DVPI Study Guide for The Digital Filmmaking Handbook Chapter 4: Choosing a Camera Evaluating a Camera The most important thing to know when

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1 1 DVPI Study Guide for The Digital Filmmaking Handbook Chapter 4: Choosing a Camera Evaluating a Camera The most important thing to know when evaluating a camera is that there s no one single spec that defines overall quality. A good camera is dependent on many different components and specifications. All cameras are not created equal and understanding the features and trade-offs of different cameras is essential to selecting a camera and using it to its full potential. Choosing a camera is a process of weighting three factors: image quality, price, and features. As a rule, the more consumer-orientated the camera, the less control you ll have over how it shoots because consumer-grade cameras are designed for the casual shooter and most manufacturers sacrifice control for ease of use. Image Quality Two factors contribute the most to your camera s image quality (or lack thereof): the camera s lens and the chips the camera uses to create an image. Today, video cameras use special imaging sensors called CCDs (charge-coupled devices) or CMOS (complementary metal-oxide semiconductors). Chip-based cameras use either a single sensor to capture a full color image, or three separate sensors to capture separate red, green, and blue data, which is then assembled into a color image. The imaging window is divided into a grid, and the finer grid, the higher the resolution of the sensor will be. The circuitry controlling the sensor can determine the amount of light striking each cell of the grid, and that data is used by the camera to build an image. Single-chip cameras have red, green, and blue filters arranged over clusters of cells in the sensor. These filter the light coming through the lens and allow the camera to record color images. In a three-chip camera, a series of prisms split the incoming into separate red, green, and blue components, and directs each of these components onto a separate sensor. Because the camera dedicates an entire sensor to each color, color fidelity and image detail are much improved over single-chip cameras. The image data gathered by the sensor(s) is passed to an onboard computer that processes the data and writes it to digital storage media. Evaluating a Sensor When evaluating a camera, first look at its color reproduction. You ll want to see if the camera can create an image with colors that are true to their originals.

2 2 It s also important to pay attention to video noise. Noise comes in two flavors: luminance noise, which appears as monochromatic speckly patterns in your image and chrominance noise, which shows up as colored botches, usually red, green, or magenta. You ll find luminance noise less annoying. Chrominance noise, however, is never attractive, and is extremely difficult to minimize in postproduction. CMOS-based cameras are immune to the above, but can be prone to visual distortion, known as the rolling shutter effect, which happens when the shutter is slower than the physical movement of the camera. The result is a Jell-O effect during pans. Tops f objects might move across the screen more slowly than their bottoms. Sensor Size The current gold standard for image sensor size is based on 35mm still photography. Higher-end DSLR still cameras try to replicate the image quality of 35mm film by using similarlysized image sensors. Micro four-thirds sensors are smaller than full-frame sensors, but they use special technology to make up for the size difference. Bigger image sensors make better-looking images. They have a greater a dynamic range, a lower tendency toward noise, and they are more capable of capturing a shallow depth of field. Compression The first place that your digital video gets compressed is in the camera. Every camera uses a compression algorithm, or codec, to turn that analog subject into a digital signal, and that processes affects image quality greatly. Sharpening Many cameras try to improve image detail by applying sharpening filters to each frame of video, just as you might apply a sharpen filter to an image in Photoshop. Apply too much sharpening, and diagonal or curved lines will appear jagged or aliased. White Balance To accurately represent color, your camera needs to know what objects in your image are white. Once the camera is calibrated for white, it can more accurately reproduce other colors. When evaluating a camera, see what white-balance options are included. At the very least, a camera should provide separate settings for indoor or outdoor shooting. Better cameras provide presets for specific kinds of lights. The ideal white-balance control is a fully manual control that takes a whitebalance reading off a white object that you hold in front of the camera and lets you save it as a custom preset. Lens

