Complete Guide to the Nikon D200- P9

Chia sẻ: Cong Thanh | Ngày: | Loại File: PDF | Số trang:30

lượt xem

Complete Guide to the Nikon D200- P9

Mô tả tài liệu
  Download Vui lòng tải xuống để xem tài liệu đầy đủ

Complete Guide to the Nikon D200- P9: As with all my books, a full draft was reviewed by volunteers to weed out unclear language and misstatements. This book is better because of them.

Chủ đề:

Nội dung Text: Complete Guide to the Nikon D200- P9

  1. V1.03 can apply exposure compensation after the fact. However, note that due to the way digital images are captured, noise is more prevalent in the “dark” areas of your image than it is in the bright areas 78. Normally you don’t see the noise as it F is buried in very dark areas that print at or near black, but when you use post processing techniques to “boost” shadow areas in an image, you’ll also be boosting noise, perhaps into visible range. Note: Photoshop histograms are calculated a bit differently than those the camera shows. One thing that confuses many NEF shooters is that Photoshop histograms only show the top 8 bits of data. If you use Capture to output 16-bit images to Photoshop, be aware of that! The D200, like the D2 series, has the ability to show individual channel histograms. So what have we been looking at? Well, something called a luminance histogram, which doesn’t take color into account. If, as I suggested earlier, you primarily use the RGB Histogram instead of the plain Histogram display, you’ll get four histograms on the screen at once: the luminance histogram (white) and a histogram for each of the Red, Blue, and Green channels. 78 Why? Because the signal to noise ratio for a pixel value of 1,1,1 is lower than one with a value of 254,254,254. Let’s examine a hypothetical example to find out why. Let’s say that your camera has random noise “base” that averages 2 photons. Further, let’s assume that the 1,1,1 value represents a photosite that’s captured 100 photons. The signal to noise ratio for that pixel is 50:1. The 254,254,254 value represents capture of perhaps 10,000 photons, so the signal to noise ratio is 5000:1. Thom Hogan’s Complete Guide to the Nikon D200 Page 241
  2. V1.03 All the same things I said about the luminance histogram apply to the individual channel histograms. Spikes at the right edge are blowouts in the highlights (in the case of an individual channel, which would be called a “channel blowout,” as in “I blew out the Red channel”). Spikes at the left edge mean shadow detail is lost. The example histogram shown here is a little underexposed. I’ve left valuable room at the right where highlight detail should be, and the shadow detail is pushed to the left margin, near black (especially true of the blue channel—and that glacier has a lot of blue in it). So why are channel histograms important? Remember those nuclear colors I mentioned before? Well, channel histograms would be the one tool on the camera that might alert you to the fact that you’ve got one. But even in some situations where you might not be expecting it, the channel histograms can save you from an exposure error. The classic example for my type of photography is the red rock country of the US Southeast (Northern Arizona and Southern Utah, for example). If you take a picture of a landscape feature that’s in bright sun, all that red in the rock has a tendency to push the red channel up, often enough to blow the channel out completely. This has an impact after the fact: when you go to post process that picture and perhaps try to alter the white balance a bit, the blown red channel will prohibit you from many manipulations you might want to do, and the tonal ramp in the areas that have been blow out may be compromised. Red rock isn’t the only thing you have to watch out for, though, which is why you just have to pay attention to the channel histograms. Any red or blue channel blowout means you need to reduce exposure. Green channel blowouts are a little less problematic 79, but if you have a large expanse of F 79 That’s because most color manipulations you’d make after the fact impact the blue and red channels more than the green, which is in the middle of the spectrum between the two. Thom Hogan’s Complete Guide to the Nikon D200 Page 242
  3. V1.03 green (like a lawn on a golf course) you still need to bring the tonal value down. Exposure Modes The D200 has four exposure modes: P Program—In this exposure mode, the D200 automatically adjusts both the aperture and shutter speed to create a properly exposed image. The combination picked is based upon a predetermined table in the camera (see “Program Exposure Table” on page < 246>). You may override the H selection chosen by the camera by rotating the Rear Command dial (called Flexible Program by Nikon). For most new-to-DSLR users, this is probably the exposure mode you 80 should start with. It gives you “semi-smart ” automation F backed with the flexibility to override. Warning: when you start using flash you’ll want to avoid this exposure mode, though. A Aperture-preferred—You