Should you turn in-camera sharpening off when processing NEFs?
By Jason Odell |
February 21, 2009 9:19 AM
There seems to be a bit of contention out there as to whether NEF shooters should disable in-camera sharpening in Capture NX when they process their images. My philosophy has always been "yes", with the core idea being that while in-camera sharpening (especially with Picture Control) is pretty good, you can get even better results when you do your own form of "Capture Sharpening" with the USM tool.
Before I go any further, let me point out that if you do not use Capture NX to process your NEF files, this issue is moot. Only Capture NX can read and apply the as-shot sharpening settings to your images; any other RAW processor will apply its own default sharpening routine independent of what you had set in the camera.
Why in-camera sharpening is good, but not great
In cameras that do not offer Nikon's Picture Control options (pretty much all of them up until the D300/D3/D700 and D90), in-camera sharpening offered limited control and behaved like USM with a threshold of 0. That meant that every pixel had sharpening applied to it as long as the difference in tonality was greater than zero levels (pretty much everything). This has the effect of sharpening noise in your image, too. Picture Control sharpening behaves slightly differently in that you have a wider range of settings (0-9), and it appears (to me at least) to use a slightly higher radius and lower intensity (amount) than its predecessor. The effect is that for sharpening settings below 5, you get a fairly sharp image with few artifacts. But just as before, the "threshold" value appears to be set at zero. Again, that means you are applying sharpening to every pixel, including noise.
The threshold setting in USM offers better control over sharpening noise
With the USM tool, as I described in my previous post
, offers photographers three parameters of control, including Threshold. This setting is the key to high quality sharpening. By adjusting the threshold level to a value other than zero, you are restricting the number of pixels that get sharpened. In backgrounds, for example, there may be slight variations in an otherwise monochromatic sky. Using threshold control prevents these variations from being sharpened. Threshold also helps prevent the sharpening of luminance noise-- the bane of digital photographers.
Real-world example of USM vs. In-Camera Sharpening
Here's an image I recently captured in Florida; a tri-colored heron. You can click on it to see a larger version. This image is fairly sharp, considering I shot it hand-held with the 18-200 VR Nikkor lens.
When I processed this image in Capture NX 2, I chose the "Vivid" preset for Picture Control, which uses a sharpening setting of 4. This is about the strongest setting I would advise for JPEG shooters to get crisp images while avoiding sharpening artifacts.
Looking at a 1:1 (100%) crop of this image, you can see some luminance noise in the background:
100% Crop, in-camera sharpening set to 4.
Then I took the NEF and processed it with USM after turning in-camera sharpening OFF (set to 0). I tried to match the settings in the original image as closely as possible, but I used the threshold control in the USM tool. My settings for USM ended up at 30/9/5 (different than my default D300 settings, but I was trying to match the in-camera sharpening). Here is the result, cropped identically to the first image at 100% view:
Image sharpened with in-camera sharpening OFF, USM 30/9/5.
What you can see from this view is that the luminance noise in the background is significantly reduced as compared to the original image. No noise reduction was applied to either image, the only difference was the sharpening routine.
USM sharpening can produce cleaner results than in-camera sharpening for NEF shooters processing their images in Capture NX. The threshold slider is paramount in helping to reduce the appearance of luminance noise in your images. Remember, if you turn in-camera sharpening off, you must apply some form of sharpening (USM or otherwise) to get a sharp image.