RAW vs. jpg and soem ?? about PSE
Jul 29, 2012 19:08:46 #
A raw vs. .jpg experiment
The discussion about lossy vs. lossless files prompted me to try something. I use a Nikon D7000 set to store both a fine .jpg and a .nef (Nikon raw). So I took a photo and opened both versions in PSE 10. The .jpg was 8.2 Mb; when PSE opened it, it unpacked it to produce a 46 Mb file in the working space. The .nef file was 19.7 Mb so presumably has more information, but when PSE pre-processed it (I also warmed it up some) and then I opened it in PSE, the working file was also 46 Mb! This suggests to me that a fine .jpg, at least on my D7000 has very little lost information.
Of course the .jpg was processed by the camera before storage, doing something similar to what I did to the .nef when I opened it in PSE. And the result was not bad, Nikon tends to like a nice conservative look (which can be altered by setting the camera differently). For 99% of the pictures I take the .jpg is acceptable, but I still like the option of messing with the .nef in the future (soon as I learn enough to do it).
If I save the .jpg file as a .jpg of course I can compress it and PSE, anyway, ASKS me how much to compress; I tried maximum and minimum file sizes and got an 8.6 and 0.61 Mb file, respectively. So apparently you can save a .jpg without loss of information if you specify maximum: file size.
Interestingly, if I saved the .jpg file as a .psd it generated a 45Mb file while the .nef generated a 44Mb .psd.
And heres something surprising (at least to me): the .jpg save-as dialogue box in PSE10 has a checkbox labeled preview which apparently does nothing! When you save a file with compression you CANNOT see the effect even if you magnify a small piece of the image. Apparently the image on your screen is unchanged EVEN THOUGH IT HAS BEEN RENAMED! If you close the file and then reopen it you will see the information loss. Or am I missing something here?
Anyway, at the end of my experiment I had the following files stored in my folder: the original 8.2Mb jpg and 19.7Mb nef; 44Mb and 45Mb .psd files; a highly lossy (renamed) 0.6Mb jpg--AND an .xmp file: alphanumeric metadata, apparently (you can open it with Notepad). Say, where did THAT come from?
Bottom line: the fine .jpg and .nef have almost the same information and detail! But the .jpeg has been processed by the camera. If you want to make your own INITIAL processing of the raw sensor data save the .nef. Have I got it right?
The discussion about lossy vs. lossless files prompted me to try something. I use a Nikon D7000 set to store both a fine .jpg and a .nef (Nikon raw). So I took a photo and opened both versions in PSE 10. The .jpg was 8.2 Mb; when PSE opened it, it unpacked it to produce a 46 Mb file in the working space. The .nef file was 19.7 Mb so presumably has more information, but when PSE pre-processed it (I also warmed it up some) and then I opened it in PSE, the working file was also 46 Mb! This suggests to me that a fine .jpg, at least on my D7000 has very little lost information.
Of course the .jpg was processed by the camera before storage, doing something similar to what I did to the .nef when I opened it in PSE. And the result was not bad, Nikon tends to like a nice conservative look (which can be altered by setting the camera differently). For 99% of the pictures I take the .jpg is acceptable, but I still like the option of messing with the .nef in the future (soon as I learn enough to do it).
If I save the .jpg file as a .jpg of course I can compress it and PSE, anyway, ASKS me how much to compress; I tried maximum and minimum file sizes and got an 8.6 and 0.61 Mb file, respectively. So apparently you can save a .jpg without loss of information if you specify maximum: file size.
Interestingly, if I saved the .jpg file as a .psd it generated a 45Mb file while the .nef generated a 44Mb .psd.
And heres something surprising (at least to me): the .jpg save-as dialogue box in PSE10 has a checkbox labeled preview which apparently does nothing! When you save a file with compression you CANNOT see the effect even if you magnify a small piece of the image. Apparently the image on your screen is unchanged EVEN THOUGH IT HAS BEEN RENAMED! If you close the file and then reopen it you will see the information loss. Or am I missing something here?
Anyway, at the end of my experiment I had the following files stored in my folder: the original 8.2Mb jpg and 19.7Mb nef; 44Mb and 45Mb .psd files; a highly lossy (renamed) 0.6Mb jpg--AND an .xmp file: alphanumeric metadata, apparently (you can open it with Notepad). Say, where did THAT come from?
Bottom line: the fine .jpg and .nef have almost the same information and detail! But the .jpeg has been processed by the camera. If you want to make your own INITIAL processing of the raw sensor data save the .nef. Have I got it right?
Jul 29, 2012 21:34:21 #
Basically, yes - if you want full control of the final outcome, shoot raw. If you are OK with the camera making the decisions, shoot JPEG.
The loss to the JPEG file occurs when the already compressed file is saved, not when it is opened. You can view (open and close without saving) a thousand times and it will not lose one bit of data.
The JPEG takes up less space, not because it is a lossy format, but because it is compressed (like a ZIP file). Raw, PSD and TIFF files will take up more because they are not compressed.
Actually, all of the image files are alphanumeric data files and can be opened with a text editor. Except for some characters near the beginning listing the file type, it will look like gibberish. The XMP is a "side car" file containing the edits made to the raw file. That is how the edits to raw files can be non-destructive.
The loss to the JPEG file occurs when the already compressed file is saved, not when it is opened. You can view (open and close without saving) a thousand times and it will not lose one bit of data.
The JPEG takes up less space, not because it is a lossy format, but because it is compressed (like a ZIP file). Raw, PSD and TIFF files will take up more because they are not compressed.
Actually, all of the image files are alphanumeric data files and can be opened with a text editor. Except for some characters near the beginning listing the file type, it will look like gibberish. The XMP is a "side car" file containing the edits made to the raw file. That is how the edits to raw files can be non-destructive.
Jul 30, 2012 09:42:30 #
Thanks for this, that is helpful. The point I wanted to make was that the "fine" .jpg saved by the camera had little or no lost information and you can save over and over if you use the "maximum" file size with little info loss. The other thing was, I was trying to use the "preview" feature in the PSE .jpg file saver dialog and could never see any effect even with compression to very small file sizes. So what good is it?
I'm guessing that photo files are not really alphanumeric but binary? A program like Wordpad can open them but after an initial ID string the following the string of bits just doesn't translate when divided into bytes? But I go all the way back to Hollerith card punching so my ignorance of things now is vast...
I'm guessing that photo files are not really alphanumeric but binary? A program like Wordpad can open them but after an initial ID string the following the string of bits just doesn't translate when divided into bytes? But I go all the way back to Hollerith card punching so my ignorance of things now is vast...
Jul 30, 2012 15:43:24 #
DonWauchope wrote:
Thanks for this, that is helpful. The point I want... (show quote)
Probably.
BTW, I've used punch cards, but only in school (IBM 360/370). I wrote COBOL on a DEC PDP-11 / RSX-11M - too many years ago.
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