control and choose the aperture setting (using the Front Command dial) and the D200 automatically picks the correct shutter speed to create a properly exposed image. Note that the shutter speed the camera picks is incremented in 1/3 stops with the default camera settings in this mode. As you get more serious about your photography you’ll discover that the aperture you select has a great deal to do with what is in and out of focus. Most serious amateurs gravitate towards this exposure mode as they master concepts like depth of field. Many professionals use this exposure mode. S Shutter-preferred—You control and choose the shutter speed (using the Rear Command dial) and the D200 automatically picks the correct aperture to create a properly 80 If you have either my D50 or D70 eBook, you may remember this as saying “smart.” Yes, those consumer cameras are smarter than the D200 and D2 series in one way: their programs try to preserve shutter speeds that would minimize camera shake. The D200 (and D2 series) use a simpler program that does not change with focal length, figuring that the camera operator is smart enough to override the program is shake might be an issue. Thom Hogan’s Complete Guide to the Nikon D200 Page 243
  4. V1.03 exposed image. The aperture chosen is incremented in 1/3 stops in this mode with the default camera settings. When you shoot sports or other fast moving action, Shutter-priority exposure mode gives you the ability to set an action-stopping shutter speed and let the camera do the rest. Professionals who shoot sports tend to use this exposure mode. M Manual—You control and choose both aperture (Front Command dial) and shutter speed (Rear Command dial); the D200 advises you on exposure by activating an analog metering bar in the viewfinder and top LCD showing what your current choices would produce: underexposure correct exposure overexposure The number of bars indicate how much under or over exposed the image may be (in the default settings, as shown here, each bar is 1/3 of a stop, so the under and overexposures shown here are 1 1/3 stop—four bars from the center correct position). Manual exposure mode gives you full control, much like the older “match-needle” cameras that were prevalent in the early days of SLRs. Many users gravitate to Manual exposure mode when they want to make sure that a particular combination of aperture and shutter speed is used (as when they meter off one area and compose in another). Some professionals use this exposure mode because it forces them to deal with both their aperture and shutter speed choice and can be a pragmatic way of “locking” exposure. Note: The references to Command dials in the previous and following descriptions can be reversed by using Custom Setting #F5 (see page < 474>). H õ To select the exposure mode, press the Mode button on the top of the camera (behind the shutter release) and use the Rear Command dial to chose the desired exposure mode Thom Hogan’s Complete Guide to the Nikon D200 Page 244
  5. V1.03 (displayed as P, A, S, or M on the top LCD; a * indicates you’re in Flexible Program exposure mode). Top LCD: Note: If the lens mounted on the D200 does not have what Nikon calls a CPU 81 (i.e. it is an AI or AI-S lens) and you are in F matrix metering with Program, or Shutter-priority exposure mode set, the camera won’t take a picture. Switch to Aperture-priority or Manual exposure mode. Flexible Program As noted earlier, the Program exposure mode uses a predetermined combination of aperture and shutter speed based upon how much light is in the scene and the maximum aperture of the lens. I call this the “program.” You can override the program by rotating the Rear Command dial when the meter is active. Note, however, that the overall exposure remains the same; in other words, if your override increases the shutter speed, the aperture is decreased, and vice versa. A small asterisk appears next to the ] (e.g. ]*) in the top LCD when you’ve overridden the camera’s program settings. Note also that once you override the program, it remains overridden my that same amount until you change the exposure mode, turn the power switch to OFF, or perform a camera reset. 81 It’s not actually a central processing unit as the name implies, but rather a chip that passes on a set of values that describe a few pieces of data about the lens (maximum aperture, focal length, focus distance). Thom Hogan’s Complete Guide to the Nikon D200 Page 245
