Complete Guide to the Nikon D200- P2 ppsx

V1.03 Thom Hogan’s Complete Guide to the Nikon D200 Page 31 In a compact camera, such as this Coolpix, light (the green arrows) goes separately to the sensor (blue line) and to your eye looking through a separate viewfinder (bottom set of green arrows). Digital point-and-shoot cameras often use this same technique, though most also show exactly what the digital imaging sensor is seeing by displaying it on an LCD as a “live preview” of the eventual image. A few now only have the LCD preview and skip an optical viewfinder entirely. The only problems with LCD preview are: it slows down the image capture (the camera has to switch from image preview to image capture, which isn’t as simple as it seems); the color LCD is difficult to see in bright light; the user tends to move the camera away from their body in order to see the LCD and thus compromises stability; and the color LCD doesn’t have a great deal of detail in it making it difficult to verify focus and even composition with really wide angle lenses. So let’s look more closely at the SLR design: • The mirror and prism make it so that virtually all of the light collected by the lens makes it to your eye. F 8 8 Film SLR users may sense slightly less light in the D200 viewfinder than they’re used to. The primary culprit is that the actual frame area of the D200 is smaller than film. A smaller frame area means less total light gets through (though the same amount gets through for any given spot; it’s a bit of an optical illusion that it seems dimmer). Think of the lens as part of a water pipe and light as water moving at a constant speed. If you make the pipe smaller, you’ll get less overall water. That’s what’s happening with the light you see in the viewfinder (which, is, after all, moving at a constant speed). V1.03 Thom Hogan’s Complete Guide to the Nikon D200 Page 32 • The prism is necessary in order to flip the perceived image into the proper orientation (lenses reverse up for down and left for right, and we’ve got a mirror in the path which flips one axis but not the other). The prism has mirrored surfaces (red) to reflect light internally. • Since the distance that the light travels via the mirror and prism to the eye is greater than the distance to the sensor (or film), we need an intermediary, called a focus screen (purple in illustration, below; shown removed from camera on the right, below). The mirror actually projects the image on the focus screen, which is the same distance from the mirror as the sensor, and the prism mechanism just acts as a viewing device so that you can see the focus screen. • The focus screen shows the image as the sensor will capture it (well, close—the D200 shows 95% of the image area). You see basically the same thing the lens presents to the sensor when the shutter is open. What you see through the D200 viewfinder, therefore, is a bright, complete rendition of what your image will capture. Because you’re looking through the lens, you’re seeing a real time presentation—there’s no delay due to electronics, no degradation of the viewing quality due to electronics, and V1.03 Thom Hogan’s Complete Guide to the Nikon D200 Page 33 you’re seeing the current state of the focus system (don’t worry, we’ll get to the details of focusing soon enough). Here’s a key difference between your D200 DSLR and a point-and-shoot digital camera: the point-and-shoot uses the digital imaging sensor to do multiple things: the imaging sensor provides autofocus and metering information to the camera’s electronics, collects white balance info, and often even measures flash output. One of the delays on these cameras is that they operate the digital sensor at a specific frame rate while previewing the image and must take some last minute updates after you press the shutter release. As in “the user has pressed the shutter release so I’d better take one last look at whether the focus should be moved, grab one last metering measurement, and then turn off video stream for a moment, let the sensor stabilize, then take a picture.” Phew! The D200 uses dedicated autofocus and metering sensors; there’s no delay because these dedicated parts work right up to the moment the camera flips the mirror out of the way. Amazingly, you can do a mechanical thing—flip the mirror out of the way and open a shutter—faster than you can do an electronic thing (at least for now with current technology). We’ll get to the autofocus and metering aspects of the SLR later in the book, but first we need to talk about what’s behind the main mirror in your D200. It’s not as simple as you might think. Behind the mirror you can see is a secondary mirror (small red line in illustration, below). We’ll get to what it does in a moment. Behind the secondary mirror is a shutter (yellow bar in front of blue sensor). V1.03 Thom Hogan’s Complete Guide to the Nikon D200 Page 34 The shutter isn’t a single “door” that hides the digital sensor on the D200. Instead, it’s like a closed window shade, with multiple slats. These slats move out of the way from one direction and close from the same direction. Think of a curtain in a theatre moving up from the floor and eventually closing by rising from the floor. The secondary mirror probably surprised you. The primary mirror has several “partially silvered” areas. If you look at the main mirror with enough light (you’ll need to take off the lens to do so), you may be able to see a rectangular area in the center of the mirror that’s “discolored.” That’s the area that passes a tiny bit of light to the