Monitor Calibration

One of the very first steps worth undertaking is to color calibrate the monitor you will use to perform your image processing. A properly calibrated monitor will help ensure the color corrections you make to the image will translate properly into its finished form, whether electronic or printed. An incorrectly or uncalibrated monitor, however, can unintentionally lead to disastrous results, since the colors that appear on other monitors or in a print version of your image can be noticeably different.

The color calibration of a monitor is easily done using tools developed specifically for this purpose, Figure 21.1. To perform the calibration, the tool is placed gently against the monitor’s surface and the calibration program is initiated. The program causes the monitor to sequentially display very specific colors, the results of which are detected by the tool and analyzed for any deviations. Once complete, the program then adjusts the monitor’s settings to correct any deviations that were found. If desired, the calibration can be repeated to confirm compliance.

Image Management

Your choice of image management strategy is a crucial decision that deserves careful thought. You will likely create tens to hundreds of thousands of images that all need to be labeled and organized for easy retrieval. Adobe Lightroom has emerged as one of the photographer’s most popular systems for helping you manage your collections of images. It has many built-in capabilities for handling just about every task imaginable. Many excellent books have been written about Lightroom’s capabilities; here our focus is on briefly describing the basics of using Lightroom to manage your photos and perform the most common tasks.

Lightroom’s basic image management structure is its virtual catalog of all your images. Your Lightroom catalog is your single, primary warehouse of information relating to your original images, and any modifications you make to them using the Lightroom program itself. The process begins by copying your images from your camera’s memory card to your computer using commands within Lightroom and importing them into your catalog in the process. Alternatively, you may copy the images yourself and import them to your Lightroom catalog separately.

An important decision is how to organize and file your photographs. One approach is to simply have a single, enormous folder containing all your images. Alternatively, you may create a separate folder for each individual photo session, even if they occur on the same day. You will likely settle on a system somewhere in between. Lightroom organizes your imported images within its library, Figure 21.2, which is its way of describing the manner in which you choose to organize your photographs; in physically separate folders, virtually distinct collections created within Lightroom, or a combination of both.

21.1 A properly color calibrated monitor is crucial to achieving correctly color balanced images. This is easily done with a monitor calibration tool, as shown here. Any incorrectly set color settings on the monitor are automatically corrected by the calibration tool and software in a process that only takes a few minutes.

21.2 The Adobe Lightroom Library—a popular way of managing all your images.

Once the images have been imported to your Lightroom catalog and appear within its library, you may begin the process of editing or developing them. After you are satisfied with the image’s appearance, you then use Lightroom to export the image into whatever format and image dimensions you desire: Joint Photographic Experts Group (JPEG), TIFF, Photoshop, etc. There are options for relabeling your images, and for synchronizing them with your social media accounts, creating slideshows, printing them, and many other possibilities. Lightroom’s ability to concurrently re-label, resize, and reformat batches of images as a single process is a tremendous time-saver. We’ll cover all these steps in the discussion below.

Image Processing—Lightroom’s Develop Module

Lightroom’s powerful and reversible image editing capabilities are remarkable. The following is a very brief overview of the basic steps you are likely to follow; you are encouraged to consult the numerous other, far more comprehensive sources and online videos available on these subjects. The following discussion also assumes you have created and imported your images in the RAW format; many of the steps described below don’t work well, or at all, with JPEG images.

Let’s go through the most common image processing steps you might like to perform. You begin by opening the image you wish to edit in Lightroom’s Develop module, Figure 21.3. Remember, if you’re unhappy with any of your results, simply click on the Reset button on the lower right corner to revert to the original image.

Color Balancing

As we saw in Chapter 10, the color we perceive for a given object depends on both its physical properties and the characteristics of the incident light. We often wish to correct the colors within images made under light sources with a distinct color cast, for example, indoor fluorescent lights (Figure 10.3), so they more closely match those made under a neutral, or white light source. This process is called color balancing. Other times, however, we wish to whole-heartedly embrace the specific tints of the light sources, for example, during the warm light of the golden hour.

There are several ways of color balancing images within Lightroom’s Develop module. The simplest approach is to use the eyedropper tool, Figure 21.3, to sample a small spot within a neutral gray, white, or black region of the photograph. Such regions should have equal intensities of red, green, and blue hues. Any excess or deficiencies in specific hues will be automatically detected and corrected.