  6. V1.03 Program Exposure Table (at ISO 100 82) F EV Aperture Shutter Speed 0 f/1.4 2 seconds 1 f/1.4 1 second 2 f/1.4 1/2 3 f/1.4 1/4 4 f/1.4 1/8 5 f/1.7 1/12 6 f/2 1/15 7 f/2.4 1/23 8 f/2.8 1/30 9 f/3.5 1/45 10 f/4 1/60 11 f/4.8 1/90 12 f/5.6 1/125 13 f/6.7 1/180 14 f/8 1/250 15 f/9.5 1/350 16 f/11 1/500 17* f/13 1/750 18* f/16 1/1000 19* f/16 1/2000 20* f/16 1/2000 * Not possible with matrix metering, as it exceeds the meter’s brightness range; camera reverts to center weighted Students who’ve been to my workshops know that I’m not a fan of Program exposure mode. That’s mostly because Program exposure mode has some hidden liabilities when using flash, but also because most users don’t take the time to understand exactly how the camera is making its exposure decisions or even that once they’ve overridden the “program” it stays overridden. Don’t be a “lazy” photographer and use Program exposure mode casually. If you’re serious about controlling depth of field, camera shake, subject motion, and a host of other 82 I believe the Nikon manual is wrong. The program seems correct for the base ISO of the camera, and would therefore be the same as the D2x program. I suspect the “ISO 200” in the Nikon manual is a cut-and-paste from a previous manual that didn’t get caught in proofreading. Thom Hogan’s Complete Guide to the Nikon D200 Page 246
  7. V1.03 factors that come up while making photographs, get out of Program exposure mode and take more direct control over what the camera is doing. ISO Sensitivity The D200 allows user controllable ISO values from 100 to 1600, in as little as one-third stop steps (you can alter the settings to half or full stops using Custom Setting #B2 [see page < 436>], but I’d suggest just leaving the camera at the H default) . The D200 also has settings of H0.3, H0.7, and 83 F H1.0, which are approximately equivalent to ISO 2000, 2500, and 3200 respectively. These last three values are not labeled with an ISO value because they’re not finely calibrated and 84 thus only approximate values . F õ To set ISO values on the D200: 1. Press the MENU key to show the menu system. 2. Use the Direction pad to navigate to the SHOOTING MENU (the camera icon tab). 3. Use the Direction pad to navigate to the ISO Sensitivity option and press the > key on the Direction pad to select it. 4. Use the Direction pad to select an ISO value and press the > key on the Direction pad to select it. If you set Auto ISO, the camera actually uses 1/6 stop increments. 83 84 As you’ll see in the examples, noise starts to impact color intensity as you boost ISO value, and color intensity is something we would interpret as an exposure cue. Above ISO 1600, the color impacts of the noise are intense enough that you might not feel like you got the full benefit of the boost. Thom Hogan’s Complete Guide to the Nikon D200 Page 247
  8. V1.03 õ Alternatively: Hold down the ISO button and use the Rear Command dial to select an ISO value. Top LCD: While it may seem that you should simply set the camera to the highest ISO value and leave it there (or use the Auto function available in the Custom Settings), don’t. As you increase the D200’s ISO value, your images gain considerable digital noise. Much as using a higher ISO film in a 35mm film body results in increased visible grain, added digital noise makes an image look rougher (most noticeable in large areas of a single color). Worse still, digital noise added by the D200 is not truly random, as is film grain. The D200 has a variety of noise reduction schemes, some of which work automatically, some of which are user controlled. Long Exp. NR (on the SHOOTING MENU) has nothing to do with ISO: it controls a type of noise that builds up when a sensor sits collecting light photons for long periods of time (8 seconds or longer on the D200). High ISO NR (also on the SHOOTING MENU) is a setting that does apply to noise caused by ISO settings. Because higher ISO values are caused by amplifying data, small inconsistencies in data are amplified as you increase the ISO setting. High ISO NR is a setting used to combat that; it Thom Hogan’s Complete Guide to the Nikon D200 Page 248
  9. V1.03 begins working at ISO 400 if turned on by you, but it always is always active in some form at above ISO 800. But noise reduction routines aren’t perfect, and they also have a tendency to reduce edge definition. All of the detailed examples in this book were taken with a Nikkor 70-180mm Nikkor lens, and use standard test charts (there’s a non-proprietary sample chart on the CD; kids, do try this at home!). The small samples I’ll show are taken from the area towards the bottom. White balance was set to Pre and measured with a gray card. The camera set to AdobeRGB color space. Sharpening is set to Normal in these examples. Histograms were carefully examined to insure that the full range of the chart fit within the boundaries. All shots here are post-processed JPEG images. The only Photoshop processing is setting white and black points and then cropping. Note that these samples are only a few of the ones I examined to make my comments. Go by what I write, not necessarily by what you see. ISO 100. Look carefully at: (1) how well the resolution holds up; (2) whether broad color patches show any grain or unevenness; (3) whether hard edges are being “damaged”; and (4) are colors staying accurate and vibrant, even in the shadows. Note that some of the colors are intentionally going out of gamut in this example. Thom Hogan’s Complete Guide to the Nikon D200 Page 249
