tag:blogger.com,1999:blog-4783276084231164782024-02-08T02:54:49.011+08:00Basic CameraLearn step by step about basic of photography using digital & manual mechanical single lens reflex cameraPhotoManhttp://www.blogger.com/profile/12261723954138591225noreply@blogger.comBlogger115125tag:blogger.com,1999:blog-478327608423116478.post-7653828617863432262008-06-30T23:13:00.000+08:002008-06-30T23:15:30.168+08:00Stuck Filter Removal<div style="text-align: justify;">Filter rings are generally made from either aluminum or brass. Lens barrels, particularly the threads to which filters attach, are usually made from aluminum.<br /><br />Filter rings, particularly aluminum ones, can sometimes "bind" to the aluminum lens threads and be difficult to remove.<br /><br />Aluminum is a relatively soft metal; attempting to remove a stuck filter by squeezing with the hand generally puts a lot of inward pressure on just the two areas being gripped; this can bend and deform both the filter ring and the lens threads, permanently weakening or damaging both and making the filter even more difficult to remove.<br /><br />Methods should be employed that apply pressure evenly around the filter ring.<br /><br />Typically this is achieved either by use of a filter wrench or by cupping the filter ring and front of the lens with a piece of fabric to protect them and provide friction, then pressing the combination against a hard surface and twisting the lens barrel.<br /><br />Other aids to stuck filter removal include using either a tightened rubber band or shoelace around the rim of the filter to improve grip.<br /><br /></div>PhotoManhttp://www.blogger.com/profile/12261723954138591225noreply@blogger.com1tag:blogger.com,1999:blog-478327608423116478.post-71349968526361984322008-06-30T23:03:00.002+08:002008-06-30T23:07:12.119+08:00Filter Sizes & Mountings - Bayonet Round Filters<div style="text-align: justify;">Certain manufacturers, most notably Rollei and Hasselblad, have created their own systems of bayonet mount for filters. Each design comes in several sizes, such as Bay I through Bay VIII for Rollei, and Bay 50 through Bay 104 for Hasselblad.<br /><br /></div>PhotoManhttp://www.blogger.com/profile/12261723954138591225noreply@blogger.com0tag:blogger.com,1999:blog-478327608423116478.post-49997810538289978862008-06-30T22:58:00.000+08:002008-06-30T23:00:59.494+08:00Filter Sizes & Mountings - Rectangular Filters<div style="text-align: justify;">Graduated filters of a given width (100 mm, 67 mm, 84 mm, etc.) are often made rectangular, rather than square, in order to allow the position of the gradation to be moved up or down in the picture. This allows, for example, the red part of a sunset filter to be placed at the horizon. These are used with the "system" holders described.<br /><br /></div>PhotoManhttp://www.blogger.com/profile/12261723954138591225noreply@blogger.com0tag:blogger.com,1999:blog-478327608423116478.post-69307056369971016062008-06-30T22:46:00.001+08:002008-06-30T22:55:55.843+08:00Filter Sizes & Mountings - Square Filters<div style="text-align: justify;">For square filters, 2" x 2", 3" x 3" and 4" x 4" were historically very common and are still made by some manufacturers. 100 mm x 100 mm is very close to 4"x4", allowing use of many of the same holders, and is one of the more popular sizes currently (2006) in use; it is virtually a standard in the motion picture industry. 75 mm x 75 mm is very close to 3" x 3" and while less common today, was much in vogue in the 1990s.<br /><br />A French manufacturer called Cokin makes a wide range of filters and holders in three sizes which is collectively known as the Cokin System. "A" (amateur) size is 67 mm wide, "P" (professional) size is 84 mm wide, and "X Pro" is 130 mm wide. Many other manufacturers make filters to fit Cokin holders. Cokin also makes a filter holder for 100 mm filters, which they call the "Z" size. Most of Cokin's filters are made of optical resins such as CR-39. A few round filter elements may be attached to the square/rectangular filter holders, usually polarizers and gradient filters which both need to be rotated and are more expensive to manufacture.<br /><br />Cokin formerly (1980s through mid-1990s) had competition from Hoya's Hoyarex system (75 mm x 75 mm filters mostly made from resin) and also a range made by Ambico, but both have withdrawn from the market. A small "system" range is still made (as of 2005) by Hitech. In general, square (and sometimes rectangular) filters from one system could be used in another system's holders if the size was correct, but each made a different system of filter holder which could not be used together. Lee, Tiffen and Singh Ray also make square / rectangular filters in the 100 x 100 and Cokin "P" sizes.<br /><br />Gel filters are very common in square form, rarely being used in circular form. These are thin flexible sheets of plastic which must be held in rigid frames to prevent them from sagging. Gels are made not only for use as photo filters, but also in a wide range of colors for use in lighting applications, particularly for theatrical lighting. Gel holders are available from all of the square "system" makers, but are additionally provided by many camera manufacturers, by manufacturers of gel filters, and by makers of expensive professional camera accessories (particularly those manufacturers which target the movie and television camera markets.