A more comprehensive method for performing color correction is with the complete palette of a color checker tool, Figure 21.4. Here, a reference image is made of the entire palette, as shown in Figure 21.4(b), under the identical ambient light conditions used to create subsequent images. This image is analyzed in Lightroom through a two-step process, and any deviations from white light illumination are corrected, Figure 21.4(c). Any necessary adjustments can then be applied to all the other images created under the same lighting conditions, Figure 21.4(d). This is a very reliable and efficient way to create images that are uniformly correct in their color balance.

21.3 The Adobe Lightroom Develop module. There are many tools available to make alterations to the current image.

21.4 Color correction using the eyedropper tool in Adobe Lightroom along with a color calibration tool including a neutral gray scale. (a) The as-shot image; (b) the color correction tool shot under the same conditions as (a); (c) the same image as (b) after white balancing and (d), the identical color corrections applied to the original image.

21.5 Four white balance adjustments to the galactic core region of the Milky Way: (a) Auto; (b) Tungsten; (c) manual adjustment; and (d)—as-shot.

The galactic core area of the Milky Way presents a unique color balancing challenge. It generally appears to be a faint white color to the naked eye, yet exhibits distinct colors in photographs made with digital single-lens reflex (DSLRs). Background colors in the night sky from light pollution or simply air glow can further complicate color balancing decisions. The initial color of the galactic core can vary significantly depending on the camera’s white balance setting. The photographer thus has wide discretion regarding the choice of how to color balance the galactic core, Figure 21.5. However, the general consensus of the landscape astrophotography community has converged on a faintly yellow color of the galactic core set against a mostly black or dark gray sky, Figure 21.5(c).

Lens Correction

All lenses suffer from a certain degree of inherent geometric distortion, in addition to the chromatic and spherical aberrations described earlier. The short focal length lenses common in landscape astrophotography are especially prone to such effects. In addition, the wide open aperture settings often used to capture the maximum amount of available light can introduce noticeable lens vignetting around the perimeter of nightscape images.

Both effects can be mitigated within Lightroom simply by checking the Lens Profile Correction box within the Develop module once an image is open. Lightroom applies the appropriate corrections after determining the specific lens used to create the image from the image’s metadata. If the lens can’t be identified via the image metadata, then there are options available for manually performing vignette and geometric adjustments.

Brightness/Contrast

The brightness and contrast of the image can be adjusted in several ways within the Basic Adjustments panel of Lightroom, Figure 21.3. The overall exposure and contrast can be adjusted directly. The highlights, shadows, whites, and blacks can be fine-tuned separately. The tone curve can be manipulated to emphasize the highlights, shadows, lights, and darks. The image contrast can also be changed through the “Clarity” control in the “Presence” sub-menu.

Noise Reduction

In addition to the noise reduction techniques described earlier, the Luminance and Color controls in the Detail panel can be very effective at reducing image noise, especially for images created at high ISO settings. Caution must be exercised, however; images with excessive noise reduction can appear too soft, and almost mimic a painting in their appearance.

Sharpening

The image sharpness can be adjusted using the sharpness feature within the Detail panel. Qualitatively similar to a contrast adjustment, sharpening effectively enhances edges within the image. It is a very effective, usually final step that can make a significant difference to your image. As is always the case, however, care must be exercised so as not to overdo image sharpening. Over-sharpened images can appear extremely noisy and bright, with all the stars showing the same brightness.

Dehaze

A recently added feature in Lightroom is the Dehaze option, found in the Effects panel. This adjustment is gaining popularity within the astrophotography community as a very effective way of enhancing the contrast of the galactic core region of the Milky Way. It is particularly effective when the background sky is relatively bright and doesn’t provide much contrast. Judicious application of the Dehaze adjustment can really bring out the abundant details of the Milky Way; as always, care must be taken to not overdo it and produce unwanted noise and other artifacts.

Color Enhancement

In addition to the global color balancing steps described above, Lightroom also offers an enormous level of detailed control over the color of the image. The hue, saturation, and luminance of each of the spectral colors within the image can be fine-tuned individually. The adjustment brush can be used to alter the hue of selected areas. The overall color temperature and tint of the image can also be changed within the Basic Adjustments panel.

Spot Removal

Spots and other local defects can be easily remedied in Lightroom using the Spot Removal tool in the Tool Panel, Figure 21.3. Lightroom gives you the option of selecting the region used as the spot replacement, as well as the size of the spot’s area. Custom areas can be altered by holding down the Shift key while dragging the Spot Replacement tool over the area in need of repair.

