Camera I

In this lesson we’re going to get familiar with the basic physical camera concepts. We’ll then explain why you need to have a strong understanding of them and how these translate into the digital world. By the end of this lesson you should have a good grasp of the camera terminology that professional photographers and CG artists use, as well as how to apply them in your projects.

BASIC CAMERA CONCEPTS

Everyone has probably used a camera (of any kind) at some point before. In this chapter we’ll learn the basic concepts of how cameras work such as Shutter speed, Aperture & ISO to demystify the process behind them. These are the three parameters that affect how bright and how clear your photo is. Nowadays modern rendering engines like Unreal Engine are built with the same functionality and terminology in mind.

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Shutter Speed

Most modern cameras have a physical shutter that physically moves inside the camera body to allow light to hit the sensor for a limited amount of time. Think of the shutter as some quickly moving curtains in front of a window. Shutter speed determines the length of time that those “curtains” remain open.

A slow shutter speed will allow more light in but will also increase motion blur if the camera is shaky. On the other hand, a fast shutter speed will allow less light in, making your photo darker but allowing you to capture fast moving objects giving you a “freezing motion” effect. Shutter speed is usually measured in seconds or fractions of a second with some common values ranging from 1/1000s to 1/30s. If you’re using a handheld camera a safe shutter speed value would be at least 1/60s to ensure your photos are not shaky. If you secure your camera on a tripod you can take long exposure photos (eg. night sky photography, light trail effects, waterfalls & rivers) where the shutter is open for many seconds.

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Aperture

Aperture controls the amount of light entering the camera by adjusting the size of the opening in the lens. It determines the exposure (brightness) of the photo and depth of field. The size of the aperture is typically represented by an f-number or f-stop. These all represent that same thing so don’t let that confuse you. Without getting into the nitty gritty, the f-number is a ratio of the lens's focal length (more on that later) and the aperture opening of the lens.

A smaller f-number means that the aperture opening is larger. This allows more light to pass through the lens making your images brighter. On the contrary, a larger f-number makes the aperture opening smaller and has the opposite effect. Due to how camera lenses work, changing the f-number affects depth of field as well. Light passing through a lens aperture converges toward its focal point. Rays closer to the centre converge sharply, while those at the edges converge at slightly different points. That means that using a small f-number will give you a strong/shallow depth of field effect, while a larger f-number will result in a larger portion of the photo to be in focus. Typical f-stop values range from f/1.4 to f/22.

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ISO

ISO is the third parameter in the equation, acting as a light sensitivity multiplier of your camera’s sensor. It determines how much light each pixel of the sensor needs to capture an image.

A higher ISO value will make the camera sensor more sensitive to the light coming in, resulting in a brighter but also noisier image. A low ISO value will result in a darker but cleaner, grain-free image. In real world photography you typically want to use the lowest ISO number possible. However sometimes you have no choice but to increase it, especially under low-light scenarios. Typical ISO values range from 100 to 3200.

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Focal Length

You can think of focal length as the "zoom" of your camera. It determines how much of the scene is captured, how large objects appear in the frame and affects the perceived depth of your image. Choosing the right focal length gives you the power to emphasize specific elements and affect the look & feel of the image.

Focal length is typically measured in millimetre (mm) and usually ranges from 24mm to 200mm. A smaller (also referred to as shorter) focal length lens will give you a wide field of view, allowing you to capture a broader scene. This is usually preferred when shooting landscapes, interiors or whenever you want to fit many subjects in a frame. Conversely, a larger (also referred to as longer) focal length will give you a more narrow field of view, allowing you to zoom in on distant object. It will also make your subjects look flatter, since it “compresses” the depth feeling between them. This is usually the desirable effect when shooting portraits, macro-photography or any other far-away objects.

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CAMERAS INSIDE UNREAL ENGINE

Ok that was a lot of information to take in at once. Don’t worry trying to memorise all of these terms, we’ll refer back to them in many different situations in the future and you can always return here for a refresh. Now that we understand how cameras in the real world work, it’s time to see apply it inside Unreal Engine. As mentioned before, Unreal Engine (also most other rendering engines out there) support cameras that have the same physical properties as a real world camera would. This is intention, because why reinvent the wheel if there’s an international standard that every arts professional is familiar with and simply works?

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Cine Camera Properties & Viewport

The cinematic camera (look for “Cine Camera Actor”) provides a much more extensive toolset compared to the standard camera in Unreal Engine. It gives you options to automatically track and focus on specific objects, control the camera shake (more on that in later lessons), accurately adjust the camera sensor size, crop, focal length & aperture parameters. If you combine them with the Cinematic Viewport, you also get access to some very helpful viewport overlays and framing tools. For starters aperture works exactly as in the real world, with lower/higher values giving you a stronger/weaker depth of field effect. You can control the shutter speed either through the motion blur parameters in a Post Process Volume or through the Media Render Queue. Lastly, we don’t have to worry about ISO inside Unreal Engine, since we are not bound on the same limitations as the physical world.

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Focal Length vs Field of View

Focal Length and Field of View are frequently mixed up as being the same thing, but they are actually inversely correlated with each other. Imagine your camera is like a pirate’s telescope. When you look through a telescope, you can see things that are far away. If you have a short telescope (like a short focal length), you can see a lot of things around you – that’s a wide field of view. But if you have a very long telescope (like a long focal length), you can only see one thing that’s really far away – that’s a narrow field of view.

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Camera Placement

One last noteworthy aspect of cameras is their placement inside the 3D space. This will really deepen on the specific goals you have set for your shot, just like in an actual photoshoot. There is a big overlap with what is covered in the Composition lesson, ****but in short you need to always consider the intended perspective and story behind the shot, give framing some thought in order to make for an interesting composition, and lastly to keep scale and depth in mind.

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RECAP

To recap, in this chapter we learned the basic camera concepts and how these translate inside a game engine such as Unreal Engine.

• Shutter Speed: Determines how long the camera’s sensor is exposed to light. A slow shutter speed lets in more light but can blur motion, while a fast shutter speed captures quick movements but lets in less light.
• Aperture: Controls the size of the lens opening, affecting the brightness and depth of field of the photo. A smaller f-number means a larger aperture and more light, while a larger f-number means a smaller aperture and less light.
• ISO: Adjusts the camera sensor’s sensitivity to light. Higher ISO values increase brightness but can add noise, while lower ISO values produce cleaner images but need more light.
• Focal Length: The ‘zoom’ of the camera, affecting the scene’s coverage and the size of objects in the frame. Shorter focal lengths capture a wider view, while longer focal lengths zoom in on details.
• Cine Camera Actor: Offers a comprehensive set of tools for camera control in Unreal Engine, including object tracking, camera shake, and precise adjustments for sensor size, crop, focal length, and aperture.
• Focal Length vs Field of View: They are inversely related. A shorter focal length provides a wider field of view, while a longer focal length offers a narrower view.
• Camera Placement: Critical for achieving the desired perspective and storytelling in a scene. It involves thoughtful framing and consideration of scale and depth.