Ysarex
Been spending a lot of time on here!
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Interesting Keith but, only parts sinking in at this stage.
I have changed my camera to Raw +L, I then just shop a general image of something near me to try see what is happening and try understand it more.
Checking my view finder in the camera I am presented with the image just taken, pulling up the file details it tells me it is a Raw +L file. So far so good. So I removed the card and plugged into the laptop, I could see 2 files, a name.cr2 file and a name.jpg file. Looking at properties of the files I see the *.cr2 is 23.1mb and the *.jpg is 5.84mb, I can see straight away the massive difference on file size and memory card space they take up!
Your camera saves a 5184 x 3456 pixel image.
So first, 5184 x 3456 = 17,915,904 or rounded off 18 megabytes or an 18 megapixel camera.
In the raw format each pixel is assigned a bit depth of 14 -- 14 bits per pixel. That means we need more than 18 megabytes to store the raw file (8 bits in a byte). Allowing for the extra 6 bits 18 megabytes becomes 28 megabytes of required storage space. Fair to assume Canon applies some degree of lossless compression to reach the 23 megabyte file size.
An RGB photo from your camera in JPEG format will be limited to 8 bits and so 18 megabytes uncompressed. JPEG's compression algorithm is responsible for the dramatic reduction in storage size. Data compression relies on the removal of redundancy. To create redundancy in your photo JPEG lays an 8 x 8 pixel grid over your photo. Photo data is dense and so each 64 pixel grid cell will likely contain 64 unique pixels -- can't compress. JPEG's job then is to alter the pixels inside a grid cell so that only 60% or 50% or 40% or even 30% are unique and the file compresses.
With your camera set to Raw + L you're saving both files to the card with each photo you take.
I then opened Canon Digital Photo Professional 4, again I can see the 2 files and the setting the files were taken at, not aware of the Raw format, other than having seen the file format name, and many others, I have always used JPG files and if I wanted better images I would use TIFF files. Having got this far, I decided to go a little further and downloaded RawTherapee 5.3 FREE software for *.Raw files. Now I can see 'some' of the benefits but, need to back off a little for a while I think, I need to get back to fully understanding the photographic triangle and get that clearly fixed in my brain.
Careful with triangles. The "exposure triangle" as named is built on a false foundation. In the hands of youtubers and bloggers and facebookers it's amazing how that false assumption can be contorted into a confused labyrinth from which you may not escape.
Exposure is a well understood and long since well defined photographic concept. We define exposure as the amount of light per unit area reaching the film/sensor. It is a function of a) the brightness of the ambient light b) time -- the shutter speed and c) any attenuation of the light through the lens typically expressed as f/stop. Notice what is not included in that definition. The triangle slip-up comes from a colloquial redefinition of the term exposure into the implied term "good exposure" or "correct exposure" or the "exposure I like." On top of that is added an incorrect understanding of ISO where it is common to assume that ISO adjustments alter the light sensitivity of the sensor/camera.
The result of the above errors produces some specific confusion involving cause and effect. New photographers get the idea that high ISO values cause noise which is incorrect. High ISO values correlate with noise; correlate and cause are two very different things. More seriously new photographers get the false idea that adjusting the three legs of the triangle (shutter, f/stop, ISO) can produce an exposure equivalence. In other words ISO 100, 1/250 sec and f/8 is the same exposure as ISO 800, 1/1000 sec and f/11 -- the action stopping power of the shutter is different and DOF is different but the exposures are otherwise equivalent -- they're not.
There is so much to learn and the grey matter in the brain doesn't take things in as fast as they used to, but thanks for the information, suggestions and help.
Take you're time -- it took me decades
Joe
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