<br /><br />Square filter systems often have lens shades available to attach to the filter holders.<br /><br /></div>PhotoManhttp://www.blogger.com/profile/12261723954138591225noreply@blogger.com0tag:blogger.com,1999:blog-478327608423116478.post-10983280735014565312008-06-30T22:38:00.001+08:002008-06-30T22:42:46.675+08:00Filter Sizes & Mountings - Threaded Round Filters<p style="text-align: justify;">The most common standard filter sizes for circular filters include 30.5 mm, 37 mm, 40.5 mm, 43 mm, 46 mm, 49 mm, 52 mm, 55 mm, 58 mm, 62 mm, 67 mm, 72 mm, 77 mm, 82 mm, 86 mm, 95 mm, 112 mm and 127 mm.<br /></p><p style="text-align: justify;">Other filter sizes within this range may be hard to find since the filter size may be non-standard or may be rarely used on camera lenses.<br /></p><p style="text-align: justify;">The specified diameter of the filter in millimeters indicates the diameter of the male threads on the filter housing. The <span class="mw-redirect">thread pitch</span> is 0.5 mm, 0.75 mm or 1.0 mm, depending on the ring size.<br /></p><p style="text-align: justify;">A few sizes (e.g. 30.5 mm) come in more than one pitch.</p><div> </div><p style="text-align: justify;">Filter diameter for a particular lens is commonly identified on the lens face by the ligature "ø". For example, a lens marking may indicate "ø 55mm."<br /><br /></p>PhotoManhttp://www.blogger.com/profile/12261723954138591225noreply@blogger.com0tag:blogger.com,1999:blog-478327608423116478.post-77776694048331851732008-06-30T22:25:00.002+08:002008-06-30T22:36:29.060+08:00Photo Filter - Materials & Construction<div style="text-align: justify;">Photo filters are commonly made from glass, resin plastics similar to those used for eyeglasses (such as CR39), polyester and polycarbonate; sometimes acetate is used. Historically, filters were often made from gelatin, and color gels, also called gelatin or simply gel filters are still used, but these are no longer actually made from gelatin, generally being instead made from one of the plastics mentioned above.<br /><br />Sometimes a color is blended throughout the filter material, in other cases the filter is a sandwich composed of a thin sheet of material surrounded and supported by two pieces of clear glass or plastic.<br /><br />Certain kinds of filters use other materials inside a glass sandwich; for example, polarizers often use various special films, netting filters have nylon netting, and so forth.<br /><br />The rings on screw-on filters are most often made of aluminum, though in more expensive filters brass is used. Aluminum filter rings are much lighter in weight, but can "bind" to the aluminum lens threads they are screwed in to, requiring the use of a filter wrench to get the filter off of the lens. Aluminum also dents or deforms more easily. (See "Stuck filter removal" below.)<br /></div><div> </div><p style="text-align: justify;">High quality filters have multiple layers of optical coating to reduce reflections and to allow more light to pass through the filter. Uncoated filters can block up to 9% of the light, while multi coated filters can allow for up to 99.7% of the light to pass through. Manufacturers brand their high-end multi coated filters with different labels, for example:<br /></p><div style="text-align: justify;"> </div><ul style="text-align: justify;"><li>Hoya: HMC (Hoya Multi Coating)</li><li>B+W: MRC (Multi Resistant Coating)</li></ul><div style="text-align: justify;"> </div><p style="text-align: justify;">Reflections can lead to flare and reduced contrast. Multi-layer coatings, which reduce this effect, are highly desirable in any filter. Exceptions to this rule are infrared and ultraviolet photography, where uncoated filters are usually used; multi-coated filters have a tendency to reflect more wavelengths outside the visible spectrum, making them unsuitable for such purposes.<br /><br /></p>PhotoManhttp://www.blogger.com/profile/12261723954138591225noreply@blogger.com0tag:blogger.com,1999:blog-478327608423116478.post-35919609383426977782008-06-28T03:34:00.000+08:002008-06-28T03:36:13.038+08:00Diopters & Split Diopters<div style="text-align: justify;">Some argument could be made as to whether these are technically filters at all, or actual accessory lenses, however they are sold by filter manufacturers as part of their product lines, using the same holders and attachment systems.<br /><br />Diopters are simple single or two-element lenses used to assist in close-up and macro photography.<br /><br />They provide some number of positive optical diopters, which magnify the subject and allow objects very close to the lens to be brought into focus.<br /><br />They are sometimes sold singly, and sometimes sold in kits of +1, +2, and +4 diopters, which allows them to be combined to produce a range from +1 to +7.<br /><br />A split diopter is a diopter in which only half of the camera's lens area is covered by the filter.<br /><br />A round split diopter has a usual filter ring, but is filled with only a semicircle of glass (or plastic).<br /><br />This allows the photographer to photograph an object which is very close against a background much further away, effectively extending depth of field.<br /><br />Careful composition is required to make effective use of this device.