#Rawtherapee tutorial iso#

#Rawtherapee tutorial iso#

With a high ISO images, one to two pixel areas are almost always noise spikes. Or stand out less in the image if you move the slider towards zero. Then RT multiplies those areas by whatever number you select to make them stand out in the image. The areas range from 1 or 2 pixels wide (Finest) up to about 16 to 20 pixels wide (Coarsest).

What this routine does is use some fancy math to select areas that have details. A tidbit of info I'll toss in to point out that in photography framing may not be everything but it is still is a good hunk of everything.) The second largest mall and one of the busiest intersections in the city was behind me. Instead of a blackbird I start with a seagull flying over a field and pond-a peaceful and quiet country scene.

Since a quick google of 'unsharp mask tutorial' will show why the world doesn't need another unsharp mask tutorial, I will talk about what happens when I go out my way to do it wrong. It wasn't until our digital days when all you had to do was move a few sliders to ' convolute them sharpening kernels' that it became part of a photographer's digital development work flow. There isn't more detail but because of the way our eye/brain system works this print will look sharper.Д«ack in those film days this was another 'great in theory' procedure that hardly anyone ever used. This combination will make a print with more edge contrast than a print made with just the original negative. When you carefully aligned the original negative and its mask and put the stack in your enlarger you have a halo around the edges of the black bird. if you defocused your enlarger you would have a blurry and wider positive of your black bird, your 'unsharp' mask. If you did this as you would with a print, well focused, you would now have a 'sharp' mask. If you projected this on another sheet of film, after development you would be back to a positive, a black bird against a lighter sky. Once you developed your image of a black bird flying up in the light blue sky, you would have the B&W negative, a white bird in a black sky. Unsharp masking goes back to a time when you would stick your head under a big black cloth and take your image on a large single sheets of film. To sharpen an image with an unsharp mask we do 'a simple linear image operation-a convolution by a kernel that is the Dirac_delta minus a Gaussian blur kernel.' As per ДЄll clear and understandable? Right? Or did you party big time the night before that early morning math class and could use a refresher explanation? Maybe you even forgot how you sharpen an image with, of all things, an unsharp mask. Or we multiply them by a range of numbers that depends on how far and in what direction we drag a point on a tone curve.

Or to decrease it by a stop, we multiply by 0.5. For example, to increase the effective exposure by a stop we multiply the image numbers by 2. Sometimes we only want to modify a pixel or two-covering up hot pixel noise-but usually we want to do mathematical operations on all or a good part of our image. And shortly after that ancient time, when monitors that could draw pictures appeared beside humongous CPU units, programmers began writing image editors to take away the tedium of doing such mathematics on these lists of numbers. Once upon an ancient time that was how data editing was done. If I still hadn't used up all my tedium quota for the day and replaced the picture data with zeros I would eventually draw a black line across the top of DSC8706. If I looked up the ascii numbers for 'This is going to be tedious!!' and individually replaced some of the zeros that sentence would show up in the metadata. Finally there are pages and pages of zeros that I could fill up with metadata. Following that is more data about the lens I used. This is a small sample of the 5,161,117 numbers that make up my DSC8706 jpg It's at the boundary between the header-the zeros at the top- and the numbers that tells a computer how bright or dark to set the three colored dots that make up the pixels on its computer screen-the hexadecimal numbers at the bottom.ДЄt the top of the header is the EXIF data-the list of camera settings.