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FINDING THE NO-PARALLAX POINT

FINDING THE NO-PARALLAX POINT
Hold up a pen in front of you, close one eye, and focus your attention on the background scene as you move your head sideways from left to right. The pen will be seen to move to the left, relative to the background. Like this: This apparent change in position of the near pen is an effect called parallax. Just as the pupil of your eye is the centre of the world it sees, so it is that the entrance pupil of the camera lens is the centre of the scene it sees. NB. Failure to rotate the camera about the entrance pupil is very likely to result in visible stitching errors. The bottom line is that if you want to check if your camera is correctly set up to avoid parallax, then you should do some tests designed specifically to reveal the presence of parallax. Related:  Tips and tricks

No-parallax point If you rotate your camera around some randomly chosen point, your images may show parallax and be difficult to stitch. With most lenses, there is one special point around which you can rotate your camera and get no parallax. This special " no-parallax point " is the center of the lens's entrance pupil , a virtual aperture within the lens. The entrance pupil is the image of the limiting aperture or diaphragm, as seen through the front of the lens. Everything considered, the best term for the no-parallax point may be (surprise!) Regardless of what you call the no-parallax point, it is easily found by trial and error. Some lenses, notably fisheyes, do not have a single no-parallax point. To facilitate finding the no-parallax point for other people, please fill the measurements you have found for your Camera / Lens / Focal Length combination in the Entrance Pupil Database See also References Kerr, Douglas A. " The Proper Pivot Point for Panoramic Photography " The Pumpkin (2005). Links

Linear Panoramas (Mosaic) Tutorial | This week in panospace Another development cycle is coming to an end. Bruno released libpano13 2.9.17 and paved the way for Hugin 2010.2.0. This version of Hugin will bring a lot of new features, amongst others a versatile masking tool and finer grained control of the control point (CP) detection process, courtesy of Thomas Modes. Good news for Windows user as well: galvanized by Emanuele Panz and his new NSIS based installer that solves the issues with distribution of patented software, also the Windows users community is on the forefront this time. Time to do some cool stuff with Hugin: mosaics. The basic functionality for mosaics has been in the repository for about a year, and it has matured well. Stitched mosaics differ from traditional stitched panorama in two major ways: In an ideal mosaic, all images depict a single, perfectly flat subject.The images are taken from different points of view. Mosaics present a few challenges of their own. Shooting Not much is flat in the real world. Order Setting the Stage

Tips & Tricks FAQ What kind of camera will I need? A digital SLR camera with interchangeable lenses is the ideal solution, but almost any camera will work if you can lock the aperture, lock the focus, and lock the white balance. Ultimately, you get what you pay for. Digital SLRs generally have more options for white balance, mirror lockup, etc… the more choices, the better! If you want a camera with the most convenient HDR shooting setup, choose a camera that has an auto-bracketing (AEB) option. Click here for a good list of cameras that have auto-bracketing (3 shots are common, but 5 or 7 is better) It also depends on how many HDRs you will be shooting and for what purpose? Back to top 4 Rules of shooting HDRs Lock f-stop (aperture – which controls your depth of field) Lock focus Lock white balance Turn off any in camera "automatic" image enhancing (i.e.: auto-contrast or auto-saturation, including sharpening) You will be bracketing the exposure time for your various exposures.

Entrance Pupil Database Wouldn't it be great if everyone entered their values for their NPP / Nodal Point / Entrance Pupil for lens and camera combinations. Some searching on the web will find a lot of people saying they want to start to create a database of some kind, but have not seen anything substantial so far (correct me if I am wrong). Please enter your own values if they are not listed. Thanks, -- Richard Korff 11:12, 13 May 2005 (EDT) To cater for all the different camera bodies and lenses, the tables have been split into 3 parts: The first table shows the position of the tripod mount in relation to the lens axis. Use as much as possible actual measurements rather than the reading on your panorama head , unless your are sure these are the same. To enter a line for your combination, edit the page by clicking edit at the top of the screen (you may need to create an account or sign-in first), and edit the table below. Tripod Mount Measurements Entrance Pupil Measurements Number of pics for 360° Related Resources

Wiki Nodal Point The Nodal Point The Nodal Point of the lens (or more correctly, the entrance pupil) can be considered as the point at which the rays entering the lens converge. It can also be considered as the centre of perspective of the lens or the apparent pupil. The term Nodal Point is used here because for decades it has been accepted as the term defining the point where the rays entering the lens apparently converge and has been referred to by this nomenclature in a considerable number of Photogrammetric papers and publications, but let us not let terminology detract from the message. It is important to know the location of this point (entrance pupil) for Photogrammetric purposes. This point is also the ideal point to rotate your lens around when taking images to 'stitch' together to produce panoramic images. Photogrammetric camera lenses are constructed so as to be 'symmetrical'. Determining the location of the Nodal Point (entrance pupil) The conventional approach ... A simple method ...