<br /><br /></div>PhotoManhttp://www.blogger.com/profile/12261723954138591225noreply@blogger.com0tag:blogger.com,1999:blog-478327608423116478.post-16368087926003117402008-06-28T03:33:00.002+08:002008-06-28T03:39:22.127+08:00Grid or Netting<div style="text-align: justify;">Various widths, colors (often black or white), and grid shapes (typically diamonds or squares) and spacings of netting, usually made from nylon, are used to provide diffusion effects.<br /><br />These are used both for the "dreamy" look and for contrast reduction.<br /><br />The homebrew approach to this sort of effect is generally to stretch a piece of pantyhose material in front of the lens.<br /><br /><br /></div>PhotoManhttp://www.blogger.com/profile/12261723954138591225noreply@blogger.com0tag:blogger.com,1999:blog-478327608423116478.post-22192081583931504392008-06-28T03:32:00.001+08:002008-06-28T03:33:18.786+08:00Transparent Diffusion<div style="text-align: justify;">Zeiss manufactures a widely noted Softar diffusion filter which is made of many tiny globs of acrylic deposited on one surface which act as microlenses to diffuse the light.<br /><br />In some versions the globs are on the inside of the filter (facing the photographer) while on others they face outwards (towards the subject).<br /><br />In various versions the globs vary in number and diameter, from approximately 97 to 150 globs each 1 mm to 3 mm wide.<br /><br />Homebrew approaches to transparent diffusion filters are generally based on modifying a clear or UV filter by placing various materials on it; the most popular choices are petroleum jelly, optical cement, and nail polish.<br /><br />Transparent filters are more commonly used for the "dreamy" or "misty" effect than for contrast reduction.<br /><br /></div>PhotoManhttp://www.blogger.com/profile/12261723954138591225noreply@blogger.com0tag:blogger.com,1999:blog-478327608423116478.post-44406272304008318332008-06-28T03:29:00.000+08:002008-06-28T03:30:56.149+08:00Diffusion<div style="text-align: justify;">A diffusion filter (also called a softening filter) softens subjects and generates a dreamy haze (see photon diffusion). This is most often used for portraits.<br /><br />However, this also has the effect of reducing contrast, and the filters are designed, labeled, sold, and used for that purpose too.<br /><br />There are many ways of accomplishing this effect, and thus filters from different manufacturers vary significantly.<br /><br />The two primary approaches are to use some form of grid or netting in the filter, or to use something which is transparent but not optically sharp.<br /><br />Both effects can be achieved in software, which can provide a very precise degree of control of the level of effect, however the "look" may be noticeably different.<br /><br />Additionally, if there is too much contrast in a scene, the dynamic range of the digital image sensor or film may be exceeded, which post-processing cannot compensate for, so contrast reduction at the time of image capture may be called for.<br /><br /></div>PhotoManhttp://www.blogger.com/profile/12261723954138591225noreply@blogger.com0tag:blogger.com,1999:blog-478327608423116478.post-20393449614118530142008-06-28T03:28:00.001+08:002008-06-28T03:28:58.802+08:00Cross Screen<div style="text-align: justify;">A cross screen filter, also known as a star filter, creates a star pattern, in which lines radiate outward from bright objects.<br /><br />The star pattern is generated by a very fine diffraction grating embedded in the filter, or sometimes by the use of prisms in the filter.<br /><br />The number of stars varies by the construction of the filter, as does the number of points each star has.<br /><br /></div>PhotoManhttp://www.blogger.com/profile/12261723954138591225noreply@blogger.com0tag:blogger.com,1999:blog-478327608423116478.post-72349093976197294262008-06-28T03:27:00.001+08:002008-06-28T03:27:48.364+08:00Neutral Density<div style="text-align: justify;">A Neutral Density (ND) filter creates a reduction in light that is neutral and equal for the film or sensor area. This filter is often used to allow for longer exposure times whenever a longer exposure would normally create overexposure in the camera.<br /><br />A Graduated Neutral Density (GND) filter is a neutral density filter that varies the effect with a gradient so it can be used to compress dynamic range across the entire scene. This can be beneficial when the difference between highlights and shadows of a scene are too great to allow for proper exposure for both.<br /><br /></div>PhotoManhttp://www.blogger.com/profile/12261723954138591225noreply@blogger.com0tag:blogger.com,1999:blog-478327608423116478.post-64683585793352910072008-06-28T03:17:00.002+08:002008-06-28T03:25:41.598+08:00Polarizer<div style="text-align: justify;">A polarizing filter, used both in color and black and white photography, can be used to darken overly light skies. Because the clouds are relatively unchanged, the contrast between the clouds and the sky is increased. Atmospheric haze and reflected sunlight are also reduced, and in color photographs overall color saturation is increased. Polarizers are often used to deal with situations involving reflections, such as those involving water or glass, including pictures taken through glass windows (this uses the phenomenon of Brewster's angle).