Edited RAW and cannot save as JPG.

The main reason that it's best to set to open in 8 bits in the editor is because it's no longer useful to use 16-bits after the raw editing.

All the edits you are doing in ACR are in 16-bits and a wider color range to take advantage of the quality your raw files. Remember that the jpegs from your camera as well as your output on your printer or display are only in 8-bits.

Why is 16-bits editing useful, and sometimes even necessary?

The main danger is 'posterization' or 'banding, the second one is to be able to apply very hard edits to your images wich will create this posterization. This defect transforms smooth gradients such as skies into adjacent 'bands' with very visible boundaries. This has to be cared for in the ACR conversion. You have read what 99jon states about what you can't do in 16-bits in Elements (layers and tools). Keep in mind what the Elements editor can do in 16-bits: nearly all global adjustments (the same as done with the ACR plugin) and most filters.

So, why continue the editing in 16-bits the editor if those adjustment have already been made in ACR? For years, I have followed the good old rule to edit in 16-bits until I had to switch to 8-bits especially for using layers. I have soon discovered that most of the time I was wasting my time. After the ACR conversion, the risk of posterization in 8-bits depends on two factors: the contents of each image and the way you'll use layers and their blend modes. So, if like me you love applying blend modes which greatly stretch the tones, beware of the risk, check the results, look at the histograms and use global edits instead in 16-bits which is generally possible. But if your use of layers is to use them in normal mode for compositing, that can't add posterization at all. For most of the tools which work only in 8-bits, note that they'll have no posterization effect (sharpening, noise removal for instance).

To keep it short, most of my editing is made in ACR, I open in 8-bits in the editor... and I never get posterization.

There are two categories of users who need to use 16-bits in all their workflow:

- the 'pros' who can see the difference because their display and printing device are better than the 8-bits device you can afford, and for whom very accurate color rendering (with color management) is a must.

- those who don't really know if they can see the difference and don't necessarily understand why and when 16-bits is theoretically (digitally) better. If they can afford using the full Photoshop, they don't have to think about it and they will be happy.