![]() Creating an "input profile" to accurately reproduce the colors.RawTherapee looks for information regarding how to interpret the image data (the black and white levels, the color matrix, and some other details, but not the input profile) in three places: You will have to shoot the photos, but you do not heave to understand or carry out the measurement - we can do that for you.In the dcraw code which is embedded inside RawTherapee.In a text file on your system which is installed with RawTherapee called camconst.json.Information is gathered from all three places, and values from camconst.json are prioritized above those from other sources. There is an exception for the input color matrix, in that if the raw file is in the DNG format and the Software Exif tag ( 0x0131) does not begin with the string Adobe DNG Converter and the file does contain a ColorMatrix2 tag, then the value from this tag is prioritized. If you made any changes to camconst.json while RawTherapee was running, restart it for the changes to take effect. What are black and white levels? A sensor is made of millions of tiny photo-sensitive elements called photosites or sensels. The bulk of the raw file consists of these recorded measurements.Įach one measures the intensity of the light which falls upon it, and records that intensity as a number - the more light, the higher the number. Each photosite has a level below which it cannot sense any light - there might be some light falling upon it, but this light is too weak to register a signal. This is called the black level, and it is not always 0. There is also a level beyond which the photosite will not register a change in light intensity even if the light does keep getting brighter - this is the white level. A photosite which cannot record any brighter light is said to be fully saturated, and in post-processing this state is called clipping. The white levels are measured based on completely overexposed photos called "white frames". ![]() Some camera models use the same white and black levels regardless of other settings, while for other models these levels depend on other factors, such as ISO sensitivity. We need photos from across the whole range of ISO values to determine this. ![]() Some cameras have built-in noise reduction, often called LENR - Long Exposure Noise Reduction. It could affect the white and black levels. If you enable it, typically it only kicks-in when the exposure time is over 1s. The steps explained further on will explain when to turn it on and off. To avoid this being a problem, set the aperture to f/5.6 or higher unless instructed otherwise.įor more documentation detailing the required photos and instructions how to measure them, read the comments inside the camconst.json file: The white levels for some camera models change depending on the aperture, but generally this only happens for wide-open apertures. If your camera has several raw modes, use the full one, uncropped, lossless compression if possible.Įach photo must be completely overexposed all across the frame. As such, it does not matter what you shoot since everything will be white anyway, but its easiest to achieve this while pointing the camera at the sky or at a white light bulb. It does not matter whether the sky is sunny or overcast, but don't point it at the sun as you might damage the sensor. ![]() It does not matter what lens you use, but it will be easier to make the whole image overexposed if you do not use a wide angle lens. We have broken down the image requirements into three sets, where each subsequent set would improve the quality of support, but would also require more effort from you and from us. In most cases, you only need to photograph the first two sets. All sets involve photographing completely overexposed white frames. ![]() Take a series of photos, one photo for every ISO value your camera supports, making sure not to exceed an exposure time of 1 second. Most cameras include intermediate ISO values, e.g. ![]()
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