<br /></div><div style="text-align: justify;"><br />Polarizers are the type of filter whose use is least affected by digital photography; while effects that may visually resemble the results of a polarizing filter can be simulated with software post-processing, many of the optical properties of polarization control at the time of capture simply cannot be replicated, particularly those involving reflections.<br /><br /><br /><div style="text-align: center;"><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjRKD4FlcjLZboyJHmP7O39jDkOshWmbGVyw8Wbw9DaKB8Q39c2OC6C-9S_5hL-GSI6o9UpPBoyvG3ULJJ-zJGtHqdbZPvcTX5sHjA6WEi0kXlx9Qtz_XyIV_xkvUDab5h8UipUFSssfBZS/s1600-h/500px-CircularPolarizer.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjRKD4FlcjLZboyJHmP7O39jDkOshWmbGVyw8Wbw9DaKB8Q39c2OC6C-9S_5hL-GSI6o9UpPBoyvG3ULJJ-zJGtHqdbZPvcTX5sHjA6WEi0kXlx9Qtz_XyIV_xkvUDab5h8UipUFSssfBZS/s400/500px-CircularPolarizer.jpg" alt="" id="BLOGGER_PHOTO_ID_5216643322266173602" border="0" /></a><span style="font-size:85%;"><span style="font-style: italic;"> The effects of a polarizer on the sky in a color photograph.<br />The picture on the right has the filter.</span></span><br /></div><br /><br /><div style="text-align: center;"><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgsjAxKDrbU7jX8kTPhopvfXRe0daDs6YmBsmkG28MwuJoIn9mScHM2kmMbuQHqrE3Bhh2TuNqRtdK9XCDoPqEgKM20xsgVmhXbC64O_YGGwebnpMO8DsafsBCuwiEAE-IUn_iYoW9P9Kzf/s1600-h/500px-Mudflats-polariser.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgsjAxKDrbU7jX8kTPhopvfXRe0daDs6YmBsmkG28MwuJoIn9mScHM2kmMbuQHqrE3Bhh2TuNqRtdK9XCDoPqEgKM20xsgVmhXbC64O_YGGwebnpMO8DsafsBCuwiEAE-IUn_iYoW9P9Kzf/s400/500px-Mudflats-polariser.jpg" alt="" id="BLOGGER_PHOTO_ID_5216643332766937218" border="0" /></a><span style="font-size:85%;"><span style="font-style: italic;">In the first picture, the polarizer is rotated to minimise the effect,<br />and in the second it is rotated 90° to maximize the effect<br />- almost all reflected sunlight is eliminated.</span><br /></span></div><br /><br /><div style="text-align: center;"><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvuNeXGKtS2kH-07OUvy6d4bVugi9KjKGc8umHhI2AVCJJ4_fjzYYEfSvrOQ6wOXomClDxSq4a0QT4wOG0qJ_00rglwg1zZcRXPHYAhXei71O7zsp-ebAcEgw1CSJhzntatBduUfod5H6S/s1600-h/500px-Polarizer_Through_Glass.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvuNeXGKtS2kH-07OUvy6d4bVugi9KjKGc8umHhI2AVCJJ4_fjzYYEfSvrOQ6wOXomClDxSq4a0QT4wOG0qJ_00rglwg1zZcRXPHYAhXei71O7zsp-ebAcEgw1CSJhzntatBduUfod5H6S/s400/500px-Polarizer_Through_Glass.jpg" alt="" id="BLOGGER_PHOTO_ID_5216643330725793522" border="0" /></a><span style="font-size:85%;"><span style="font-style: italic;">On the bottom you can see how the window is reflecting<br />the outside environment, while on the top the filter<br />is turned 90° making it possible to see<br />through the window.</span></span><br /></div><br /><div style="text-align: justify;">There are two types of polarizing filters generally available, linear polarizers and circular polarizers (or CPL filters). With the exception of how they interact with some autofocus and metering mechanisms, they have exactly the same effect. Both transmit one of two states of linearly polarized light.<br /><br />The difference is that a circular polarizer alters the light leaving the filter and entering the camera by using a quarter-wave plate to circularly polarize that light. This has the same effect photographically as a linear polarizer, reducing glare in the scene<br /><br />The metering and auto-focus sensors in certain cameras, including virtually all auto-focus SLRs, will not work properly with linear polarizers because the beam-splitters used to split off the light for focusing and metering are polarization-dependent. Circular polarizers work with all types of cameras, because mirrors and beam-splitters reflect both circular polarizations equally.<br /></div><br /></div>PhotoManhttp://www.blogger.com/profile/12261723954138591225noreply@blogger.com0tag:blogger.com,1999:blog-478327608423116478.post-53480330053617544942008-06-28T03:12:00.003+08:002008-06-28T03:16:06.680+08:00Contrast Enhancement<div style="text-align: justify;">Filters are commonly used in black and white photography to manipulate contrast. For example a yellow filter will enhance the contrast between clouds and sky by darkening the latter. Orange and red filters will have a stronger effect. A deep green filter will darken the sky too but will lighten green foliage and will make it stand out against the sky. Also see diffusion filters, which are used to reduce contrast.<br /></div><br /><div style="text-align: center;"><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj-pHT86lHw8RBSLHJwtb_NqV8roQ2gQ5qMVc46KIBDO7mwwT7F_R3Tt8p07KmT15wioEradSC9cXBhS91eczipvBvTzoCiJAIRbVB9sn9BARNie2Ox0Llq0VUJGD_Dtl9qM6Nsht-t6d1j/s1600-h/460px-El_Gouna_Egypt_BW_Filter_Comparison_EN.png"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj-pHT86lHw8RBSLHJwtb_NqV8roQ2gQ5qMVc46KIBDO7mwwT7F_R3Tt8p07KmT15wioEradSC9cXBhS91eczipvBvTzoCiJAIRbVB9sn9BARNie2Ox0Llq0VUJGD_Dtl9qM6Nsht-t6d1j/s400/460px-El_Gouna_Egypt_BW_Filter_Comparison_EN.png" alt="" id="BLOGGER_PHOTO_ID_5216641870253067458" border="0" /></a><span style="font-size:85%;"><span style="font-style: italic;">Effects of using a polarizer and a red filter in<br />black-and-white photography.