|
Forums >
Photography Talk >
Avoid distortion
Hi guys! I would like to ask on how to avoid distortion. Thank you!! May 23 16 09:44 am Link Don't turn the amp up so high. Also, be more specific. What kind of distortion? May 23 16 12:00 pm Link Remove it in camera raw May 23 16 03:30 pm Link Avoid hallucinogenic drugs. Especially during a shoot. May 23 16 03:58 pm Link Solas wrote: unfortunately, that only corrects rectilinear distortion, but not the circular distortion or stretching that occurs at the edges of the frame. there are many ways to avoid it, depending on many factors, including 1. what kind of distortion 2. the constraints imposed by the physical and visual requirements 3. the amount of money or time you have available. but the general hints are: May 23 16 08:54 pm Link Stay at least 6 feet away from the speakers or model. May 23 16 09:43 pm Link Get a Marshall jubilee series amp stack Worst $1000 I ever spent...guitar sounded so flacid... Oh wait May 24 16 08:02 pm Link Avoid wide angel lenses. May 25 16 03:02 am Link Black Z Eddie wrote: The distortion complaints associated with wide angle lenses, are usually issues with short subject distances. It's not the lens that causes the issue, but the fact that you are so close to the subject. May 25 16 03:56 am Link Black Z Eddie wrote: How else can you photograph a fat angel? May 25 16 06:24 am Link Rob Photosby wrote: you use four shortnin to your advantage. May 25 16 02:17 pm Link May 25 16 02:33 pm Link if you are talking about the kind that comes from using wide angle lenses, i try to avoid having people right at the edges of the shot when i'm doing a group shot. but sometimes distortion is what you're after. depends on what you're up to i suppose. personally i don't like standing so far back that i have to use a megaphone to talk to my groups. May 25 16 05:28 pm Link Rob Photosby wrote: Lol, yay, somebody got it! May 25 16 11:11 pm Link "Distortion" is a hard term to define. In particular, when you use an extreme wide-angle lens, there is usually very little rectilinear distortion, in the sense that straight lines in the subject show up as straight lines in the image. The reason that such images look distorted is that the viewer is usually much further away from the image than would be necessary to reproduce the original field of view. In other words: Suppose you're using a lens with a focal length that is the same as the long dimension of your sensor. If you're using an APS-C camera, the sensor is about 16x24mm, so imagine using a 24mm lens on such a camera. Because the focal length is the same as the long dimension, the distance between camera and subject is the same as the long dimension of the subject coverage. In other words, if you stand 10 feet away from your subject, the side-to-side coverage will also be 10 feet. In order to view an image taken by that lens with the same perspective as the original, your eyes need to be as far from the print (or display) as the long dimension of the image. So, for example, if you have an 8x12 print, your eyes need to be 12 inches away from the print for the perspective to match. That's pretty close, but doable. If you were to use a 12mm lens, which is usually considered an extreme wide-angle, you would need to be 6 inches away from an 8x12 print for the right perspective. That's unlikely in practice, and the substantial difference between the perspective-preserving viewpoint and the actual viewpoint is what causes the perceived distortion. If you're still with me, you now know enough to answer the original question: The way to avoid distortion is to use a lens with a focal length that corresponds to the intended viewing distance. For example: My computer monitor is 25 inches side to side, and when I'm sitting in the posture I use when I'm paying attention, my eyes are about 27 inches from the monitor. That means that for ideal perspective from my usual viewpoint, I should use a lens that is about 10% longer in focal length than the horizontal dimension of the part of the image that I intend to use after cropping. If I'm using an APS-C camera, that means a focal length of about 26mm. Longer than that, and the perspective will look flatter than in real life; shorter than that and there will appear to be corner distortion. I'm guessing that these ratios are not particularly unusual, which explains why such focal lengths are popular. May 26 16 08:10 am Link Andrew Koenig wrote: ...How did you reach this belief? What do you think it means to talk of viewing a 2D object with the same perspective as a 3D one? May 26 16 11:42 am Link thiswayup wrote: It means to view the 3D object from a single viewpoint--i.e., with one eye closed, or from far enough away that binocular vision doesn't matter. May 28 16 08:57 am Link Use a view camera. May 28 16 09:04 am Link A view camera is, indeed, the best way to avoid "convergence", which is not really "distortion". The point-projection geometry onto a tilted plane (film or sensor plane that is not parallel to the subject,e.g., not vertical) also occurs naturally in your vision. To avoid convergence in architectural photography, the film/sensor plane must be accurately vertical (use a hardware-store torpedo level; the levels built into cameras are often inaccurate), which is straightforward with a view camera with lens rise. With a "fixed" (no motions) camera, you can make the back vertical, but throw away roughly the bottom half of the image (if you have lots of pixels or film area) and get the same effect. Jun 01 16 08:42 am Link Some enlargers used to have tilting lensboards, which allowed for correcting converging parallels in the darkroom while maintaining focus (the same way one would do so in a view camera). These days, it's easy to do in software. Jun 01 16 09:59 am Link The OP never came back. Maybe WE are the distortion he is trying to avoid. Jun 01 16 01:32 pm Link Toto Photo wrote: He probably thinks that since we are picking on him, we are unwilling to answer his question seriously. Jun 01 16 04:00 pm Link |