secondary mirror. So why do we need some light going somewhere other than the viewfinder? As I mentioned earlier, SLR designs have dedicated sensors for many things. In the case of the D200, that light is bouncing off the secondary mirror down into an open area at the bottom of the camera that houses the autofocus sensors. At the bottom of the mirror box looking up is a set of autofocus sensors. If you could squeeze your head into the mirror box chamber and look down from the secondary mirror you’d see them. I’m not (yet) willing to take apart my D200 to photograph this part, but here’s what the part looks like on the D50 and D70s (looking down from the secondary mirror): V1.03 Thom Hogan’s Complete Guide to the Nikon D200 Page 35 The D200’s part looks more like this: In other words, a small amount of light is split off from the viewfinder so that seven F 9 autofocus sensing areas in the bottom of the mirror box get some light. You may have noticed that Nikon specifies that a lens has to be f/5.6 or faster (larger physical aperture opening) for the autofocus system to work. That’s partly because the autofocus system doesn’t get all the light coming into the camera, just a small slice of it that manages to get through the partially silvered area of the main mirror. The D200 has another dedicated sensor besides the autofocus sensor array. In the prism area of the camera resides a 1005- segment CCD F 10 . This CCD (blue line in prism area in illustration, below) is dedicated to measuring exposure (both normal and flash exposure). It actually looks at the focusing screen at the bottom of the prism to get its slice of light (the purple lines indicate where it is looking). 9 Yes, I said “seven.” It appears that the inner vertical sensors are split into three for the default autofocus ability. I’ll have more to say about this in the section on autofocus later in this eBook that begins on page <315>. 10 Charge-Coupled Device. A CCD is a type of digital light sensor. Note that the D200 has two CCDs: one in the viewfinder for doing metering, and the main image sensor (see “The D200 Sensor” on page <66>). V1.03 Thom Hogan’s Complete Guide to the Nikon D200 Page 36 Let’s talk for a moment about the “order” in which things are done in an SLR. Remember, with compact digital cameras, they execute a sequence of things using a single sensor, which slows them down. In a DSLR, many things happen simultaneously once you’ve press the shutter release partway down: • You observe what the lens sees via the main mirror and prism. This allows you to compose your picture or follow action. • The autofocus sensors get light through the partially silvered portion of the mirror and look for phase detection that indicates that the subject is in focus. This is even more complex than it sounds, as there are lots of focus options on a D200, but in essence, all seven autofocus sensors get information that has been split by separator lenses just on top of them (see illustration, below). The sensors provide a stream of information about the separated data (distance between them) to the camera’s main computer. The computer calculates whether the optimal “split” has been achieved; if it hasn’t, it tells the lens to move its focus point, as necessary (if the lines are too widely spaced, the focus is in back of the best point; too narrow indicates focus in front of the best point; thus the camera knows which way to turn the lens). Light (green lines) coming down from the secondary mirror reaches a plane that’s the same distance from the lens as the sensor (large rectangle in above illustration) but the separator lenses are placed just below this, meaning that the focused light beam is already broadened a bit before it hits the separator lenses (two small ovals in the illustration). These lenses refocus the light to the AF sensor below. The light reaching should be a known distance apart when it reaches the AF sensor. If the distance is shorter than expected, V1.03 Thom Hogan’s Complete Guide to the Nikon D200 Page 37 focus is in front of the desired position. If the distance is greater than expected, focus in back of the desired position. In practice, the focus plane, separator lenses, and AF sensing unit are all part of the same seven sensor AF part I mentioned earlier (in other words, we’re looking at what happens in a cross section of the actual AF sensor here). • The 1005-segment meter in the prism is capturing exposure info. The dedicated metering CCD is concurrently providing a stream of exposure information to the camera’s main computer. Based upon your camera settings, the exposure information is updated in both the viewfinder and the top LCD of the camera. At this point the camera’s computer is looking at all your camera settings plus the information streams coming to it from the various sensors and is making decisions about how to expose and focus the camera. So far, almost everything is electronic (the lens movement for focusing is mechanical). But the moment you press the shutter release all the way down, a series of additional actions occur, some of which are mechanical: • The flash may fire a preflash. If the flash is active (up and ready for use) and set for automatic (TTL F 11 ) use, a very brief series of preflash pulses are fired from it and reflections off the subject from those flashes are measured with the CCD in the viewfinder. When I say brief, I mean brief. The preflash comes so close to the actual flash during the main image exposure that you can’t usually see it. The preflash has to occur before the mirror