  10. V1.03 ISO 200. Not much to note so far. ISO 400. Still not much is happening in our image. If you look carefully at the color swatches (bottom sample is at 200%) you can see some noise is starting to appear, and that it is more visible in the darker patch. This is typical for the D200: noise first appears in shadow tones, but highlights, even at higher ISO values tend to stay relatively noise-free. Thom Hogan’s Complete Guide to the Nikon D200 Page 250
  11. V1.03 ISO 800. Here’s where I start to see the first clear signs of the image changing. It may be a little difficult to tell from these small samples, but we’re losing some detail, and the noise is getting more visible in the darker areas of the image (above the green head, middle image). There’s clear noise in the darker color patch (bottom), though it’s still under control. Some colors are changing slightly, but not enough to worry about. ISO 1600. Noise lurks everywhere now, with it more visible in darker areas than bright. Colors have lost a bit of their subtlety and dark colors are drifting darker. We’re also losing a tiny bit of detail. Quite usable, overall. Thom Hogan’s Complete Guide to the Nikon D200 Page 251
  12. V1.03 ISO 3200 (H1.0) Everything has noise in it now, and that noise tends produce darker and non-subtle colors. Colors are no longer accurate. Detail is clearly lost due to the noise. As I noted earlier, ISO 3200 is definitely usable for JPEG shooters (these are all JPEG shots with as much NR turned off as possible), but much less so for NEF shooters, especially if they don’t convert with Capture (which picks up and mimics some of the camera’s noise reduction). Thom Hogan’s Complete Guide to the Nikon D200 Page 252
  13. V1.03 Note: Underexposing is a bit like setting a higher ISO. Some of the complaints I’ve heard from D200 users about “noisy, unsaturated images” can be attributed to this. For example, let’s say you were shooting at ISO 200 but underexposed by two stops. Do your images look as if they were shot at ISO 800 when you run a correction on them in post processing? I’m betting that, yes, they do. Just like with the D2x, I see an almost direct one-to-one correspondence between results from underexposure and higher ISO use on the D200. Remember, as you increase ISO you’ll find that colors tend to lose a bit of their punch (e.g. get “muddy”), and contrast is lowered. At the extreme, it can result in the equivalent of a 2- bit or higher reduction in individual color values, which is easily seen in images. H1.0 very obviously loses color saturation, but the effects begin as early as ISO 800. When the D200 appeared, I was asked many times about whether it was usable for indoor sports. As I did with the D2x, I decided to test the question, so during one of my weekly basketball games, I brought my D200 and set it to essentially the worst possible scenario (one stop underexposed, Auto white balance, H1.0 ISO, noise reduction turned off as much as possible). Here’s the result (at 175%): Thom Hogan’s Complete Guide to the Nikon D200 Page 253
  14. V1.03 Yes, there’s noise evident, but it’s quite “usable” noise and free from false colors and typical digital noise problems. Cleaned up with noise reduced by Neat Image, you may be able to see that the edges and detail have a bit of “grit” to them, but otherwise things look pretty good (look at the edges of the ball and rim, which have picked up a slightly artificial look): Thom Hogan’s Complete Guide to the Nikon D200 Page 254
  15. V1.03 Still, a remarkably good result from a camera no one was expecting to be used for indoor sports. (Hint: it will be.) Noise Reduction Settings The D200 has two noise reduction abilities built in: • Long Exp. NR—performs a dark frame subtraction on long exposures to remove hot pixels (photosites where the data values get “stuck”). Surprisingly, this is a relatively necessary function on the D200, as it produces hot pixels easily, though not as bad as the worst Nikon body in this respect, the D1x. If you shoot long exposures (anything over 8 seconds) you should probably turn this option On. • High ISO NR—performs in-camera noise reduction on images taken at ISO 400 or higher. The manual and menu system seem a little out of sync with one another here. Off Thom Hogan’s Complete Guide to the Nikon D200 Page 255
  16. V1.03 means no noise reduction is applied at ISO 400 and 800, but a minimal amount is applied at ISO 1000 through H1.0. On (Normal) means a minimal amount is applied at ISO 400 and 800 and a moderate amount at ISO 1000 through H1.0. On (High) means a moderate amount is applied at ISO 400 and 800 and a large amount is applied at ISO 1000 through H1.0. Since this is apropos to a discussion of ISO, let’s look at how noise reduction fares at the highest ISO value, H1.0. Here’s High ISO NR set to Off at ISO H1.0. (Remember, the camera always applies some noise reduction at this ISO value). Note especially the grain-like noise in the middle sample (green face and red above it). Here’s High ISO NR set to On (Normal) at ISO H1.0. Still a lot of noise in the green face and above it, and the tonal patches Thom Hogan’s Complete Guide to the Nikon D200 Page 256