Local Adjustments—Brush Tool

Local adjustments can be made to images in Lightroom using the Adjustment Brush, Figure 21.3. This is an extremely powerful method for bringing out key regions of the image. The Adjustment Brush allows you to select a sub-region of the image, whose size you control, and independently vary an enormous number of its qualities, including the exposure, white balance, contrast, sharpness, and more. The results can mimic the results obtained through time-honored burning and dodging methods applied during film developing and printing in a traditional darkroom.

Image Exporting

Once you are finished editing the image in Lightroom, the final step is to either print it directly from Lightroom, or save a copy for sharing or potentially further editing in Photoshop. This latter task is accomplished by “exporting” the image from Lightroom; here again is where Lightroom is very helpful. You have the option of saving a copy of the image in nearly any format you wish, including JPEG, TIFF, or PSD. You also have the option of resizing and automatically renaming the image during the exporting process. Finally, you have the ability to perform these functions on a batch of files automatically, which can add up to enormous time savings.

Adobe Photoshop

Adobe Photoshop gives you the ability to create incredible images and art. Our discussion will focus on only a very select few of Photoshop’s techniques and capabilities that are of special relevance to landscape astrophotography. You are strongly encouraged to explore the many powerful image-processing capabilities in Photoshop through online tutorials as well the excellent sources provided in the Bibliography section.

Perhaps the best way to illustrate Photoshop’s utility for editing a single image is by way of a simple example, Figure 21.6. Let’s work with a basic RAW file saved straight from our camera. Opening the RAW file within Photoshop automatically launches the Adobe Camera Raw (ACR) module, Figure 21.6(a). The ACR module is an intermediate step that allows you to make changes to the image similar to those you might otherwise make in Lightroom. We are presented with a very similar panel of adjustments as were described for Lightroom above—color balance, brightness, contrast, exposure, and so forth. After modifying various settings, we arrive at the result shown in Figure 21.6(b). Once we’re satisfied, we click on the Open Image tab, which then automatically launches the file within Photoshop, Figure 21.7. Of course, if you open a file in Photoshop that was exported from Lightroom in a PSD format, then the ACR step is skipped, and the file is launched directly within Photoshop.

21.6 The powerful Adobe Camera Raw (ACR) tool showing (a) the as-opened image and (b) after basic adjustments.

21.7 A basic image opened in Adobe Photoshop. Like Lightroom, there are an enormous number of tools available for making changes and adjustments to the image.

You may be perfectly satisfied with the editing performed within Lightroom and/or ACR. Other times, you may wish to further edit the image from within Photoshop. In fact, there is a great deal of overlap between the three programs; you may find yourself mostly using one or the other. In addition, Photoshop includes an ACR filter option, so you can easily apply all the normal ACR adjustments to any image or layer already open in Photoshop at any time.

Now that we have our image open in Photoshop, we can continue to edit its appearance to match our personal interpretation of the scene. We are presented with several menus, both along the sides and the top of the screen. First, let’s recognize that the default is to open our image as what Photoshop calls a background layer. A good first step is to make a separate, duplicate layer from within the Layer menu. Any changes we make to this duplicate layer can be deleted simply by deleting the layer, leaving the original image intact.

As you may imagine, there are opportunities to perform many of the same basic image editing processes in Photoshop that are available in Lightroom and ACR. In fact, ACR is one of the filters that can be applied to your duplicate layer. Doing so brings up the same ACR module seen when we originally opened a raw file from within Photoshop. This step can be very helpful when editing JPEG files that normally don’t launch the ACR module.

Removing Airplane Lights/Satellite Trails

Let’s explore just one example of how to use one of Photoshop’s sophisticated tools to remove pesky airplane lights, a common step in landscape images. A typical situation is shown in Figure 21.8(a) where a beautiful nightscape image is marred by the presence of a trail of airplane

21.8 The process of removing an airplane trail in Adobe Photoshop: (a) Original image with airplane trail; (b) Close-up of region containing the airplane trail; (c) Close-up of the same region after removing the airplane trail; and (d) Final image after removing the airplane trail.

navigation lights. The clone tool, Figure 21.8(b), easily handles the situation. The airplane light trail is removed simply by dragging the tool along the airplane trail after first selecting a reference point to one side. Photoshop’s algorithms thus manage to replace the airplane trail areas with very similar content, Figure 21.8(c), without introducing clearly discernible artifacts, Figure 21.8(d).

