Simple photoshop steps for depth of field synthesis in post-production

Many people like to take photos with a shallow depth of field that are "clear in front and hazy in the back". There are also many online tutorials. What should you do if you want to take photos that are all clear? In some cases, For example, in macro photography, even if you close down the aperture, you still cannot solve the problem of too shallow depth of field. If you want to take a macro shot of small objects (such as insects) and want the entire subject to be clear, you need to use focus stacking. That is to take multiple photos from front to back with different focus positions, and then use PS to overlap and combine them together, and finally obtain a work where all the photos are clear.

The following will introduce how to use Photoshop to simply combine several photos with different focus positions:

Here are three photos with shallow depth of field focusing on the front, middle and back parts of the screen. The photos, and because they were taken handheld, the frames are not even aligned. See how we merged the three depths of field in Photoshop CC.

1. File → Script → Load the file into the stack.

2. Browse → Select the photos you want to merge.

3. Select these three photos → Edit → Automatically align the layers.

4. At this time, the three photos have been automatically stacked. Use the cropping tool to cut away the edges.

5. Start merging depth of field. Edit → Auto-Blend Layers.

Stack images → OK.

6. Complete!

The afterimages of two of the boxes come from an incomplete overlapping process, which can be avoided by using a tripod during shooting.

Extended information:

Even if you shrink the lens aperture to the minimum or change the focus point, there is no guarantee that the picture will be from the nearest to the farthest. is clear.

We all know that when you raise the camera to shoot, a focus point will appear in the viewfinder. The focal plane that this focus point is aimed at must be the clearest, and then according to the size of the aperture you use, Different focal planes will have different sharpness. For example, if you use an aperture of f8 to aim at a mountain in the distance, the distant view will be the clearest, while the foreground very close to you will be blurry. This is a natural physical phenomenon of the lens. But this is also what we don't want to see. Therefore, in order to avoid this situation, we can only use some kind of technology to overcome it.

And this technology is to break through the limits of the lens and create infinite depth of field - depth of field synthesis

(1) Preparation before shooting:

First of all, you Bring a tripod that is stable enough, as any slight shake of the camera will cause trouble for you in post-assembly. Of course, you also need a reliable shutter cable, which can effectively avoid jitter when pressing the shutter. (I do not recommend using time-lapse shooting instead of a shutter release. In situations where the light changes rapidly, the 2 seconds of delay may make you miss the only opportunity)

(2) Settings when shooting :

When you determine the composition, the first step before shooting is to make some camera settings.

1. Set the camera to aperture priority shooting mode.

Some people ask why you don’t shoot in M ??mode. This means that the exposure is locked. Wouldn’t it be easier to stitch together in post-production? Although the m-stop can make the exposure of a series of captured materials completely consistent, aperture priority can immediately calculate a reasonable exposure parameter based on the ambient light. In some situations where the situation changes suddenly and the light is fleeting, speed is more needed.

2. Set the photo quality to RAW. In order to retain more highlight details in the dark areas, allowing more space for later processing.

3. To adjust the lens from autofocus to manual focus, that is, adjust the lens from af to mf. (I use Canon, it seems that Sony and Nikon can switch the focus mode on the body)

4. If your wide-angle lens has anti-shake, be sure to turn off anti-shake

5. Settings The camera metering mode is global metering

6. Set the aperture

If the wind is strong and the light in the foreground is very dark when shooting, you often use a larger aperture with a high ISO. Increase your shutter speed to freeze the foreground. If there is almost no wind at the scene and the foreground light is good, you can reduce the aperture to a smaller size. The smaller the aperture, the deeper the depth of field, which can reduce the number of shots taken and improve efficiency.

(3) Operations during shooting:

First, twist the focus ring of the camera lens to the closest position. There is a small transparent window on the lens body. This window can intuitively observe the changes in the focal length of the lens.

I use Canon 16-35. For this lens, I just twist it to the closest focusing distance, that is 0.28. Then press the shutter button to take the first photo. Then turn the lens focus ring a little toward the larger value, and then press the shutter to take the second picture. Next, twist it a little in the direction of a larger value, and take a third picture... until the lens is turned to infinity and the last picture is taken.

Don’t screw the Canon wide-angle lens all the way, screw it to infinity and back a little, so that the scale line is just at the vertical line of the L-shaped line in front of the infinity scale line, which is infinity. As for Nikon and Sony's lenses, it seems that you can twist them all the way to infinity.

As for the degree of twisting when shooting, it is all up to you. If you are more conservative and it is your first time to try this technique, and the aperture is relatively wide, or you are shooting a very important scene, you can adjust the angle to a smaller extent and take more photos with different depths of field, which will be safer. And if you are bolder, or there is sufficient light when shooting, and the aperture is narrowed, you can adjust it to a larger range. Generally speaking, taking 5 or 6 photos can basically cover the panoramic depth from the nearest to the farthest.

Tip:

After taking a set of depth-of-field shots, to be on the safe side, I usually do another set of depth-of-field shots to ensure nothing goes wrong. Because this technology has very high requirements in the early stage, it must be perfect in the early stages of shooting. And when shooting, you should pay attention to the exposure of the picture, because sometimes the light changes very quickly. For example, the sun suddenly emerges from the clouds and it will be very bright. The sun may be blocked by clouds in an instant, and then the light will be very dark. At this time, you need to quickly add or subtract exposure compensation to make the exposure of a group of depth-of-field composite pictures basically the same.

