Doh! It took me too long to type my response and beerguy slid in there. Here's what I wanted to say.
Misled (and now Doug) is correct, and here's why.
When the camera saves a pic as a jpg, it applies what it thinks is the proper white balance. High color temperature lighting, such as we often use for reef tanks, is beyond the range of color temps that camera manufacturers think people shoot under. So the camera is not capable of applying proper automatic white balancing. The resulting jpgs are way too blue.
One can attempt to use a custom white balance along the lines of capturing something white and having the camera use that as a basis for white balancing. In my experience, while an improvement over auto white balance, this is still more hassle and results in less accurate colors than shooting in RAW mode and setting the white balance during post processing.
When you shoot in RAW mode, the camera is not saving a jpg which the camera has already applied white balance to. The camera saves the raw image sensor data, not a final image. This is one reason raw files are much larger than jpgs. During post processing, the human, whose eyes are much better visual imagers than any camera sensor ever made, applies the appropriate white balance to yield very accurate colors.
This is not "photoshopping" a picture. It is white balancing the image during post processing to yield the most accurate representation of what the eye sees as possible. There are a number of programs which allow one to post process raw files.
Also, it is not the program adding back colors which aren't in the picture. It's the program applying white balance under human control to the raw data that the image sensor captured. Then the image can be saved as any image file type, such as jpg.
"Photoshopping" a pic often refers to altering an image in a deceitful way, typically cranking up the saturation to present the subject as much more colorful than it actually is, or adding visual elements which weren't present originally.
To sum up, camera cannot auto white balance high color temperature lighting. It is not made to. Saving the raw image sensor data instead of a jpg in the camera allows the photographer to white balance the image data later, producing a very accurate image of what the photographer saw when he snapped the pic.
Does that make sense?
FWIW, I also am not a fan of shooting under T5s, as for me, the pictures look very pale and flat, compared with shots under MHs. But I can get the colors right!
