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The DIY Fisheye Lens €? Using Nothin’ But A Pair Of Old Glasses And Some Tape



3. An easy way to add a splash of colour to your snaps is to make use of a colour filter on the flash. Some flash models will come with their own set of colour gels or you can pick up a cheap set like these colour lens and flash filters, which as the name suggests, can also be held over the lens for colourful effect. Alternatively you can make your own filters for next to nothing using coloured sweet wrappers or by colouring a piece of sticky tape or clear plastic with a marker pen.




The DIY Fisheye Lens — Using Nothin’ But a Pair of Old Glasses and Some Tape


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17. Investing in extra lenses for your camera can get a little pricey so a DIY approach might save you some pennies. You can create the effect of a fisheye lens by holding a glass over the lens while shooting.


The node of a lens is its optical centre point. Parallax errors in panoramic pictures can be eliminated by placing the rotation point of the camera at the lens node point. Some lenses have their nodal centre at a point within the front lens group while other lenses seem to have their nodal points near the exit or rear of the lens. Some zooms like the Fuji XF10-24mm have the same nodal point irrespective of focal length selected while other Fuji zooms have nodal points that vary with each focal length setting of the lens. There is absolutely no way to accurately guess a lens nodal point but there is an easy way to discover it using a tripod, a nodal shift plate and some basic household implements. See my method detailed below.


Shift photography using a medium format lens on e.g. full-frame, APS-C or MFT solves the fisheye distortion by moving the sensor left and right (for horizontal panos). Basically with the lens fixed on the tripod its the camera that shifts so that the perspective changes (removing fisheye).


The dome system, which the San Diego Hall of Science called "Omnimax", uses films shot with a camera equipped with a fisheye lens that squeezes a highly distorted anamorphic 180 field of view onto the 65 mm IMAX film. The lens is aligned below the center of the frame, and most of the bottom half of the circular field falls beyond the edge of the film. The part of the field that would fall below the edge of the dome is masked. When filming, the camera is aimed upward at an angle that matches the tilt of the dome. When projected through a matching fisheye lens onto a dome, the original panoramic view is recreated. Omnimax wraps 180 horizontally, 100 above the horizon and 22 below the horizon for a viewer at the center of the dome. Omnimax premiered in 1973, showing Voyage to the Outer Planets (produced by Graphic Films) and Garden Isle (by Roger Tilton Films) on a double bill. IMAX has since renamed the system "IMAX Dome", but some theaters (primarily those opened before the 2000s) continue to call it "Omnimax".


To create the illusion of depth, the IMAX 3D process uses two separate camera lenses that represent the left and right eyes. The lenses are separated by a distance of 64 mm (2.5 in), the average distance between a human's eyes. Two separate rolls of film are used to capture the images they produce. The IMAX 3D camera weighs over 113 kg (249 lb). By projecting the two films superimposed on the screen and using one of several available methods to direct only the correct image to each eye, viewers see a 3D image on a 2D screen. One method is to use polarizing filters to oppositely polarize the light used in projecting each image. The viewer wears glasses with polarizing filters oriented to match the projector filters, so that the filter over each eye blocks the light used to project the images intended for the other eye. In another method, the two projections rapidly alternate. While one image is being shown, the projection of its mate is blocked. Each frame is shown more than once to increase the rate and suppress flicker. The viewer wears shutter glasses with liquid crystal shutters that block or transmit light in sync with the projectors, so each eye sees only the images meant for it.


The parts you'll need are: 1. The camera and lens to be modified 2. Two pairs of identical paper anaglyph viewing glasses 3. A method of mounting (paper, tape, and scissors; optionally, a lenscap and drill) This method works with most cameras and lenses, but works much better with some than with others and is a little touchy about some details. Don't be scared by the large number of steps in this instructable -- that's just trying to make sure that you get things working as well as possible without a trial-and-error process. This is easy. Cost? Well, you probably have most of the stuff you need. The paper anaglyph viewing glasses are widely available for free in small quantities. I've bought hundreds at an average cost of $0.32 each including shipping, which would bring the "new purchase" cost to $0.64 for the two needed... easily under $1. Using a lenscap instead of paper printout for mounting adds about $1 to the cost, but yields a "more professional looking" and more durable device. Note that the post processing described in steps 12, 13, and 14 is optional. You don't need a computer to make anaglyphs by the method described here.


