Right part – shadows in shot #1861 after conversion in ACR with +1.67 EV exposure correctionĪ tone curve applied when rendering a JPEG takes care of matching of whatever the middle grey is in RAW to the standard 18% grey in JPEG. Left part – shadows in shot #1866 after conversion in ACR. Lets look at the shots of the scene we have already used in the article “Why Bother Shooting RAW if Culling JPEGs”.įigure 5. In fact it is not cheating, because in most cases the ISO speed is defined for the processed output (JPEG) and not for RAW. This is what often causes the rumors that camera makers cheat with ISO. To provide extra room for the highlights, camera makers tend to calibrate the exposure so that it shifts middle grey down to 13% (instead of 18%), and often even lower than that. Why is this so? Modern cameras have relatively low noise, and customers often complain that the highlights in their exposures are blown out. While placing important highlights at the top, let's take advantage of one very well-known and stable feature of the camera: cameras are calibrated in such a way as to provide the exposure that will result in the rendering of whatever was under the spotmeter as "middle grey".įor a JPEG middle grey is defined as 118 RGB in sRGB color space, which corresponds to the proverbial 18% grey (and L* = 50 in Lab color model, too).įor RAW, middle grey is not fixed by common standards, and camera makers have some freedom while placing it. Reliability and repeatability, however, come with manual metering in the spotmeter mode. You can use RawDigger or FastRawViewer to see how close you are be prepared for more misses than hits, in part because the complex metering modes are optimized for JPEGs rather than for RAW. One can try different metering modes with the camera, with mixed results when it comes to optimal exposure for RAW. Unfortunately the metering systems of our cameras are not designed to provide the proper placement of the highlights right out of the box (this is partially because to do so, the camera's AI needs to make a guess as to what a photographer considers to be "important highlights", and if it guesses wrongly, it may arrive at an unacceptable exposure). By the way, if one tries to set exposure low to keep from clipping all the light sources and specular highlights, he is, most probably, also wasting a couple of stops of dynamic range. That is, if we try to expose a pixel hotter than its capacity allows, everything that is above the capacity will pour out, causing blown-out highlights. In digital photography we know this as highlight clipping. In a sense, one can say that dynamic range characterizes the depth, and starts from the top, while the bottom is sort of fuzzy because of individual tolerance to noise, viewing conditions, size of the output, etc.īack to our bucket analogy – if one tries to pour, say, 2.5 gallons in it, an overflow happens, and half a gallon will end up on the floor. This immediately means that in order to use the dynamic range of the camera to its fullest and simultaneously to have as little shadow noise as possible, the whitest whites where you want to keep some texture details need to be exposed so that they are just below clipping. If your whitest white is not exposed to the maximum, the top portion of the dynamic range is not being used. If you do not fill it up to the top, some volume is wasted. Imagine a bucket having a volume of 2 gallons. The thing with a camera's dynamic range is that those exciting numbers become valid only when the signal reaches the maximum that is, the exposure is the hottest possible for the given camera at a given ISO. Zoom into shot #4152 that was exposed according to the in-camera exposure meter.Īpplied Shadow Boost and +1.67 EV exposure correctionĪs we can see, shot #4152 exhibits significant noise everywhere below midtone.
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