User:Mvuijlst/Restoring images

So, how exactly do you go about restoring images? (outline for a crash course in image restoration)

Introduction

 * Who is this course for?
 * What is this course about?
 * Tools
 * Assume Photoshop
 * Get someone to do GIMP?
 * File formats
 * Lossy/lossless
 * Intermediary formats
 * Final formats for Wikipedia
 * Colour & colour spaces
 * Storing images
 * Where? (en / fr / nl / de vs. commons)
 * Something about licenses?
 * Metadata to add?
 * Getting images
 * LoC
 * Other?

[more stuff goes here]

Where are we going
Restoring an image is like restoring a house: you have to decide what you're restoring it to.

Things to do
Possible operations (non-exhaustive):
 * Clean-up: remove dust and scratches, rotate, crop, minor histogram work
 * Retouching: simple clean-up + remove tears & stains, add/repair minor image elements (e.g. corners, non-relevant background), major histogram work (reinterpret colours, treat parts of image differently)
 * Reconstruction: retouching + add/repair major image areas (e.g. body parts, elements only present in other images, interpolation).

Places to go
Possible targets (non-exhaustive, can be combined):
 * The image as it was first produced (e.g. a photo just after developing, a painting just after being finished).
 * The subject as it is now, minus photographic artefacts (e.g. a photo of a painting or building: remove only dust and scratches on the photo, not on the painting or building) (e.g. a
 * The subject as it would be if you were looking at it in ideal circumstances (e.g. remove double exposures in photos, correct over/underexposure, correct faded colours)
 * A better image (e.g. straighten horizon, different crop, selective sharpening)

Philosophical intermezzo
When (not) to do what + examples

Principles of restoring

 * Garbage in, garbage out: start with as high resolution, well scanned images as possible.
 * Small to large: start with the smallest operations (e.g. dust), work towards the larger operations (e.g. tears).
 * Primum non nocere: work non-destructively if at all possible (e.g. adjustment layers)
 * Be a packrat: keep all intermediary changes (if at all possible in layers in one file)
 * Be anal: document what you're doing

Old photos are not digital photos

 * Explain about photographic process?
 * Grain is not noise. Megapixels have no meaning.
 * Techniques: glass negative, emulsion, yadda yadda

How do pictures degrade?

 * Digitizing: dust, loss of resolution, colour depth, etc. (can a scanner capture iridescence?)
 * Deterioration of the support due to age: cracked glass negative, cracks in emulsion, fading, etc.
 * Physical damage: tears, stains, fading, fold marks, etc.

Starting out
Get a rough idea of the final result you're looking for.

Don't do unnecessary work: indicate the final crop and rotation of the image to get an idea of the area you're going to be dealing with. But do not, under any circumstances, work on a rotated or cropped version. Rotate and indicate the crop, then go back and work on the original image.

Low-hanging fruit
First of all: tackle obvious dust and scratches. Put on some music, we'll be here for a while.


 * Zap using the Healing Brush tool
 * [add principles, techniques & examples]
 * [explain the clone brush / healing brush-two step]
 * Patch Tool for simple stuff
 * Clone Brush

Out, damn'd spot! out, I say!
Even when it all looks clean, it isn't. Step two: remove non-obvious dust and scratches.


 * Levels adjustment layer to enhance contrast
 * Over the top sharpening to bring out unnatural image elements
 * Clean at high magnification (200% - 400%), zoom out to 100%, clean again, zoom to 50%, clean again. Lather, rinse, repeat.

Fill in the blanks
Sometimes the information is just gone.


 * [cloning, techniques, etc.]
 * Dealing with texture
 * Dealing with edges

Colour and contrast

 * The Histogram Is Your Friend&trade; -- today is Better Know A Histogram Day
 * Tools:
 * Levels
 * Curves
 * General adjustments
 * Local adjustments
 * Vignetting, fading and folds
 * Large stains

Stuff to fit in there somewhere

 * Stains and discolorations
 * Sharpening
 * Despeckling
 * FFT

Final prep

 * Cropping / rotating
 * Naming