We will give you a detailed analysis of the photoshop software and share the tutorial on using curve adjustment layers.
Tutorial sharing:
Before officially starting this PS tutorial, we will first introduce the main points of the tutorial:
1. How do tones, contrast, and curves work;
2. Read the tone curves and histograms;
3. How to use control points;
4. Adjust the operation sequence;
5. How to adjust the local contrast using the curve.
Part 1. Dynamic Distribution
After creating a curve adjustment layer, Adobe Photoshop provides a "histogram" and some other settings. This is the so-called dynamic distribution. First, we need to introduce the concept that each digital photo is composed of countless pixels and each pixel corresponds to a gray intensity value. The dynamic distribution of image tones refers to the gray-scale tones from black to white. For example, in an 8-bit grayscale digital image, each pixel is independently and uniquely distributed among 256 grayscale intensity levels.
A histogram represents the pixel intensity distribution in the form of an image. Essentially, the histogram tells you from another angle that each gray value corresponds to the number of pixels in the screen. In this way, you do not need to directly view the photo itself to know the gray-scale distribution of the image pixels. This visual separation of pixel information method is very convenient and useful, and will be further explained below.
Part 2. How to read the Tone Curve and histogram
The upper part of the curve histogram is the highlights, the middle part is the middle part, and the bottom part is the dark part. The curve tool operates on the histogram. The x axis represents the input value, the y axis represents the output value, and the XY axis is set to 0 to 255.
1. The lowest left bottom point indicates Black, the pixel intensity is 0, the rightmost top is 255, and the pixel intensity is the highest White.
2. The right side of the zero point is the dark area, and the center area at both ends is the center-dimmed area, and the rightmost side is the highlighted area.
Figure 01
Curve slope control contrast
Contrast indicates the difference between tones, including global comparison of the entire screen and local comparison of specific areas. Each new curve is a straight line 45 ° diagonal, which indicates that the ratio of light to dark output is exactly. At this time, the filter will not produce any effect.
Changing the curve slope is to change the relationship between the input and output. Adjusting the slope to a value greater than 45 ° increases the contrast, and a value lower than 45 ° reduces the contrast. The upper and lower displacement of the curve also adjusts the light darkness. Moving down the entire image will reduce the output value, so that the image becomes darker and moving up will increase the output value and the image will become brighter.
In the histogram above, we can see that most of the pixels of the image in the example are concentrated in the central adjustment area, which is evenly distributed between the high light and the dark area. However, a considerable number of pixels are in high light and shadow, which means that the color distribution of the image is relatively uniform and the exposure is relatively adequate.
Figure 02
In fact, the contrast of the image exported directly from the camera is not as high as imagined, and this is normal. Because, in order to keep the highlights and shadows as much as possible, digital camera manufacturers generally adopt a relatively conservative method to directly display the original unprocessed image information ingested by the sensor on the photo. Therefore, compared to the loss of important image details and abnormal contrast, it is a good choice to start from retaining details and images with relatively low contrast.
Effect of contrast
Our eyes are easily attracted by contrast. Imagine that polar bears are hard to be found because of their white hair. This is low contrast. The spotted pattern of Snow Leopard is easy to find in the snow, because of its high contrast. Although subjective, a proper contrast is to ensure that White is not too white or black.
In general, contrast is the difference between the bright and dark parts. Enhancing this difference will make the image more prominent, and lowering it will make the image more mediocre. Global Contrast adjustment is useful, but not the most useful. Local adjustment works better when dealing with specific scenarios. Whether you increase or decrease the contrast, local adjustment of the image contrast may produce an attractive effect. Then, the histogram is used to understand and adjust the dynamic distribution of tones, so as to properly guide the viewer's visual focus. How to adjust the local contrast depends on the image content and the designer's idea.
