As I briefly mentioned
earlier, noise is something all digital photographers have to deal
with sooner or later but, the smaller the sensor in your camera, the
bigger the noise problem.
Even if you can't see the
noise, it's always there, making your files bigger. Even invisibly
low levels of noise can double the file size. It's worth getting rid
of it just to save the memory space and make emailing pictures
quicker and easier.
What
is noise?
Noise is variation
between adjacent pixels where there should be no variation. Up close
and personal, it looks blotchy, like the darker parts of this
stonework.
It happens more in lower light, or with a smaller sensor, for two different reasons. Each pixel in your camera catches a bunch of photons but it's inexact so it's actually a bunch plus or minus a bit. Bigger sensors (this is physical bigness, not how many pixels), catch bigger bunches but the bit remains the same. Here's an example.
It happens more in lower light, or with a smaller sensor, for two different reasons. Each pixel in your camera catches a bunch of photons but it's inexact so it's actually a bunch plus or minus a bit. Bigger sensors (this is physical bigness, not how many pixels), catch bigger bunches but the bit remains the same. Here's an example.
20 photons +/- 1 =
variation of 2 out of 20 or 10%
100 photons +/- 1 =
variation of 2 out of 100 or 2%
Those numbers are
completely made up but it shows that bigger pixels have less
variation, so less noise.
The second cause of noise
is lower light levels. The lower the light level, the more +/- you
get. This happens in two ways too. If your whole subject is dark,
your camera's shutter has to be open for longer. The longer it's
open, the bigger the +/- bit gets for your whole photograph. If you
take a bright picture with really dark shadows (like my church
window), the shadowy bits haven't had enough time to fill their
pixels and you get a bigger +/- bit but only in those dark details.
More numbers coming up:
100 photons +/- 1 =
variation of 2 out of 100 or 2%
100 photons +/- 5 =
variation of 10 out of 100 or 10%
How
do I get rid of it?
Top
tip: Noiseware Community Edition is a free program that removes noise
better than anything else I've used.
Noise reduction should
always be the last thing you do to a photograph, because it removes a
lot of the hidden information that Photoshop uses but you can't see.
You won't get such good results if you try photoshopping after using
Noiseware.
There are a load of
pre-set levels of noise reduction but start with the default setting
(obvious really) and see what it does. If you zoom in on your image
until you can actually see the noise, you'll also get to see how much
disappears. Holding down the mouse button over the image shows you
the “before” and letting go shows you the “after” so you can
compare.
90% of the time, the only
change I make to the settings is to add a touch of sharpening (+2).
Try it and you'll see why.
You can sharpen images in
Photoshop and I'll talk about that later, but Noiseware (Default +2
sharpening) is a quick and easy way to clean up a photo.
In this detail of a
butterfly, you should be able to make out the grainy texture of the
noise in the green background. Noiseware (set on default +2
sharpening) has made it all go away without any detriment to the
detail of the butterfly.
The “before” image is
209K and the “after” image is 40.4K. That's less than 20% of the
original file size and no loss of visible detail. It just goes to
show you how much hidden information there is in a digital photo. If
you're posting on social media sites, people will appreciate the
smaller file sizes. Here's the “before” and “after” of the
full picture.
Now you can see how far
we had to zoom to see the noise. The full image is about 12 million
pixels and went from 6.6MB right down to 1.3MB but I defy you to spot
any loss of quality.
Seriously, why wouldn't
you do that to every picture?
By default, Noiseware
saves it's results with “_filtered” appended to the original
filename so you'll be able to go back and edit the original if you
feel the need. Remember, you've just stripped out a lot of hidden
detail you might need if you want to edit it again. I strongly recommend you keep both
copies. I have a separate folder for my unfiltered photos and I dump
them into there just in case.
Just-in-cases include
wanting to make some tricky colour profile changes to an image for
professional printing. So I was glad to have that backup copy.
As mentioned right at the
beginning, I recommend keeping the original, completely unedited
photo too. As your skills improve, you may want to take another crack
at tweaking a photograph. You cannot take the same photo twice so
don't be a disk space miser. Keep copies.