side of the histogram. In such case, the ETTR principle of maximizing exposure to the point where the raw histogram is aligned to its right edge, requires a seemingly counterintuitive negative exposure compensation. This may be explained with the ETTR principle: to make best use of the additional DR, available with wide-DR sensors, the extra DR is used to expand the shadows end of the recording range, without increasing the raw highlight headroom. If the resulting shadows are unable to be processed to acceptable noise or tonal range, one has simply encountered a situation that cannot be taken with a single shot, and consideration could be given to HDR (High Dynamic Range) techniques requiring multiple exposures. If the latter is infeasible due to scene or camera motion, one may revert to the technique of exposing to the important highlights (abbr. ETTIH), which is in fact just a slight generalization of ETTR. With ETTR, exposure is maximized up to the constraint of preserving all highlights at the right edge of the histogram (a constraint implied by the hard saturation of the digital sensor). With ETTIH, exposure is maximized a bit further; the constraint is relaxed so that only the highlights deemed important are preserved before the right edge of the histogram, and the highlights deemed unimportant may fall into the saturation zone of the sensor. Typical examples of unimportant highlights include the sun, other very bright light-sources, and sharp-edged specular highlights like chrome car bumpers in the sun; however, one should avoid blowing areas with smooth luminosity gradients, for instance the sky around the sun, because these likely lead to visible sensor saturation artefacts (banding). Many cameras have over-exposure "blinkies", showing the location of blown highlights which is not evident from the histogram. Some cameras also have under-exposure "blinkies" as an exposure aid. Mirror-less cameras often have "preview zebras", which is another aid for being aware of and correcting over-exposure. Raw processing software may feature "highlights reconstruction" algorithms (currently unavailable in-camera) which are able to partially mitigate the negative visual impact of digital hard saturation of the three color channels, thus extending the range of blow-able unimportant highlights slightly. In general, whether one is dealing with a high-DR scene or a low-DR scene, both the process and aim of ETTR are the same: exposure is adjusted (forgetting the meter) until only dispensable highlights are clipping, thereby resulting in an image with