I use my iPad to display my reference image(s) as I work.  Here’s some helpful tips that I have learned to make my life easier.

How to create a reference folder on your iPad with all of your reference photos. 

Create a black and white copy with three clicks

Need to see those eyes a little better?  Here’s how to zoom in and save just one section of your image

Here’s an app that I use when I need to isolate a certain color

Here is a great online way to quickly create a posterized version of your image.  No expensive software required!

PIXLR is an online program that does pretty much everything you would need to manipulate your photos.  It’s free and you can access it on any device that has a web connection.