Just my opinion..
firecracker wrote:
Do all photo's need to be processed?
No. Some photos look good enough without further processing.
firecracker wrote:
How do you know if it needs it or not?
If they don't look so good, then they could probably use a little Lightroom love, or a lot.
firecracker wrote:
Or is it subjective?
To a large extent, yes. But also, sometimes a photo is just severely lacking in contrast, and so black-point (and/or contrast) really needs to be adjusted, and almost all viewers would agree.. (barring artsy considerations as you said..). Likewise, if photo is severely underexposed (or over-exposed).. etc. etc.
Bottom-line: along with subjective considerations, it's a matter of experience - knowing what a photo needs, and how much, and what you can and can't do...
PS - I can almost always improve a photo if I spend enough time with it, but sometimes it's just perfect the way it is - I end up backing out any adjustments I make.. - hard to know ahead of time, especially if you are new to this stuff..
Have fun,
Rob