Ok, I know you don't want to hear about the theory behind this, but I'm a professor, so you're going to. Beyond that, although the method is quite simple, there are details that can make a huge difference in how effective the method is. The key is understanding what happens to the out-of-focus (OOF) portion of an image. An image is nothing more than the sum of what the lens does to each point of light in the scene. Most people, including many otherwise really smart people writing fancy image-processing algorithms, think that an OOF image of a point of light looks like a Gaussian blur -- but that's not how lenses work. For a typical well-corrected lens, the image of an OOF point light source is actually a bright disc whose sharp outline is shaped like the lens aperture. In fact, there are a couple of instructables that take advantage of this fact to make OOF points take-on interesting shapes, giving lenses very distinctive bokeh. Technically, the shaping is caused by hard-clipping of the point spread function (PSF) of the lens by the aperture. That implies the light near the edge of the OOF point's image actually came through the lens near the corresponding edge of the aperture. Since opposing edges of the aperture have a distance between them, all we need to do is distinguish rays coming through near the leftmost and rightmost edges -- we can capture a stereo pair in a single shot with a single lens! A larger distance between the edges allows a greater interocular distance and a more extreme stereo effect. I've been working on methods that can computationally perform this separation for well over a year... it's a very hard problem. However, it isn't hard to separate the two views by imposing a special, color-coded, aperture. An appropriately-coded aperture can directly produce the stereo pair encoded as an anaglyph. In fact, J. D. Songer's 1973 patent, #3,712,199, teaches coloring of the halves of an aperture to capture anaglyphs. The discontinued and rare Vivitar Series 1 Qdos 70-210mm lens even implemented this trick using a special segmented internal filter. The method described in this instructable is conceptually very similar, but is much simpler and cheaper to implement -- and it captures higher-quality anaglyphs.


You are going to make an aperture stop that will be placed in front of your lens, not unlike the stops other instructables have suggested for bokeh shaping. However, precision matters more here, so we're going to go through the technical steps to maximize the probability that it works for you. Fisheye and other ultra-wide-angle lenses often have bulbous front elements that don't provide a simple front-mounting option for a new stop. You can't use one of them unless you put the stop elsewhere, and that's beyond the scope of this instructable. Sorry. For many lenses, there is a thread for screw-in filters. If your lens has that, note the filter thread diameter marked. Relax; mounting will be neat and easy. If your lens doesn't have a thread (most compact camera lenses don't), use a ruler to measure the diameter of the rim around the lens. Be careful to measure only the portion that moves with the front glass element for an extending lens, not the diameter of the whole assembly. We will treat this number as your filter thread diameter, although mounting will be less elegant, perhaps using a little sticky tape.


There are many places you can get color filters to use for making anaglyphs. If you want to experiment, the Roscolux Gel Sample Swatchbook contains many calibrated theatrical lighting 1.75x2.75" gels and sells for about $2. However, we really want the viewing and capture filters to match, so cutting-up an extra pair of cardboard viewing glasses to get the filters works nicely. Anaglyph viewing glasses come in many color combinations, but all color combinations are not equally effective for anaglyph capture. The primary reason is that most digital camera sensors distinguish colors using a Bayer filter with a repeating pattern containing two greens, one red, and one blue. Thus, in order to minimize ghosting and balance capture resolution between the left and right views, we are forced to code one side as green and the other as magenta (red plus blue). It doesn't matter much which side is which, but green-left glasses are most common. Red/cyan glasses would be the obvious second choice among the commonly-available viewing colors. Of course, you have to use the same color combination for both capture and viewing (unless you do some fairly scary post-processing). These are all gel filters that scratch easily, so avoid handling them. 350c69d7ab


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