Colour spaces

Janice

Janice

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Janice
Edit My Images
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I have always used srgb in camera and in photoshop.
Today I thought....hmm most people seem to use adobe 1998 so I will use that too. I adjusted the Pointsettia image in photoshop and it looked nice and bright red...but when I posted it it was all drab and dark red.

After converting it back to srgb it was fine again.

I though Adobe 1998 colour space was for images which would end up printed....does this mean they will look wrong on the web??
 
I had the same problem initially - I solved it by calibrating my monitor (and printer) with Adobe gamma.
 
So how come peoples shots look nice on here...even though they are using adobe rbg? Does that mean they will print out rubbish? :shrug:
 
You need to do a little bit of reading on color spaces. Technically Adobe RGB has wider gamut than sRGB so when converting to web it will "clip" certain colours.

A lot of pros who want to supply as wide a market as possible shoot in Adobe RGB where as most internet/web shooters use sRGB (default in most cameras).

Will look for a resource I once used to get my head round it and add in later.
 
Thanks for that. good reading. I still however dont know what to do to make images bright enough for web (ie, on here) but good for printing too.

Do you have to sacrifice one for the other?

I dont want to put dull images on here :thumbsdown: but if I use srgb then will they be ok for sending to Photobox etc?
 
I'm sure we've discussed this loads of times before. :thinking:

sRGB was a joint endeavour between Hewlett Packard and Microsoft, which came out around the mid 90s (ish) The 's' stands for 'Standard' and the whole idea of it is to provide as standard or uniform a viewing experience as possible for everyone viewing an image on the web given the vagaries of all their different monitor types and settings. To this end sRGB is the default system used by windoze. As stated above it has a smaller colour space than Adobe RGB, but often that means very little in visual terms in practice.

sRGB isn't claimed to be the best colour space option, but that isn't really why it was introduced.

On the subject of Adobe RGB I'll just quote Ken Rockwell. I'm paraphrasing him a little, but not much IIRC.

" Shoot in Adobe RGB if you're doing your own printing and you really know what you're doing, otherwise you're at the mercy of commercial printers who's understanding of it and ability to implement it is often open to serious doubt"
 
Thanks CT. I will stay with sRGB then...as I am happy with the results when posting on the web and happy with my own printing of it too. If it aint broke!

I was just wondering how you others post pics on the web in adobe rgb and they arent dull.
 
As CT states, teh web uses sRGB colour space so when you post your Adobe RGB images on the web they have colours clipped and don't look as nice. Using Adobe though allows for a greater colour gamut and when printing your printer or lab should be able to accept this colour space.

When posting on the web it's best to convert the web file to sRGB and post that.

My camera is set to Adobe RGB and Photoshop is also set up for Adobe RGB but when posting on the web I'll convert to sRGB.
 
Janice said:
Thanks for that. good reading. I still however dont know what to do to make images bright enough for web (ie, on here) but good for printing too.

Do you have to sacrifice one for the other?

I dont want to put dull images on here :thumbsdown: but if I use srgb then will they be ok for sending to Photobox etc?
Click to expand...

It's a complex subject but I'll try and keep this as readable as possible....

Firstly if you're shooting RAW the camera setting for colour space doesn't matter, you set it when converting the file in ACR, etc.

You can use aRGB for prints and sRGB for web. You need to set your editing s/w working space to aRGB and edit away as normal. When you want to create a version for the web do as you normally would but before you save it convert (NOT assign) it to the sRGB profile. Then it will look (roughly) the same in your web browser as it did in editing software.

The reason aRGB images look darker in the web browser is because aRGB has a "wider gamut" than sRGB. What this really means is that colours can saturate further than sRGB so a colour value in aRGB will look duller if it's displayed uncorrected in sRGB space. As an example bright green in sRGB is 0,255,0 but in aRGB it might only be 0,180,0 to give the same appearance because aRGB has more saturation.

aRGB is generally a lot of hassle because of reasons like this but it's also a waste of time unless you are going to use really high-end pro printers, here's why:

You need to use 16bit images to support the greater space in aRGB - apart from limiting your editing possibilities in CS2, etc. you also need a printer driver that supports 16bit files. Your standard Canon, Epson, HP printer doesn't and nor do Colab, etc. You can "print" a 16bit file but it will be converted to 8bit by the printer driver. There is a £500 Windows app that will print 16bit images on certain printers (top of the range A2 jobs) so it's not exactly a viable option.

Secondly - your monitor is 8bit and a lot closer to sRGB than aRGB (again some high end monitors are aRGB spec but costs thousands) and the way colour management works means you will never see the extra colours aRGB provides. You edit in aRGB space the but the s/w is converting the image to your monitor profile on the fly - basically aRGB gives you extra colours you can't see on screen and won't appear in print.

