Mirror or Lens: A Simple Guide to the Technical Differences - lens mirror and prism

 2024-09-19 01:39:42

And they can be closer if you want, just depends on how much of rush you are in I suppose....close enough where the cello can spin, but not hit a light.

I've just bought a grow tent for my violin drying and saw this thread. I'm just wondering whether this 50w UVA floodlight would be enough to dry the violin https://www.ebay.co.uk/itm/324342581015?_trkparms=ispr%3D1&hash=item4b84530717:g:S0QAAOSwBsRfj~Ar&amdata=enc%3AAQAGAAACgPYe5NmHp%2B2JMhMi7yxGiTJkPrKr5t53CooMSQt2orsSvhAqMt0wg86xg8aAkgjQJI7vyLyhSi%2FyxnotyvsJEBtSEr%2BAVTxcsMD6nvzrbDbjFSw8xJx80StHuJ3u%2BfwKOOUaYgS1wHYaTma4spgNmpz9PcKe5sKrnhAdNs9rQJZWl%2BT8kWhKK7E%2Fp0UMPhwm3aSY1Gc%2Fur8RGprgoMPBgVDrXjxi2scyKpL9i%2FmVJWnnu7LBO0pGAdEuSdAOH1DAvwsuAK4VrWrCbU%2FGzjm6Fc2hWiRtBH2pXmtdbjLKG3YU2qZ2A1j5G5mdDh2NPAf3DB%2BLuaBMPnYDQU2sNiJCtumsUjU%2Bll3%2BKOEjzndN8CC9lwzARQnPQfLm8aTXpri%2FwFSXhX0c%2FKwnQf2g%2Fpppq9L%2F9hzr5Z%2BFR4fp6fSsRWUVjIS7FkpVsQ9SxvJTkowLumHszALx9PGbIWJ9XjV2PLJwisSnf5I4m1cZq2ue%2Bd2emFLUxJDn72P4jm3eQXnJAh7Tr5n5JsZTw3RjUIpoxbRICRi%2BX5Bv1mG1z%2FZV1h%2Boou44LRuzlQI8mtJ7Zp8IaPPR00ppwJzNyPEDXMPrA7PX%2FsZj1T59gb2W3zX%2FAiF7vTbKxmjp4nujjHDsuoK7tYuYFsDXGMi7mdi%2FE9YoZqFUcZ7ilOBiJm4mS97ZfWkduBaKVzN85%2FCIFj0uMH%2B2eZu%2FGCo3EyevJEWnOAVnFEaS%2F5w9HaJswaWq15CSQpr0diLkqTiyrIRuA1ndI5ybZY3RcJpG0TNFcIL8py9YrWk8yQwqQxueFUU7EIC0Tveu5paNroBhpdGWeCD4znKgD9X1S%2Fank0bDJAjdElVzK%2F0%3D|ampid%3APL_CLK|clp%3A2334524

While depth of field is generally measured in macroscopic units such as meters and feet, depth of focus is typically measured in microscopic units such as fractions of a millimeter or thousandths of an inch. In optometry depth of focus is usually measured in dioptres.

Depth of focus is a lens optics concept that measures the tolerance of placement of the image plane (the film plane in a camera) in relation to the lens. In a camera, depth of focus indicates the tolerance of the film's displacement within the camera and is therefore sometimes referred to as "lens-to-film tolerance".

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The choice to place gels or other filters behind the lens becomes a much more critical decision when dealing with smaller formats. Placement of items behind the lens will alter the optics pathway, shifting the focal plane. Therefore, often this insertion must be done in concert with stopping down the lens in order to compensate enough to make any shift negligible given a greater depth of focus. It is often advised in 35 mm motion-picture filmmaking not to use filters behind the lens if the lens is wider than 25 mm.

The simple formula is often used as a guideline, as it is much easier to calculate, and in many cases, the difference from the exact formula is insignificant. Moreover, the simple formula will always err on the conservative side (i.e., depth of focus will always be greater than calculated).

the long and the short of it is that there are pre existing products out there that will work for the box instead of having to build and then line one with reflective material

uv lights in general are much cooler operating than other lamp sources, but these ones do generate some heat, most of which seems to pool in the back of the light housing

the frame of the grow tent is made from metal tubes so there are plenty of ways to suspend the instrument and lights...two lamps on the floor, two lamps suspended , with the instrument hanging in the middle works well, or you can search Joe Robsons posts {using google} he has a cool way of rigging a steel garbage can to turn it into a good drying "box"

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the actual distance of the light face to the instrument can be quite close but I was using about 4-6" off the instrument

but LED lamps in all spectrum, in this case black uv, are the way to go now, far superior type of lamp, the one I got were black lights they would sell for parties , flat panels , about 6"x 10" with a small frame that allows you to prop them up, WAY powerful and dries uv reactive finishes very well

There are a lot of different options nowadays, but I honestly think normal fluorescent UV tubes (black or not) are still the best. If they are long enough they still ensure the best light diffusion, and if the rheostats are kept outside the box they are probably still the ones that heat the inside less. They are probably also the cheapest, but I'm not sure of this if you also consider the complete electrical system to be done to bring the rheostats outside.

The same factors that determine depth of field also determine depth of focus, but these factors can have different effects than they have in depth of field. Both depth of field and depth of focus increase with smaller apertures. For distant subjects (beyond macro range), depth of focus is relatively insensitive to focal length and subject distance, for a fixed f-number. In the macro region, depth of focus increases with longer focal length or closer subject distance, while depth of field decreases.

