Adobe Photoshop Touch
This version of Photoshop brings the core features of the desktop suite to the iPad, so users can retouch and combine images easily. It even works with layers.
£6.99
www.adobe.co.uk

Filterstorm Pro
An all-in-one application for photojournalists that offers photo-editing features, as well as IPTC metadata tagging and image-delivery capabilities. The app is so comprehensive in features that the developers had to release Gridditor, a scaled-down version.
£8.99
www.filterstorm.com/pro

Photogene
A photo-editing app on steroids, Photogene offers a series of presets or filters, while letting photographers adjust brightness, exposure, shadows, colours, curves, and so on. Images can also be retouched, enhanced and, if you upgrade to the Pro version, watermarked.
£1.99
www.mobile-pond.com

William Klein - Great Photographers
Produced by Contrasto, this app [above, middle] showcases 393 images by one of photography's true living legends, as well as videos, essays and interviews. Users can even select their favourite images to build a virtual exhibition they can share on social networks.
£7.49
www.contrastogreatphotographers.com

Reuters' Wider Image
The Wider Image has been designed "to bring Reuters photography and information to life through an entirely new interactive experience" - and it succeeds. It is structured around stories, 100 of which are already available, shot by the agency's photographers and complemented with interactive elements such as slideshows, sequences and sounds. 
Free
widerimage.reuters.com

Elliott Erwitt: Personal Best
Elliott Erwitt looks back at 60 years of his career in this app that showcases 343 of his best photographs. It includes behind-the-scene videos and commentary, in which Erwitt recounts how he captured some of the 20th century's most historic moments.
£3.99
www.teneues.com

Eyewitness
The Guardian relaunched its Eyewitness app this year, with a new premium feature that gives access to more images, as well as tips from the newspaper's photographers, all for £1.49 a month.
Free (app only)
www.guardian.co.uk/mobile/eyewitness

Apple iPhoto
This app [top] shows how multi-touch gestures can be used to easily sort through, edit, enhance and retouch images on the iPad. The app offers an array of effects and allows users to share images via its Photo Journals service.
£2.99
www.apple.co.uk

Snapseed
It remains one of the most downloaded photography apps on the iPad, and this year Snapseed was updated to support the iPad 3 and images of up to 20 megapixels, as well as raw photos if transferred using the Camera Connector Kit. Its ease of use makes it a must-have app, which is perhaps why Google snapped it up in September.
Free
www.snapseed.com

Photo Ephemeris
Another trusted app for many photographers, Photo Ephemeris can tell you the time and direction of the sunrise, sunset, moonrise and moonset, and even lets you know when the sun will appear from behind a hill.
£5.99
www.photoephemeris.com

Adobe Nav for Photoshop
If you use Photoshop on a Mac, the Adobe Nav iPad app can help streamline your workflow by displaying a series of toolbars, and allow you to browse, reorder, view and zoom in on up to 200 open Photoshop documents. These documents are then cached on the iPad in high-res for offline viewing.
£1.49
www.photoshop.com

Blux Camera
This app brings the kind of user interfaces you usually find in a compact or digital SLR camera. It's an intuitive app to use - you control the look of the images in real-time using a series of scene modes. The app can even detect the weather and adjust its white balance accordingly.
£1.99
www.bluxtouch.com

Camera+ for iPad
Photographers can control the exposure and focus of their shots with Camera+, but it can also be used to retouch, apply effects, add layers, adjust, rotate, straighten, correct, crop, caption and share images, with some of these features only available on the iPad.
£1.99
campl.us

BONUS APP: The Silent History
This is a novel, in effect, developed for the iPad, using serialisation, exploration and collaboration to tell the story of a generation of children born without the ability to create or comprehend language. This app demonstrates how a narrative can work for the iPad. Storytelling photographers take note.
£1.49
www.thesilenthistory.com