空影

Today we mainly studied the adjustment of high and low-key images, as well as high and low contrast images.

Low-key has highlights, high-key has shadows, this is a basic aesthetic principle.

According to the histogram judgment criteria learned yesterday, we can divide images into two categories: low-key and high-key. Generally speaking, the relationship between the brightness and darkness histogram of a normal image and its boundaries can be classified into three types:

1. Hitting the wall and rising (overexposed)
2. Hitting the wall but not rising (moderate)
3. Not hitting the wall (underexposed)

From the literal meaning, it can be seen that the state of hitting the wall but not rising (moderate) is the best for images, as it can ensure the details of the brightness and darkness. Here are some suggestions for fixing several possible situations:

Adjustment of low-key images#

Shadows in the dark#

1. Preserve the details in the shadows $\to$ Hit the wall but not rise
2. Night sky/background does not require hierarchy $\to$ Hit the wall and rise

Here is an example of a black and white photo of a sunrise:

From the histogram, it can be seen that there are more pixels in the shadows of the overall image, and there are not many pixels at the edges of the highlights and shadows, and the highlights have "risen a bit", which makes the contrast a bit low (probably due to the previous filter). This is a special image similar to a silhouette. I think the black trees would look better without hierarchy. Here is how to adjust the histogram to achieve the goal of "hitting the wall and rising":

• "Trim" the low-light part without pixels to reduce the sense of hierarchy
• Reduce the highlights to increase the overall brightness (the highlights of low-key images are generally not less than 230)

Highlights in the dark#

1. Maintain the best state $\to$ Hit the wall but not rise
2. Highlight the highlights in the dark $\to$ Not hit (adjust to around 230)
3. Hit the wall and rise (unless for special effects, this state should be avoided as much as possible)

Take this gardenia flower as an example: It can be seen that the dark areas have hit the wall and cannot restore the details, but the highlights have not hit the wall (there are no pixels between 188 and 255), making it look dim without contrast.

Here, adjust the brightness to just hit the wall:

Adjustment of high-key images#

Highlights in the bright areas#

1. Preserve the details in the highlights $\to$ Hit the wall but not rise
2. Solid color/background does not require hierarchy $\to$ Hit the wall and rise

This image is relatively perfect, the highlights hit the wall but not rise, and there are enough pixels in the dark areas:

Shadows in the bright areas#

1. Maintain the best state $\to$ Hit the wall but not rise
2. Highlight the shadows in the highlights $\to$ Not hit (at least have pixels around 20)

An image taken on a foggy day: Both parts of the image are blurry and lack details. Here, adjust according to the principles mentioned above:

Control the shadows to hit the wall, control the highlights to hit the wall

Another example: Increase the value of the shadows

Low contrast grayscale#

These types of images are "moderate", with very small overall contrast, and the tonal range is in the middle. The shadows and highlights of the histogram are almost not distributed, which is very aesthetically pleasing. (This is probably the histogram characteristic of the "film texture" mentioned by @jackyoung.)

Here is an example of a photo I took in the rain, the image feels a bit dark, so I will brighten it up a bit:

High contrast images#

These types of images are usually for the purpose of pursuing effects, deliberately losing many details.