Tuesday, September 13, 2011

Image Averaging - increase detail and remove noise

Last night I was researching on ways or techniques to shoot hand held on low light. I found two different articles with different methods or approach regarding this topic. I really wouldn't consider these as techniques but more on post processing. The first method was stacking under exposed photos and adding these photos to arrive at a proper exposed photo. The next method is taking several photos at high iso and averaging the photos to remove the noise and increase detail. I decided to test both method and found the image averaging to have better results. 

The image averaging methods allows you to shoot at the highest iso on your camera still capture details on your photo with minimal noise. The first step you will need to do is to shoot at a high iso to prevent blur on your pictures and to shoot on burst mode. It is important that you take at least 4 or more photos in order to have better image quality.

Once you are done you open all your images on Photoshop and stack them. For those who aren't familiar with Photoshop you can find the image stack command on (File>Scripts>Load File into stack). Check attempt to automatically align source images.

Once the images are loaded you adjust the opacity or fill of each layer on your stack. The first layer or the most bottom layer will be 100% fill/opacity. The next layer will be 100/(what number of layer) so for the second layer it would be 100/2 which is equivalent to 50%  fill/opacity. Third will be 100/3 which is 33% and so on and so forth.

Single Image ISO 3200
9 images averaged at ISO 3200

Cropped single image at ISO 3200
Cropped 9 images averaged at ISO 3200

 After testing this method on a couple of subjects I realized that this technique has its limit. This method can't be applied on moving subjects at low light. It won't be useful if you can't reach a shutter speed that can be shot hand held on a high iso since the shots will still be blurred.

This method can be useful on taking photos of inanimate objects on low light conditions. I will most probably use this on taking food shots on the restaurants that I visit for my food blog since most of the restaurant tend to have inadequate lighting. You can also use this on taking low light city shots or interior shots, I'm sure though if you can still be able to capture light streaks with this method.

This won't replace a good old tripod but it surely will help you on those instances where you found an interesting subject on low light situation but forgot to bring your tripod.

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