moves because the preflash is measured by the CCD in the viewfinder. • The mirror flips out of the way. This is the big physical action the camera makes and accounts for much of the sound your hear from a DSLR. When the mirror is out of light path, you no longer see what the lens sees (the viewfinder “blacks out” momentarily) and the autofocus 11 Through The Lens. Stands for the fact that flash output is measured through the lens instead of by a dedicated flash sensor on the outside of the camera or flash. V1.03 Thom Hogan’s Complete Guide to the Nikon D200 Page 38 sensors no longer get light. No need to worry though, the camera’s computer had a stream of data from the autofocus sensors and can “guess” what the next data point might be—called predictive autofocus—so even if your subject is moving, the camera usually still focuses correctly on it F 12 . • The aperture is set. Inside the camera there’s an arm that physically moves to set the lens aperture (the opening in the lens that the light goes through) to the proper value (as set by you and/or the exposure system). • The shutter opens. The curtain that sits in front of the main imaging sensor opens. The main imaging sensor itself is turned on and begins collecting light. • The flash goes off. If flash is active, it goes off once the shutter curtain has completed opened. The camera detects the point where the curtain is open and sends an electronic signal to the flash to start, and later, to stop (assumes TTL BL or Standard TTL flash, the usual methods we use with flash; Manual and Automatic flash modes only send a start signal to the flash as the flash itself figures out when to stop, and TTL FP fires the flash continuously in a low pulsing action from start of shutter opening to the end). • The shutter closes. The curtain that sits in front of the main imaging sensor closes. The main imaging sensor itself is turned off and the data it collected is moved to the other electronics within the camera, where it is measured, manipulated, and saved. • The aperture is reset. The activation arm returns to its resting position and the physical aperture in the lens is reset to the largest opening (so that the most light gets through to the viewfinder and sensing systems). 12 A lot of the footnotes in this first part of the eBook, like this one, are really just reminders that things aren’t always as simple as they first seem. Yes, there’s a caveat to what was written above: it is possible to set the D200 so that it focuses once on a target and doesn’t refocus if the subject moves. We’ll get to the nuances of autofocus settings in the section on that later in the eBook, but for now just believe what I wrote. V1.03 Thom Hogan’s Complete Guide to the Nikon D200 Page 39 • The mirror returns to it’s normal viewing position. The mirror returns to its main viewing position (and the secondary mirror unfolds behind it so that the AF sensors can again get information). Here’s the amazing thing: all that mechanical movement (mirror, shutter, and aperture arm) happens so fast that it can be done several times a second. And even when the D200 is operating at full speed (5 frames per second), the mirror is down in its viewing position more than half the time (it has to be for the metering and AF systems to work between shots). I’ll have much more to say about each and every one of the subsystems within your DSLR as we progress further into the eBook, but suffice it to say that the engineering that goes into designing cameras like the D200 is pretty sophisticated. Before we move on, let’s take one last at some important generic items before we move to the specifics of the D200. Photographic Terms That Are Important to Know I’ve already introduced some terminology that’s specific to photography, and in some cases specific to SLR cameras. This isn’t a book called Introduction to Photography, so I don’t want to get bogged down in basic photographic concepts (this eBook will already tax your reading capacity, as you’ll be reading well over 700 pages). On the other hand, some of you are coming from cameras that automatically controlled some of these things and thus you may not have encountered the terminology. So before we go on, let’s get some basic definitions out of the way for those of you new to all these terms. Aperture. The physical opening in the lens that light goes through. This opening can be changed in size from very small in physical size to the full size of the glass used in the lens. Aperture blades (usually between five and nine blades that form a near circle) are used to make this adjustment. We refer to the aperture opening as an f/stop, as in f/2.8. Lower numbers make for larger openings. Thus, f/2.8 is a large V1.03 Thom Hogan’s Complete Guide to the Nikon D200 Page 40 physical opening letting in a lot of light, f/22 is a small physical opening letting in a little light. Apertures are one of the ways we use to control the amount of light that gets to the sensor, and thus the “exposure” (see below). Common apertures you’ll encounter go in the following sequence (all one stop apart): f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22. The D200 allows you to set these values and values that are either 1/3, 1/2, or 1 stop in between. The observant amongst you will notice those full-stop values I just listed are all 1.4x apart; if you memorize any photographically-related number, that’s the one you want to remember, as it can be used for a lot of things F 13 . Same lens, two different aperture settings (f/5.6 on left, f/16 on right; aperture opening