Before ending my work in PS I am always catched by two questions unsolvable for me.
1. I have been told that after changing from 16 to 8 bit I can't go any more to the mode LAB> Luminosity for further sharpening. Is this true?
2. I use Save for the Web because I can find the exat pixel I need for posting in the web. Many persons says instead that is surely better the normal Save with name.
What is the truth? Thanks very much.
Posted by Carol Hyman on October 27, 2007 at 12:10 PM
Hi Giuseppe, I'm going to suggest that when you save "for the web," you do a "save as." That way you have your original tiff or psd image untouched and can use it for other reasons other than simply posting an image on the 'net. When you do a "save for the web," you are changing your DPI to 72, your image dimensions, and the size of the file to 200 KB. You can't do much with those images other than place them on a web page.
Hopefully someone else can address your bit and luminosity question.
Gigi, I use LAB > lumiinosity on my 8-bit images. But then, they were 8 bit to start with. Therefore, a question back to you: How do I get the images to be 16 bit at the start?
Posted by David Bostedo on October 27, 2007 at 2:53 PM
Catherine - If you're shooting RAW, the RAW converter may output a 16-nit image. If you're shooting JPG, it's always an 8-bit file.
Giuseppe - The difference between "save for web" and "save as" (I think) is that the color space information isn't saved, helping to get a smaller file size with less compression. (It may also get rid of EXIF data, but I'm not sure.) "Save for web" will also preview how your image is going to look at various compression amounts. So if you have a 720 pixel image (like we post here) using "Save for web" might let you save at 60%, where "Save as" might force you down to 45%.
Carol - You've mentioned something that I've seen several times and always try to correct : DPI is completely meaningless to PS and for web applications. I could take the same image set to 72 dpi, or 72000 dpi, and it would look identical on the web. The only place it can matter is in applications that have a true concept of inches - like a print driver (perhaps coming out of PS). Otherwise, things should always be specified by absolute resolution - like 720x400 pixels.
Think about it this way : Assume I have an 800x600 image. I could view it on a 24" monitor set to 800x600 display pixels and it will fill the screen viewed at 100% (or on a webpage). I could pull up the same image on a tiny 12" monitor set to the same resolution, and it would also fill the screen. Obviously, the picture will be much smaller on the small display. This is completely regardless of the "dpi" setting that you see in PS or other programs. All that matters is the actual pixels - inches don't mean anything.
Posted by Toni Lankerd on October 27, 2007 at 3:17 PM
Gigi, I can't answer your first question because I save my Raw files as 8 bit Tiffs, do my editing, then save the large edited version. I will save a duplicate and downsize using Marcus' sharpening technique of downsizing to about 1000 or 1200 pixels, Sharpen once or twice, then downsize to about 625 pixels.
As for the second question, David is right...when you "save for web", you lose all EXIF data. If the image doesn't have a lot of information, I simply "save as", but if it means a lot of compression, I will use "Save for Web". All my images are 300 dpi, by the way and no, saving for web does not reduce the dpi, as far as I know.
Posted by David Bostedo on October 27, 2007 at 5:23 PM
Once again, Toni, the DPI setting is completely meaningless as far as the web and your screen are concerned. The image would appear to be identical if you saved it at 1 dpi. The only difference is that print software (and anything in PS in inches) might report that your image is 720 inches wide, which it obviously wouldn't be.
Posted by Toni Lankerd on October 27, 2007 at 10:15 PM
You are right, David, and I knew that. I guess in a way I was correcting what Carol said, not realizing that you had already mentioned it.
Thanks for your answers. Now I am working as Toni does: Save As if I don't have to compress the file, Save for Web if compression is needed. I understand that I can continue in this way. I use Save As also when I save without posting soon. In this case I prefer to save in TIFF because if I would make some more work later I wouldn't have to save twice in jpg with loss of quality.
As to LAB mode, if Catherine uses LAB>Luminosity with 8 bit regularly I can do the same thing when changing from 16 bit to 8 bit.
Thanks very much.
Posted by Wim Reyns on October 28, 2007 at 3:52 PM
Also save for web ( at least as of version CS3 ) will automaticly convert your image to sRGB which is the preferred web color space.
