What is noise and how to handle it? (in 5 minutes ;)


posted on 18th of may, 2012

Hi everyone,

I think noise (or “grain” as called in the analog photography) is the most common problem of most of us, especially for photographers who work outdoor without artificial lighting. There are many softwares, plugins and filters who try to deal with noise issue and most of us use them as “subtle” as possible, just because whenever you try to clean noise, you clean some of the valuable details off of your photos too...

Whatever software you use to clean noise, you should first know what are you trying to clean and how you should fight against noise?!

What is noise and why it happens?

Before I give a couple of tricks about handling noise, I think we should know a little about our ennemy!

%99 of stock photographers use digital cameras and digital cameras use a digital sensor. Digital sensors are made of thousands of photodiodes. Small tiny parts which are sensitive to light.

When we boost ISO value, photodiodes become more sensitive to light and heat, as a result they warm more than normal and spread heat to their neighbours. Thus they all go crazy and send wrong values to the image processor of the camera. (That’s why bigger sensors have less noise, they have more area for photodiodes, which makes it easier to isolate them from each other)

Another cause of noise is the base noise of sensor itself. We boost the base noise, when we use higher ISO values. Unfortunately base noise is increased with long exposures too, because sensor have much more time to collect it’s own noise.

Generally, underexposed images or dark parts of images have much more noise. I think, it’s because the left side of the histogram (dark side) is able to contain much less color information then the right side (highlight side). So the difference between mistaken values are bigger and more visible! On the white side, there are same amount of mistakes, but there is much more color information, making the steps smaller and less visible. (I wish I was a native English speaker, I don’t think I can explain myself perfectly here)


So...How to handle noise?

Noise can be handled in two basic ways, during photo shoot and during post process.
During a photoshoot; if you have to boost your ISO value during a shoot. Use +0,7 exposure value, which means +0,7 step more ISO. You will get a brighter shot, which will create less “visible” noise.

During the postprocess; (assuming you have a RAW file) use the raw converters noise reduction very subtly (maybe, until you clean the noise from the brightest parts of the image). Leave the rest to image editor program.

As I already mentioned and most of us already know; dark areas have much more noise. This means we are going to use separate layers during noise reduction. Dark parts of the image don’t grab attention and a viewer doesn’t expect nice details in the dark parts and that gives us the opportunity to boost the noise reduction value.

So we will use 2 different noise reduction values; one for darks and one for highlights (if needed).


Here is how to do it step by step :)

-Duplicate the background layer (ctrl+J)
-Menu>Image>Adjustments>Threshold... this filter will create a totally black and white image. Use the single lever until you get your shadows black and the rest of the image white. (Staying around 60 – 80 will be nice)
-Menu>Filters>Blur>Gaussian Blur... to add some graduation to the treshold image you just created. Do not apply too low or too much, you should have a nice graduation, so that viewers won’t understand the different noise reduction process. Sorry I don’t have any ratio or exact value for this part.
-Press ctrl+A select all...
-Now that we created our mask, go to Channels window and create a new channel using the “Create New Channel” button at the bottom of the window.
-Press ctrl+V to paste the treshold image in the new channel window.
Now that we have the dark parts black (which means “unselected” in a mask), we have to invert our channel to make them white, thus “selected”.
-Press ctrl+I to invert the channel (this shortcut doesn’t work on keyboards with different languages. Menu>Image>Adjustments>Invert is the “longcut” of this shortcut :)
-Press ctrl+D to deselect all
-Now go back to the Layers panel and delete the treshold layer.
-Duplicate the background layer again (ctrl+J)
-Go back to the Channels panel and ctrl+Left click on the new channel. This should create a selection.
-Press ctrl+2 or simply click on the RGB channel on top of the Channels panel list.
-Go back to the layers panel and select the duplicated layer.
-Click on the “Add Layer Mask” button, at the bottom of the Layers panel. (small circle in a rectangle)

If you click on the EYE icon next to the background layer, you will see that we only have dark parts of our image visible. You can modify your mask using brush tool, use black paint to mask out unwanted parts. Remember that you should click on the mask, before painting (I always always always forget it LOL)

Now use noise reduction on that layer. Then re-duplicate the background layer, invert the channels mask and apply it on the new duplicated layer to have a “highlights” layer. Use your noise reduction on that layer too...

Please remember that we cannot save every noisy photo. You better keep an eye on the exposure, because even you are on a low ISO value like 100-200, you can get noise just because you pic is underexposed.

Here in this particular image of a spiral staircase, I used local noise reduction. The marble stairs were brightly lid and there was no visible noise, while background and some parts of the ground have some noise issues. Since the image was already in BW, I just inverted it and made some basic modifications to create my noise reduction mask.

Please correct me if there are any mistakes in this artictle. I'll be happy to learn from you...

Here is a nice "noisy" picture :)) (added post-process noise)

Cheers :)

Comments (37)

Posted by Parkinsonsniper on December 04, 2013
Thank you Melih :) I just saw your comment, sorry...
Posted by Mturhanlar on March 24, 2013
very useful article thank you very much !! wish you many sales
Posted by Parkinsonsniper on October 01, 2012
Afagundes, I think you mean raw process noise reduction...and yes I agree with you, combining 2 versions with the lightness mask is a good idea.

