I was wondering whether what image types are best for digital editing. JPEG, for example, is it of good enough quality for broadcast quality projects?

People in the broadcast industry tend to use TARGA fles (.TGA). But now a days you can use pretty much any format you want (JPG, BMP, TIFF etc etc).

What does matter though is the resolution of the digital images, and the size of them. But even this now adays is not so imported as most NLEs will sample them to the correct aspect ratio and size.

However if the resolution is lower than the TV standard (720x480 ntsc 720x576 pal) then obviously the quality will not be so good when braodcast at full resolution.

Targa (TGA) files and TIFF files are commonly used (especially in visual effects) because they support Alpha channels, whereas most of the other formats do not.

Ed's right though, you can pretty much use whatever format you want, or actually whichever format your editing software supports, when it comes to still frame images.

Thanks for that guys, answered my question. Cheers

JPEGs and GIFs are reduced resolution. Use TIFFs, TGAs.

I would second Keith. You can use pretty much any format, but if you're going to be doing a lot of work to it you want to stick with a "lossless" format. In short, formats like JPEG use heavy compression algorithms that throw away a lot of information. The algorithms are smart enough that the human eye can't really tell, but every time you open the file and resave it, it gets recompressed and more information gets lost. Over time, this adds up and you can get pretty bad results.

Most professionals will instead use a format that doesn't throw away any information, like TGAs or TIFFs (although beware - TIFF can use JPEG compression inside of it!) to avoid this, and only use "lossy" formats like JPEG as a final output format after they've finished all editing.

Myself, I've grown pretty fond of the TGA (Targa) format for three reasons:

1) You can save an Alpha channel with it
2) Just about every "serious" image/video editing software package supports it flawlessly, because
3) It's a butt simple file format.

3 is probably completely unimportant to most people, but as a software developer I've actually written my own custom image manipulation stuff in the past, and Targas are amazingly simple to work with, so I really like that format.

With that said, Targa and Tiff are great. If you're doing all your work in Photoshop, its native PSD format is great and adds a ton of flexibility, but it's not excessively portable and it tends to eat up disk space. PNGs are also nice (and lossless, again), and a ton of other formats are also useful.

I would shy away from JPEG or GIF format except for final output.

are apps compatible with photoshop document files? (.psd)

Some, but not a lot. Anything by Adobe (Photoshop, Premiere, Illustrator, etc.) will be. If you're using software by somebody else, probably not, although a few apps do support it. Even when there is support, though, it's often limited. Most non-Adobe applications that I've used will "flatten" .psd files when you open them, if they support them at all.