(4) Post-stage steps:

1. Screening

First, import several sets of depth-of-field composite photos into lightroom for screening. I will repeat the comparison and Zoom in on the details to determine which of the next few groups to keep. The selected group of photos is the material we will finally use for depth-of-field synthesis.

Then zoom in and view each picture in the set of photos left behind, and compare the position of the focus point and the clear area of ??each photo. Because when you turn the zoom ring to shoot, there will always be clear areas in some photos that are similar and overlapping due to the magnitude of the rotation. This step is to delete the pictures in a set of photos with more overlapping focal planes, and finally leave only the pictures whose focal planes can basically complement each other.

This step can not only reduce the computer running time when stitching, but more importantly, if there is wind when shooting, the flowers and plants in the foreground will definitely be displaced, and if many photos are put in together and stitched together, it will It will interfere with the computer stitching algorithm and produce misalignment and ghosting.

The shooting conditions were like the windy weather I mentioned. The wind was very strong, and the flowers and plants in the foreground moved very much. Below I have excerpted his description below the work, so that everyone can appreciate the difficulty of shooting and compositing:

Taking this photo was probably the most challenging of all my photography experiences. I heard that the wildflowers were in full bloom along the Columbia River at the border of Washington and Oregon, so I took advantage of the proximity to the water and drove to the Columbia Hills, a famous wildflower spot. I encountered strong winds with a speed of 35 miles per hour when I visited the location before. Due to the situation, I had to give up and take pictures elsewhere. The weather forecast on Monday morning predicted a breeze of 9 miles per hour, so we arrived at the shooting location with great anticipation an hour before sunrise. As soon as I opened the door, the door was blown back by the strong wind, almost missing my hand. Walking into the field, I found that the wind was no weaker than when I stepped on the field. Under the ravages of the strong wind, most of the yellow wildflowers were bent down and turned into a sideways position facing Mt Hood in the distance. The wind roared continuously and rarely stopped for a moment. This creates great difficulties in composition - it is difficult to judge the position and form of the flower when it is at rest. I kept wandering among the flowers with my camera in hand, thinking that I must complete the composition of the scene in the Venus Belt before the sun shines directly on the ground. When I finally decided on the composition, I started looking at the repeated captures of depth-of-field synthesis that lasted for half an hour. The ISO went from 800 to 4000 to "pin" the swaying flowers and plants. Stacking a complete depth of field requires moving the focal plane 3-4 times continuously. The occasional respite from the strong wind only gave me the opportunity to capture 1-2 shots at most, which was not enough to complete a whole group of shots. What is even more difficult is that there will be no obvious displacement of flowers and plants between the two pictures. So I can only hope that by grabbing a few more groups, I can select enough materials to complete the depth of field synthesis. Until I got home and started post-selection, I wasn’t completely sure that I would be able to complete it. Fortunately, after two days of continuous processing, the scene in my mind was finally fully presented.

2. Adjustment

Make a basic adjustment to the photo in lightroom to lay a solid foundation for subsequent stitching in PS. Usually correct the exposure, do a basic color correction on the photo, noise reduction and sharpening, etc. After making adjustments to a certain photo, you need to apply the effect to all pictures in this group.

Select all pictures, click "Sync Settings", check all options, and then click "Sync". In this way, all adjustments made to a certain photo will be copied to all pictures simultaneously, so that the effect will be consistent.

Tip:

If the light changes quickly when shooting, there may be some differences in the exposure of each photo, which requires separate settings for each photo after synchronization settings. Adjustment.

3. Synthesis

After completing the basic adjustments to the photos in LR, import all the pictures into PS.

Select all images, right-click, select "Edit in Application" in the pop-up window, and then click "Open as layer in Photoshop". In this way, all pictures will be automatically loaded into PS and superimposed as layers on the same canvas.

Then select all layers and click "Edit - Automatically Align Layers" on the toolbar above PS. In this way, all layers will be automatically aligned by the software.

This alignment operation It is to overcome the breathing effect of the lens. When we twist the focus ring, the lens will move the floating lens to focus. The movement of the floating lens will inevitably bring about changes in the optical structure, so the focal length will change. Therefore, although the camera position is fixed, the captured images must be slightly deformed and displaced. At this time, we must rely on the powerful alignment function of PS.

After automatic alignment, there are white edges around the screen. This is the extra pixels that appear blank when the program stretches the image to match pixels.

After aligning, whether you want to blend the pictures together or select all layers, click "Edit-Automatic Mix Layers", select "Stack Images" in the pop-up dialog box, and check " Seamless tones and colors", then click OK, and the software will begin to blend automatically.

In the final fused image, there is a mask next to each layer, which is automatically calculated and generated by the software. This function can calculate and capture the clearest part of each layer and then fuse it.

Next we merge the layers. If a tripod is not used when shooting or there is strong wind at the scene, it will cause the elements in the picture to shift and shake. At this time, you cannot completely rely on the automatic synthesis of PS software. An additional step before joining this step is to manually adjust the masks of each layer and use a brush to remove the clear parts. This process is more technical and time-consuming.

After merging the layers, use the crop tool to cut out the blank and blurry parts around the screen. Therefore, we should try our best to leave room in the composition when shooting, leaving room for cropping in the later stage.

This is the final cropped photo. We can see that the picture is clear and sharp from the nearest to the farthest.