Noise Reduction Question

[alex]

EDIT


Just got back from a shoot last night, got some (hopefully) good shots and long exposures of water features.


Uploaded the shots today, and I've noticed a fair number of hot pixels showing up in most of the shots. I've already searched the forum for topics addressing cleaning the sensor (see http://community.the-digital-picture.com/forums/p/1808/13583.aspx#13583).


My question is about the shots that I have already taken out of the camera. I didn't shoot with the Noise Reduction features in-camera because I wanted to conserve battery power, save time, and I figured it would be easier to do it in post anyway.


I am using DPP. I guess I need to apply Noise Reduction to the images I already have loaded on the computer?


1) Will Noise Reduction work to remove hot spots?


2) Which noise reduction should I use, Luminance or Chroma? I've never understood the difference between the two. Do the names refer to what CAUSES the noise to show up, or do they refer to what the noise LOOKS LIKE?


3) I already tried Luminance on one image just to test it. I used a setting of 1 (a weak setting) and the hot spots didn't go away. Does using a stronger Noise Reduction setting soften the image at all? I really don't want to do that.


Obviously, it would be incredibly tedious to go through each shot and use the spot tool to take out the hot spots.


Hopefully some of you know a better way!


Just for fun, I added a poll.


[Poll]


Thanks in advance,


Alex

[Daniel Browning]

I didn't shoot with the Noise Reduction features in-camera because I wanted to conserve battery power, save time, and I figured it would be easier to do it in post anyway.

That's true, but you might be interested to know that the "long exposure noise reduction" feature isn't really "NR" in the typical sense. It's dark frame subtraction. It does not smear detail or have any of the negative effects typically associated with "NR". And it can't be done in post.

I am using DPP. I guess I need to apply Noise Reduction to the images I already have loaded on the computer?

I don't think DPP has any good algorithms for hot pixel reduction. Many other converters do, including Bibble, Adobe, and probably many others.

1) Will Noise Reduction work to remove hot spots?

I would think so, but it will also smear detail all over the image.

2) Which noise reduction should I use, Luminance or Chroma?

Neither. I suggest an algorithm that is optimized for hot pixel interpolation instead. They can remove the hot pixels without smearing detail everywhere else in the image.

I've never understood the difference between the two. Do the names refer to what CAUSES the noise to show up, or do they refer to what the noise LOOKS LIKE?

What it looks like.

Does using a stronger Noise Reduction setting soften the image at all?

Yes.

I really don't want to do that.

Then you're going to have to use some different software I'm afraid. (Or use long exposure NR next time.)

Hopefully some of you know a better way!

Here is another option:

http://www.pixelfixer.org/

After a bit of work learning it and setting it up, the software will create new raw files from your original raw files.

HTH

[alex]

Daniel, Thanks a bunch, I'll look into those other software options and try something other than NR in DPP.


Good to know about Long Exposure NR in-camera. I'll use it next time for sure.


Again, thanks!


Alex