focal length是什么

A shorter focal length… - Captures more of the scene (= has a wider angle of view) - Makes distant objects appear smaller (= has lower magnification)

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Telephoto lenses provide an angle of view that is much narrower than human vision. 70-200mm lenses provide the classic telephoto focal range.

Depth offocus

Ultra-wide-angle lenses exaggerate perspective so distances between objects look bigger. When combined with the wide field of view, it can bring out a sense of space.

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You need a very long focal length to capture a detailed close-up picture of the moon without cropping. The image above was captured at 1600mm using an 800mm lens and a 2x extender.

Focal distance vs focallength

Lenses are classified as wide-angle, standard, or telephoto depending on their focal lengths. Ultra-wide-angle lenses are a subset of wide-angle lenses, whereas medium telephoto and super telephoto lenses are subsets of telephoto lenses.

Light entering the lens converges (crosses) on its way to the image sensor. This convergence point is known as the optical centre of the lens and has the sharpest focus. The focal length is the distance between this convergence point and the image sensor.

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Ultra-wide-angle lenses take in so much that they are perfect for capturing grand scenes and large objects that are right in front of you, especially in tight spaces where you cannot move further back.

A longer focal length… - Captures less of the scene (= has a narrower angle of view) - Makes distant objects appear bigger (= has a higher magnification)

FOV to focallength

Depending on the scene and your intentions, you might not need to go ultra-wide to frame what you want to show perfectly.

This focal length is measured when the lens is focused to infinity (far into the distance). This is because when the lens is focused to infinity, light rays enter the lens almost parallel. When focused on a nearby subject, they enter the lens at an angle.

Due to physics, a lens with a shorter focal length has a wider angle of view, and one with a longer focal length has a narrower angle of view. And that’s how we came to use focal length to describe the angle of view of a lens!

"Convert 300 F to C". WorksheetGenius.com. Accessed on November 5, 2024. http://worksheetgenius.com/unit-converter/convert-300-f-to-c/.

When picking a lens, one of the first things you must decide on is the focal length or focal range that you want. This is because the focal length describes the angle of view, i.e., it tells how much of the scene in front of you the lens can capture.

"Convert 300 F to C". WorksheetGenius.com, http://worksheetgenius.com/unit-converter/convert-300-f-to-c/. Accessed 5 November, 2024

Learn more about how to make the most of wide-angle lenses in: Exploring Wide Angle Lenses Part 1: Photo Effects of Wide-Angle Lenses 24mm Closeups: 3 Simple Exercises for Mastering Wide-Angle Perspective

Learn more about what you can do with a standard lens in: Standard Lens Techniques: Using the Point of View to Draw the Viewer In 50mm Portraits, My Style: Creating A Picture of a Memory

Sometimes when you work with conversions from one unit to another, the numbers can get a little confusing. Especially when dealing with really large numbers.

Focallengthformula

Almost all units work using conversion factors. This is a number that can be used to convert from one unit to another by multiplying or dividing it.

In this article I will show you how to convert 300 degrees fahrenheit into degrees celsius. Throughout the explanation below I might also call it 300 F to C. They are the same thing!

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When you look straight ahead with your bare eyes, the field of view in focus is around 50° to 60°. Wide-angle lenses are any lens that gives a field of view wider than that. Ultra-wide-angle lenses are a special kind of wide-angle lens.

The way I calculate this is to use a base unit. This means that all temperature units are first converted to the base unit, and then converted to the correct final unit.

Notice how the buildings don’t appear to converge towards the top. They would on a wide-angle lens due to perspective exaggeration.

To determine which unit is best, I decided to define that as being the unit of measurement which is as low as possible, without going below 1. Smaller numbers are more easily understood and can make it easier for you to understand the measurement.

At 16mm, we can capture the entire façade of the fire station as well as the road and the hedge in the foreground. As the focal length increases, details appear bigger in the frame while more of the foreground and the building is cropped out. 200mm gives us a good close-up of the building name and the crests below it.

Learn composition techniques that leverage on the characteristics of different lenses in: Professional Composition Techniques (3): Making Good Use of Lenses

Also see: Why Is a Super Telephoto Lens Necessary for Sports Photography? What is the difference between a 200mm and 300mm telephoto lens?

Learn the best ways to create amazing images and videos, share your works with the community and be inspired by our community.

A standard or “normal” lens gives a perspective that is very close to that of human vision. Most kit lenses are standard zoom lenses. The popular RF50mm f/1.8 STM “nifty fifty” lens is a standard lens on a full-frame camera, whereas the RF28mm f/2.8 STM is a slightly wider standard lens on an APS-C camera.

Let’s look at what happens when we shoot at different focal lengths from the same position. Note: For ease of illustration, the angles shown in this article are the horizontal angle of view.

focal length中文

The focal length also affects many other aspects of your image, such as perspective and depth of field. To find out more,  see 4 Lens Concepts to Revolutionise Your Photos.

Getting up close to birds and other wildlife requires a special type of telephoto lens: a super telephoto lens. You may want to combine it with an extender for even further reach.

Any focal length above 135mm full-frame equivalent is considered telephoto. However, 70 to 135mm (full-frame equivalent) is considered short or medium telephoto. These are popular for portrait and product photography due to their natural perspective and comfortable working distance for close-up shots.

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We usually describe a lens by its focal length. What does it refer to and how does it affect your images? Find out in this article.