convert to profile or assing profile. What is the difference? Pictures included.

[Alex]

<p>Could someone share with me what is the difference between this two?<br>

Also I have being using sRGB as the base file coming from ACR to work the final image; I understand that Adobe RGB is a larger color space and then ProPhoto even larger. My question here is, if the final profile for printing is going to be of smaller size what difference does it makes what color space am I coming from. Lets suppose that I have an empty 1 gallon bucket as my destination file for printing and my original files are a 2 gallon bucket sRGB file, a 3 gallon bucket Adobe RGB file, and a 4 gallon bucket ProPhoto RGB seems to me that I am going to waste all the exess water (color info) on all 3 buckets (source files) anyway.<br>

I fugure there have to be a reason as to why start with a larger color space but I can't figure what that is.<br>

Here is a quick experiment I just did. I opened and image in CS5 as a prophoto file and diplicate the image twise I converted one to Adobe RGB and the other one to sRGB them I duplicated all 3 files after the convertion and converted that into the same Costo profile one from the prophoto file, one from the Adobe RGB and one from the sRGB file.<br>

What you see on this image is top left the original prophoto. Top middle is a copy of the prophoto file converted into Adobe RGB. Top right A copy of the Prophoto converted to sRGB. The bottom ones are the corresponding duplicates converted to Costo profiles.<br>

Thanks for your thoughts.<br>

Alex</p>

[RaymondC]

<p>If you want to print, like sRGB to your lab, use convert.<br>

Basically the colors on your screen will be the same, but it willbe invisibly modified so that the destination matches your screen. </p>

<p>If you have a scanner and it has been calibrated you use assign. <br>

Basically, it alters the colors. The scanner might be too red, so the color becomes less red on your monitor. It corrects your version. </p>

[divo]

<p>Digital devices calculate colours by asigning them a number for Red, Green and Blue. The combination of numbers (255,255,255 for example) determines what colour is displayed relative to what is known as a colour space or gamut. These gamuts come in differnet sizes; think of it as the size of your box of Crayola crayons. Profoto is a large colour space, Adobe RGB 1998 slightly smaller and sRGB even smaller.</p>

<p>Sadly, the numbers don't mean the same thing in each gamut. So, if you take 34,72,86 in sRGB, it will be similar but not eactly the same as 34,72,86 in Adobe RGB 1998.</p>

<p>Enter Assign or Convert. <strong>Assign </strong>takes whatever numbers you have now and assigns the colour from the gamut you choose: This will probably result in a colour shift under certain conditions. <strong>Convert </strong>translates the numbers from your source colour space to another colour space and tries to maintain colour fidelity when moving between colour spaces.</p>

<p>Profoto gives you the greatest flexibility, which is one reason why Lightroom uses it as its native colour space. For web applications, it is usually recommended to convert to sRGB. Individual printing labs etc. will have their own preferences and their software may affect what they can handle accurately.</p>

[divo]

<p>The simple answer is edit in the largest gamut to allow for the greatest flexibility, then downsize for specific applications. </p>

[jerry thirsty]

<p>Here's a better analogy than the bucket thing: If you try to mix cake batter in a bowl that is exactly the same size as the amount of batter, you'll likely slop some over the sides and lose it unless you are very careful. You want to do your mixing in a bigger bowl so that you've got room to work in. Trying to manipulate images in a small color space is the same way.</p>

[digitaldog]

<p>Assign specifies the scale of the numbers, it doesn’t change them. Convert changes the numbers. <br>

See: <a href="http://www.adobe.com/digitalimag/pdfs/phscs2ip_colspace.pdf">The Role of working spaces in Adobe applicaitons</a><br>

We need <em>Assign Profile</em> when we have a big pile of RGB or CMYK numbers without a scale (no embedded profile). Numbers without a scale are ambiguous. For example, if you ask the distance from my home to yours and I say 900, that could be 900 feet, meters, miles, etc. 900 is meaningless as is. R23/G89/B120 without a scale (sRBG, Adobe RGB (1998), myEpsonRGB) is equally meaningless. Assign Profile provides the scale, the color space associated with the numbers. The numbers don’t change but the color appearance does because Photoshop now understands the scale. </p>

 

[martin-s]

<p>What Andrew said; see also <a href="http://www.colormanagementinfo.com/page1/page10/page10.html">Assign vs Convert</a></p>

[dave_redmann]

<p><em>The simple answer is edit in the largest gamut to allow for the greatest flexibility, then downsize for specific applications.</em></p>

<p>If you are editing with enough bits per channel, that's probably true. But for any given bit depth, using a larger gamut increases the risk of banding and reduces the smoothness of the tonality, and if your image does not extend to the larger gamut, you haven't gained anything in return. The importance of these issues depends on the bit-depth-per-channel of your original image and how radically you color-correct and/or apply curves or similar tools.</p>

 

[Alex]

<p>Thank you all for the great responses. A special thanks to Andrew and Martin for the links there are very informative.<br>

Again thanks to all for the feed back<br>

Alex</p>