#REMOVING TEMPORARY RAWTHERAPEE FILES MANUAL#

Keep the lens de-focused while taking the flat-field shot. The focus setting of the lens while taking the flat-field shot for camera/lens aberration correction does not need to match that of the image you want to apply it to (this is not true if you take flat-field shots for dust removal, as explained in that section). You do not need to merge flat-field shots since merging serves to increase the signal:noise ratio, and this is unnecessary as the flat-field image gets blurred and should have a low ISO. It is sufficient to shoot a single flat field image using the same camera body and lens setup as the images you want to apply it to - you do not need several flat-field images with identical settings, unlike dark-frame shots where in order to get higher quality you do need to take several shots with identical settings and merge them. 6 Flat-Field File Browser Context Menu Optionsġ Creating and Using Flat-Field Images for the Correction of Camera/Lens Aberrations.4 Algorithm Specifics & Concise Summary.2 Creating and Using Flat-Field Images for Dust Spot Removal.1 Creating and Using Flat-Field Images for the Correction of Camera/Lens Aberrations.Pasting it to different images will result in independent auto-selection of the appropriate flat-field for each of them. This includes the flat-field 'Auto-selection' option. These settings can be copied and pasted to other images just as any other setting. The same level of correction is applied to the 'real' image when it is flat-field corrected.Īll parameters in the 'Flat-Field' panel are saved to the processing profile. The histogram of the bottom 'after' image indicates that the corrected image does not have any variation in the tones - exactly what one would expect from a uniform (flat) field. Flat-field correction removes both color and luminance non-uniformities and results in a perfectly uniform image.

There is a noticeable light falloff asymmetry shown in the 'before' image at the top, as well as a green color-cast. To illustrate flat-field correction, a flat-field image has been applied unto itself. The creation of flat-field images for both purposes is described in the next section.ĭemonstration of the effects of flat-field removal from the flat-field photo itself.

At present only the main preview in the Editor tab and the output image can be flat-field corrected.Īccuracy of the flat-field correction is largely based on use of the appropriate flat-field image which should fulfill the requirements of the sort of correction you desire - either lens/camera non-uniformity, or the same including the removal of dust spots. Thus in RawTherapee flat-field correction can be applied to raw files only.ĭue to performance considerations, thumbnail images do not reflect flat-field corrections. Flat-field correction is performed only on linear raw data in the beginning of the imaging pipeline and does not introduce gamma-induced shifts. The 'Flat-Field' correction tool in RawTherapee allows both automated and user-guided modes.

#REMOVING TEMPORARY RAWTHERAPEE FILES MANUAL#

Manual correction of these effects in post-production is quite difficult, especially when needed to be reproduced on a series of images captured under various conditions, and would rarely be perfect. An alternate name for this type of function used by some other raw converters is 'LCC correction', ie 'lens color cast correction' or just 'lens cast correction', but flat-field correction is the better name as it can as decribed correct for many sorts of non-uniformity not just lens cast.

Another set of examples of capture non-uniformity is due to light leakage in the camera, thermal non-uniformity of the sensor or defects/irregularities in the sensor readout electronics. Both of these examples of non-uniform image capture can be further complicated by a possible misalignment of the lens mount or by the usage of a tilt-shift lens. Another example, more familiar to users of digital medium format cameras, is the lens cast effect - both color and luminance non-uniformity of the image field. A well known example of such non-uniformity is vignetting - a peripheral darkening of the image, more pronounced in the corner areas. Notice the correction of both luminosity and color non-uniformities.įlat-field correction is used to compensate for the non-uniformity characteristics of the camera and lens combination. From the left: before correction, after correction, and the flat-field image used.

Removing temporary rawtherapee files