Understanding Camera Raw's Unique Circular Slider

The circle thing in camera raw is reversed because lenses are circular and produce a circular image, whereas sensors are rectangular. The image circle produced by the lens must be wide enough to fill the rectangular sensor. This means that 41% of the image produced by the lens is thrown away. A circular sensor would allow for more megapixels without increasing density or decreasing sensitivity, and the same lenses could be used with the same optical properties.

The circle thing in camera raw is reversed to allow for the 3:2 aspect ratio

The 3:2 aspect ratio is expressed as width:height or w:h, with the formula being width/height or wh. This means that for every 3 units of width, there are 2 corresponding units of height. For example, a 6 x 4-inch image has an aspect ratio of 3:2, while a 1000 x 1000-inch square image has an aspect ratio of 1:1.

The 3:2 aspect ratio is commonly used in photography and art prints, as well as large and medium format cameras. It is also the standard ratio for images framed at 1080 x 720 pixels or 6 x 4 inches.

While the 3:2 aspect ratio is commonly used, other aspect ratios such as 16:9 and 4:3 are also popular for different applications. The 16:9 aspect ratio is the current international standard for presentation slides, computer monitors, and widescreen TVs, while the 4:3 aspect ratio was the standard until the late 2000s.

The choice of aspect ratio depends on the intended use of the image or video, with different ratios being better suited for desktop vs mobile or blog vs social media. Using the right aspect ratios ensures that images or videos are displayed as intended without stretching or loss of resolution, enhancing the end-user experience.

The 3:2 aspect ratio is a result of human binocular vision

Humans have a maximum horizontal field of view of about 190 degrees with two eyes, of which approximately 120 degrees make up the binocular field of view. This provides a wider field of view compared to using a single eye. The 3:2 aspect ratio, also known as the 35mm photo format, has long been recognised as a suitable ratio due to human binocular vision.

The advantages of binocular vision include improved depth perception, enhanced ability to detect faint objects, and better performance skills such as catching, grasping, and locomotion. It also allows humans to navigate over and around obstacles with greater speed and assurance.

While the aspect ratio of human vision is typically close to 5:4, it can vary slightly depending on factors such as eye shape, distance between eyes, and age. However, the 3:2 ratio remains a standard that works well within the context of photography and human vision.

The image circle produced by lenses is bigger than the sensor to avoid making lenses heavier and more expensive

The image circle produced by lenses is larger than the sensor to avoid making lenses heavier and more expensive. This is because the image circle produced by lenses is circular, whereas the sensor is rectangular. The image circle must be large enough to fill the rectangle.

A full-frame sensor is 36x24mm, or 864mm². The image circle produced by the lens must be at least wide enough to fill this rectangle. The radius of the circle is calculated as √ (18² x 12²) = √ (324 + 144) = √(468) = 21.64mm. This gives an area of 1,471mm² for the whole image circle.

Using a circular sensor with the same technology as today's rectangular sensors would increase the megapixels of certain cameras. For example, the Canon EOS 80D could be pushed from 24.2 to 41.1 megapixels. This is because the circular sensor utilises more of the image projected by the lens, which is also circular.

However, creating circular sensors would result in more waste during the manufacturing process, as it is more efficient to stack rectangles (such as current sensors) together. This would increase the cost of sensors by at least 50%.

Additionally, lenses would need to be redesigned to accommodate a circular sensor, as they are currently optimised for rectangular sensors. This would add further expense and complexity to the process of switching to circular sensors.

In conclusion, while using circular sensors could offer some benefits in terms of megapixels and convenience when shooting in different orientations, it would also introduce significant costs and complexities to the manufacturing and design process.

A full-frame sensor is 36x24mm, or 864mm²

A full-frame sensor is a digital camera sensor that is 36mm by 24mm in size, or 864mm². This is the same size as traditional 35mm film photography, and is larger than other digital camera sensors such as APS-C or Micro Four Thirds. The larger sensor size offers several advantages, including improved low-light performance, wider dynamic range, and shallower depth of field.

The size of a full-frame sensor is often referred to as a "full frame" because it is the same size as a frame of traditional 35mm film. This film size was established in the early days of photography and has been widely used ever since. The 36mm x 24mm dimensions of a full-frame sensor result in an aspect ratio of 3:2, which is considered to work well due to human binocular vision.

The large size of a full-frame sensor allows for larger pixels, which can capture more light and produce higher-quality images, especially in low-light conditions. The dynamic range of a full-frame sensor is also wider, allowing for better retention of highlight and shadow details. Additionally, the shallower depth of field provided by a full-frame sensor can create a more three-dimensional feel to images, with a stronger separation between the subject and the background.

While full-frame sensors offer these benefits, they also come with some trade-offs. Larger sensors can result in larger and heavier camera bodies, and the lenses required for full-frame sensors also tend to be larger and more expensive. Full-frame sensors are typically found in high-end DSLR and mirrorless cameras, catering to professional photographers and enthusiasts who require the highest image quality.

The circle symbol on a camera marks the exact placement of the sensor or film plane

The circle symbol on a camera, also known as the focal plane mark, film plane mark, or film plane indicator, indicates the exact placement of the sensor or film plane inside the camera body. This mark is usually found at the top part of the camera body, near the viewfinder, and resembles the Greek letter Phi (a circle with a line through it).

The focal plane mark serves multiple purposes in photography. Firstly, it is used to determine the minimum focus distance, which is the closest distance your lens can be to the subject while still maintaining focus. This information is particularly useful for macro and product photographers, as it helps them plan their shots and avoid bumping into the subject. Secondly, the mark serves as a reference point for measuring the focus distance to the subject. By knowing the exact position of the focal plane, photographers can calculate the depth of field and use the optimum aperture value during a shoot. Thirdly, the mark provides a consistent reference point for measuring the distance between the subject and the camera, which is essential for post-processing tasks such as merging or creating composite images. Additionally, this distance information is used in set records to mark the position of the subject during shoots, ensuring repeatable results.

Apart from its practical applications in photography, the focal plane mark is also used for technical purposes. It helps technicians calibrate camera lenses by accurately identifying the position of the focal plane, ensuring optimal quality and sharpness in lens focusing. While the symbol is generally located near the viewfinder, its specific position and design may vary across different camera models and lens systems. Therefore, it is recommended to refer to the camera or lens manual for specific information on how the focal plane mark is indicated in a particular system.

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