Are the settings "Active D-Lighting, NR" in Nikon DSLR necessary evil or should this be turned off (managed through image editor)? What is the effect of this setting on processing time and battery life?
Active D-Lighting isn't necessary at all. It works by doing two things: slightly underexposing (by 1/3 to 2/3 stop) and applying some adjustments to raise the shadows back up
- It isn't needed if you shoot RAW as you can underexpose and raise the shadows in post
- It is only relevant if you are shooting high dynamic range scenes with bright highlights and dark shadows - you get slightly improved highlights at the expense of noisier shadows
- It slows down JPG processing slightly. You would only notice this if firing at a high burst rate
- I suppose it has a very small affect on the battery, but I would expect this is almost negligible
You can achieve the same thing by underexposing high-dynamic range scenes by 1/3 or 2/3 of a stop, then in post-processing, lift the shadows a bit.
You also mention NR. There are two settings on most Nikon cameras. One for High ISO noise reduction and the other for Long Exposure noise reduction.
Long exposure noise reduction
- worth using if you are taking long (20-30 second) exposures of night time scenes or astrophotography.
- significantly lengthens the processing time (doubles it in fact, by shooting a second "dark frame" and then subtracting out hot pixels).
- you can avoid using this feature if you shoot "dark frames" manually and apply them later in software. Otherwise, using long exposure NR in-camera has definite benefits
- It affects RAW images
- doubling the processing time will affect the battery usage
High ISO noise reduction
- will reduce noise at the expense of losing some small detail.
- You can turn this on in-camera, or you can use noise-reduction in post processing.
- There is probably a negligible affect on JPG processing.
- It does not affect RAW.
For a discussion about whether it's better to do in-camera or post: Is in-camera high-ISO noise reduction worthwhile?
I have turned my D-lighting and NR off because:
D-lighting is not perfect. It tries to alter exposure locally, but the smallest area cannot be small as few pixels. So if you have some small bright object on relatively homogenous background (like sun in the blue clean sky, reflection somewhere..) it will create dark "blob" over it reducing locally the exposure.
NR in camera is not as good as the one in your post processing editor.
I shoot raw. And with raw I mean "the most raw I can get", without additional processing by camera. All these processings will be always better on PC, you have the option to not to do such processing and finaly you save battery.
Active D lighting and NR are both not evil and not necessary, they are tools, they are pretty good at solving the problems they are designed to solve and useless if you don't have those problems, also, like almost everything in life, those features involves tradeoffs.
Active D lighting can increase the dynamic range of your camera (or at least the perceived dynamic range) by a little bit, this is useful if your scene exceeds the camera's dynamic range by a little bit and you pay for this with a little added noise.
If you never exceed the camera DR, want to make the DR related choices yourself or you really hate noise this isn't for you.
NR (not long exposure NR, that's something completely different) let you get a reasonable quality JPEG strait out of camera when otherwise the image would have been ruined by too much noise, you pay for this in less details and some loss of sharpness.
If you only shoot raw this doesn't effect you in any way (except for the raw file preview) and you can get better NR in post processing
Both should have negligible effect of battery life and processing speed, after all the camera has a specially designed processor for doing those thing.