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Nikon DSLR Cameras
D7100
D7100 "too much" camera to start with?
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<blockquote data-quote="WayneF" data-source="post: 215028" data-attributes="member: 12496"><p>f/stop is about the diameter of the lens aperture. f/stop number = focal length / aperture diameter.</p><p>This is why f/4 on one lens can be same exposure as f/4 on a radically different lens, more or less.</p><p></p><p>Primarily, a more wide open aperture (a lower f/number) increases the amount of light it passes (the exposure). Like opening a window blind. One f/stop step is 2x the light. See <a href="http://www.scantips.com/lights/fstop.html" target="_blank">Photographic Tables, F/stop, Shutter Speed, ISO and EV</a> about the definition of the numbers.</p><p></p><p>Secondarily, as we stop down (larger f/number) we increase the zone of sharpness of focus, called depth of field. We still have to tend to exposure however. And there is a practical limit to how much we can stop down. Stopping down in any degree causes more diffraction (Airy disk formula for example), but with a DX camera, if we pass f/11, it starts being a practical limit, sharpness suffers, so we avoid that without good reason.</p><p></p><p>As to choosing a zoom lens with certain apertures.</p><p></p><p>Some inexpensive zoom lenses show two specification, like Nikon 18-55mm f/3.5-5.6G ED II AF-S DX Zoom-Nikkor lens. It is a $100 lens (we can pay $1900 for a 24/70 f/2.8 lens). The two numbers means it is a f/3.5 mm lens at 18mm, and a f/5.6 lens at 55mm, and intermediate maximums in between. Maximum changes as we zoom focal length (f/stop = FL / diameter).</p><p></p><p>Other better lens are constructed with fixed maximum aperture.</p><p></p><p></p><p>For outdoors, your wife will learn about the <a href="http://en.wikipedia.org/wiki/Sunny_16_rule" target="_blank">Sunny 16 rule - Wikipedia, the free encyclopedia</a>, as being typical exposures in bright sun, hazy sun, overcast, etc. No issues with a f/5.6 lens in bright sun, but overcast and shade means we have to open more, and a f/5.6 lens becomes very wide open then (always best to stop down a stop or two, but not always possible).</p><p></p><p>Worse, flash inside is best as bounce flash, flash aimed at ceiling, but it takes a lot of flash power, and about ISO 400 f/4 becomes a common exposure. If a f/2.8 lens, f/4 is no big deal. If a f/4 lens, it is wide open (not best).</p></blockquote><p></p>
[QUOTE="WayneF, post: 215028, member: 12496"] f/stop is about the diameter of the lens aperture. f/stop number = focal length / aperture diameter. This is why f/4 on one lens can be same exposure as f/4 on a radically different lens, more or less. Primarily, a more wide open aperture (a lower f/number) increases the amount of light it passes (the exposure). Like opening a window blind. One f/stop step is 2x the light. See [URL="http://www.scantips.com/lights/fstop.html"]Photographic Tables, F/stop, Shutter Speed, ISO and EV[/URL] about the definition of the numbers. Secondarily, as we stop down (larger f/number) we increase the zone of sharpness of focus, called depth of field. We still have to tend to exposure however. And there is a practical limit to how much we can stop down. Stopping down in any degree causes more diffraction (Airy disk formula for example), but with a DX camera, if we pass f/11, it starts being a practical limit, sharpness suffers, so we avoid that without good reason. As to choosing a zoom lens with certain apertures. Some inexpensive zoom lenses show two specification, like Nikon 18-55mm f/3.5-5.6G ED II AF-S DX Zoom-Nikkor lens. It is a $100 lens (we can pay $1900 for a 24/70 f/2.8 lens). The two numbers means it is a f/3.5 mm lens at 18mm, and a f/5.6 lens at 55mm, and intermediate maximums in between. Maximum changes as we zoom focal length (f/stop = FL / diameter). Other better lens are constructed with fixed maximum aperture. For outdoors, your wife will learn about the [URL="http://en.wikipedia.org/wiki/Sunny_16_rule"]Sunny 16 rule - Wikipedia, the free encyclopedia[/URL], as being typical exposures in bright sun, hazy sun, overcast, etc. No issues with a f/5.6 lens in bright sun, but overcast and shade means we have to open more, and a f/5.6 lens becomes very wide open then (always best to stop down a stop or two, but not always possible). Worse, flash inside is best as bounce flash, flash aimed at ceiling, but it takes a lot of flash power, and about ISO 400 f/4 becomes a common exposure. If a f/2.8 lens, f/4 is no big deal. If a f/4 lens, it is wide open (not best). [/QUOTE]
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D7100
D7100 "too much" camera to start with?
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