. Keep these coming. I love learning this tips as I might not have otherwise explored them in your software. I’m especially interested in what Blake Rudis’ options might offer.

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  2. Interesting way to enhance structures. I’m not going so far with the sketch-like look. And I put with my first attempt an origin developed image copy on top of the layers, brushing in by a mask only partial the sketch-o-graphs results. I tried it with an image of fall leaves on a ground and looks pretty well in regards to visual depth improvement.
    The only thing I was surprised was how strong colors have been effected (much too bright, washed out,e tc.) by first application with the sketch-o-graph.
    Thanks for sharing and providing this tool.
    All the best and stay healthy from Bavaria / Germany

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    1. Thanks for trying the technique, Oskar. I also use the mask and opacity to selectively apply the sketch at times. It varies from image to image. Dark colors do definitely get lighter initially, but pulling the Levels slider to the right edge of the histogram, as mentioned in the article, darkens them again. I find color saturation to be more of an issue than color brightness since the Levels adjustment can control the brightness considerably. But again, it probably depends on the image. Every image is a little different with this technique, and there are a number of factors that play into how well it works.

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  3. Hello Tony, Another fine and exciting undertaking. Thank you. I’m going to give it a go very soon. My best always, Guy

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