Monday, October 5, 2015

Nikon Camera Settings: ADL, Sharpening and Clarity

Nikon D7200 with ColorChecker Passport

Camera manufacturers sets their image defaults differently from each other. This leads to the general impression that one camera will have one particular "look" compared to another, or that one brand has better skin-tones than the competitor. While this can be the case, the truth is that much of a camera's default JPEG output can be tuned to one's taste with a quick dive into the menus. The following is with regards to Nikon cameras, but the principles apple to all digital cameras.

We'll be focusing on three specific optimizations: Active D-Lighting (dynamic range optimization), and from within the Picture Controls menu, sharpness and clarity. The reason why is that all three settings can be used to produce a crisper and punchier looking image, but at a cost of low-level image quality. The key is knowing how much to use and when to use it.

(Just as an aside, the use of the ColorChecker Passport is a bit of a camera-reviewer joke. These things have a proper use, but you almost always see them as part of ISO targets.)


Active D-Lighting


D-Lighting as applied after the picture is taking boosts shadows from dark to light. The main purpose is to make up for back-lit situations where flash is not possible (or was not chosen). Active D-Light (ADL) works at the time of image capture. Unlike regular D-Lighting, ADL will also adjust the exposure to protect highlights.... if the camera senses that the dynamic range of a scene is extreme enough to warrant it, the camera will reduce the exposure (either shorten the shutter speed or stop-down the aperture depending on the exposure mode) and then apply boosting to produce a balance between shadows, mid-tones and highlights.

For quality photography, ADL should be turned off. Any amount of shadow-lifting increases the perceived amount of noise and is better done in post-processing. As well, ADL in introduce colour shifts depending on how strong the settings is. The following was shot with a D7200 on center-weighted metering and at ISO 3200. Click on image for 100% crop view.

From D7200: ADL Settings

The most accurate exposure is with the ADL off setting. Even at the ADL-Normal setting, image noise is visibly accentuated, and the brighter colours are starting to wash out. At the ADL-High setting, image noise has produced a visibly course image, the colours are washed out and the blacks are boosted into grey. The take home message is that if the dynamic range of the scene is not excessive (having extremes of dark and bright), then the camera will do just fine without ADL.

Sharpness

Sharpness is first the first item that Nikon owners adjust in the Picture Control menu, as the default Nikon setting is "softer" than with other brands. Sharpening isn't a free ride. You can get something out of it, but you won't be paying nothing. Nikon tends to have a conservative mindset about this and other manipulations of the image data. Though you can get crisp looking images out of the camera, the enthusiast-level give you the most when the sharpening and contrast are turned down in order to preserve data quality for post processing.

This is all well and good, but the documentation is what you would call technically correct: it gives you the correct information about the technology, but it doesn't give you a sense on how to use it. To that end, the following is an example of a a scene shot on a D7100 at ISO 3200. This is more or less where noise becomes intrusive enough to affect subjective image quality. In this situation, the would be balancing the benefit of increasing the sharpening setting against the intrusion of more prominent sharpening artifacts.

Click on the sample for 100% crops from the out-of-camera JPEG's. Sharpening levels are denoted below each sample.

From Nikon D7100: Sharpness Settings

For reference, +3 is the the default factory setting. The lettering in the soda bottles is the most crisp at +9, but the overall image quality suffers because the sharpening also accentuates the noise. Conversely, sharpening set at the lowest setting has the smoothest looking noise, but also the softest detail. Many people settle on +5 to +6 as their preferred sharpening setting for out-of-camera JPEGs, as it gives a good balance between sharpness and artifacts. For comparison, this is what the sharpness slider looks like on the D7200. (Click on image for 100% crop view)

From Nikon D7200: Sharpness Settings

Even if the camera is different or if the processor is a newer generation, the same principle applies; sharpening enhances edges at the expense of accentuating noise or coarsening the texture of the image.

Clarity


Clarity was added in the EXPEED 4 generation (D7200, D5500, etc.) to picture controls. It's ultimate goal is to increase subjective perceived contrast, primarily by boosting mid-tones relative to shadows and highlights. Clarity is essentially like looking at a foggy scene after the fog is removed. Clarity can have a dramatic effect on the picture output if the extreme settings are used. The default setting is +1.

From D7200: Clarity Settings

Looking at the extremes in the above examples, -5 is like looking at the scene through a layer of fog. The opposite setting a +5 looks very "clear" but the alterations to the tone curve have also reduced colour accuracy. Used in moderate does, a slight bump in clarity combined with a bump in sharpness can produce fairly striking results.

Note that if you have ADL and clarity turn up, they are in a small way, working at cross purposes. ADL will boost shadows and turn black tones to grey, whereas clarity will turn lighter greys towards black.





With thanks to Broadway Camera

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