Nodal Point While it is not entirely essential to accurately position your camera for each image, it does make things a LOT easier if the lens is rotated as close as possible around its nodal point. By doing so, you remove parallax errors which may require a lot of retouching to make things look right in the finished panorama. Determining the nodal point of a lens is quite easy to do visually. You will need two vertical features to use as reference points e.g. a doorway, flag/light pole, corner of a all etc... The diagram below shows what happens in the three possible situations. Creating Panoramas with PTGui and Panotools We will now create a panorama by using 5 photos, shot handheld in portrait mode. If you want to follow the tutorial by using my example pictures, you can download them here (1.8 MB) and extract them to a folder called "C:\tutorial". In comparison to the previous versions of PTGui, Ver. 5 has tons of new features - one of them is a very helpful Assistant which we will heavily use for creating our panorama. Before we start for the first time, we have to define some helper applications - at least an image viewer to be able to preview our stitching results. Go to the menu "Tools" - "Options" and select the tab "Directories & Files".

Panoramic Image Projections An image projection occurs whenever a flat image is mapped onto a curved surface, or vice versa, and is particularly common in panoramic photography. A projection is performed when a cartographer maps a spherical globe of the earth onto a flat piece of paper, for example. Since the entire field of view around us can be thought of as the surface of a sphere (for all viewing angles), a similar spherical to 2-D projection is required for photographs which are to be printed. Narrow Angle of View(grid remains nearly square) Wider Angle of View(grid is highly distorted) For small viewing angles, it is relatively easy to distort this into an image on a flat piece of paper since this viewing arc is relatively flat. If all the above image projection types seem a bit daunting, try to first just read and understand the distinction between rectilinear and cylindrical (shown in bold), as these are the ones which are most widely used when photo stitching digital panoramas. Cylindrical Mercator

Panoramic Photography Revealed. Part II: Creating Perfect Panoramas, The Open Source Way « Tilman Bremer – Photography & Blog Diesen Artikel auf Deutsch Introduction Panoramic photography is a very specialized field of photography and in contrast to, let’s say portraits and nature photography, it’s not the first thing you get started with when getting your first camera. buy a panoramic tripod head for a couple of hundred bucks,buy various editing and stitching software for even more couples of hundred bucks andbuy a Flash-based software to present your work on your website. For me, there is definitely to much buying involved here! Other Articles in “Panoramic Photography Revealed” Part I: Hardware for Panoramic Photography, DIY Part II: Creating Perfect Panoramas, The Open Source Way (this one) Part III: Creating Perfect Virtual Tours, The Open Source Way Part IV: Appendix / Frequently Asked Questions The Toolchain as Abstract First of all, I will give you the complete toolchain for creating perfect 360°x180° panoramas exclusively with free and open source software. The Toolchain in Detail So, let’s get started! 1. 2.

Panorama Tutorials-Home The links to the left details my experience and methodology over the last ten years taking and creating interactive panoramic photographs. My camera and equipment has been changed during this period as digital SLR cameras have evolved. My current setup is here: The Manfrotto 055 Pro tripod with Leveling Centre Column 555B The 360precision panorama head Canon 5D - using manual white balance, manual exposure, and manual focus Canon 15mm f/2.8 Fisheye lens Canon remote release For each node, I photograph 6 around, 1 up and 2 down. The creation of the panoramas from each collection of 9 photographs is quickly performed by either Realviz Stiticher Unlimited (RVS U) 5.5 or by using PTGui 6.0.3, both these software packages are available for Apple Mac OS X or MS Windows XP. Additional post-processing is done by using actions in Adobe Photoshop CS2 and ClickHere's CubicConvertor.

Masking for enblend with SVG and Inkscape Here is an incredibly simple two shot panorama: ..notice that there are people right in the middle where the shots overlap. The Hugin 'Preview window' shows this quite well in 'difference' mode: ..where you can see the people and their shadow cover nearly the entire overlap area. ..after rendering for some time, you can see that enblend has done a reasonable job by deciding to place the seam to include the people in the middle: ..though the seam cuts through their shadow in a strange way. Now lets try to change the blend using Inkscape. (this takes a while as it is tracing the alpha channel outlines and converting them to SVG clipping masks) ..once that is done, this SVG file can be opened in Inkscape. Layers can be turned on and off. ..note that the polygon is a series of spline curves and can be re-edited easily. ..releasing the mask turns it into a 'normal' polygon. ..and create a combination of the two with the 'difference' function: ..save the SVG file and close Inkscape if you like.

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