May 27th 2009 Digital photography

David S gave a gave a full length presentation on Digital photography: the free software perspective.

He started by pointing out that:

• images are data: the marginal cost of an image is zero

• optical physics is maths: post-processing is open to anyone with a computer

• information wants to be free: there has been a net-powered explosion of both ‘customers’ and ‘publishers’.

It has become a democratised art where the only limit is your imagination. For example, Panoramio can compute control points on ’photos to create a panorama around several people’s personal ’photos. This conflicts with the old publishers approach.

Now you can take a ’photo with your ’phone which makes them spontaneous and ephemeral, especially when your ’phone gets stolen and save it

• to another ‘phone

• to a memory card and print it at the supermarket

• via a cable from the camera to the printer (with Pictbridge)

• via a cable from USB mass storage to the PC — Xcept Canon/Nikon which needs gphoto2

Displaying

• Viewers

  • GQview/Geeqie

  • Gwenview

  • gThumb

• Printers

• Digital picture frame

• DVD slide show

which turns a computer into a media hub unaffected by developments such as the cloud.

Image managers

• F-Spot

• digiKam

• Picasa (needs wine)

Organising

Organising may be:

• filestore centric

• application centric

• online

Publishing

• flickr — not very generous

• Panoramio — landscape photos

• fotopic.net — esp. trains, buses [no longer available]

• Picasa — more generous

• ImageShack or photobucket — bargain basement

• MySpace

• Facebook

• Twitpic n.b. not very secure; don’t actually delete pictures when you think they have been deleted

There are also specialised sites; choose the site that suits you; for example, flickr has local Bradford forums. Use geotagged ’photos for geotagged sites. For uploading ’photos Pixelpipe [no longer available] is very good

Licensing

• National Media Museum distinguishes copyright status where possible

• Crown Copyright expires after 50 years

• US Federal Government material is not copyrightable

• GPL but must supply a copy of the licence

• Creative Commons — does not require you to supply a copy of the licence; you can use it to say there is no copyright

Understanding image capture

Image capture faults include:

• poor focus

• colour balance

• poor geometry

• motion blur

• underexposure

• overexposure

• blooming (digital cameras only)

• sensor noise (= grain)

Exposure is controlled by:

• sensitivity (user setting)

• aperture (per image)

• → shutter speed

Because JPEG has lossy compression, the quality settings on cameras (resolution, colour balance, saturation and contract and sharpness) and are all about JPEG — always use the highest quality.

Post-processing

• GIMP

• Krita

• CinePaint

• F-Spot

• digiKam

• Picasa

Order

• geometry: rotate, straighten, perspective

• crop/resize

• brightness/contrast

• colour: white balance/saturation

• sharpen

• histograms/curves

• EXIF tags

Use curves and histograms to compensate for under/overexposure; a posterised image needs a RAW image; always consider perspective.

Never

• re-edit

• enlarge

• add borders

• add captions — use EXIF tags instead

• use sepia

Specialised tools

• ExifTool: date/time, camera details, location — n.b. Firefox extension lets you see when ’photo taken; use date/time if cross timezone or battery flat and wrong date; consider privacy implications

• gpscorrelate: to add location to EXIF [now abandoned]

• Fulla — to correct lens faults, e.g. barrel distortion, vignetting, chromatic aberration; n.b. needs a database of lenses — but owner now charges for details of latest lenses

• Lensfun — possible free alternative to Fulla

Formats

• JPEG — 8 bit

• RAW — all proprietary

• TIFF

• EXR

Converting

• UFRaw

• Luminance HDR AKA Qtpfsgui — HDR tonemapping

• Enblend/Enfuse — Enfuse uses an algorithm to calculate most important pixels and uses three (or more) ’photos with different exposures to create a better ’photo; n.b. don’t bother with noise reduction

• hugin — panoramics

David then listed the other topics one might cover and gave examples of a wide range of photographs which had been manipulated in one way or another. He argued that this had led to democratisation in that:

• everyone is a journalist

• everyone is an artist

• everyone has freedom to use works

• we have a better historical record.

We have lost

• the ‘cathedral’ culture

• craft

• authenticity and

• the long term survival of images.

Past Meetings