3 3 A digital video camera uses a lens to focus light onto the imaging window of a sensor. The quality of the lens on your video camera can mean the difference between sharp images with good color and soft images with muddy color. At the high-end consumer level, most digital video cameras have fixed zoom lenses; that is, you can t change the camera s lens as you might on your DSLR camera. At the professional level, digital video cameras have interchangeable lenses that left you select from variety of zoom ranges, wide angles, and telephoto options. Lens Quality When evaluating lens quality, look for changes in brightness across the image. Does the lens produce images that are brighter in the middle than at the edges, also known as vignetting? As you zoom the lens in and out, does the image get darker as the lens foes more telephoto? Look for distortion around the edge of the image, particularly at wide angles. Look for changes in sharpness and detail throughout the lens s zoom range. Chromatic aberration occurs when the lens does not equally focus all wavelength of light. Lens flares are those weird circles that appear when the lens is pointed into a bright light. A lower-quality lens will flare very easily, and most lenses will have trouble with flares when shooting bright light sources at very wide angles. F-stops vs. T-stops Still cameras and most video cameras rate their lenses in f-stops, but motion picture film cameras and high-end digital cinema cameras rate their lenses in t-stops. T-stops are highly calibrated to account for any absorption of light by the lens itself (for example, light that won t make it to the image sensor.) Lens Features Depending on the quality of their controls, some lenses are easier to use than others. Interchangeable Lenses Zoom Lenses. Lenses with variable focal lengths, or zoom lenses, are often the first purchase for camera owners looking to build a collection of these lenses. They offer the flexibility that we ve all become used to, thanks to camcorders with built-in zoom lenses. If you re shooting under hectic circumstances where changing lenses isn t an option, or just hoping to travel light, having a good basic zoom lens is important. Prime Lenses. Fixed focal length lenses are called prime lenses. Prime lenses typically offer a sharper image than zoom lenses, and they can also have very low f-stop ratings, which mean they can be great for low-light photography. A basic set of primes usually includes a wide angle, a normal angle, and a telephoto lens.

4 4 Cinema Lenses. High-end motion picture lenses are a little different that still photography lenses. They are designed with the specific needs of motion photography in mind and have very accurate focus marks to facilitate manually pulling focus. At some point, you need to take a step back and look at the images produced by the cameras you are considering. You may find that you like one image better than another, and you may have no idea why. That s okay. If you prefer one image over another, but can t find a technical reason for your preference, don t worry about it. In the end, your subjective opinion is more important than any technical benchmarks or specifications. Camera Features Smaller cameras typically lack connectors, such as HDMI video output or audio jacks. They usually don t have as many manual features, and they practically never include such niceties as lenses with aperture and focus markings, sharpening controls, and refined image-quality adjustments. On the other hand, small size makes a camera easier to carry and ideal for surreptitious shooting. On the other hand, you simply won t be able to get the beautiful shots that you see in great-looking feature films with a consumer-level camera. As you look at cameras, don t ignore the camera s physical feel. To get the footage you need, you must be able to move the camera with great precision. Camera Body Types Pocket Cameras. Tiny point-and- shoot cameras. Consumer-grade Camcorders. Handheld camcorder models are a little bigger than pocket cameras and are designed to fit comfortable in your hand. Professional Camcorders. Entry-level pro cameras feature a relatively light-weight camera. Professional shoulder-mount cameras. Larger shoulder mount cameras sport three chips for better image quality, and they weigh 10 lbs. or more. The heavier weight makes for easier handheld shooting and smooth, steady camera moves. Digital Cinema Cameras. Are built to handle lots of added-on hardware and to support big lenses. DSLR Cameras. They offer high image quality and are relatively full-featured, at least in terms of image control. Frame Rates Most HD camera record a variety of frame rates, starting at 24fps and going as high as 60fps. True Slow Motion Many cameras offer a slow-mo setting, but they don t offer true slow motion. True slow motion requires the ability to shoot at a higher frame rate- at least 60fps. Aperture Control

5 5 Being able to control the size of the iris, or aperture, manually is a crucial camera feature. A camera set to auto iris will try to correct for these changes, and the result is often an image that gets brighter and darker as things move around. Image Stabilization There are two kinds of image stabilization: electronic and optical. Digital image stabilization (DIS, sometimes called electronic image stabilization) requires an image sensor with a larger imaging size that is digitally displayed. Optical stabilization (OIS) doesn t alter your image, but instead changes the internal optics of the camera to compensate for motion. In an OIS system, the lens can reshape some of its optical elements to redirect light onto the correct part of the image sensor(s) to compensate for camera shake. Since OIS doesn t ever touch your image data, there s no chance that it will corrupt your image. Viewfinder Most video camers have two viewfinders: an eyepiece viewfinder and a flip-out LCD viewfinder. Because you can tilt an LCD into different viewing angles, flip-out LCDs afford you a wider range of shooting options. However, because an LCD drains your battery quickly and can be difficult to see in bright light, you might not be able to use it all the time. Some higher-end cameras include a feature called zebra stripes that displays diagonal black-andwhite lines in areas of your image that are overexposed. These lines are not recorded; they only appear in the viewfinder. If you re manually setting your shutter and iris, zebra stripes are a musthave for situations when you don t have an external monitor to look at. Many professional should-mount video cameras and digital cinema cameras do not have LCD displays, but in some cases, there are special separate LCD viewfinders that can be added onto the camera. Interface At the lowest end, you ll find the menus written in plain English; at the high-end, unless you re an experience camera operator, you ll need the manual to make sense of the menu items. In addition to the menu option, most video cameras offer status displays in the viewfinder or on the LCD screen. Audio It s pretty safe to say that the microphones included on almost all camcorders are lousy. Low-quality to begin with, their usefulness is further degraded by the fact that they are often pick up camera motor noise, as well at the sound of your hands on the camera itself. Consequently, an external microphone jack and a headphone jack are essential for quality audio recording.

