Low pass filter example - Reflexion filter diy.

Low Pass Filter Example

low pass filter example
    pass filter
  • A band-pass filter is a device that passes frequencies within a certain range and rejects (attenuates) frequencies outside that range. An example of an analogue electronic band-pass filter is an RLC circuit (a resistor–inductor–capacitor circuit).
  • A low point, level or figure
  • A particularly bad or difficult moment
  • A state of depression or low spirits
  • an air mass of lower pressure; often brings precipitation; "a low moved in over night bringing sleet and snow"
  • in a low position; near the ground; "the branches hung low"
  • less than normal in degree or intensity or amount; "low prices"; "the reservoir is low"

Lake Artemesia, College Park, Md.
Lake Artemesia, College Park, Md.
[Fui ISO200 color negative film, Nikon N80+ Tamron 28-80 F11-F13 > CVS processing > Epson V300 scanner 4800dpi cae dg 1.8 ael -3 > Gimp] The "solar flare" here was too interesting to pass up. Now this I have to hand to film, at least with the G9 I wouldn't have even had the nerve to try this. Not only did it AF well but it caught the flare just fine. Though the contrast might be a bit low here and the sky is a little more washed-out than I'd like to see. Still not bad at all. Though I have to say that I've seen enough pictures of Lake Artemesia (it does make a good test-ground) shot with both ISO200 and ISO400 35mm film and various digital cameras, the 5D, A200, G9 all shot raw, to know that scanned 35mm film isn't able to really compete with even a 12MP camera (with a good UV filter & lens, well-focused, stable, properly stopped-down and exposed, shot raw at low ISO with the raw files well-processed with a good raw-converter, good demosaicing algorithm, the proper gamma, saving the files to a good format, no NR, proper sharpening & so forth), in terms of fine-detail and the grain is always going to be an issue even more so if the shot is cropped. Of course I have not yet shot digital & film with the same lens but I doubt that that is the problem, with Tamron lenses. Also there's a slight performance advantage in the Epson V300 over the V100 but that's not the main problem. I can't see the two formats having exactly the same levels of fine-detail if for no other reason than they take completely-different paths to form an image. You might get comparable levels of fine-detail with different film, better negative film or transparency/slide film or printing directly to paper, but not by scanning negative film, at least not with these scanners, not by just slapping the film down on a plastic holder above a glass table on a flatbed scanner. And while the difference may not be huge at VGA resolutions like the above it's definitely significant at 2MP on a 15" display not to mention in larger format. If I wanted to get hard numbers I'd have to shoot a test chart but I don't need to do that to see what I've seen over dozens of images of the same scenes produced from raw files and with scanned 35mm film. Digital is clearly winning the fine-detail battle. So I have to chalk the photographic advantages of digital over film (and I mean good digital cameras over good film, and in terms of the final image not in the picture-taking process) as, at the very least, that digital has better fine-detail at a given display-size (certainly <300dpi), obviously the lack of grain and virtual freedom from surface-defects. Film is clearly winning in terms of the "ease" of processing from there, turning a blind-eye to both grain and the effort of masking or cloning-away surface defects, and the cost to get into the gear and to take pictures in the first place. The shot above effectively cost me $125 to produce, and sure you can get 8-12MP digital cameras for less than that, I also could get film gear for far less than $125. $15 at most for this shot and 23 more like it. The financial difference is not huge but it's still there, and it adds up as you buy more gear, especially if you have a hankerin' for DSLR gear. So if you can shoot the same lenses, i.e. you're talking 35mm SLRs vs fullframes that support the same lenses, the fullframe will probably win out in the end, in the long run, with careful ICC calibration, at least at low ISOs and high SNRs and color-sensitivities. The medium/high ISOs *might* swing back to film, maybe. The catch is that this is less of an issue the closer one gets to the subject, the less that one really needs super-high fine-detail, the less sky and bright, solid areas that are in the shot, the harder it is to see grain & surface-defects of a reasonable nature, given the relatively high price of fullframe and even subframe gear the edge swings decidedly back to SLRs and film. You almost can't go wrong at current eBay prices. In fact I'd say that good fullframes certainly beyond the 5D are prohibitively expensive for most amateur photographers so cost-conscious eBayers end up buying subframes and subframe lenses at least for wide-angle shooting and trying to get their moneys' worth out of them. But for landscape shooting that's really only possible at the lowest ISO or two, and for most everything else ISO400-ISO800 again you might as well just shoot film. Film can just do too much too well too cheaply to ignore. So I might get better shots with a fullframe, but I know that I will get decent shots with film especially in small-format, < 20" diagonal. And having "good" one always has the dilemma whether to just try to improve what one can get from what one has, or to make a wholesale change and try to get to "great", and then rationalize the extra cost, because if nothing else it means buying unnecessary gear. And that
regenerative frequency divider
regenerative frequency divider
In the lab we sometimes have an oscillator at one frequency and need to create another oscillator at some fixed multiple of that frequency. For instance, at LLO we have a 24.484150 MHz oscillator and we also need an oscillator at exactly 5/2 times that frequency. I was wondering how this was done. I looked inside the box and saw a "frequency multipler" (?5) connected to a "frequency divider" (?2). Huh. I asked Hartmut how these things work, and as an example he sketched something resembling this figure. Recursion always seems clever, and even moreso in electronics (where it typically goes by the name "feedback".) Here we have a box that takes in a signal at frequency 2f and produces a signal at half that frequency, 1f. How does it do that? Well, pretend that it's already doing it. Then we can take the 1f output and mix (multiply) it by the 2f input. When you multiply two sinusoids, you get a signal containing sinusoids at the sum and the difference of the original frequencies. So mixing 1f and 2f gives us a signal containing 1f and 3f. Low pass filter and keep the 1f. Done! You have frequency divider. How this thing is bootstrapped--what it does when you first turn it on--I don't know. Similar tricks get you other multiples of the original frequency. For instance, here we could insert a tap before the low pass filter and get 3f as an output.

low pass filter example
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