<br /><br /><br /></span></span></div>PhotoManhttp://www.blogger.com/profile/12261723954138591225noreply@blogger.com0tag:blogger.com,1999:blog-478327608423116478.post-9095318325662265052008-06-28T03:10:00.000+08:002008-06-28T03:11:52.650+08:00Color Subtraction<div style="text-align: justify;">Color subtraction filters work by absorbing certain colors of light, letting the remaining colors through.<br /><br />They can be used to demonstrate the primary colors that make up an image.<br /><br />They are perhaps most frequently used in the printing industry for color separations, and again, use has diminished as digital solutions have proliferated.</div>PhotoManhttp://www.blogger.com/profile/12261723954138591225noreply@blogger.com0tag:blogger.com,1999:blog-478327608423116478.post-8855768585615942592008-06-28T03:04:00.002+08:002008-06-28T03:08:28.493+08:00Color Correction<div style="text-align: justify;">A major use is to compensate the effects of lighting not balanced for the film stock's rated color temperature (usually 3200 K for professional tungsten lights and 5500 K for daylight): e.g., the 80A blue filter used with daylight film corrects the orange/reddish cast of household tungsten lighting, while the 85B used with tungsten film will correct the bluish cast of daylight. Color correction filters are identified by numbers which sometimes vary from manufacturer to manufacturer. The use of these filters has been greatly reduced by the widespread adoption of digital photography, since color balance problems are now often addressed with software after the image is captured.<br /></div><div style="text-align: justify;"><br /><br /><div style="text-align: center;"><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiXq0hVBNOXjVsiXVw8IsEjiXMKso5GpTvWbWfPw4Q59CiuZ6mQnA31w1mbSH1HTc1RbRtsXmx4NCqvS2vH5QMZ9gAR6dwB5qH1DKZWH1v_Opnjf2EWtB2Bp6wvq-boFBs7wAUoobC4oaaJ/s1600-h/80a_comparison.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiXq0hVBNOXjVsiXVw8IsEjiXMKso5GpTvWbWfPw4Q59CiuZ6mQnA31w1mbSH1HTc1RbRtsXmx4NCqvS2vH5QMZ9gAR6dwB5qH1DKZWH1v_Opnjf2EWtB2Bp6wvq-boFBs7wAUoobC4oaaJ/s400/80a_comparison.jpg" alt="" id="BLOGGER_PHOTO_ID_5216639582047325554" border="0" /></a><span style="font-size:85%;"><span style="font-style: italic;"> Although the 80A filter is mainly used to correct for the excessive<br />redness of </span><span style="font-style: italic;">tungsten</span><span style="font-style: italic;"> lighting, it can also be used to<br />oversaturate scenes that already have blue.<br />The photo on the left was shot with<br />a polarizer, while the<br />one on the right was<br />shot with a polarizer<br />and an 80A filter.<br /><br /><br /></span></span></div></div>PhotoManhttp://www.blogger.com/profile/12261723954138591225noreply@blogger.com0tag:blogger.com,1999:blog-478327608423116478.post-17080527935821975932008-06-28T02:59:00.003+08:002008-06-28T03:09:42.413+08:00Clear & Ultraviolet<div style="text-align: justify;">Clear filters, also known as window glass filters or optical flats, are completely transparent, and (ideally) perform no filtering of incoming light at all. The only use of a clear filter is to protect the front of a lens.<br /><br />UV filters are used to reduce haziness created by ultraviolet light. A UV filter is mostly transparent to visible light, and can be left on the lens for nearly all shots. UV filters are often used for lens protection, much like clear filters. A strong UV filter, such as a Haze-2A or UV17, cuts off some visible light in the violet part of the spectrum, and so has a pale yellow color; these strong filters are more effective at cutting haze, and can reduce purple fringing in digital cameras. Strong UV filters are also sometimes used for warming color photos taken in shade with daylight-type film.<br /><br />While in certain cases (such as harsh environments) a protection filter may be necessary, there are also downsides to this practice. Arguments for and against use of protection filters incude:<br /><br />For:<br /><ul><li>If the lens is dropped, the filter may well suffer scratches or breakage instead of the front lens element.<br /><br /></li><li>One can clean the filter frequently without having to worry about damaging the lens coatings; a filter scratched by cleaning is much less expensive to replace than a lens.</li></ul> <p>Against:</p> <ul><li>Adding another element degrades image quality due to aberration and flare.<br /><br /></li><li>It may reduce the use of lens hoods, since threading a lens hood on top of the clear filter might cause vignetting on some lenses, and since not all clear filters would even have threads allowing a hood to be attached.</li></ul> <p>Additionally, users of UV filters must be careful about the quality of such filters. There is a wide variance in the performance of these filters with respect to their ability to block UV light.<sup id="cite_ref-4" class="reference"></sup> Also in lower quality filters, problems with autofocus and image degradation have been noted.