I was wondering why...(colour space question)

[vlarcombe]

Re: I was wondering why...(colour space question)

Hi,

Simply put the colour profile is a map between numbers and colours. As different devices react to/generate different colours for the same number profiles are used to try and ensure that all the devices end up with the same representation of the colour. sRGB and AdobeRGB (and others) are standard descriptions between known colours and numbers. (i.e. a particular shade of green will be different values in the two colour spaces) As described in the article in the link in Jim's mail the profile also describes the range of colours available with sRGB being designed with a more limited range (also known as gamut if you're reading other articles) than AdobeRGB as it was designed for CRT monitors which can not produce all colours.

In the camera the sensors will record a number for each of the colours. If you shoot raw this raw, i.e. unconverted number is saved in the file. If you shoot jpeg the conversion is done in the camera and the colour space of the image (and hence the range of colours it can hold) is fixed. A profile of some sort will always be applied by the raw conversion software on input to produce the rendered image, this will be camera specific (some raw conversion software lets you select, others are fixed). The sRGB/AdobeRGB type profile selection in the raw conversion software is setting the output profile (which is often stored in the image to assist ICC aware software).

The suggested workflows seem fine to me and the "best" colour space to use will depend on what the final use of the image will be (as already noted by others in the thread). If the images are mostly for display on the web sRGB as the final output will be best, if printing AdobeRGB would be the better option but when posting pictures on the web they may appear "dull" unless they are first converted to sRGB (I posted an example of this on the old forum. I'll try and find the link). This latter is the workflow I follow, using QImage to do the colour space conversion for any images I prepare for the web.

Hope this helps more than hinders.

Vernon.

[vlarcombe]

Re: I was wondering why...(colour space question)

Here are some links to threads from the old forum when I was struggling with colour spaces/profiles that show the problem of posting pictures in the AdobeRGB colour space:

This message has a small image showing the loss of vibrant colours:
http://dpnow.com/bb/help.pl?read=235 (note the change in colour of the rust).

This thread was working out how to best do the conversion:

It starts with: http://dpnow.com/bb/general.pl?read=1227

and after working out (with assistance) how to do the colour space conversion I ended up with this: http://dpnow.com/bb/general.pl?read=1258 (if you don't want to work through the intermediate posts).

It was quite a journey but I was frustrated that I could not post what I was seeing in all the ICC aware software and prints from my machine.

Vernon.

[StuartR]

Re: I was wondering why...(colour space question)

Thanks for the continuing debate guys, it's all intriguing stuff.

Two of the interesting sentences for me in Mike Chaney's article (thanks for the link Jim) are:

"So if you have the time, the software, and the know-how, Adobe RGB is the way to go unless you are shooting in raw mode, which gives you even more flexibility as the color space decision can be made later, when you develop the photos."

"If you have/use ICC aware software, there is a strong argument for using Adobe RGB in that it is a larger color space and can store a wider range of color. You can't get back what you didn't record in the first place! After all, if you are familiar with ICC aware software, you can easily convert from Adobe RGB to sRGB should you need to email someone some photos or upload photos to a web site."

I tend to only only shoot RAW so I'm taking the above to mean that it really doesn't matter whether I have the camera set on sRGB or Adobe 1998. Having said that, I guess I could set it to Adobe for the rare occasions I shoot jpg (normally only when the memory cards are all full or I've left them at home by mistake and only have a 128MB "emergency" card - been there, done that ).

I said I'd check what my RAW converter (DxO) was using and it's set to "Display device's profile"! I hadn't even noticed the option so I wonder if it was set this by default. But then, why would it be?

So I'm now at; RAW in camera (Adobe for jpgs), Adobe in DxO, Adobe in PhotoShop CS2 and convert any images I send to PhotoBox or by email to sRGB. I guess that should include submissions to this forum or images I put on my own web site.

Anyone like to disagree ?

[Stephen]

Re: I was wondering why...(colour space question)

So I'm now at; RAW in camera (Adobe for jpgs), Adobe in DxO, Adobe in PhotoShop CS2 and convert any images I send to PhotoBox or by email to sRGB. I guess that should include submissions to this forum or images I put on my own web site.

Anyone like to disagree ?

Only to say what do you do with the ones you don't send to Photobox, or email, or put on your website, or post on this forum

[StuartR]

Re: I was wondering why...(colour space question)

Store them by the 1,000, all big Tiffs, on two external drives probably never to see the light of day . I just can't bring myself to delete anything - even my numerous "test shots" to prove that f/11 produces a better quality image than f/32 etc.! I've even got a folder of shots testing for dust on the sensor that I've long got rid of by various wet or dry methods.

I think it goes back to the time that years worth of 35mm & 120 negatives were consigned by 'er indoors to the skip during a clear-out . Perhaps I need help?

Now, in the future, probably all stored in Adobe colour space, mmmmm...wonder how future-proof that is? Although I keep all the RAWs as well mmmmm...wonder if that's future-proof?

[vlarcombe]

Re: I was wondering why...(colour space question)

I'm another one who can't bring myself to delete any original files.

"Future proof" is very difficult in the fast moving world of computers. You need to ensure that you have the files on media that you can still read and a computer/operating system that will still run your software. Tiff files should be OK (as long as you can read the media, ZIP disk anybody?) Raw files could be more of an issue, one possibility now is to convert the raw files from the camera manufacturer format to the generic Adobe DNG "raw" format. I'm not sure if this saves any/all camera specific data but at least it would have the raw bytes in a published generic format.

Vernon.