Features of DSLR Cameras

DSLR01When choosing to shoot with DSLR cameras, you need to know some basics.

If you have used a standard video camera, are a still photographer, or are a filmmaker, then you'll see the overlap in equipment and vernacular However, some unique processes, gear, and workflows apply specifically to shooting video on DSLR cameras.

Features of DSLR Cameras

Until Nikon released the D90 in 2008, buyers had to choose between a digital still camera or a digital video camera. Filmmakers were using film or traditional video cameras for production. When the D90 and, quickly afterward, the Canon SD Mark II were released, you finally had the ability to shoot digital stills and HD video on the same device.

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At the time, HD video on a still camera was very controversial. A lot of photographers worried that improvements to the still camera would be limited because it seemed all the attention was being placed on the video side of the camera. Independent filmmakers took one look at the early footage and realized the vast potential of this new technology. HD video has been around since the 1990s but was practically available only on traditional video cameras. The design and function of traditional video cameras prevented a lot of the cinematic qualities that traditional film cameras provided.

DSLR cameras allowed filmmakers to easily and inexpensively use interchangeable lenses to craft the look of their film more like traditional filmmaking. These factors, along with an available shallow depth of field and low-light capabilities, were not available on most traditional video cameras. These features, coupled with the price and quality of the video image, helped supersize the growth of the DSLR market.

Since the launch of the Nikon D90 and the Canon 5D Mark II, manufacturers have released several more DSLR cameras. In the upcoming years, the still/HD video hybrid will likely become the norm for DSLR cameras. As more models hit the marketplace, you will need to be able to compare models and find the right functions and price point for your project.

Sensor Size

If you are not a photographer and not accustomed to dealing with sensor sizes, let's put it in motion-picture film terms. Sensor size is a bit like choosing whether to shoot on 8mm, 16mm, Super 16mm, 35mm, Super 35mm, or 70mm film. Just as with motion-picture film stock, you choose your sensor size based on your budget, the depth of field, and the aesthetic look for your film. In general, the bigger the sensor, the more expensive (just like 35mm or 70mm film); the smaller the sensor, the cheaper the camera. Again, this is a generalization, because some higher-end cameras have small
sensors.

A full-frame sensor is approximately the same size as a single frame of 35mm film from a traditional still film camera (Figure 1.1).

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Figure 1.1 A full-frame sensor and 35mm still film are the same size; the sensor area is 36x24 mm, or 864 mm-,

Any non-full-frame sensor is referred to as a crop sensor (Figure 1.2). These sensors vary in size but are smaller than a single frame of 35mm film from a traditional still film camera.

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Figure 1.2 A crop sensor is smaller than 35mm film. The Canon APS-C sensor area is 22.2x14.8 mm, or 329 mml .

The sensor size affects the "grain" in your image as well as your depth of field. At the time of this writing, there are two dominant sensor sizes: full-frame sensors and APS-C crop sensors.

APS-C is a crop sensor and is currently in all non-full-frame Nikon cameras and the Canon 7D, EOS 60D, and Rebel T2i. To make things slightly more confusing, there is a slight difference between the Canon APS-C and Nikon APS-C sensors (Figure 1.3): specifically, the Nikon APS-C sensor (22.2x14.8 mm, or 329 mm-) is slightly larger than the Canon version (-23.6x15.7 mm, or about 370 mm-).

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Figure 1.3 Nikon APS-C (left) vs. Canon APS-C sensor (right). The Nikon sensor is also used by Pentax and Sony. Notice the Canon APS-C Sensor is slightly smaller than the Nikon APS-C sensor.

If you are using a crop sensor, be aware of how this affects your lenses. Shooting with lenses from traditional 35mm film cameras will not match up with the given focal length on the lens. Some people will say that the focal length will be shortened when used on a crop ­sensor camera, but that is not really accurate. Standard still lenses Were designed so the field of view would cover the full frame of the 35mm film. A crop sensor is smaller than a standard 35mm film frame, and when a standard lens is used, the field of view is greater than what is captured on the sensor (Figure 1.4). This creates a "magnification" effect. For example, your 50mm lens will have a narrower field of view. This does not in any way change the actual focal length of the lens, just how much of the area of view is captured.

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Figure 1.4 Field of view comparison between full frame (blue) vs. cropped sensor (red)

The various sizes of crop sensors have their own multiplication factor specific to that size of sensor; these are referred to as either the crop factor or the focal length multiplier. Specific crop factors range between 1.3 and 2 depending on the size of the sensor.

The way the crop factor is determined is a simple division of the size of the sensor by a full frame. For example, a full-frame sensor is 36x24 mm, and a Canon APS-C sensor is 22.3x14.9 mm.

If you divide 36 by 22.3, you get 1.614, which we round to 1.6. If you are using a standard 24mm wide-angle lens on a 1.6 crop sensor, your field of view is more like a 38mm lens than 24mm. This can hurt you if you are shooting in a really tight location, because you may not be able to achieve a wide enough angle.

