25

There is no hardware solution, short of some crazy* arrangement of mirrors to extend the actual optical distance. That's because perspective distortion solely related to distance, but there might be a software one, if you're able to throw a computer at the problem and able to accept some limitations. For a computational approach, see this paper: Perspective-...


15

The lens corrections aren't part of the firmware itself (i.e. a particular firmware doesn't mean you have a particular lens correction). They are profiles that can be stored in the camera, and you need to register them with the camera if they aren't in the default set. Canon DSLRs that support lens corrections (Peripheral Illumination and/or Chromatic ...


14

Most post-process lens corrections will cause a loss of detail, as they are not just modifying how the raw pixels are interpolated and what mathematical curves and adjustments may be applied...they change the position of pixels throughout the whole image. At the very least, you'll lose some amount of sharpness, and fine detail may be lost in some areas of ...


12

Classic standards have always been more like 2 meters Minimum distance for portraits. 3 meters is common in professional studios, for even better perspective. Too little distance (like 1 meter) will exaggerate and enlarge closer features like noses. This distortion will not please the subjects. The standard notions are the 105 mm lens is good for head and ...


11

Are you working with RAW or JPEG? RAW will not use the in-camera correction but JPEG will.


8

For lensfun <= 0.2.8, you may download http://wilson.bronger.org/db/version_0.tar.bz2, and extract its contents over your old database, which usually resides in /usr/share/lensfun (clean this directory first). For lensfun > 0.3.0, a simple "lensfun-update-data" on the command line, possibly with a "sudo", is enough. Both methods install the current (...


8

RawTherapee, darktable, and other programs use lensfun for lens correction. If your lens appears to be absent from the database... Check the Lensfun coverage database to make sure it really hasn't been added yet. If it's already there, you may need to update your local copy (sudo lensfun-update-data). If your lens is not supported, you can read about how to ...


7

I've done comparisons using my Canon EF-S 17-55mm F/2.8 IS USM lens turning the profile on and off, and I can't actually notice any drop in sharpness as @jrista stated. I guess it would depend on the lens being used, but for that lens I automatically apply the lens profile on import. It gets rid of noticeable vignetting as well. I expected some slight ...


7

The answer is probably more profane than you think: Instead of developing a real sophisticated algorithm to get the best resolution out of the source image, the software developers went the "safe" way: add enough crop that will always and under all circumstances deliver an image that is "properly cropped" (whatever that means). I'm saying this as a ...


7

This type of distortion in the corners is one of the trade offs for having a rectilinear lens that can render a wide field of view that covers a spherical area into a flat rectangular image. If you want things near the edges of such a wide field of view to appear undistorted, then you need a fisheye lens. But the fisheye lens will not produce a rectangular ...


6

To answer the first part of your question: As wikipedia says, it is for correcting lens effects, such as barrel distortion and and perhaps more important vignetting. Basically it is data about a lens that is applied to an image, a lens that is known to have -1EV of vignetting at the edge of the photo will be corrected by applying +1EV at the edges. Or if ...


6

Pincussion or barrel distortion is corrected to the ideal rectilinear lens of the appropriate focal length, one that obeys the pinhole projection model perfectly (all straight lines remain straight). It's an unambiguous correction (I.e. there is one right answer). The image will be copied to a rectangle, altering the effective focal length.


6

Many modern digital cameras are designed with the expectation that lens compromises will be... de-compromised... in RAW processing. That appears to be the case here. The preview image is based on the JPEG rendering, which includes this processing. The RAW file, however, does not. The amount of apparent vignetting will not be dependent on the scene, but on ...


5

Perspective correction is possible in a film/enlarger/paper process, by setting up the paper in a non-parallel relationship to the film. The paper is typically held by an easel which holds it flat. Propping up the easel on one side brings the paper closer to the enlarger head on that side, which in turn increases both magnification and exposure on that side....