I added a 100w black light (60+60+100=220w total) the temperature is still acceptable. I will maybe buy an other 100w ( to get 320w). Then it cost a bit when running during severals weeks ( but not much in regards to the instrument)

In astronomy, the depth of focus Δ f {\displaystyle \Delta f} is the amount of defocus that introduces a ± λ / 4 {\displaystyle \pm \lambda /4} wavefront error. It can be calculated as[4][5]

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I'm trying to keep costs down, so I ended up buying https://www.ebay.co.uk/itm/403129598363 this 40w black light bulb. I have a car inspection light which I can hang in the grow tent and it has a protective glass encasing so hopefully it won't get too hot.

where t is the total depth of focus, N is the lens f-number, c is the circle of confusion, v is the image distance, and f is the lens focal length. In most cases, the image distance (not to be confused with subject distance) is not easily determined; the depth of focus can also be given in terms of magnification m:

the tents have ports for fans and some vents, if you leave them open it makes it so the tent gets warm , but not hot, generally aids in drying, particularly in winter months

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Let us know how that type of bulb works out. Be aware though that the protective glass casing on the fixture may allow significantly less UV to reach the instrument.

Your drying chamber won't necessarily dry varnish faster than sunlight. The advantage is that you don't need to worry as much about bird poop, insects sticking to the varnish, rain, cloudy weather, high winds, the radiant heat from direct sunlight, theft, or the neighbor kids mistaking your hanging violin for a pinata.

the chamber is cheap, lamps are not cheap. I have no idea if the small lamp as asked above work fine - their function seems to be heat production. The big led panels have ip66 Label which for sure contribute to their cost.

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The phrase depth of focus is sometimes erroneously used to refer to depth of field (DOF), which is the distance from the lens in acceptable focus, whereas the true meaning of depth of focus refers to the zone behind the lens wherein the film plane or sensor is placed to produce an in-focus image. Depth of field depends on the focus distance, while depth of focus does not.

edit; also, keep in mind, that larger objects with more varnish, {than a small violin}in enclosed spaces , will be out gassing much more solvent and in general dry slower as oxygen crosslinking will be hampered by the solvent vapor displacing the oxygen in the local vicinity of evaporation

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You may need more lights for a cello, to dry "quick" ,it should dry as is, but you could put a couple more on a cello, my original advice was thinking it was a violin, but I think the grow tent is the way to go for guitars and cello, or multiple violins . Seems like its working out good.

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Following historical convention, the circle of confusion is sometimes taken as the lens focal length divided by 1000 (with the result in same units as the focal length);[2][3] this formula makes most sense in the case of normal lens (as opposed to wide-angle or telephoto), where the focal length is a representation of the format size. This practice is now deprecated; it is more common to base the circle of confusion on the format size (for example, the diagonal divided by 1000 or 1500).[3]

due to this fact I suggest making sure that if you are hanging them, make sure the backs do not have direct contact with the tent, the ones that you put on the floor I suggest putting on some dinner plate or a piece of tile or something to buffer the light from the floor, as a precaution

I measured the temperature on my 4ft tubes and found that the tube and the electronics were each 10C above ambient temperature while the metal casing was at ambient. Considering the small surface area of the electronics compared with the tube I thought it wasn't worth the effort of rewiring, and fitted a small fan. Now I run all 4 tubes with no water dish and wick and don't worry about temperature and humidity.

Depth of focus can have two slightly different meanings. The first is the distance over which the image plane can be displaced while a single object plane remains in acceptably sharp focus;[1][2][clarify] the second is the image-side conjugate of depth of field.[2][clarify] With the first meaning, the depth of focus is symmetrical about the image plane; with the second, the depth of focus is slightly greater on the far side of the image plane.

I lined an old kitchen cabinet with aluminum foil and mounted 2 3OW LED "party" blacklight floodlights. Thoroughly dries a violin in 4 hours.

In small-format cameras, the smaller circle of confusion limit yields a proportionately smaller depth of focus. In motion-picture cameras, different lens mount and camera gate combinations have exact flange focal distance measurements to which lenses are calibrated.

I would buy a cheap grow tent {if you can in france} and then I would go get 4 led uv black lamps...they give off just the right heat {much less than regular lamps} and use much less electricity

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Unfortunately there are lots of variables, like for one, the varnish, who's or what is it? Do not expect any varnish that NEEDS uv to dry to dry fast, except modern varnish like zero'res. Conifer linseed based varnishes are notorious for being slow drying varnishes , and that as long as it dries tack free {you can place your hand on it for a minute and then pull it off with no sticking or imprinting} your doing good, hell your doing great, eventually you can make up some sherpas in the mountians story about all that dry time needed for these special varnishes and charge to watch paint dry...but in the mean time if you are getting your varnishes to dry in your dope growing tent as fast as you can get them to dry outside you're doing great! but you know some gentle air flow isn't bad

as I do not know these lights you have, I would test run them to make sure they dry well {varnish test scrap} as well as get an idea of how hot they get your tent, smaller tents may get too hot and may need to be fanned or to leave the zip flap open.

The magnification depends on the focal length and the subject distance, and sometimes it can be difficult to estimate. When the magnification is small, the formula simplifies to