Grain, grain, go away!
Low light, high-ISO photography has never been easier and image quality has never been better than it is today. But there’s still digital noise. Let’s take a look at Nik Dfine, a popular noise-reduction plug-in.
My new DSLR is amazing! I can dial the ISO to 2000 in low light and easily get usable results. Even at ISO 3200 the graininess is acceptable in an 8x10-inch print when reduced to black-and-white. The noise in those images reminds me of Ilford HP-5, one of my favorite films, which I used to push to ISO 800 and thought that was as good as it would ever get. But what if I wanted to push the envelope and shoot at really high ISOs in color? The RAW images do get fairly noisy at 3200 and above. What would happen when I applied noise reduction?
To find out, I got a hold of Nik Dfine 2.0, a Photoshop plug-in that many pro photographers use to reduce the grain in their photos. I then took some pictures of Niko The Dog at multiple ISOs, and applied Dfine to them. Here’s what I got.
Meet Niko. He’s my dog. He’s resting on his favorite spot on the couch here, and he is in desperate need of grooming. Since his eyes are pretty much obscured by his hair, I focused on his nose. This picture shows a scene with a high dynamic range that is a bit too much for my camera; the first thing I noticed at the higher speeds is that the highlights got blown out. I shot this at ISO 2000; If I underexposed a stop, I got better highlight detail but the shadows blocked up. I wanted to see some detail in his black nose. So, taking a page out of Bryan Peterson’s playbook, I corrected the exposure in my RAW editor, then open up the shadows in Photoshop. Now I had a slightly better dynamic range, but more grain, especially in the shadows. Enter Nik Dfine 2.0…
Dfine’s interface (above) is simple enough: Once you’ve installed Nik Dfine, simply open full-blown Photoshop (or, in this case, Photoshop Elements 9) and select Filters > Dfine and this screen pops up over the regular Photoshop workspace. As the image is processing, the software automatically selects key areas of the image (the little squares that might need more intense application of noise reduction.
The Loupe screen in the lower right corner provides a 100% enlargement showing with/without Dfine so you can gauge the effectiveness of the noise reduction. You can move around the image within the Loupe screen to check local areas.
No noise reduction: This is the original image RAW output at ISO 2000, “pushed” one stop. There is a good amount of noise and multiple colors in the shadows.
Processed through Dfine’s automatic setting, the grain is substantially reduced, but the image is softer overall, and the colors introduced by the grain in the shadow darker areas remain. So, Niko is a bit fuzzier than usual.
As a final step, I applied Unsharp Mask to the image to reduce the overall softness that was introduced through noise reduction. A bit of grain returns along with the more defined edges, but it’s not as pronounced as it was before applying Dfine.
Tri-X? HP-5? Just for fun, I also made a black and white version the original RAW image. At ISO 2000, it looks grainy like a classic ISO 400 film!
I shot the same image at ISO 6400, my camera’s maximum ISO, in RAW. Even at screen resolution you can see noise artifacts, especially in the shadow areas in the upper right corner. Dynamic range? Not so great, and not something Dfine could fix, but let’s see what we can salvage here.
At 100% blowup, noise is very visible and detail is lost due to the noise and lower dynamic range. This might be OK for a snapshot, but for a mid-range APS camera and a top prime lens, not so cool. Can we do anything about this with Dfine?
Nik Dfine effectively reduced the digital noise in this picture. While it still is not a technically ideal shot—Dfine couldn't bring back data lost to lower dynamic range—this illustrates what Dfine is capable of when you push the envelope.
While these two examples show what Dfine can do at high-ISOs, it is very effective at more commonly used speeds. At ISO 200-800, it virtually removes all grain and at 1000-1600 knocks it down to the point where it’s barely noticeable even at 100% blow-ups. For an 11x14-inch print viewed at a normal distance, it takes marginal shots and makes them acceptable.
As with any noise reduction software, there is always the issue of sharpness and detail loss as well. I recommend creating an Unsharp Mask layer and adjusting the opaqueness until you have a balance of low grain and sharpness that meets your needs.
Dfine 2.0 has other features including selective noise reduction, specialized noise reduction for skintones, shadows only (very useful if you plan to open up shadows in post production) and other more selective areas. I found the auto setting, , to be very easy to use. It creates a Dfine layer, which you can apply fully or use the slider to allow some of the underlying image to show so it’s totally controllable. The only downside is that it took a while for the software to render my large, full-sized 18MP image files. A bit more RAM might have helped there.
Conclusion and recommendation
Nik Dfine 2.0 was easy to use in automatic settings and I found it to be an effective way to remove digital noise from images. It offers a host of manual options that give you more power to selectively apply noise reduction in local areas within an image, and gives you the flexibility to change things via layers. Processing was a bit slow on my slightly under-RAM’d iMac so be sure you put a good amount of computing muscle behind it to maximize its efficiency. For less than $70, it’s a great deal. It can save borderline images, and is an especially useful tool if you do a lot of high-ISO and low-light photography.