There is the use of this obscure dpi factor. Inches and dpi will translate into pixels. You need to know at what dpi this size is needed. I suppose that your customer needs 16x24 inch pictures, which is quite big. In the same sens, images with a lot of changes are dificult to compress.Ī property of Jpeg is that when you open a Jpeg file and you resave as Jpeg without modification, the introduced artefacts will increase.
An image having only one colour would be best compressed.
The compression rate depends on the image. At a quality factor of 100 (12 in Photoshop), you do not notice any loss of quality, but even then, your picture may be highly compressed. Highly compressed images show noticable artifacts. The quality factor tells here, how much of the data gets lost. This process is destructive, meaning that a compressed image cannot be reconstructed to be exactly equal to the original. The aim here is to transform in a way that is effective but not or barly noticable for the human eye. So this means that in a worst case scenario and with 14 bits a Raw picture has a storage need of Xres*Yres*14bits/8bits+some bytes for storing parameters needed.Ī Jpeg file has 3x8bitsxResolution, so this file should be bigger in size, if there would not be mathematical transformations, allowing to rearrange the pixels in such a manner that it is easy to compress. Ech pixel is availablein 12 to 14 (most modern sensors have 14 bits) bits, compressed in a nondestructive way. Developping RAW pictures means interpolating these Bayer pattern values into real colour information. Normally the are arranged in what is called a Bayer pattern. Colour is captured by adding filters to the sensor pixels. The sensor is normally colour blind (favon sensor from Sigma is an exception to this). There is generally no good reason to increase that resolution to get better image quality. You sensor has a physical resolution and that one will determine the size of your picture. This is different for an other parameter pair: resolution in pixels. As a rule of thumb this parameter is set to something between 200 to 300, without having any influance on the quality. Infact you could add this parameter from 1 to very high, without changing one single pixel of your image.
First: DPI is only an indication how a picture should be printed at 100%.
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