Sorry for my late reply, I was in vacation for 2 weeks :) and thank you for your contribution. I appreciate it.
Posted by Afagundes on September 19, 2012
Great article Parkisonsniper, I would just add another possibility, you can process two versions of the image, one using the noise reduction very little the other highly "denoised", than use your technique to mask the shadows on the denoised version leaving the lights with the less denoised more detailed image.
I think the denoising algorithms are better during the processing than later.
Posted by Vcarmstrong on September 19, 2012
Very informative ... thank you. :)
Posted by Parkinsonsniper on June 04, 2012
Thanks for your comment CncPhotographylee.
Posted by Cncphotographylee on June 04, 2012
Thank you for the advice ... will try this next time
Posted by Parkinsonsniper on June 02, 2012
As you took the subject out of the borders of photography, I think one of the most unknown and dangerous pollution is light pollution. I love city lights but I don't think birds and some animals agrees with us. That might be counted as some kind of noise too...
Posted by Alishaday on June 02, 2012
Article contain so good information in it. Noise is unwanted sound and is among the most pervasive pollutants today. Noise from road traffic, jet planes, jet skis, garbage trucks, construction equipment, manufacturing processes, lawn mowers, leaf blowers, and boom boxes, to name a few, are among the unwanted sounds that are routinely broadcast into the air.

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Posted by Parkinsonsniper on June 01, 2012
Thanks for the comment, feel free to contact me if you have any problems.
Posted by Lejoch on May 31, 2012
Thanks for sharing, I'll try!
Posted by Parkinsonsniper on May 30, 2012
Thanks, please do not hesitate to contact if you have any problems :)
Posted by Effavale on May 30, 2012
very interesting! I will try to do it. Thank you!
Posted by Parkinsonsniper on May 24, 2012
Thanks :) I'm glad you liked it...
Posted by Artistforearth on May 23, 2012
I appreciate the details - thanks
Posted by Marugod83 on May 21, 2012
thx for sharing. I will try it out
Posted by Parkinsonsniper on May 21, 2012
Laqhill, I'm glad that you enjoyed it. I'm trying to create a serie of tutorial blogs with step by step instructions :)
Posted by Laqhill on May 21, 2012
I liked the part about WHAT noise is and how we end up with it. It was very informative. Thank you.
Posted by Parkinsonsniper on May 21, 2012
Your welcome :) please feel free to inform me about other subjects that you think people needs tutorials. My next is going to be "high-end sharpening" or maybe "split frequency cloning"...I don't know! :) if you will repeat it enough, you will make it as easy as a reflex :)
Posted by Rosedarc on May 21, 2012
That's great, thanks a lot for this nice tutorial Parkinsonsiper! I've got it now, the only thing is I'm not too sure how much to de-noise without geting into the "too many filters applied". Anyway I'm giving it a try. The hard thing now will be to memorize each step! Although I understand the process I still can't remember it very well. Your tutorial is in my useful box, though, so I can always check it. Hope you get a free credit for this, it's well deserved :-)
Posted by Parkinsonsniper on May 21, 2012
Janceluch, what you wrote is the perfect proof of "In Photoshop there are many ways to achieve a particular goal" :) thanks for your input...using "color range - shadows" will select almost the same area with threshold #80 :) what a nice coincidence :)) thanks again...you added a bonus shortcut to my blog :)

Rosedarc, what I understand is; you managed the first part, but you are stuck in the second (highlights) part. You should just re-do what you did for darks. The only difference is you are going to invert the channel. I think I shouldn't keep it short and write it all over for the darks too.

Try this...

- Duplicate the background layer again
- Go to channels panel and invert the channel mask, which you created for the dark parts
- Apple + left click on it (select the channel)
- Press Apple+2 or simply click on the RGB channel on top of the Channels panel list.
- Go back to the layers panel and select the duplicated layer.
- Click on the “Add Layer Mask” button, at the...(More)
Posted by Janceluch on May 21, 2012
Nice tutorial Parkinsonsniper.
For those, who got lost in the process, here is a logic framework (you can achieve results by many different ways - use the ones you are familiar with):
Have two duplicate image layers, denoise the top one and use mask to mask away the brighter parts of denoised layer.
The result is the image with denoised dark parts and untouched bright parts.
(tip: to select the shadows for layer mask you can simply use Selection>Color Range> and pick "shadows" from preset choices in dropdown menu, click ok, than feather the selection by 2-4 pixels and create mask out of selection... ) but the Parkinsonsniper's guide allows nice fine tuning and full control in deciding which tones to include in denoising and which tones don't need it... nice!
Posted by Rosedarc on May 21, 2012
Ok, I think I've got it until Then re-duplicate the background layer, invert the channels mask and apply it on the new duplicated layer to have a “highlights” layer. Use your noise reduction on that layer too...
What is it I"m meant to do here?
Posted by Rosedarc on May 20, 2012
Thanks Parkinsonsniper. I manage pretty well until the actual noise reduction part... I"ve got a photo that just needs what you're teaching but I just can't seem to be doing it right! Always quite tricky following instructions without actually seeing it done!
Posted by Parkinsonsniper on May 20, 2012
Hi Rozenn, thanks for your interest :) I forget to mention in the tutorial. it is written in PC language, so you should use Apple + left click on the layer thumbnail. this will create the selection you need. I hope it is going to be useful for you and add something to your photography :)
Posted by Rosedarc on May 20, 2012
I'm very interested in your method. I've been trying it out but I don't quite understand the step
-Go back to the Channels panel and ctrl+Left click on the new channel. This should create a selection.
Nothing happens when I do ctrl + left click (I've got a mac). Can you explain? Thanks!
Posted by Onime on May 19, 2012
great article :)
Posted by Mudplucker on May 19, 2012
I tried to translate this to GIMP language and got lost. Any way you could film a tutorial & post to youtube and give us a link ??? If so, thanks :)
Posted by Sobek85 on May 19, 2012
good information
Posted by Scottysally2 on May 19, 2012
Thank you for sharing, very helpful. :)

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Photo credits: Parkinsonsniper.

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