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www.photographyworlds.comDSLR Camera Focusing Tips explains the difference between focusing for stills and movies and how to master it. Aside from shutter speed, one of the biggest differences between shooting stills and video with DSLRs is focusing. Much like the aforementioned shutter speed, many of the same basic tenants of focusing still apply when shooting video, with one major twist; the lack of autofocus.
Why Should You Manually Focus ? DSLRs have long had incredibly capable autofocus features built in, allowing the camera to do a very good job of quickly finding sharp focus. Video, however, is a little different. Autofocus has also existed in the video world for a long time, but is exclusively the sole preserve of low-end consumer cameras. The reason? Simply put, autofocus systems are not good enough to judge what should and shouldn’t be in focus reliably throughout the course of a shot. If, for example, you are filming a group scene with one person talking, and one person gets up and walks in front of your shot, the camera’s autofocus will readjust to capture the closer passing figure, assuming as it is closer it needs to be in focus, thus throwing the speaker out of focus, when in fact you wanted him to remain the focal point of the scene. Worse, once the subject in the foreground has walked out of frame, the camera will attempt to refocus on the original group. This constant ‘hunting’ will make your video unwatchable, and will likely infuriate your audience! This is compounded when shooting video on DSLRs, as their large sensor allows a desirable,
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shallow depth-of-field aesthetic to be achieved, which makes accurate auto (and manual) focusing even harder. The autofocus functions on DSLRs will work during video recording, but they will be slow, inaccurate and very noisy — particularly problematic for dialogue scenes. This is why focusing is almost universally achieved manually on all professional video and film shoots. With so much movement going on in the frame, and the focus often needing to be shifted multiple times in the course of one shot, to follow a character moving through frame or to draw the audience’s attention to something important, for example, autofocus just won’t be able to keep up. Ultimately, the camera can’t read your mind! Newer model Canon DSLRs (the 650D in particular) actually have a new continuous autofocus system based around a new sensor technology and motors in lenses like the 18-135mm kit lens. These STM motors will allow much quieter and quicker autofocus to be achieved throughout the filming of the video. In practice, while this is a huge improvement over older autofocus systems, it is still quite slow to change focus points. It’s certainly a viable option for certain kinds of video making, but on the whole you’re still going to be better off focusing manually. Putting Knowledge Into Practice So, you’re going to have to learn how to set, and most importantly judge and adjust focus, manually throughout the course of a shot. This can be quite a hard task at first, especially if you’re used to the camera doing it for you. Unfortunately, this task is made even harder when shooting on DSLRs for a number of reasons. Firstly, if you’re using the kit lens which came with your camera, or indeed most modern photography lenses, the lens will lack hard stops (i.e. the focus ring stops moving when it reaches the point of minimum or maximum focus). This, when combined with the lack of focus marks on the lens barrel, and the very small focus throw of stills lenses (i.e. the physical distance you have to move the focus ring between focus distances) conspire to make fine and accurate adjustments very hard. Thankfully, there are a few things you can do to help. Using the built-in digital zoom allows you to zoom the image into an area of high contrast (eyes are a good area to judge focus) allowing you to set focus easily before shooting. Another good tip is to use the camera’s autofocus system before the start of shooting to initially get the subject in focus, and then adjust the focus from there. This is where the aforementioned new technology in the Canon 650D could really come into its own, allowing you to quickly get your subject in focus. Another good option is to invest in a Zacuto Z-Finder, which is a precision focus viewfinder. Not only will this improve the stability of your camera work, but it will give you a much clearer and enlarged view of your subject, making focusing while recording that much easier. One final tip; generally speaking zooming in to make setting focus easier, then zooming out is a great way of easily setting focus manually. However, be careful when using photography zoom lenses, as unlike their video equivalents, they aren’t par focal (i.e. they often do not maintain their focus when the zoom position is adjusted). If you’re using the kit lens which came with your DSLR these often have variable apertures, which change as you zoom in. This can also make focusing using this method more difficult, as the image will often get darker as you zoom in. For these reasons, it’s much better to use the digital zoom function instead.
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Ultimately, while these tips will help, learning to manually focus and pull focus accurately all comes down to practice, so get out there and shoot some video! Top 10 Tips for Focusing Use the digital zoom in function to focus before the start of the shot When zoomed in, use areas of high contrast, like eyes, to make judging accurate focus easier A deeper depth-of-field makes pulling focus easier, f/4 is a good compromise Unless using Nikon fit lenses (which focus backwards) remember to turn the focus ring clockwise for closer focus, and anti-clockwise for more distant focus If you can, measure the distance between the camera and the position you’ll be pulling focus to before the start of a shot Practice the focus pull a couple of times before rolling cameras to get used to the movement and ensure a more accurate focus pull If you have the time, use the autofocus function to initially get your subject in focus before commencing filming Using a magnified eyepiece like the Zacuto Z-Finder will increase the clarity of the DSLR’s screen and make setting and pulling focus that much easier Don’t forget to be careful when using zoom lenses – they won’t maintain focus if the zoom position is shifted Practice makes perfect!
