Ornamentation with vignettes

In Photography, the ornamentation with vignettes is the darkening of the periphery of an image caused either by an insufficiency of the photographic Objectif, or by the use of an objective whose image does not completely cover the format of the film.

Description

When the effect is not marked too much, one observes especially an obscuration of the edges or angles of the image and the transition between the central part and the edges (obscured) is progressive.

The ornamentation with vignettes is observed especially with full opening of the diaphragm. It is generally enough to close this last of a notch or two to make insensitive this effect, considered most of the time as awkward. In the case of a Zoom, the ornamentation with vignettes will be also stronger with the focal shortest.

All the objectives give an image whose periphery and particularly corners are darker. It can be insensitive (lower than 0,1 IT), visible (from 0,3 IT) with awkward (1 IT and +). They are the objective great angle and the zooms which suffer more EC defect. It is particularly visible on white zone and also on a uniform blue sky.

The ornamentation with vignettes is measured in IT (Exposure value): the value indicated measurement the difference in IT enters the quantity of light received by the edges and that received in the center.

False ornamentations with vignettes

Reasons plus ground with ground can also cause obscursissement edges (and angles) of the image:
  • a Sun visor badly adapted which enters the field of catch of sight (example: a sun visor for objective of 85 mm used with one 35 or one 28 mm);
  • an objective unsuited, to the circle-image too narrow. For example:
    • an objective for numerical catch of sight used on a silver apparatus,
    • an objective of room covering the 4x5 inches used on a room 20x25 cm.

In these two cases, by closing the diaphragm, one obtains a franker delimitation between the darkened zone (often completely black), whereas for a true ornamentation with vignettes, it is by closing the diaphragm that it is eliminated.

Voluntary “Ornamentation with vignettes”

Sometimes one chooses to darken voluntarily the edges of an image in order to create effects, to draw the attention on the center of the image. This can be carried out by the use of specific filters or software of final improvement of image, or quite simply by using apparatuses or objectives of bad quality (see the Lomo LC-A or especially the Holga ).

Correction

In silver it is necessary to create and use masks with the pulling - reserved to the very tested amateurs…

Only the digital technique allows a simple treatment of the ornamentation with vignettes. First of all, the software DXO allows, after loading of the " profil" objective used, automatically to correct the ornamentation with vignettes and the distortion starting from the focal distance and of the opening which this objective at the time of the catch of sight had.

If not, with the majority of the software of photo final improvement, one can create a layer filled with a circular gradient of the black towards the white and use it either in superposition and restore luminosity and contrast, or in mask of adjustment of the luminosity. With a little patience on the adjustment of the transparency and the mixture, while helping oneself of the outline, one manages to compensate.

In the event of nonuniform ornamentation with vignettes, this mask can also be created starting from the original image and of a local average on a great number of pixels (example Paint Shop Pro: Blur-Gaussian Blur parameter maximum). It is also possible to compose a mask related to the objective by photographing a uniform white surface and by using the technique above.

Despite everything, because of non-linearity of various conversions carried out, the compensation will be imperfect but the result will be nevertheless largely higher than the original.

See too

Random links:Clear Philippe | Draftsman | Getafe pool | Yohan Bouzin | The Circle (film, 2005) | Comté_de_Benton,_Washington