The APS-C crop sensor is almost identical in size to the standard 35mm film that Hollywood uses. So, don't get worried if you have a crop-sensor camera. If you have a choice, look at some footage from the cameras you are looking to shoot with and choose the one that best aesthetically matches the movie you want to make. Decide the speed of film (ISO on your camera) and the grain tolerance (sensor size) and choose as you would between standard film stock, Kodak Vision stock, and so on.

Full-frame sensors are becoming more popular, and the Canon 5D Mark II and the Nikon D3S are the two leading cameras in the DSLR space with full-frame sensors. The great part of the full-frame sensor is that traditional 35mm film lenses retain their true focal length.

If you have your trusty 35mm or 50mm lens (or any lens, for that matter), then there' is no learning curve for what image you will get. It will look the same as when shooting still images. The strange part of a full-frame digital sensor vs. 35mm still or motion-picture film is that a full-frame digital sensor is in fact larger than 35mm film. In reality, a full-frame sensor is almost "VistaVision" size.

Because of the lack of speed of the film stock at the time, usually productions blasted the scenes with light to create a very large depth of field and usually didn't take advantage of the ability to have a narrow depth of field. Because DSLR cameras are so sensitive, for the first time filmmakers are able to shoot at narrow depths of field previously not seen on a mass scale.

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Figure 1.5 Various motion-picture film sizes

The major benefits of using a camera with a full-frame sensor are that it is more light-sensitive, creates less noise in your image, and offers the ability for a narrow depth of field.

More Light

Sensitivity

The reason that a camera with a full-frame sensor has more light sensitivity is easy-there's more space for light to hit the sensor and bigger pixels collect more light (photons). The full-frame sensor has more than double the area of the APS-C crop sensor. The bigger (fatter) pixels catch more of the light than the smaller sensors.

Less Noise

By having the larger pixels to catch the light, the camera doesn't have to amplify them in order to match the same ISO from a smaller sensor. Think of it as blowing up your image. The larger the image you begin with, the less noise in your final print. The larger the sensor you start with, the less noise in your final footage.

Depth of Field

Most filmmakers were never happy with the look of video. When HD came into existence, it was touted for its "clear" and "sharp" image. Many filmmakers didn't like the look because it didn't look cinematic. That all changed with the release of the Canon 5D Mark II and subsequent DSLR cameras. The ability to have a shallow depth of field and the more natural color rendering of flesh tones (this is for all flesh tones not just Caucasian), made HD video acceptable and in some cases desirable to many filmmakers.

Depth of field is what we unconsciously think of when we want something to look cinematic. Look at your favorite movies to see how much you see of the background in any given shot. You will see that most scenes have a shallow depth of field where the background is more or less out of focus. With your traditional home video camera, you have a very deep depth of field, and when you view your footage, you will see that most things are in focus almost as far back as you can see.

The larger the sensor, the more shallow depth of field is possible; the smaller the sensor, the deeper the depth of field will be. Also, shooting at lower f-stops will cause a shallow depth of field vs. a higher f-stop on any sensor size.

With DSLR cameras, we are now creating our films like Hollywood does. We can choose a lens and paint with light just as they have since the dawn of the movie industry. And that is why shooting on an DSLR camera is revolutionary. We are making movies that look just the way we have been watching movies for as long as we can remember.

Frame Rates

The current DSLR cameras offer a range of frame rates depending on which camera you buy or rent. Let's talk for a moment about the standard frame rates in both film and video production. We call these frames per second (fps), These are the most common, or "standard," frame rates:

24 fps is the standard rate at which motion-picture film gets run through the camera. So, any movie that is shot on film that you see in the movie theater was shot at 24 fps and is the holy grail of the "film feel" of your footage.

25 fps is the standard in most of the world (outside the United States and Japan) for video broadcast. This is close to the "film look" and was widely sought after in video cameras in the United States for filmmakers looking to get away from the 30 fps look of U.S. video cameras.

29.97 fps is the standard for broadcast in the United States. Most people refer to this as 30 fps, but there is a huge difference between 30 fps and 29.97 fps when it comes to broadcasting or viewing your footage in traditional formats (that is, TV, DVD, VHS, and so on).

30 fps is the standard more or less for web video. On the Web, there are no rules for frame rate. 

Slow motion would be any frame rate greater than 30 fps and be very useful to the videographer who is shooting sports. The two most common frame rates on DSLR cameras are 50 fps and 60 fps. This means you are recording double the amount of frames as you would at 25 fps or 30 fps, and you can (in post) play these shots back at half speed smoothly, giving you slow motion.

In our next installment of the DSLR Revolution: Is it right for your class, we will begin a closer look at interchangable lenses and the selection of gear.  Joe Dockery will share more of his experiences in the actual classroom environment.