Note from Patty and Bill - In order to illustrate this article, we needed to put in a number of images.  If you are connecting to the web via modem, the images may take a few minutes.

Neat Image – Get the noise out of your digital images.

by Patty Hankins and Bill Lawrence

Here at Hankins-Lawrence Images, all of our photos become digital images at some point. Either they start as images we take with our digital cameras or they start as photos taken using a film camera, and then are scanned to capture the image digitally. In either case, we occasionally have to deal with noise in the images.

 What is noise?  It is the speckles in an image that distort what otherwise would be smooth features in a photograph.  Take a close look at a portion of a photograph which has a clear blue sky – this tends to be a good place to look, particularly for digital images.  Significant noise will show itself as small variations in the color and brightness (if you are looking at a black-and-white image, then the variations will only be in brightness).  See below for examples of noise in images.

 Noise occurs in both digital and film photography. In film photography, the noise is due to the film grain, or the size of the crystals used in the emulsion to generate the image. While smaller crystals give a more even tone, they are less sensitive to light and thus have a lower ISO value.  In digital photographs, noise is due to variations in the readings given by individual pixels in the camera sensor.  Scanning film gives the opportunity for both sources of noise to be present.  For both digital and film photography, using lower ISO tends to reduce the noise present in an image.

 Sometime noise can be desirable in an image. This is why some films that are considered to have large grain are still popular with photographers.  Many times, however, noise can detract from the overall image. With some consumer-grade digital cameras, images taken at ISO equivalents above 100 are noisy enough to distract the viewer from the image.  On our Canon D60, we are usually hesitant to go above ISO 400 due to the noise.   For these times, a program called Neat Image (www.neatimage.com) can be a life-saver.

 Neat Image is a stand-alone program that is designed to filter out noise in digital images. It lets us extend the range of useful ISOs on our digital cameras by being able to accurately reduce noise without sacrificing image quality.  Neat Image also works well for scanned film.  We’ve  found it to be especially valuable when we scan underwater photos, where the blue water frequently has a large amount of noise.

Neat Image is not very difficult to use.  First you tell the program what is noise – either by selecting areas without any detail (and thus only noise) in the image, or by specifying a noise profile based upon the specific camera and ISO level.  While the site has a selection of profiles on it, it is not difficult to make your own profile by taking a photo of a featureless sky or a 18% gray card.  Once the noise profile (either image-specific or a saved profile for the imaging device) is specified, you can see a preview of the filtered image, and tweak the amount of filtration and sharpening until you get the best image.  Then, it is simply a matter of clicking on the “Apply filter” button, and waiting for the filtered image.

 The Neat Image filter is slow.   On a P4 2.4 GHz machine running Windows XP, it takes about 90 seconds to filter a 6 mega-pixel image.  The program gets around this issue to some extent by having a nice batch function.  As long as all your images are going to be filtered with the same noise profile, then you can set the program to do a number of images automatically while you are doing something else (like taking more photographs or having a cup of coffee).

 A downloadable demo of the program is available on the Neat Image website.  This demo has limited functions, but it is more than enough to see the benefits of the program.  We have the “Pro” version, which can handle 48-bit images – this version is only $59.90.  In late May, 2003, Neat Image released the “Pro+” version, which includes the “Pro” stand-alone version plus a Photoshop compatible plug-in version, and sells for $74.90. We’ll be updating to the “Pro+” version soon, since having to flatten a layered Photoshop image, save the file (we use 16-bit TIFF files) and then filter in a separate program gets somewhat annoying. The “Pro+” version will eliminate some of these steps. We’ll include an update evaluating the plug-in in a future issue of the newsletter.

 If you’d like to see what Neat Image can do without downloading the demo – scroll down for some samples. This program is not for everyone, but if you have digital images which you find too noisy, we highly recommend this program.  Stop by their site and download the demo to try on one of your images – it is worth the time to check it out!

*** Annotated Samples of Noisy Images and Neat Image ***

The photo of the great blue heron below was taken in Vancouver, BC.  The photo was taken with a 28-135 mm zoom sometime around sunrise on a very overcast day (so overcast that we couldn't figure out when sunrise actually was).  The photo was taken with the camera handheld, so in order to get a fast enough shutter speed, it was taken with a Canon D60 digital camera set to ISO 1000 (the highest ISO you can set on this camera).  The image on the left is essentially straight out of the camera, the image on the right has been filtered with Neat Image (I also applied a little color balance to warm the tone, and sharpened it slightly).

Canon D60 - ISO 1000, unfiltered

Filtered with Neat Image (Copyright © 2003, William Lawrence)

Take a look in the water around the head of the heron, in the unfiltered version, you can see small specks of blue and red in the water, which are not nearly as visible in the filtered version on the right.  This is somewhat difficult to see on a web version, so the images below show an actual-pixel magnification taken from the images above.

Unfiltered image, zoomed to 100% size.

Filtered image.

In the magnified image the noise is readily apparent.  In the image on the right, the noise is much reduced, but the detail in the heron's head is preserved.

In order to do the filtering, you can either highlight areas in the photo that have no detail in them (e.g. the water around the heron's head above), or take a separate photo using the same settings with large amounts of featureless areas, create a device noise profile, and apply to other photos.  The former method was used on this image, since there are large areas in the photo without detail.  We've used the latter approach for "busy" photos in which there aren't enough areas without detail in order to create a filter.  Once you have a filter set up, you can do a folder full of photos (done with the same camera at the same ISO setting) in the batch processing mode.

Sometimes noise is desirable.  The image below was taken on the same morning as the heron photo above.  This image was taken at ISO 400, but there is still visible noise in the featureless areas of water.  The area was converted to a monochrome image, and then to a quadtone using Michael Reichmann's (www.luminous-landscape.com) formula for creating selenium toned images.

Stanley Park Waterfront, Vancouver, BC.  Canon D60, ISO 400 (unfiltered) (Copyright © 2003, William Lawrence)

If you look closely at the water in the above image, you can see noticeable noise, even at the reduced web-sized version of this photo.  However, in this image, we found the noise adds to the overall image.  While we could have filtered this image, from an aesthetic standpoint, we would prefer not to.  Likewise, digital photos taken at low ISO settings in bright sunlight  most likely will not need to be filtered through Neat Image since these are optimal conditions for low-noise images.

For land photography, if we use digital cameras, then we tend to use either a Canon D30 or D60.  At ISO 400 or lower, these cameras have very little noise (although even at ISO 400, filtering can be helpful on selected photos).  For underwater, we use either a film camera, or a Canon G2 digital camera.  Even at ISO 100, there is a notable level of noise (though no worse than scanned film).  The images below show a filtered image, with close-ups before and after filtration.

3 Queen Angels, French Reef, Key Largo, FL (Copyright © 2002, William Lawrence)

Lower right Angel, pre-filtration

After filtration

There is a slight loss of detail in the scales, but it is barely noticeable, and there is a remarkable reduction in noise.  Neat Image also includes a number of settings which enable reduction in  the amount of filtration if the loss of detail is too large.

We highly recommend Neat Image.  This program allows us to take photos at higher ISO settings than we would normally use, with excellent results.  It also reduces the almost inevitable noise in images created from scanned film.

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