So, how exactly do you go about restoring images? (outline for a crash course in image restoration)
- 1 Introduction
- 2 Where are we going
- 3 Principles of restoring
- 4 Photography backgrounder
- 5 The process
- Who is this course for?
- What is this course about?
- Assume Photoshop
- Get someone to do GIMP?
- File formats
- 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
- scanning images
- how to
[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)
When (not) to do what + examples
Principles of restoring
Garbage in, garbage out
Start with as high resolution, as well scanned images as possible. Start, if at all possible, with lossless formats.
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)
Document the different stages of the restoration.
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.
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.
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
Living on the edge
Edges are often hard:
- wear & tear
- spots & stains
- peeling/cracked/... negatives
Avoid doing unnecessary work: clean up right up to the major problem areas, then decide on a crop area and do the rest.
Use a crop mask to preview the crop.
Colour and contrast
- The Histogram Is Your Friend™ -- today is Better Know A Histogram Day
- General adjustments
- Local adjustments
- Vignetting, fading and folds
- Large stains
Stuff to fit in there somewhere
- Stains and discolorations
- Cropping / rotating