  17. V1.03 at the bottom are starting to have a curiously mottled look to them. Here’s High ISO NR set to On (High) at ISO H1.0. That green face has cleaned up a bit, but the price is a small loss of detail. Note also that the 200% view of the sample patches, at bottom, isn’t perfect. There’s quite a bit of mottled look to the darker tonal ramps. Thom Hogan’s Complete Guide to the Nikon D200 Page 257
  18. V1.03 Overall, my assessment is that the in-camera noise reduction should be a last resort: use it only if you really can’t afford to have the grain-like noise effect in your images and can’t afford to use post-processing noise reduction. I actually prefer the noise reduction to be Off—the colors are brighter at the expense of “sharp” film grain-like noise in the JPEG images. A good noise reduction program can do better than the camera, in my opinion (see “Other Manipulation Tools” on page < 707>). H Auto ISO The AUTO ISO option (see “Custom Setting #B1 -- Automatic ISO Setting” on page < 433>), while tempting, tends to be H misunderstood by virtually all users; it does not operate quite as you’d expect and has definite limitations (my suggestion: avoid it). What happens when AUTO ISO is active depends upon what exposure mode you’re using: • In Manual exposure mode, the ISO is changed if the shutter speed and aperture combination you pick won’t achieve a proper exposure (manual exposure bar centered at 0: ó). For example, if you were at ISO 200 and set f/8 at 1/125 but the meter thought the exposure should be f/5.6 at 1/125, the camera will boost the ISO one stop to Thom Hogan’s Complete Guide to the Nikon D200 Page 258
  19. V1.03 400 (f/8 is one stop underexposed compared to f/5.6 in this example). • In Shutter-priority exposure mode, the ISO is changed when the camera runs out of aperture range to use. For instance, assume that the initial ISO value is 200 and the aperture set by the camera to the lens’ maximum of f/2.8. If the lighting changes such that f/2 is required, the ISO will be boosted one stop to 400 (f/2.8 is one stop underexposed compared to f/2 in this example). • In Program and Aperture-priority exposure modes, ISO isn’t changed until the exposure reaches the extreme at either end of the shutter speed range (1/30 second at the bottom end unless you set a different value with CSM #B1); the upper limit is always 1/8000). As long as the camera will set a shutter speed between those two extremes, the ISO value won’t change. One nice touch is that you can set the maximum ISO value (between 200 and 1600) for the camera to use when AUTO ISO is active. Plus the camera sets the ISO value in sixth stop increments when this feature is active. Another nice touch is that D200 shows the ISO value being used in the viewfinder (and blinks the ISO-AUTO indicator). The Top LCD only shows the ISO-AUTO indicator: Top LCD: Note: If you use flash, Auto ISO turns off and your previously set ISO is used! The ISO-AUTO in the viewfinder stays lit (does not blink). This is Nikon’s subtle reminder that “more light” is better than “higher ISO.” To activate the AUTO ISO option, see the instructions for Custom Setting #B1 on page < 433>. H Thom Hogan’s Complete Guide to the Nikon D200 Page 259
  20. V1.03 How ISO Values are Created You might wonder how higher ISO values are generated by the camera. All ISO values above 100 are created by amplifying the data coming into the Analog-to-Digital converter. In other words, the sensor always works at the 100 sensitivity, but underexposed data values coming from the photosites are boosted by an amplifier to produce the higher ISO values. As you might guess, this means minor differences between photosites get magnified and may become visible. Imagine a photosite that captures 150 light photons and an adjacent one that receives 155 photons. This difference is insignificant when these are black values and end up getting interpolated into, say, a pixel value of 10,10,10 versus 10,11,10. But if these values are being amplified several times and now represent middle gray values, the difference may be significant and visible. ISO Operating Suggestions To optimize image quality, follow these guidelines for setting ISO values: • Use the lowest ISO setting (100) whenever possible. If you suspect that the scene you’re photographing might produce moiré, use only the lowest ISO value—once noise gets interlocked with moiré, both become very difficult to remove. • Expose to the right. Underexposure can generate additional noise issues with the D200. Keep your exposure histogram pushed towards the highlights (but don’t blow out highlights by going too far and pushing it off the right edge). Indeed, the minimum amount of noise for a low contrast, gray target would be generated by overexposing the gray target so that the histogram spike was well right of center, then using Capture or Photoshop to re-center the exposure (Curves, Gamma, Exposure Compensation, etc.). What you generally don’t want to do Thom Hogan’s Complete Guide to the Nikon D200 Page 260
Đồng bộ tài khoản