</p><br /></div>PhotoManhttp://www.blogger.com/profile/12261723954138591225noreply@blogger.com0tag:blogger.com,1999:blog-478327608423116478.post-36468809887971221382008-06-28T02:55:00.001+08:002008-06-28T02:58:30.970+08:00Uses of filters in photography<p style="text-align: justify;">Filters in photography can be classified according to their use:</p><div style="text-align: justify;"> </div><ul style="text-align: justify;"><li>Clear and ultraviolet<br /><br /></li><li>Color correction, also called "color conversion" or "white balance correction"<br /><br /></li><li>Color separation, also called Color Subtraction<br /><br /></li><li>Contrast enhancement<br /><br /></li><li>Infrared<br /><br /></li><li>Neutral Density, including the <span class="mw-redirect">Graduated ND filter</span> and <span class="new">Solar filter<br /><br /></span></li><li>Polarizing<br /><br /></li><li><span class="mw-redirect">Special Effects</span> of various kinds, including <ul><li>Graduated color, called <span class="new">color grads</span></li><li>Cross screen and <b>Star</b> diffractors</li><li>Diffusion and contrast reduction</li><li>Sepia tone</li><li><span class="new">Spot</span></li><li>Close-up or macro <b>diopters</b>, and <b>split diopters</b> or <b>split focus</b></li></ul></li></ul><div style="text-align: justify;"><br /></div>PhotoManhttp://www.blogger.com/profile/12261723954138591225noreply@blogger.com0tag:blogger.com,1999:blog-478327608423116478.post-18074740409576328002008-06-28T02:46:00.002+08:002008-06-28T02:54:45.123+08:00Photographic Filter<div style="text-align: justify;"><div style="text-align: justify;">In photography, a filter is a camera accessory consisting of an optical filter that can be inserted in the optical path. The filter can be a square or rectangle shape mounted in a holder accessory, or, more commonly, a glass or plastic disk with a metal or plastic ring frame, which can be screwed in front of the lens.<br /><br />Filters allow added control for the photographer of the images being produced. Sometimes they are used to make only subtle changes to images; other times the image would simply not be possible without them.<br /><br />The negative aspects of using filters, though often negligible, include the possibility of loss of image definition if using dirty or scratched filters, and increased exposure required by the reduction in light transmitted. The former is best avoided by careful use and maintenance of filters, while the latter is a matter of technique; it usually will not be a problem if planned out properly, but in some situations does make filter use impractical.<br /><br />Many filters are identified by their Wratten number (labeling system for optical filters).<br /></div><br /><br /><div style="text-align: center;"><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi4fJDF5yQP75SksKsvR_wWnNpsDB24pGvNlFTTUTKXyFrZAXF9GJ1gWfB2OjZBqcM-Jvuja9dwbGTgeHdHBGS9H2T8GpgT2JRcQmPrNgryHsdZ4_e8gIAhy6K3ZUQTBzirGnnwFdpVyNkw/s1600-h/300px-LensFilter-001.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi4fJDF5yQP75SksKsvR_wWnNpsDB24pGvNlFTTUTKXyFrZAXF9GJ1gWfB2OjZBqcM-Jvuja9dwbGTgeHdHBGS9H2T8GpgT2JRcQmPrNgryHsdZ4_e8gIAhy6K3ZUQTBzirGnnwFdpVyNkw/s400/300px-LensFilter-001.jpg" alt="" id="BLOGGER_PHOTO_ID_5216636094538226418" border="0" /></a><span style="font-size:85%;"><span style="font-style: italic;">62 mm ultraviolet, polarizing,<br />and fluorescent lens filters.</span></span><br /><span style="font-size:85%;"><span style="font-style: italic;"></span></span></div><span style="font-size:85%;"><span style="font-style: italic;"><br /><br /></span></span></div>PhotoManhttp://www.blogger.com/profile/12261723954138591225noreply@blogger.com0tag:blogger.com,1999:blog-478327608423116478.post-24676068100793523972008-06-27T02:48:00.001+08:002008-06-27T02:50:00.612+08:00Environmental & Safety Issues<div style="text-align: justify;">Many photographic solutions have high chemical and biological oxygen demand (COD and BOD). These chemical wastes are often treated with ozone, peroxide or aeration to reduce the COD.<br /><br />Exhausted fixer and to some extent rinse water contain silver-thiosulfate complex ions. They are far less toxic than free silver ion, and they become silver sulfide sludge in the sewer pipes or treatment plant. However, the maximum silver concentration in discharge is very often tightly regulated. Silver is also a somewhat precious resource. Therefore, in most large scale processing establishments, exhausted fixer is collected for silver recovery and disposal.<br /><br />Many photographic chemicals use non-biodegradable compounds, such as EDTA, DTPA, NTA and borate. EDTA, DTPA, and NTA are very often used as chelating agents in all processing solutions, particularly in developers and washing aid solutions. EDTA and other polyamine polycarboxylic acids are used as iron ligands in color bleach solutions. These are relatively nontoxic, and in particular EDTA is approved as a food additive. However, due to poor biodegradability, these chelating agents are found in alarmingly high concentrations in some water sources from which municipal tap water is taken. Water containing these chelating agents can leach metal from water treatment equipment as well as pipes. This is becoming an issue in Europe and some parts of the world.<br /><br />Another non-biodegradable compound in common use is surfactant. A common wetting agent for even drying of processed film uses Union Carbide/Dow Triton X-100 or octylphenol ethoxylate. This surfactant is also found to have estrogenic effect and possibly other harms to organisms including mammals.