Adobe added a tone curve and pressure sensitivity adjustment function to Photoshop for iPad on the 19th.
The tone curve function allows non-destructive adjustment of contrast, exposure, and highlights. Many of the main features of the desktop version were desired to be installed on the iPad version. Tone curve adjustment for all channels and selection of multiple nodes are supported, and the display has been improved for easy touch operation and pen input.
At the moment, adjustment by numerical input is not implemented, but it will be added in a future update together with the eyedropper tool.
The pen pressure sensitivity adjustment function can change the degree of pen pressure detection during pen input by moving the slider for setting. It enables the most suitable pen input according to the user’s preference and enables more accurate work.
It is also possible to change pen pressure sensitivity and this works with optional $100 iPad stylus as well. Photoshop for iPad is available for free but there are many in-app purchases that are required to make the app useful.
You can of course try it for free with its 30 day trial. You can use same PSD files on iPad that you use on Windows or Mac.