5

Even I had experienced similar problems while shooting night sky photos and later stacking them together although not as apparent of a moire pattern as you have. after a bit of troubleshooting, I found out that by disabling Lens Correction before stacking the photos and applying it after stacking eliminates the problem. A side note would be that I used ...


5

I'm guessing this has to do with two overlays that were very slightly misaligned from each other such that the small variations in each image due to the Bayer matrix become apparent. If so, this is a rare case where working in raw is actually hurting. Put another way, the raw data has some regular high frequency content due to the Bayer matrix. Normally ...


5

If you shoot RAW, the in-camera lens correction is not directly applied to the RAW data, it is appended to the tagged data. The lens correction is applied to the in-camera preview JPEG thumbnail viewed on the camera's screen. If your selected camera output is JPEG then the in-camera lens correction is applied at the time the file is processed in camera. As ...


5

As far as free alternatives you can try Fred's defisheye script for ImageMagick, or Fulla, which is a command line tool that comes with Hugin. Fisheye-Hemi is superior to these, though, as instead of using a standard remapping to a rectilinear projection that softens the edges and requires an aggressive crop it uses a custom mapping algorithm that preserves ...


5

I fixed this in the sources of Lensfun. It will be part of the next release. Until then, you can edit the file mil-panasonic.xml, probably in /usr/share/lensfun. Search for "12-32" in that file, and expand the lens model name to "Lumix G Vario 12-32mm F3.5-5.6 Asph. Mega OIS".


5

More image information? Yes. Better image quality? No. The parts being truncated don't scale well because of the rectangular pattern of your sensor's pixel wells versus the curved shape of the correction. So a lot of artifacts can show up in those areas. Like many products intended for mainstream consumption (as opposed to niche products used by experts in ...


5

The problem with the outline of the ball not being a circle is not a sign of pincushion or barrel distortion. Indeed let us assume an idealised perfect lens. There is one focal point (the distance of that point from the sensor is the focal length). Now for any point of an object that you photograph, just consider the line through that point and the focal ...


5

Since the cloth is white, and the other colour is black, you could simply desaturate( remove all saturation) at whole region of cloth. I've done the same multiple times


4

When you correct lens distortion, the rectangular image is warped into a non-rectangular shape. Since we generally want our finished images to be rectangular, the image is then cropped to a rectangle that fits inside the warped shape. This means that objects near the edge of the original image may be cropped out of the finished image. That's a trade-off that ...


4

I use Gimp and the MathMap plugin, together with a few scripts of mine to convert the fisheye image into whatever projection better fits the subject: either rectilinear, stereographic, or Mercator. Mercator is my favorite: it's a kind of panoramic cylindrical projection that looks quite similar to the Fisheye-Hemi projection and is free of local distortions (...


4

The lensfun website explains how to update lenses without root permissions (see how database files are found and loaded). What worked for me was: cd mkdir -p .local/share/lensfun cd .local/share/lensfun Then download and extract the updated lenses: wget http://wilson.bronger.org/db/version_0.tar.bz2 bunzip2 version_0.tar.bz2 tar xvf version_0.tar The ...


4

The unflattering faces due to perspective is from being way too close. The nose is significantly closer than the ears. The left ear and right cheek are seen from different angles. That is unlike how faces are normally seen. back up. Don't take a picture from closer than you would normally view someone. The size distortions are easily corrected. The ...


4

The EOS Lens registration data is intended to be used by either: The camera when processing the raw data from the sensor to produce a jpeg image (or to produce a jpeg preview image when the file is being saved as raw data). At a minimum the camera uses the information to do Peripheral Illumination Correction. Some but not all Canon EOS cameras can also ...


4

Unfortunately, as of right now, darktable doesn't have a very good way of doing ad hoc distortion correction for a lens you don't have a lensfun profile for. The following is a dirty hack that may be useful in cases where the barrel distortion at the wide end of a zoom is so strong that even "incorrect" correction might be an improvement... In the lens ...


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