Part 3. How to use control points
The above introduction sounds like a color order adjustment, but the main difference is that the curve can be precisely adjusted through key control points, rather than the approximate range adjustment in black and white. The control point is located on the curve and is dragged up or down to change the input and output values of the color tone range of the control point. As shown in the following figure, there are three control points on the curve, which are located at the bottom, center, and top. You can adjust the curve to the "S" shape through the three control points.
Figure 03
The "S" adjustment curve increases the contrast of the intermediate tone, reduces the contrast of the highlight and shadow, and fades the highlighted part and the shadow part. This is a common adjustment step. Although direct movement of control points is not intuitive, it is quite convenient to complete the adjustment simply by dragging.
Figure 04
Tip: Select a control point and press the arrow key to fine-tune it. Press Tab to switch between control points. Drag the control point from the histogram and release it to delete it.
Part 4. Adjust the operation sequence
Through the above introduction, we have learned how to operate curves and control points. Let's see how to adjust the local contrast.
Step 1: complete global correction and adjustment
In many cases, we need to perform batch operation. After batch operation, we can perform specific optimization based on the characteristics of each photo. Because most photos are exported from a single camera, you can save a lot of effort to make global optimization based on camera features. If you process some images in advance, the adjustment will not be synchronized, and it will increase the difficulty for synchronous processing of images. In short, we first make global adjustments to all the photos.
Here we can consider using "S" to adjust the curve, which can basically meet the requirements before making detailed adjustments.
Step 2: complete necessary local correction
Some photos require additional remediation. Complete necessary local correction before starting local adjustment. For example, Blur correction, bucket distortion, edge, and chromatic aberration. If adjustments are completed before correction, local correction will be difficult to complete, so local correction should be done first.
Step 3: evaluate the plan
After global correction, adjustment, and local correction, the photo looks more pleasing to the eye. At this time, pay attention to the highlights of the photo content and how you feel about improvement. Write down these questions.
Figure 05
Then, consider what elements need to be emphasized on the screen, what needs to be enhanced, or some needs to be reduced. These are the questions you need to ask yourself when adjusting the photo, and write down the questions and their answers. In this way, the adjustment process becomes logical and intuitive, and the adjustment changes are connected. Therefore, you need to always check the image to assess whether the image has achieved the desired effect. If the image has not reached the next step, how should we proceed.
Step 4: complete local adjustment
After thinking about it, the operation will become pure. Add a new adjustment curve for the region to be adjusted.
Step 5: reevaluate and compare
After a round of adjustment, stop and check whether the image is as you think. Maybe your understanding of the photo content will change. It doesn't matter. Keep down your thoughts. At the same time, compare the photos of the same series to see if they have been adjusted. If not, you need to continue the adjustment.
Part 5. How to adjust the local contrast using the curve
In the example, the "S" adjustment curve can be used to complete the global adjustment, but as you can see, there are some parts that need to be adjusted. In the photo, the sky looks too dull and requires some changes. Coarse and dry wood grain and fluffy clouds are good details. They can increase the overall depth of the image and need to be further highlighted. So how should we do it? Our goal is to darken the sky so that the clouds are more prominent and the shadows of ships and the coast are dimmed.
Step 1: Add a curve adjustment layer
Create a curve adjustment layer and add a control point in the tone range to be adjusted. Select image sampling and click the finger icon, as shown in the following figure. The control points are added.
Figure 06
This control point is the color of the area where the sky is located. It goes down and fades the color of the sky. At this time, it will be seen that in addition to the sky, other areas such as the beach in the same color range has also changed, so you need to make appropriate adjustments to compensate for this change. The application characteristics of curves can make the adjustment effect better than the color order.
Step 2: use a mask to control the application scope of curve adjustment
Just like other adjustment layers, the curve adjustment layer does not directly change the image pixels, and the curve adjustment layer is matched with a layer mask, so that you can use a mask to control the application scope of curve adjustment. You can use a black paint brush in the area that you don't want to adjust.
Figure 07
Use a paint brush with low hardness and opacity to remove unnecessary areas. In this example, the tires and vessel shadows of the foreground have become too dark and should not be dimmed.