Here are some common terms you may hear with explanations of why they are important SHARP | SOFT In focus | Out of focus RACK FOCUS/FOCUS PULL Adjust the focus from one point to another during the course of a shot, often to follow an object or character’s movement through the frame. DEPTH-OF-FIELD The distance between the nearest and farthest objects in the shot that appear acceptably sharp in focus. CODEC A codec, short for compress/decompress, (AVCHD or H.264 are common in DSLRs/CSCs) is the means by which the images captured by the camera are compressed and stored. As the name suggests, the images are compressed during this process and therefore lose quality — much like a JPEG file. It’s important to understand the strengths and weaknesses of the codecs your camera uses in order to maximise the quality of the final image recorded.
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APERTURE Controls the amount of light entering the lens, and is measured in f-stops. It also controls the depth-of-field in an image. A larger aperture (smaller number) lets more light into the lens, creating a shallower depth-of-field and blurring the background out of focus. This is a key element in creating the film look. (Also see ND filter). ND FILTERA A neutral density filter is best described as being like sunglasses for your camera. It is a filter which fits over the end of the lens and reduces the amount of light entering the camera. This is the best way to control exposure, as it allows you to use the aperture to control depth-of-field, and allows the use of wider apertures even in bright sunlight. AUDIO More than half the picture, recording good audio is a vital part of creating a good video. It can be diegetic (recorded live at the time of filming, e.g. speech) or non-diegetic (added afterwards during editing, e.g. music or sound effects). Learning how to record quality audio and combining it with music and other sound effects is vital to the success of your video project. FOCUS Focusing when shooting video needs to be achieved manually, as auto-focus technologies cannot accurately keep up with a moving object, meaning the operator has to manually pull focus to keep a moving object in sharp focus. This can take some practice! EDITING A necessity when shooting video, it refers to the construction of a programme, usually with a cohesive story, from the elements captured during the shoot. It is necessary to shoot for the edit when creating a video, meaning to think about how the different shots you are gathering will fit together, and ensuring you capture enough footage to guarantee this can occur. FRAME RATE The number of still frames that the camera captures per second, giving the impression of a moving image when played back concurrently. The UK standard is 25 frames per second (fps), which gives a filmic sense of movement in the resulting video. Higher frame rates e.g. 50 and 60 frames per second give a smoother, more soap opera video look, or can be slowed down when editing to give a nice slow motion effect. ISO This setting changes how sensitive the camera is to light. The higher the ISO the more sensitive the camera is, allowing you to shoot in low light conditions. DSLRs are generally very light
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sensitive, and allow the use of higher ISOs than traditional video cameras. However, you must be careful not to use too high an ISO, and shoot in multiples of 160 to avoid unpleasant noise in the image. PICTURE PROFILE A very important setting which alters how the camera produces the final image. As DSLRs are not meant for shooting video, some important tweaks need to be made to set the camera up to shoot good quality video. RESOLUTION A measure of the size and number of pixels the video contains. Most DSLRs will shoot in 1080p HD, which is 1920 pixels horizontally and 1080 pixels vertically. Similarly, 720p is 1280 pixels horizontally and 720 pixels vertically. SHUTTER SPEED The rate at which the shutter opens and closes per second. Unlike stills photography, to maintain a constant sense of movement the shutter needs to be kept constant throughout filming, and cannot be used to control exposure. For a filmic look, its best to use a 180 degree shutter, which for 25fps is 1/50sec. WHITE BALANCE Is a setting which tells the camera to capture the colours it sees correctly, even under different light sources. Unlike when shooting Raw stills, white balance cannot be altered after filming when shooting video on DSLRs, so it’s important to get it right when filming. You can still use auto white balance, or balance manually. As a general guide, around 3200K is correct for tungsten (red shifted) light, and between 5600 and 6000K is correct for daylight (blue shifted) light. 180 DEGREE SHUTTER RULE The 180 degree shutter rule refers to the optimum shutter angle to use when filming video to ensure a normal amount of motion blur between frames, and to ensure your video has a desirable, filmic sense of movement. The name comes from the fact that film cameras have mechanical shutters which are semi-circular in shape, (i.e. 180 degrees of a circle). DSLRs express their shutter angle in terms of shutter speed. Therefore, to easily calculate the correct shutter angle, you must simply double the frame rate, and keep your shutter speed set to the resulting value. For example, at 25fps, correct 180? shutter angle = 1/50sec, at 24fps, correct 180? shutter angle = 1/48sec. If you follow this rule, your footage will have the correct amount of motion blur, and a correct sense of movement. Higher shutter speeds give a more staccato sense of movement with less motion blur, as used in movies like Saving Private Ryan, while lower shutter speeds add a lot of
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undesirable motion blur. www.photographyworlds.com www.photographyworlds.com Check Out The Full Indepth Details Here: DSLR Camera Focusing Tips
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