Oct 19, 2014, 04:36
This is my non-expert amateur description and based on my own testing.
The big differences between RAW and jpeg stems from the bit depth - the 'volume' of colours recorded. Most DSLRs record in 12 bit precision or 4096 levels. JPEG is 8 bit or 256 levels of colour - so the on-camera processing does a LOT of work to reduce the number of levels and in so doing makes a lot of sometimes irreversible decisions on white balance, colour compression etc.
For a more elegant description of all this have a look here:
http://www.cambridgeincolour.com/tutoria...format.htm (one of my 2 favourite resources on all things DSLR, but watch out, if you've never visited the site allow several hours as you'll probably chase of in all sorts of interesting directions
But 'so what' if I'm happy with the jpeg? Well if your like me there are a number of times when I have an image where the colour balance is not right; the exposure is off; or more specifically the shadows are too dark or highlights are blown (and because of the in-camera compression the detail is lost); etc. In these case RAW truly comes into its own because nothing is pre-processed in-camera. In PS Adobe Camera RAW (and presumably LR) I can adjust all of those with ease.
Another important point is jpeg is 'lossy' compression as mentioned previously. Well the camera has already discarded a lot of info, if I save, edit, save, edit repeatedly on a jpeg the lossy compression is rerun each time with continual reduction of quality - if you want to test, take a copy of a full range jpeg, use levels to deliberately make the image very light or very dark, save, re-edit and try to find the the detail you lost. Usually my editing efforts are not that extreme but it does illustration the point.
Do the same thing with ACR. If you check the disk folder afterwards you will find an additional file with the same filename. This 'sidecar' file contains all the edits you saved on the raw file (whether you 'saved' the raw or 'Opened in PS as a tiff). Re-edit the raw and they are all there; you can reset or change individual settings at will, or even delete the sidecar file and start again. Note PS always converts raw to 16bit TIFF so even subsequent re-editing will not loose detail (means you have to convert to jpeg as a final action for web or some printing programs.)
So what do I do? I always set for RAW+JPEG to save on-camera; I use branded, quality class 10 memory so the save time is at a minimum, read into a computer is quick (I know most cameras can't 'outsave' a C10 but the cost difference in minimal so its a small attempt to future proof my memory.) When I work with the images Iuse jpegs most of the time as most of my stuff is 'snapshots' but for the images I really like, or those needing more than curves and sharpening I use the RAW. For me that's typically 10 or 20% I guess. Finally I archive the jpeg contacts, the raws, and just the jpegs I finally used.
Dave
The big differences between RAW and jpeg stems from the bit depth - the 'volume' of colours recorded. Most DSLRs record in 12 bit precision or 4096 levels. JPEG is 8 bit or 256 levels of colour - so the on-camera processing does a LOT of work to reduce the number of levels and in so doing makes a lot of sometimes irreversible decisions on white balance, colour compression etc.
For a more elegant description of all this have a look here:
http://www.cambridgeincolour.com/tutoria...format.htm (one of my 2 favourite resources on all things DSLR, but watch out, if you've never visited the site allow several hours as you'll probably chase of in all sorts of interesting directions
But 'so what' if I'm happy with the jpeg? Well if your like me there are a number of times when I have an image where the colour balance is not right; the exposure is off; or more specifically the shadows are too dark or highlights are blown (and because of the in-camera compression the detail is lost); etc. In these case RAW truly comes into its own because nothing is pre-processed in-camera. In PS Adobe Camera RAW (and presumably LR) I can adjust all of those with ease.
Another important point is jpeg is 'lossy' compression as mentioned previously. Well the camera has already discarded a lot of info, if I save, edit, save, edit repeatedly on a jpeg the lossy compression is rerun each time with continual reduction of quality - if you want to test, take a copy of a full range jpeg, use levels to deliberately make the image very light or very dark, save, re-edit and try to find the the detail you lost. Usually my editing efforts are not that extreme but it does illustration the point.
Do the same thing with ACR. If you check the disk folder afterwards you will find an additional file with the same filename. This 'sidecar' file contains all the edits you saved on the raw file (whether you 'saved' the raw or 'Opened in PS as a tiff). Re-edit the raw and they are all there; you can reset or change individual settings at will, or even delete the sidecar file and start again. Note PS always converts raw to 16bit TIFF so even subsequent re-editing will not loose detail (means you have to convert to jpeg as a final action for web or some printing programs.)
So what do I do? I always set for RAW+JPEG to save on-camera; I use branded, quality class 10 memory so the save time is at a minimum, read into a computer is quick (I know most cameras can't 'outsave' a C10 but the cost difference in minimal so its a small attempt to future proof my memory.) When I work with the images Iuse jpegs most of the time as most of my stuff is 'snapshots' but for the images I really like, or those needing more than curves and sharpening I use the RAW. For me that's typically 10 or 20% I guess. Finally I archive the jpeg contacts, the raws, and just the jpegs I finally used.
Dave