<br /><br />Development of more biodegradable alternatives to the EDTA and other bleaching agent constituents were sought by major manufacturers, until the industry became less profitable when the digital era began.<br /><br />In most amateur darkrooms, a popular bleach is potassium hexacyanoferrate (III) (common name potassium ferricyanide). This compound decomposes in the waste water stream to liberate cyanide gas. Other popular bleach solutions use potassium dichromate (a hexavalent chromium) or permanganate. Both ferricyanide and dichromate are tightly regulated for sewer disposal. In order to meet the regulation, the solution must be diluted 20 000 (twenty thousand) times or more. All of these popular black and white bleaches are damaging to the environment, and should be replaced with any of the existing eco-friendly alternatives.<br /><br />Borates, such as borax (sodium tetraborate), boric acid and sodium metaborate, are toxic to plants, even at a concentration of 100 ppm. Many film developers and fixers contain 1 to 20 g/L of these compounds at working strength. Most non-hardening fixers from major manufacturers are now borate-free, but many film developers still use borate as the buffering agent. Also, some, but not all, alkaline fixer formulas and products contain a large amount of borate. New products should phase out borates, because for most photographic purposes, except in acid hardening fixers, borates can be substituted with a suitable biodegradable compound.<br /><br />Developing agents are commonly hydroxylated benzene compounds or aminated benzene compounds, and they are harmful to humans and experimental animals. Some are mutagens. They also have a large chemical oxygen demand (COD). Ascorbic acid and its isomers, and other similar sugar derived reductone reducing agents are a viable substitute for many developing agents. Developers using these compounds were actively patented in the US, Europe and Japan, until 1990s but the number of such patents is very low since late-1990s, when the digital era began.<br /><br /></div>PhotoManhttp://www.blogger.com/profile/12261723954138591225noreply@blogger.com0tag:blogger.com,1999:blog-478327608423116478.post-48257995394979168942008-06-27T02:46:00.001+08:002008-06-27T02:48:09.549+08:00Further Processing<div style="text-align: justify;">For black and white emulsions both negative and positive, further processing may react the silver with other elements such as selenium or sulfur to produce a more permanent image.<br /><br />In these cases the silver in the image is changed to silver selenide or silver sulfide, which are more resistant to oxidising agents (pollutants) in the atmosphere.<br /><br />Successful selenium or sulfide toning requires complete fixation. In other cases, the silver may be chemically bleached using a potassium hexacyanoferrate (III) solution and then re-developed in a range of toning formulations.<br /><br />This two-step technique is collectively called "indirect toning." Depending on the toning solution, sepia, red and blue colors may be obtained.<br /><br />If color negative film is processed in conventional black and white developer, and fixed and then bleached with a bath containing hydrochloric acid and potassium dichromate solution, the resultant film, once exposed to light, can be redeveloped in color developer to produce an unusual pastel color effect.<br /><br /></div>PhotoManhttp://www.blogger.com/profile/12261723954138591225noreply@blogger.com0tag:blogger.com,1999:blog-478327608423116478.post-14943505221698490482008-06-27T02:32:00.000+08:002008-06-27T02:33:32.273+08:00Color Processing<div style="text-align: justify;">Color negative developing (C-41 process) and color print developing (process RA-4) are very similar. The principal difference is in the color developer formula in the first step; and the combining of the bleach and fixer steps in process RA-4 with a bleach-fix mixture (blix), which dissolves both the silver halides and the elemental silver leaving only a dye image.<br /><br />Mixing the bleach and fixing agent in process RA-4 is optional; they are often mixed to minimize the number of processing steps.<br /><br />In color reversal processing the film is developed in an MQ (metol/hydroquinone) developer similar to a black-and-white developer, followed by a rinse or a stop bath. The film is fogged in the reversal step, and is then developed in a color developer.<br /><br />Next, the film is then bleached to remove the black-and-white negative image (metallic silver is removed by the bleach), while keeping the color positive image (dye is not affected by the bleach).<br /><br />The film is optionally washed to minimize the carry-over of the bleach to the next bath, fixer. Film is then fixed, washed and dried conventionally. In some old processes, the film emulsion was hardened during the process, typically before the bleach. Such a hardening bath often used aldehydes, such as formaldehyde and glutaraldehyde.<br /><br />In modern processing, these hardening steps are unnecessary because the film emulsion is sufficiently hardened to withstand the processing chemicals.