Many new photographers use P mode or auto mode in shooting. In some cases, especially low light condition, a common question pops out: Why are my photos grainy?
Grainy images make photographers frustrating. Grain lowers sharpness and contrast of an image. Knowing how to control grain, you know how to create crispy sharp image too.
Why Photos are Grainy
There are many reasons behind a grainy photograph. To help you understand better why your images are grainy, you should first know what grain is.
Grain is actually noise. When there is electric signals pass through your camera sensor, noise is always there. The fact is, sometimes, some setting creates more noise while some setting can eliminate most of the noise.
In film ages, ISO800 is already called high ISO film. However, nowadays, we use even higher ISO to shoot, like ISO6400.
The higher ISO you use, stronger electronic signal will pass through your camera sensor, therefore, more noise will be generated.
To minimize grain that is generated by ISO setting, you should use the lowest possible ISO.
When you lower your ISO setting, this is going to lengthen your exposure time, which is another grain producer.
Frankly, only super long exposure time will generate noticeable grain. The type of grain generated by exposure time is different from ISO. This is called hot pixels.
Your camera sensor produce heat when exposing. The heat will create some error pixels in your images and those errors are hot pixels.
Hot pixels normally come in a solid red, blue or green color. They also appear in the same location under same exposure setting and environment.
Pushing too much in post process
Another source of noise is post processing. You may not know, every step you make in Lightroom or Photoshop will generate some noise.
Some people may teach you to shoot 1 or 0.5 stops dimmer than normal so as to prevent white clipping in highlight area. However, you are scarfing image quality by adding more noise to your images.
Bumping up exposure and opening shadow create most noise in every post process workflow. You can see these two process as pushing your ISO in post.
It is not too difficult to shoot grain free images once you understand the cause of grain, or noise.
Use Lower ISO
As we discuss just now, higher ISO will result in more noise. To keep minimum grain level, you should use the lowest possible ISO setting.
On the other hand, in some cases, lowering ISO setting will require a longer shutter speed. If the shutter speed is too long, you may end up with burry images. To solve this, you may consider to use a tripod.
Use Long Exposure Noise Reduction
If you are using very slow shutter speed, say 20 or 30 seconds, then long exposure noise reduction is a good function to help you with hot pixels.
When you turn on this function, you camera are going to take a second shot with the same setting but with a close shutter.
This dark frame will help you to subtract hot pixels generated during long exposure.
Use Larger Aperture
If your aim is not doing super long exposure and want to use a lower ISO, another choice is to use a larger aperture.
However, there are always compensation. If you choose to use a larger aperture in exchange with lower ISO, you will create images with shallower depth of field. Also, as large aperture lens is normally more expensive, you need a more expensive lens.
Try Blending Exposure Instead of Pushing in Post Process
Another method to reduce noise level is to use digital blending technique to help with.
Many photographers think this is too much work and some may think this is not ethical. The fact is, blending two exposure is the best way to create noise free images.
For example, if I use a single exposure raw image and open up the shadow part of this photo. The shadow area become extremely grainy.
The solution for me is to capture the exact same photo with a longer exposure. The whole photo will become brighter including the shadow area. And then I blend the brighter shadow into the original file instead of opening it up.
Use Noise Reduction in Post Processing
Noise reduction is an important step in post. I believe you have try your best to keep grain in a very low level, and you still asking why are my photos grainy. If this sound familiar, you may need to practise noise reduction skill in post.
There are many software which can help you to get the job done, including Lightroom, Photoshop and lots of plug-in like Topaz DeNoise (Read my review here) and Nik Define.
I strong recommend these two noise reduction plug-in because it do a much better job than Photoshop function. They also support layer masking so that you can apply the effect in specific area only.
Most photographers do not like grain, however it just appear and become a big topic in digital age. By learning these different skills, I hope you are able to capture photos with less noise. If you like this post, please share with your friends and fellows.