11/13/2012

Dealing with Noise

As you know, in less than desirable lighting conditions, we have to compensate for the lack of light in the scene by bumping up our ISO setting.  This is great in theory, but the problem with using these high ISO's numbers is the noise that it produces in your images - (noise looks like grain or speckles through your image) The higher your ISO, the more noise will appear.  Unfortunately, entry level cameras do not handle noise particularly well,  and is the probably the most cited reason for wanting to upgrade cameras (and in fact is one of the reasons I want to upgrade from my trusty Canon Rebel) This is because entry or mid range cameras are usually cropped frames, which means they have a smaller sensor size. Whilst using high ISO's with a cropped frame is never going to give you beautifully noise free images, there are a couple of things you can do to at least minimise the noise and get the most out of your camera. And here's how.....




- The easiest way to combat noise is to let more light into your camera another way so you don't have to ramp up the ISO.  One way is to use a wide aperture to maximise the amount of light you are letting in. If you are working with the kit lens that came with your camera the lowest you will be able to go is probably 3.6 which won't help you very much in low light. Try to get a lens with a wider aperture like 1.8 - you'll be able to let a lot more light into your camera that way. 

- Get as much light on the scene as you can in other ways - open the windows, shutters, reposition your subject, use an external flash - whatever increases the light where you are!  Light is the number one way to combat noise. I tend to take a lot of my photos outdoors for this very reason. 

- Most entry and mid range cameras will produce decent images with up to ISO400.  If you possibly can, try to use an ISO number under this and keep it as low as you can. 

- However, do not be afraid to bump up your ISO if you need to - you'll just be swapping problems as your shutter speed will need to be slower to compensate and that will lead to blurry images - even if it is just enough to lose the clarity.   So, as low as you can without sacrificing shutter speed. You'll need at least 1/125 even if your kids are pretty still, but I would go a little higher than that - 1/125 should be the bare minimum for kids not the ideal! 

- Get your exposure right in camera.  Although editing software can do wonders with your photos, with noise it is much, much better to nail your exposure correctly in the shot than fixing later. Noise in definitely worse in the darker areas of your image so for that reason, underexposed images will show more noise - again aim to get it right in camera and even over-expose slightly to keep noise to a minimum.  

- For low light scenes, try to shoot in RAW. RAW editing programs give you more options for dealing with noise, as long as your exposure was pretty close in camera. 

- If you do have noise in your photos, there are applications and programs out there that can help remove it.  The problem is that these noise reduction programs can be quite destructive to your image as you will start to lose image detail. Use sparingly - it's better to have an image with some noise that one that is soft and lacking in detail - you'll just have to visually see how far you can push it before you lose detail. 

- If you do get images affected by noise, they will look a lot better if you only use them for smaller prints - the grain that will not be noticeable on a 6x4 print can look horrific on a large one.  

- This is probably just a personal preference, but if I have a lot of noise in an image I usually find myself converting it to black and white. I just think that some grain can actually add to a b&w image. Not always, but sometimes.

- High ISO images will just not look as sharp as low ISO images (especially on a cropped sensor camera) There is not much you can do about that apart from try to keep your ISO down in the first place.

- If you do a lot of low light or indoor photography, consider upgrading to a full-frame camera (in the Canon range this would be the 6D , 5D Mark II and 5D Mark III )  They have a larger sensor which handles noise better, but unfortunately have a higher price tag to match!

As I can never post without images (I think it's definitely better to show and tell!) Here are some examples of what I have been talking about here.  This first image is taken at ISO6400 and the image is a bit underexposed. You can clearly see the noise in this image (well, as clear as you can online!)



As this image was underexposed, here is it corrected in Photoshop.  The noise is even more noticeable in this image I would say.



Next, is the image shot one stop over (showing as being over-exposed) in camera.  There is still noise (I'm at 6400 remember!) but it is much less visible than in the above picture.



Last one,  this is my moving the apple under a light source (in this case a lamp as it was dark outside when I conducted this little experiment!)  and you can see that the image has less noise than the rest.


Hardly scientific but hopefully it demonstrates the point about getting exposure right in camera. 

My main way of dealing with the noise I get on my Rebel is to shoot outdoors as much as possible, or near the windows when indoors. If I have to ramp up my ISO, I overexpose slightly to try to minimise the noise in the shadows.  I hope this helps some of you struggling with the same problems as I am!

Other Posts You Might Like: 

Metering Part 3:  Exposure Compensation 
Quick Tutorial on Camera Exposure
How to Shoot in Manual Mode 


4 comments:

Jan said...

interesting that the overexposed did better than the underexposed.

Audrey said...

I thought so to when I first heard about it, gave it a try, and it does work out a bit better! (Still want a full frame though...)

Ava said...

You always seem to post the right stuff when I need it most. Thank you for this. I'm too, trying to work on upgrading my camera... but in the meantime I'm going to try and overexpose when I have to.... and take more control of my ISO.

Thank you!

Audrey said...

Thanks Ava, I'm glad my timing is good! Grain in photos must be one of my biggest complaints but these tips do help work around it a bit!

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