shown here highlighted in red). This particular lens (a Tamron 90mm Macro) uses an opening defined by nine “blades” to approximate a circle. Note that you can see a bit of lopsidedness in the opening (especially true of the smaller aperture, at right). Badly mishapen openings or ones made with fewer blades can produce objectionable artifacts in the out-of-focus areas of your image. The Japanese refer to this as the “bokeh” of the lens. Shutter Speed. This term refers to the amount of time the shutter is open and letting light hit the sensor. Shutter speeds go in increments a little more predictable than apertures, as each doubling of the time is another stop (doubling) of 13 E.g., if you know the Guide Number of your flash for one ISO value, 1.4x gets you the Guide Number at double the ISO value; or: the light from your flash falls off one full stop for each 1.4x the distance it has to travel. [...]... camera to measure the amount Thom Hogan’s Complete Guide to the Nikon D200 Page 41 V1.03 of light hitting the scene The process of metering establishes an exposure, and that exposure is a specific combination of aperture and shutter speed (Are you starting to see that many of these terms are closely related?) Stops When photographers talk about “stops of light” (as in “I needed another stop to get the. .. capacity and so too does our digital sensor If we were to let too many light photons into the bucket, the bucket would overflow and we wouldn’t be able to count the results accurately Likewise, if no light photons got into a bucket because we restricted their flow too much, we might not be able to count that level accurately, either, because we couldn’t differentiate the number of light photons getting... had to show the major genealogy of the Nikon DSLRs, it would go something like this: 14 Exposure Value Thom Hogan’s Complete Guide to the Nikon D200 Page 42 V1.03 D1 D1h/D1x D100 D70 D2h D70s D2x D200 D50 That should tell you something about the D200: it’s the little sister in the professional lineage and not the big brother of the consumer lineage Along with the D200, one new lens was announced, the. .. you know how to use one, you’ll be most of the way towards knowing how to use any other • From the D2 series the D200 gets a similar four-channel ADC that allows for fast frame rates (5 fps) with large amounts of data (10mp) Unique to the D200 are the following: Thom Hogan’s Complete Guide to the Nikon D200 Page 47 V1.03 • The D200 uses a completely new autofocus arrangement, with 7 sensors that can... Hogan’s Complete Guide to the Nikon D200 Page 55 V1.03 I’ve used all three in the field and would be happy with any of these DSLRs; my personal choice would be the Nikon, with the 5D a close second In particular, the D200’s flash system is more reliable and I find its autofocus system more flexible Most people find the Nikon user interface more approachable and direct That’s not to bash the Canons—they... Hogan’s Complete Guide to the Nikon D200 Page 59 V1.03 D200 Basics In this section we’ll look at the controls of the camera, how it is powered, how images are stored, and the important things you’ll need to set up before you first use it D200 Design The D200 is a completely new Nikon body design, though it includes many carryovers from previous Nikon designs The only truly new parts in the D200 are the. .. ranges from the middle to the low end of brightness transfer An f/2.8 lens would provide a brighter image in the viewfinder, as all autofocus lenses are always viewed at their maximum aperture, and f/2.8 would also allow more light to get to the autofocus sensors than f/3.5 or f/5.6 (the range of the maximum aperture of the 18-200mm) Which brings us to those abbreviations: • G The letter following the maximum... body that really demands a better lens H The D200 with the 18-200mm lens mounted If you’re wondering about the thing on the side of the camera, that’s a Really Right Stuff L bracket, which is how I mount my D200 to the ball head on my tripod Thom Hogan’s Complete Guide to the Nikon D200 Page 43 V1.03 Virtually every autofocus lens Nikon has made will work on the D200, as will most manual focus lenses... on the D200, anything over 55mm would be considered telephoto Wide angle lenses are used to frame a large area all at once, telephoto lenses are used to isolate a single item and bring it closer H Thom Hogan’s Complete Guide to the Nikon D200 Page 44 V1.03 On the left, a wide angle view of a Patagonian glacier (24mm lens used); on the right, a telephoto view of one small section of the scene near the. .. perfectly fine cameras in their own right In most users’ hands, though, neither a Nikon nor Canon DSLR is going to be “better.” At the base ISO values, there’s little to distinguish the image quality, and at the higher ISO values, both the Nikon and Canon products start to show different issues (the D200 has more noise, but very little chroma noise; the 30D and 5D have less noise, but when the noise appears . things. In the case of the D200, that light is bouncing off the secondary mirror down into an open area at the bottom of the camera that houses the autofocus sensors. At the bottom of the mirror. you the Guide Number at double the ISO value; or: the light from your flash falls off one full stop for each 1.4x the distance it has to travel. V1.03 Thom Hogan’s Complete Guide to the Nikon. “metering” the scene, which means we’re using the facilities of the camera to measure the amount V1.03 Thom Hogan’s Complete Guide to the Nikon D200 Page 42 of light hitting the scene. The process