Q&A with Tim Grey – X-Rite Coloratti
by Sandra Kehoe – June 12th, 2016
Tim Grey – Photographer, Author, Educator and X-Rite Coloratti answers your questions on Photography, Photo Editing in Lightroom + Photoshop, Color Management and more.
|How can I remove color cast from a portion of a picture?|
|The basic process involves painting with the desired color on a new layer in Photoshop, employing the Color blend mode.|
|The first step is to add a new empty image layer directly above the Background image layer. To do so, first click on the thumbnail for the Background image layer. Then click the “Create a New Layer” button (the blank sheet of paper icon) at the bottom of the Layers panel.
To help stay organized I recommend renaming the new layer to something like “Color Fix”. To rename, simply double-click on the name of the layer, type a new name, and press Enter/Return on the keyboard to apply the change.
Next, change the blend mode for this new layer to Color. The default blend mode is Normal, which you’ll see reflected on the popup near the top-left of the Layers panel. Click that popup and choose Color.
You can now choose the Brush tool, and configure the tool to use a soft-edged brush (a low Hardness setting). I generally use a simple round brush, but you can use different shapes if it is helpful for your painting.
To select the color you want to paint with, hold the Alt key on Windows or the Option key on Macintosh and click within the image to select the desired color. For example, one of the images I have used to demonstrate this technique featured a horse with some green foliage in the foreground causing a color cast. In this situation I would hold the Alt/Option key while clicking on an appropriate color from the horse.
With the desired color selected, you can now paint in the area of the image that exhibits the problematic color cast. Note that to produce the best result you’ll generally need to sample a variety of different colors from the image while painting.
For example, if the horse in my sample image was brown, there would actually be many different shades of brown found within the horse. Therefore, I couldn’t simply choose a single shade of brown and paint over the entire area requiring color correction. Instead, I would sample various different shades of brown as I was working to resolve the color cast.
This technique is quite simple to implement, but can help you produce excellent results even with complicated color problems in the image. In effect, you are retaining all of the underlying texture while only altering the actual color appearance of the image, thanks to the Color blend mode.
|Is there a way in Photoshop Elements to blur the background of a photo to reduce the depth of field? I have tried selecting the background and applying Gaussian Blur, but that produced an effect with a really bad transition between the foreground and background.|
|You can actually produce an excellent result selectively blurring specific areas of a photo by simply replacing the Gaussian Blur filter with the Lens Blur filter. I addressed the step-by-step technique in the article “Step by Step: Blurring a Background” in the March 2015 issue of Pixology magazine (http://www.pixologymag.com). That article was focused on Photoshop, but the same basic process works with Photoshop Elements as well. Note that the Lens Blur filter was added in Photoshop Elements 11, so it won’t be available in older versions.
As noted above, it is possible to simply create a selection and then apply the Lens Blur filter. However, I prefer a slightly different approach that can provide a bit more flexibility. Here are the steps I recommend:
|What is the difference between the long exposure noise reduction option in camera and the noise reduction with Lightroom or Photoshop. What is the best option for long exposure with a 10-stop ND filter?|
|These two types of noise reduction are actually fundamentally different, with the in-camera option relating to how the camera actually behaves while the post-processing option can only analyze pixel values in the photo. For long exposures I recommend employing both in-camera and post-processing noise reduction.|
|The in-camera noise reduction option provides a unique advantage, in that it is able to compensate for the actual behavior of the image sensor at that specific time under the current conditions.
As you may be aware, there are a variety of factors that can impact overall noise, including the design of the image sensor, the duration of the exposure, and the amount of heat buildup on the sensor. In-camera noise reduction provides the best opportunity to compensate for these various factors. In most cases this function operates by essentially capturing two exposures. First, your actual exposure is captured. Then a “black frame” is captured, where a photo is captured with the same exposure duration, but with the shutter closed to prevent light from reaching the sensor.
This black frame exposure can then be used to determine the noise behavior of the image sensor under the current conditions, so that the camera can then process the actual capture to subtract out the noise. This is, of course, a rather sophisticated operation, and it can be very effective at reducing the noise in the initial capture.
When you are applying noise reduction in post-processing, you only really have the pixel information to work with. Thus, noise reduction software uses a variety of techniques to evaluate and reduce the appearance of noise in the photo.
Since both in-camera and post-processing noise reduction employ a different approach to reducing noise, and since they compensate for different limitations, I recommend using both of them. I generally consider in-camera noise reduction to be the more important of the two, but there will likely be some degree of problematic noise remaining in the image even after in-camera noise reduction has been applied. The careful application of additional noise reduction in post-processing can help ensure the best image possible from the perspective of noise.
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