What are the steps of editing

5 steps image correction

Retouching, tonal value and color correction, scaling and sharpening

Of course one can discuss the processing of photos - one person does not want to touch his photos as originals and swears by the documentary character of photographs, the other sees the photo as a complete work and spends long hours in search of perfection.

Since the first days of photography, photographers have spent nights grooming and re-exposing, we have mounted and retouched with passion. Digital photography hasn't made post-processing the photo any easier. It's just not as uncomfortable and lonely as in the darkroom.

The way to the perfect photo is to post-process the photo in the image editing software. The abundance of functions for image correction also harbors doubts: Is my procedure optimal or wouldn't another technique be appropriate here? In the photography courses in Duisburg, Cologne and Bonn we are repeatedly asked about the best approach to image processing.

The systematic correction brings solid ground to image processing. Of course, an experienced photo editor can use one technique or another to get more out of the photo or give more space to his or her personal taste.

With a fixed workflow or workflow, you can quickly get a grip on any image processing program: Lightroom or Darktable, Photoshop or Gimp.

Corrections process in the image processing program

The order of the steps is especially important when editing photos in JPG format. In the case of photos in the RAW program, the order of the corrections is irrelevant until the image is fetched from the RAW program into an image processing program. The same applies to the editing of photos in Adobe Lightroom and Darktable: There the corrections do not change the physical photo, but the corrections are only displayed on the monitor until they are exported for the Internet and for printing.

Nevertheless, the sequence of brightness corrections before color corrections also makes sense for RAW photos. In the RAW program, too, the brightness corrections clarify the colors.

Working in the largest possible color space

The main principle of image correction is:

Optimize first, then reduce!

If possible, corrections are made in the original color space of the data source (scanner, digital camera) and with the original color or bit depth.

The image processing reduces the brightness levels in the color channels anyway and may even lead to gaps. The later in the editing process the color depth is reduced and the color space is changed, the later the image is reduced or enlarged, the better.

Step 1: straightening, rotating, blotting, lens corrections

Pixel movements are performed before the brightness corrections.

  • Do small retouching such as staining have to be carried out, does a shadow or an annoying piece of furniture have to disappear or should a section of the image be chosen so that the annoying stain on the jacket disappears anyway?
  • For scanned images, can I remove lint or stains? The scanned image is blotted out before the further processing steps.
  • If the camera was tilted: It is also rotated and rectified before the brightness and color corrections, as long as the pixels are still soft and there are no jumps due to brightness corrections.
  • If black and white or duplex is required, the image is converted to a grayscale / duplex image before the brightness and contrast corrections are made.
A small group of visitors removed the stamp, then the lens correction (here just rectify), because now the gradients are still soft and the full tonal range is still available.
The rectification of the photo creates empty areas of the image, i.e. cut them out. The photo is cropped before all brightness and color corrections. For a certain image format - e.g. for a postcard - the image section must be determined. The cropping tool is particularly well suited because it darkens the area around the cropping and thus creates a better overview for the design of the cutout.

Step 2: brightness and contrast

Brightness and contrast corrections are made before the color corrections, as these corrections also change the colors of the image.

In addition, the majority of the color errors are already eliminated in the tone value correction / gradation curve by “Set shadows”, “Set white point” and “Set midtone”.

Step 3: color corrections

The tonal value correction and the gradation curves have eliminated color casts that affect the entire image or certain areas of the image's brightness. Color casts that exist in limited areas of the subject - local color casts such as a magenta cast in the skin tones of the portrait or a false red in a red dress - are corrected after the brightness corrections.

If an individual color is not reproduced as desired in an image area, it can be shifted slightly (in the sense of "something") in the color scale with Hue / Saturation.

Color corrections are made before sharpening, as the Unsharp Mask filter affects the contrasts and colors on the contours.

Most image editing programs use the Lab color space for local color corrections, in which colors and brightnesses are controlled separately from one another:

  • Hue shifts the hue,
  • Saturation or saturation enhances or desaturates a color,
  • Lightness regulates the brightness of a color.
Brightness and contrast corrections are made before the color corrections, as these corrections also change the colors of the image.
The brightness correction with the gradation curve and the setting of the shadows and the neutral tone has already clarified the colors. Correct hue and saturation to taste.

Step 4 image size, resolution and interpolation

Only after the brightness and color corrections have been made is the image enlarged or reduced, because the brightness and color corrections are more precise and without breaks in the fine gradients, the higher the resolution and color depth of the photo.

Centimeters and the printer resolution are important for printing - the printer resolution (DPI or dots per inch) is almost always 200 to 300 DPI for photos.
And the DPI for photos for the website? There are no dots per inch for websites, only the pixels count.

Step 5: sharpen photos

Sharpening takes place only after enlarging or reducing the photo, because sharpening in the image processing program can only ever alleviate the consequences of interpolation, but not really improve the sharpness of poor focusing.

The subsequent sharpening - almost always with an »unsharp masking filter« - only serves to reduce the soft focus effect that occurs when the image is enlarged. The loose rule applies here: images with flat colors and few details tolerate less sharpening than images with many fine structures. The larger a picture is, the more strength can be set.

The E6 process of the analog darkroom

In the analog darkroom in the commercial laboratories there was a standardized process for developing the photo: the E6 process. Until the E6 process was introduced, every photo lab had its own processes and many photo labs were reluctant to adapt to the E6 process - the individual techniques could certainly lead to better exposures.

Overall, however, the E6 process has brought a high level of reliability and quality to the development of analog film. A well-understood process produces better results than experiments and gut instinct. The same applies to a workflow for correcting digital photos.