In addition to Photoshop’s extraordinary control over the process of editing your images, its ease of use can be greatly advanced through the use of additional software called plug-ins or added features such as actions and scripts. Plug-ins, actions, and scripts are available online for many common editing steps. They can eliminate the need to learn how to perform these processes step-by-step on your own. Several are described in the following section. Many are freely available, or can be created yourself; others are available for a fee.

Plug-Ins—Nik

The Nik plug-in suite from Google is my go-to set of editing filters, Figure 21.9(b). They make it incredibly easy to accomplish many of my single-image photo editing tasks. The suite includes six separate plug-ins that each serve a special purpose, and when launched, creates and opens a new layer within Photoshop for editing. An example of an image created during civil twilight is shown in Figure 21.9(a, c), before and after editing with the Nik tools. You have options for fine-tuning the color, contrast, noise, and many other image features. All the Nik tools also offer the ability to create extremely detailed adjustments to small regions of the image using a similar feature as the adjustment brush in Lightroom.

Star Spikes Astronomy Action

Creating diffraction “spikes” around stars can impart an extra “pop” to some images if used judiciously. One very straightforward method for doing so is with the “Astronomy Tools Action Set,” which includes several different diffraction spikes options. A before and after example with diffraction spikes added to the stars is shown in Figure 21.10. The set of actions are simply loaded into the Actions panel within Photoshop, and then executed on the currently open image. When operated on a duplicate layer of the current image, they are completely reversible.

As is the case with most post-processing techniques, thought must be given to your purpose in using this filter. While it is possible to apply the filter to only those stars within a given constellation, the result can appear artificial and distracting. Of course, the ultimate choice is entirely yours—this again is the beauty of nightscape photography!

Plug-Ins—Fisheye-Hemi

Fisheye lenses find widespread use in landscape astrophotography, especially for images containing the aurorae or the Milky Way. Their ability to capture enormous swaths of the night sky is unsurpassed. A major drawback to fisheye lenses, however, is their inevitable distortion, as seen in Figure 21.11(a). The Fisheye-Hemi plug-in is a very good tool for correcting this distortion, or “defishing” images created with fisheye lenses. Once installed, it is implemented simply from within Photoshop’s Filter menu. Like the other plug-ins, when operated on a duplicate version of the image created in a separate Photoshop layer, if you are unhappy with the results, you can simply delete the layer.

21.9 A before and after comparison of the same image after making adjustments using the Nik plug-ins for Photoshop. This image shows the Strokkur geyser in Iceland during the dim light of twilight.

21.10 Diffraction spikes add a certain “pop” to starry skies: (a) before and (b) after made using the commercially available “Astronomy Tools Action Set.”

21.11 A before and after comparison of the same image after making adjustments using the Fisheye-Hemi filter for Photoshop. The artifact of a curved jib of the sailing vessel, “Nordic Song,” (a), has been corrected in (b). This image was taken during an extraordinary auroral display during a geomagnetic storm that occurred while docked in the Apostle Islands National Park in Wisconsin.

Fisheye-Hemi is very good at correcting fisheye-lens induced distortion in landscape-oriented images containing a horizon at the image’s midplane. However, it can leave behind a noticeably curved horizon if the horizon is located near the top or bottom of a landscape-oriented image. This is the result of its tendency to remove curvature parallel to the length of the image but to leave behind curvature perpendicular to the length.

One clever way around this, as described by the Lonely Speck site, is to extend the canvas of the image roughly 225 percent, give or take, with the original image at its bottom. Doing so converts the overall canvas from landscape-oriented to portrait-oriented, even though the original image is still in a landscape orientation at its base. Running Fisheye-Hemi on this new, portrait-oriented canvas now removes the distorted horizon, since the horizon’s curvature is now perpendicular to the length of the canvas.

Finally, you may wish to de-fish your fisheye images in Lightroom or Photoshop directly. You have the option of making both automatic and manual lens-distortion corrections under the lens profile (Lightroom) and lens effects (Photoshop) using the ACR filter described earlier. In general, however, the Fisheye-Hemi plugin correction is superior compared to a rectilinear lens-corrected fisheye image, especially on nightscape images with stars and foreground objects near the edges.