<br /><br /></div>PhotoManhttp://www.blogger.com/profile/12261723954138591225noreply@blogger.com0tag:blogger.com,1999:blog-478327608423116478.post-2691383642056719262008-06-27T02:27:00.002+08:002008-06-27T02:34:39.135+08:00Monochrome (Black & White) Reversal Processing<div style="text-align: justify;">Black and white reversal processing (to make black and white positives) has two additional stages. Following the first developer, the developing action is stopped by an ordinary stop bath, and the film is then bleached to remove the negative image produced by development.<br /><br />The film then contains a latent positive image in the form of unexposed, undeveloped silver halide. The subsequent steps therefore fog the film, either chemically, or by exposure to light, after which all the remaining silver halide is developed in the second developer.<br /><br />This allows the silver halide crystals that were not originally exposed in the camera to be developed into a positive image. Finally, the film is fixed, washed and dried conventionally.<br /><br /></div>PhotoManhttp://www.blogger.com/profile/12261723954138591225noreply@blogger.com0tag:blogger.com,1999:blog-478327608423116478.post-35395025565284018282008-06-27T02:18:00.001+08:002008-06-27T02:20:34.840+08:00The Process<p style="text-align: justify;">Whether processing at an amateur or commercial level, the film is treated in chemical baths. Each of these baths is closely monitored and maintained at a specific temperature and treatment time. Developer baths are most sensitive to deviations from the standard processing conditions (e.g., time and temperature); other baths are less sensitive.</p><div style="text-align: justify;"> </div><ul style="text-align: justify;"><li>The developer, which turns the latent image to metallic silver.<br /><br /></li><li>A stop bath, which stops the action of developer, typically a dilute solution of acetic acid. In modern automatic processing machines, this step is replaced by mechanical squeegee or pinching rollers. In small scale darkrooms, stop bath may use citric acid or other organic acids, or simply plain water. Any of these treatments removes the bulk of the carried-over alkaline developer, and the acid, when used, neutralizes the alkalinity to reduce the contamination of the fixing bath with the developer.<br /><br /></li><li>The fixer makes the image permanent and light-resistant by dissolving any remaining silver halides. The fixer is sometimes referred to as "hypo," a misnomer originating from casually shortened form of the alchemist's name hyposulphite. None of "hyposulphite," "hyposulfite" and "hypo" is used to mean thiosulfate in modern chemistry.<br /><br /></li><li>Clean water wash to remove any fixer, as residual fixer can deteriorate the silver image, leading to discoloration, staining and fading. The washing time can be reduced and the fixer more completely removed if a washing aid (also known as hypo clearing agent, or HCA) is used after the fixer.<br /><br /></li><li>An optional final immersion in a film conditioner. This is a solution of a non-ionic <span class="mw-redirect">wetting agent</span> in water which helps uniform drying and eliminates drying marks from hard water.<br /><br /></li><li>Film is then dried in a dust-free environment, and finally cut (if roll film) and put into protective sleeves.</li></ul><div style="text-align: justify;"><br /></div>PhotoManhttp://www.blogger.com/profile/12261723954138591225noreply@blogger.com0tag:blogger.com,1999:blog-478327608423116478.post-79418185455176438762008-06-27T02:15:00.001+08:002008-06-27T02:17:06.244+08:00Processing Apparatuses<div style="text-align: justify;">Before processing, the film must be removed from the camera and from its cassette, spool or holder in a light-proof room or container.<br /><br /><br /><span style="font-size:130%;"><span style="font-weight: bold;">Small scale processing</span></span><br /><br />In amateur processing, the film is removed from the camera and wound onto a reel in complete darkness (usually inside a darkroom (with the safelight turned off) or a lightproof bag with arm holes). The reel holds the film in a spiral shape, with space between each successive loop so the chemicals may flow freely across the film's surfaces. The reel is placed in a specially designed light-proof tank (called daylight processing tank) where it is retained until final washing is complete.<br /><br />In case of sheet film, they can be processed in trays, in hangers (which are used in deep tanks), or rotary processing drums.<br /><br /><br /><span style="font-size:130%;"><span style="font-weight: bold;">Commercial processing</span></span><br /><br />In commercial processing, the film is removed automatically or by an operator handling the film in a light proof bag from which it is fed into the processing machine. The processing machinery is generally run on a continuous basis with films spliced together in a continuous line. All the processing steps are carried out within a single processing machine with automatically controlled time, temperature and solution replenishment rate. The film or prints emerge washed and dry and ready to be cut by hand. Some modern machines also cut films and prints automatically, sometimes resulting in negatives cut across the middle of the frame where the space between frames is very thin or the frame edge is indistinct, as in an image taken in low light.<br /><br /></div>PhotoManhttp://www.blogger.com/profile/12261723954138591225noreply@blogger.com0