Figure 08
Press Alt and click the thumbnail of the mask to see the red film effect of the layer mask. Here, the red part needs to be painted. Use a paint brush with an opacity of 50% in some places to avoid being too clear lines. The red part above is the part that has masked the curve adjustment effect, and the other part is still applied for adjustment. The effect is as follows:
Figure 09
Now the sky has been adjusted. The highlights of vessels, clouds, and water need to be highlighted below. Create a new adjustment layer.
Step 3: repeat the steps
Like the sky color, this time we choose to color the hull, get the control point and drag it up to increase the brightness of the hull.
Figure 10
As in the previous section, because only the ship's sides need to be highlighted, other areas such as the sky and beach need to be excluded from the adjustment range, so layer masks are also used for control. As it is only a small part of the brightness, we use reverse Ctrl + I for reverse selection control.
Figure 11
From the figure above, we can see that the masking effects vary, and the effects of curve adjustment vary. After such adjustments, the visual focus of the image will first capture the high-gloss part of the ship, rather than the Stones, reflective sea water or clouds on the beach.
Figure 12
Potential problems
Like other adjustment methods, there are always some defects. Because the curve is used for adjustment, it will actually stretch or compress the color range of the screen. If the deviation is too far, the so-called color separation will occur, which can be understood as improper adjustment.
Figure 13
If you only adjust the color of a small area, the color separation will easily occur. Of course, this is an exaggerated result. In actual application, the curve will not be used in this way, but it also shows that if the curve is adjusted too much, this will lead to such a bad effect. If you are not sure, you can perform operations from large to small. If you cannot adjust all layers within one layer, try to use multiple layers. One layer solves the problem. The scope of the problem is from large to small, and the layer name is named accordingly. In this way, you can find the problem in the adjustment process and solve it in an organized manner.
Basic completion
Just like other adjustments, it would be better to be a little less. If you need to reduce the color tone adjustment effect, you can choose to reduce the opacity. Try to combine layers whose opacity needs to be reduced into a layer Group. In this way, the opacity can be reduced at one time through the layer Group, or you can choose to lower the opacity one by one. You can reduce the opacity to 25% to 75%.
Figure 14
Complete
The following figure shows how to adjust the effect chart.
Figure 15
Looking back at the initial image, it will be a bit dull, and each object is located in the middle color area of the histogram. There is no big difference between the light and dark parts in the image. Although adding the overall contrast adjustment is helpful, it is still not enough. And sometimes we don't want to adjust the entire image, especially when most of the pixels in the image are in the same color area, we need to make some adjustments to attract the attention of the readers.
At the beginning of the photo adjustment, there were very few differences between ships, tires, beaches, and the sky, but they had their own feature details, therefore, we need to adjust the local contrast to highlight their features. If the clouds are bright enough, lowering the color of the sky can show the clouds. For ships that need attention, the beach and water need to be adjusted by curve adjustment layers and masks so that attention can be drawn by highlighting the highlighted area.
Precise application of curve adjustment
Curve is one of the powerful tools of Photoshop, and it gets better and better as the PS version is updated. We recommend that you carefully study the curve and familiarize yourself with the curve settings and effects to apply them to different types of photos.
It is easier to start with a grayscale image because you don't have to worry about high saturation and you can easily see the changes. In addition, black and white images are suitable for high-contrast adjustment methods and are suitable for exercises. Of course, not all images require high contrast, which can also be reduced when the contrast needs to be reduced.
We recommend that you first use the curve to see how the preset works on the image, and then apply the learned image to the actual image adjustment. Keep in mind that adjustments must be truthful without exaggeration; otherwise, exceptions may occur. You can also apply a layer mask to mask or control the adjustment range.
All right, the above information is the detailed tutorial on using curve adjustment layers for photoshop users, you can see that the software users here, Xiaobian believes that everyone is now very clear about the tutorial, so all users are going to follow the small series above the tutorial to try it out.