Posted by Fred Stearns on October 28, 2007 at 7:23 PM
If you are going to post your pictures on the Internet, you may want to make sure that you are identified in the METADATA file. This is one way to prove that your picture is indeed yours. Saving for web does not retain this information. You have to save in RGB. As has been said above, you must convert to sRGB in order to have your picture look as you intended. Well, as close as you can as most viewers have probably not heard about calibrating their screens. I seem to remember reading somewhere that save for web uses the original 256 colors used on the original color, VGA(?), CRT's when they first came out, not even the full sRGB palette.
Posted by Ed Cordes on October 28, 2007 at 9:02 PM
However you save be sure to save a web processed image under a different name. I use the standard file name, X3O123 for instance and make it X30123Post. This way I don't accidentally overwrite the original TIFF file (I convert all RAW immediately to TIFF for processing so I don't over write the original RAW file).
David B: yes, I shoot in RAW and it goes through the converter (ACR in CS3) as a 16 bit file. When it opens in CS3 after conversion, it is as an 8-bit file. Do I want to be working on a 16 bit file? When do you guys change it 8 bits?
Catherine, the importance of 16 bit file is the possibility of working in PS with much more color and tone informations than with 8 bit. Therefore the changement in 8 bit it the very last action that you do before saving for web or printing.
Save a 16 bit psd or tiff master file then make duplicates and convert those to 8 bit. Eight-bit files will make gorgeous prints and they don't bog down your system and your printer.
By the by: 8 bits per color channel produces 256 colors per channel or 67.7 million colors. Our eyes can only decern about 10 million colors and tonal differences of about 1 %. 16 bit data produces a file with over 281 trillion colors! Since we can see only about 10 million colors, 16 bit files may be over the top because we simply can't perceive that many colors.
Discussion
14 replies1. I have been told that after changing from 16 to 8 bit I can't go any more to the mode LAB> Luminosity for further sharpening. Is this true?
2. I use Save for the Web because I can find the exat pixel I need for posting in the web. Many persons says instead that is surely better the normal Save with name.
What is the truth? Thanks very much.
Hopefully someone else can address your bit and luminosity question.
Carol
Giuseppe - The difference between "save for web" and "save as" (I think) is that the color space information isn't saved, helping to get a smaller file size with less compression. (It may also get rid of EXIF data, but I'm not sure.) "Save for web" will also preview how your image is going to look at various compression amounts. So if you have a 720 pixel image (like we post here) using "Save for web" might let you save at 60%, where "Save as" might force you down to 45%.
Carol - You've mentioned something that I've seen several times and always try to correct : DPI is completely meaningless to PS and for web applications. I could take the same image set to 72 dpi, or 72000 dpi, and it would look identical on the web. The only place it can matter is in applications that have a true concept of inches - like a print driver (perhaps coming out of PS). Otherwise, things should always be specified by absolute resolution - like 720x400 pixels.
Think about it this way : Assume I have an 800x600 image. I could view it on a 24" monitor set to 800x600 display pixels and it will fill the screen viewed at 100% (or on a webpage). I could pull up the same image on a tiny 12" monitor set to the same resolution, and it would also fill the screen. Obviously, the picture will be much smaller on the small display. This is completely regardless of the "dpi" setting that you see in PS or other programs. All that matters is the actual pixels - inches don't mean anything.
As for the second question, David is right...when you "save for web", you lose all EXIF data. If the image doesn't have a lot of information, I simply "save as", but if it means a lot of compression, I will use "Save for Web". All my images are 300 dpi, by the way and no, saving for web does not reduce the dpi, as far as I know.
As to LAB mode, if Catherine uses LAB>Luminosity with 8 bit regularly I can do the same thing when changing from 16 bit to 8 bit.
Thanks very much.
Thanks, Gigi, sure glad you asked about this!
Save a 16 bit psd or tiff master file then make duplicates and convert those to 8 bit. Eight-bit files will make gorgeous prints and they don't bog down your system and your printer.
By the by: 8 bits per color channel produces 256 colors per channel or 67.7 million colors. Our eyes can only decern about 10 million colors and tonal differences of about 1 %. 16 bit data produces a file with over 281 trillion colors! Since we can see only about 10 million colors, 16 bit files may be over the top because we simply can't perceive that many colors.
-PB