6 6 Ideally, you want a camera that has XLR mic connectors that can be switched between mic and linelevel inputs. Many lower-end cameras offer a small TRS mic jack instead of XLR which is okay if it suits the type of mic you plan to use. A headphone jack is a must-have to ensure that you re actually recording audio. Manual audio gain controls let you adjust, or attenuate, the audio signal coming into the camera, making it easy to boost quiet voices, or lower the level on a sudden roaring car engine. Many cameras have an auto gain control for or auto limiter, which will automatically try to limit loud noices. Unfortunately, like many automatic features, since you have no control of an auto gain feature, you can t always be sure it s not limiting your sound more than you d like or perhaps worse, boosting the audio unnecessarily. Recording Sound to a Separate Device You ve probably heard that most DSLR shooters opt to record audio on a separate device, aka dual system sound. Having a camera with limited audio features isn t the only reason to use a separate audio recording device. It also frees the camera from lots of unwieldy cables and can work well for multi-cam shooting. Media Type Cameras today record to a variety of media: SD cards, flash memory, optical discs, and digital videotape. SD cards and flash memory use solid state technology, which is more stable than bard discs that spin, because there are no moving parts. Also, damage to one part of the drive doesn t necessarily result in the failure of the whole family. Cameras with Hard Drives If you are using a pocket camera or cell phone to record to a built-in hard drive, you camera will be occupied while you download these files to your to your computer. Plan for lots of down time if you re shooting lots of footage Working with SD cards Not all SD cards are created equal. Rather, there are several classes of SD cards available, and for shooting HD; the top of the line class 10 is recommended.. Wireless Wireless video transmissions is available at the very low end and the very high end, although neither can handle streaming full-quality HD. There are several small camcorders that can stream video wirelessly via Bluetooth. Batteries and AC Adaptors Having a battery die mid-shot is more than just an inconvenience; it s a waste of time and money. Unfortunately, most cameras ship with batteries that won t last over a long shoot day. When purchasing, find out what other batteries are available, and how long they will last.

7 7 Ideally, you ll want enough battery life for several hours of shooting. Battery cost should be factored into your assessment of final camera cost. Note that using an LCD viewfinder will consumer your batteries faster. If you know you ll be using the LCD a lot, you ll need more batteries. This is also true for any other energy-intensive operations, such as lens-based image stabilization and mechanical zooming. Some cameras can accept AC adaptors that let you plug them into wall outlets. Naturally, this affects ease of movement, but it can be worth having an AC adaptor on hand just in case. DSLRs DSLRs, or digital single lens reflex cameras, are digital still photography cameras and some of them are equipped to shoot full-sized HD video. Not every digital still camera is a DSLR and not every DSLR can shoot full-sized HD video, but the handful that are capable of it produce amazingly highquality images that rival those of high-end digital video cameras. Because they are designed to be still photography cameras first and video cameras second, there are some trade-offs. DSLRs have two features that give them the capability to record better images than most other video cameras; large image sensors and the ability to use interchangeable lenses. But there are two other features that DSLRS are clearly not as good at handling as the average handheld camcorder; movement and sound. First on almost all DSLRs, you ll have no auto focus when shooting video. At the time of this writing, a few models get around this problem, but all other DSLRs were limited by the nature of DSLR viewfinders and design. So you ll be using all manual focus, all the time. This can require a camera assistant, and because you can only use the LCD screen when shooting video, you might need an extra monitor or LCD shade if you re shooting in bright light. Second, the body style of DSLRs is not designed for movement, and many of the working parts are difficult or awkward to use while shooting. To get around these issues, there are all sorts of accessories out there, from follow-focus mechanisms to add-on viewfinders to specialized camera rigs. Lastly, the CMOS sensors in DSLRs are particularly prone to the rolling shutter problems described earlier. Although there are postproduction solutions, sudden camera movement and very fast subject matter is going to be something to avoid. In addition, DSLRS were not designed with much attention to audio recording, so although they do record audio, they often do not record it well. Tripods There is absolutely no substitute for a good tripod. A tripod is also essential for some complex camera motions, such as smooth pans with simultaneous zooms. Camera movement is part of your visual vocabulary, and most camera movements require a tripod. Shooting without one limits your vocabulary.

8 8 The ideal video tripod has a fluid head for smooth movement and easy-to-find handles for locking and unlocking each axis of the tripod s motion: pan, tilt, and pedestal. Check for stability and sturdiness and make sure the tripod can support the weight of your camera, along with anything else you may need to have attached. It can be easy to get caught up on all the bells and whistles, but the bottom line is that if the camera can get the shots you want, then it s the right camera for the job.