I'll give a shot to some of these too:
2. That X:Y ratio is the 'magnification' of the macro lens in question, meaning that the object will be at X/Y times its real size on the frame. X can be larger than Y, it actually is that way in very expensive, very professional macro lenses.
Dedicated macro lenses are required on SLR cameras because the rear element is at some distance from the film/sensor plane due to the mirror assembly. Compacts do not have a mirror, allowing the lens to sit very closely to the sensor. Couple that with the tiny sensor size, and you have that insane zoom range and macro performance associated with compact superzooms.
5. This one is also pretty uncharted territory for me, but for all I know circular polarizers can only eliminate reflections that occur within a certain angular range between the light source, the reflecting surface and the observer. This is why the effect is augmented when the observer is at a relatively right angle to the sun, and reduced otherwise. Therefore, the 'problem' with the fish could be attributed to their rapid change of orientation inside the water, while the water remains relatively fixed.
Also, polarizers can not deal with surfaces producing highly specular reflections, e.g. metal surfaces and mirrors. Certain fish has that type of quality to their skin (especially scaled ones), which might explain the issue.
7. Linear polarizers fool the autofocus systems of modern SLRs, otherwise the effect is said to be the same as circular ones. After all, not all cameras are SLRs and not even all of them have autofocus. For those, linear polarizers could be more convenient (if I'm not mistaken, they are cheaper and less likely to cause vignetting, but don't quote me on that).
10. More elements in more groups is better. That's all I know about this, and that's probably all shooters up to 'very serious amateur' level should know.
11. A 'pentaprism' is a solid block of glass the shape of an irregular pentagon. It takes the light reflected from the mirror, refracts it in certain angles in order to basically shoot it out of the viewfinder, so that we can see through the lens. A 'pentamirror' does the same thing, albeit with a set of mirrors assembled similarly. By nature, reflection loses more light than refraction, so the viewfinder display is comparatively darker. On the other hand, a pentaprism is both heavier and more expensive to manufacture. That's why you don't see one in small, cheap entry-level cameras.
12. Technically they could, but the lens elements are sufficiently larger to compensate for that. Plus, using IS/VR allows for stopping down a little more using the same shutter speed, which also reduces vignetting.
13. DSLRs had a shutter at the outset because early models were simply film cameras with a bulky digital back strapped on. Nobody cared to remove things that didn't hurt, in order to keep the processes simple - even for the less complicated, from a serial-manufacturing point of view 'change' is always costly. As DLSRs evolved, the shutter was retained basically to keep dust off the sensor and eliminate unnecessary exposure to light (which overheats the sensor and causes noise). The compacts never had a shutter (at least one that we're familiar with), and the Micro Four-Thirds finally got rid of that in the DSLR realm as well.
14. The mirror box exists b/c otherwise we could not get a direct optical view through the lens. That's the 'R' in SLR. Lose that and you defy the whole idea. The OVF is probably no longer needed. It was needed in the early days because LCD technology had not matured enough to allow a comparably crisp view. Now that it does, perhaps the mirror will go away someday. It already did in the Micro Four-Thirds. BUT, the whole mirror thing has one advantage, it allows operating dedicated autofocus and metering sensors, which gives the modern DSLR its impressive speed and image quality. Lose that, and you're stuck with contrast-based autofocus, which is still a tad bit slow for everyday use, and mortally slow for pros.
The Micro Four-Thirds will probably not be the standard for 'all' cameras, because despite the hype, it's not earth-shatteringly innovative. Essentially 90% of 'all' digital cameras already operate in the same principle. From a practical point of view, it doesn't lose the mirror box and the shutter from an SLR, it actually adds a larger sensor and interchangeable lenses to a compact. That way, it suddenly sounds much less innovative, right?
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Nikon D80 | AF-S Nikkor DX 18-135 mm f/3.5-5.6G ED | AF Nikkor 50 mm f/1.8D | AF Nikkor 70-210 mm f/4
Last edited by Hailstorm on Fri Sep 19, 2008 8:54 pm, edited 2 times in total.