Tagging Files

[catem]

I tend to scan in all files, whether b&w or colour, as RGB, and change to sRGB for the web. I find that if I use the "Save As" function in photoshop, the tag remains embedded no matter what. If I use the "Save for Web" function, though, the tag seems to 'disappear" and it becomes an "untagged" file. Is this a communication glitch somehow or is it really happening - if so it seems a bit odd. Can anyone enlighten me?

 

[Keith Taylor]

I tend to scan in all files, whether b&w or colour, as RGB, and change to sRGB for the web. I find that if I use the "Save As" function in photoshop, the tag remains embedded no matter what. If I use the "Save for Web" function, though, the tag seems to 'disappear" and it becomes an "untagged" file.

Stargazer,
When you use the "Save for Web" function, there's a box labelled "ICC Profile" that by default is unchecked. When that's checked, the file will be automatically be saved with the embedded profile.
Keith.

 

[catem]

Stargazer,
When you use the "Save for Web" function, there's a box labelled "ICC Profile" that by default is unchecked. When that's checked, the file will be automatically be saved with the embedded profile.
Keith.

So there is.... . Thank you

 

[artonic]

Some versions of MSIE would get confused by the embedded data, and fail to display the image. Web browsers ignore profiles anyway. Also, without embedded tag data, the image files are a little smaller and a little faster for the web.

 

[catem]

This is what 'wikipedia' has to say about sRGB. It's generally agreed to be the best way to get your photo viewed as close as you wish to your original on a wide variety of systems/monitors.

sRGB color space is a standard RGB (Red Green Blue) color space created cooperatively by Hewlett-Packard and Microsoft Corporation for use on monitors, printers, and the Internet. It has been endorsed by the W3C, Exif, Intel, Pantone, Corel, and many other industry players, is also well accepted by open-source software such as the GIMP, and is used in proprietary and open graphics file formats such as SVG.

sRGB is intended as a common color space for the creation of images for viewing on the Internet and World Wide Web (WWW), the resultant color space chosen using a gamma of 2.2, the average response to linear voltage levels of CRT displays at that time.

It is important to realize that sRGB was designed to match what current (in 1996) CRT monitors do, not to be an ideal color space. Vast amounts of software, both professional and personal computer software, assumed an 8-bit image file placed unchanged into an 8-bit/channel display buffer will display with these colors and intensities. Modern non-CRT hardware, such as LCD, digital cameras, and printers, although they don't naturally produce an sRGB curve, have been built with compensating circuitry or software so that in the end they also obey this standard (this is somewhat less true for high-end professional equipment). For this reason you can assume (in the absence of embedded profiles or any other information) that any 8-bit image file, and any 8-bit image API or device interface, is in the sRGB color space.

I'm thinking also it's possible that when photoshop converts in the 'save for web' option the default IS sRGB - even though it says it's untagged - which only changes if you check the ICC profile box, (and want to preserve a different profile) but I can't find anything to confirm this at the moment - if anyone knows I'd be grateful otherwise I'll just keep the box checked.

 

[Keith Taylor]

I'm thinking also it's possible that when photoshop converts in the 'save for web' option the default IS sRGB - even though it says it's untagged - which only changes if you check the ICC profile box, (and want to preserve a different profile) but I can't find anything to confirm this at the moment - if anyone knows I'd be grateful otherwise I'll just keep the box checked.

Cate,
If you save the same image twice, one in sRGB (Save As) and the other via Save for Web WITHOUT the ICC Profile box checked, the resulting images do look different when compared side by side. I'm no colour management expert however, so I can't explain to you what's happening here, but I'd suggest keeping the box checked for now
Keith.

 

[artonic]

"Save for Web" is so named because in that environment, profiles and other image metadata is excess baggage, ignored by the web browser. In some cases the extra data prevents the image from displaying. So, if the file is going on the web, use "Save for Web".

Today's browsers are not colour managed, so they simply display the image in the system's colour space which is usually closest to sRGB. Therefore you will want to convert the image to sRGB just before "Save for Web".

If the file is not for web display, then you will want to retain image metadata. Also the "Save As" will offer more file format choices, especially uncompressed/lossless formats.

Cheers, Gary

 

[catem]

Today's browsers are not colour managed, so they simply display the image in the system's colour space which is usually closest to sRGB. Therefore you will want to convert the image to sRGB just before "Save for Web".
Cheers, Gary

Hi Gary,

That's what I've been doing, but if the ICC box is unchecked (I'm using CS2 btw) the 'tag' disappears after saving (in Save for Web) which is the mystery. If the ICC box is checked it remains listed as a profile. I have a feeling that the default photoshop colour space in the latest versions is sRGB (I use Adobe RGB as my working colour space) which may mean that 'untagged' after S for W - as long as you've converted the profile - actually means sRGB. But not according to Keith's experiment. I'll check it out soon as I have time! Thanks.

 

[catem]

For anyone interested in this there's a fairly good tutorial here. Look at it when you've got a fairly clear head LOL

What I gather from it is tagged sRGB is best for the web, therefore the file should be converted if necessary and the preserve profile box checked. Any default would be whatever you've set your working space in photoshop to be (in my case I set it to Adobe RGB) - It seems a file can have a particular profile, but be tagged or untagged, and as I said, tagged is the better option. But if anyone has other interpretations don't hold back :confused:

 

[frugal]

Web browsers ignore profiles anyway.

Some browsers on the Mac as far back as IE 5 have supported ICC profiles. I'm pretty sure Safari does.

 

[Keith Taylor]

Some browsers on the Mac as far back as IE 5 have supported ICC profiles. I'm pretty sure Safari does.

This is a posting on the Macintouch website, albeit from 2005, by Andrew Rodney who's written numerous books on colour management. It deals specifically with whether Safari (and other browsers) can handle profiles.

"Any untagged image (which makes up the majority of web images) is assumed not to be in sRGB but rather the display profile of the users display or the Generic RGB profile for viewing the images. By assigning sRGB, the file is no longer untagged and Safari now uses the embedded profile for previews.

sRGB is "assumed" to be the best color space for the web because the vast majority of web users are working on displays that can produce sRGB specifications (usually though calibration).

For untagged images, the software has to make some kind of guess about what the color space is. So some use sRGB, Safari uses the users display profile."

Keith.

 

[artonic]

Oops, my information was a little bit dated... thanks for that.

So, which Windows-based browsers are colour managed?

 

[catem]

Also, FYI the soft proofing available through photoshop (View > Proof Set Up) shows how your file would look on an uncalibrated monitor (either gamma @ 2.2/PC/ (& Mac) or gamma @ 1.8/some Macs. On any calibrated monitor, (eg if tagged sRGB), it should look exactly as it does on your own monitor (as long as that is correctly calibrated, and set at the same gamma - 2.2. seems the recommendation for both PCs/Macs). Ultimately we can't do anything about systems that are not colour managed so this seems the best to aim for, and the best realistically that can be done.

Gary, the article in the link I gave includes a bit about colour management and browsers.