Finally if you do work in aRGB and print in 8bit you run the risk of banding or clipping in subtle gradients. 8bit is only 256 shades per colour, aRGB can give you more (esp. in magenta/green) but the way colour matching works means the software will either scale all the colours to fit within the space available (resulting in banding) or go as far as it can and then level off (clipping). Imagine you image has 512 shades of grey in it. Either you divide all of them by 2 to fit in the 256 shades available or you go as far as 255 and then stay there - the gradient would be clipped at the max value halfway across.

aRGB is often proclaimed as the best working space to use under the assumption that you get more colours. You do but only if your output devices can support those colours, otherwise you are simply running the risk of banding and/or clipping.

Of course you can happily edit and print using aRGB as a working space as long as you realise you're not really gaining anything from it - your prints will still match pretty closely assuming you've got good profiles for your monitor and printer.
 
Thanks pxl8. What a knowledgeable fellow!! (y)
Everything I needed to know there. :)
 
I must admit I shoot RAW at 16bit in Adobe1998 do whatever PP I want then the convert to 8bit & sRGB just before I do my save for web.
 
Janice, assuming you're using Photoshop and you want to view your photos on the web as sRGB then make sure you 'convert to profile' before you save your resized JPEG for the web. It'll then appear as it looks in Adobe RBG (or as near as damn it so you wont notice the difference).
 
The chapter of Martin Evening's Photoshop book that deals with colour spaces is available as a free download from here:
http://www.photoshopforphotographers.com/pscs2/colormanage.htm

It's worth reading but in a nutshell:

- Shoot Raw as Raw files have no real colour space until they're converted to something else.
- When you convert the Raw file, give it an Adobe RGB colour space.
- Do all your normal processing on the photograph.
- Before saving any web/internet version of your image, go to Edit > Convert to profile and change the colour space to sRGB. This is assuming you're using Photoshop CS2, other versions may have the 'Convert to profile' option located elsewhere.
 
fingerz said:
The chapter of Martin Evening's Photoshop book that deals with colour spaces is available as a free download from here:

- When you convert the Raw file, give it an Adobe RGB colour space.
Click to expand...

That's a bit misleading - the article (rightly) says aRGB is better if your destination is CMYK separations, eg. magazine work. But don't confuse CMYK with a printer or a photo lab which are still RGB based.
 
You should keep the master (PSD) file in the best quality possible.

If you start out Adobe RGB and convert it to sRGB later then it will look pretty much identical to how it would look if you started out sRGB in the first place, but you retain the option of having that master file in a wider gamut (Adobe RGB).

If, however, you start out sRGB then you can't widen up the gamut later without resorting to artificial means, which will degrade the image slightly.

Bottom line: if you don't think one of your photographs will ever be printed CMYK then don't bother with Adobe RGB. But how can you be sure that you'll never need to have something printed CMYK? What if a magazine emails you tomorrow (as has happened to a lot of our forum users now) asking to use one of your images?

The choice of colour space doesn't affect the file size so why not just keep your master files in a big gamut and convert them to a smaller gamut if needed?
 
The problem is that unless you're working on a monitor capable of displaying the increased saturation of aRGB you won't take advantage of the wider gamut.

If you increase the saturation of the green channel you would stop as soon as it looked right on screen - you've naturally limited the image colours to fit within the space of the monitor profile and not the working space. If you were to go to the limit of the working space you would either see clipping or loss of tonality on screen and it would "look" bad.

The main reason for using colour management is to ensure good matching between devices - we get it looking right on our monitors and then want a print to match. If it looks right on the monitor then that's as large a space needed for the image colours to fit inside.

Ideally the working space and device profiles should be as close as possible in size to minimize the compromises of moving values between one profile and another.
 
You're not meant to take advantage of the wide gamut on screen. The same argument could be applied to shooting Raw - Raw files are 12 bits and a monitor can only display 8 bits, so why bother shooting Raw if you can't see the difference on a monitor?

Because when you start editing an image, it's very handy to have that extra data since it fills in the gaps that get created when you start tweaking levels and curves.

Matching colour between devices isn't a problem. If you send your picture to someone else who's using colour profiles (another Photoshop user, for example) then their computer will recognise the profile and display the colours correctly (assuming they've calibrated their monitor). If you're sending your picture to someone who's not using colour profiles (eg you put your photo on a website and it's seen by a random person browsing the internet) then all you have to do is convert to the standard sRGB before saving.

The basic point I'm making is this... If you wok in Adobe RGB you can downgrade to sRGB later (if needed) with no loss. If you work in sRGB, you cannot upgrade to Adobe RGB and get the benefits of wider gamut without artificially boosting the saturation somehow.

It's like working on an 800-pixel-wide image instead of the master (eight megapixel, or whatever) image. You could argue that since you're only uploading to a website, there's no need to process the image at full size. But by downsizing it prior to processing, you lose the range of options that allow you to choose these things later on.
 
I understand your basic point and completely agree. Converting from sRGB to aRGb doesn't give any benefits.

If you think about it this is exactly the situation you are in if you're producing images for devices that are sRGB such as web and consumer inkjets. Using aRGB as a working space has no advantage.

The aRGB advantage only shows up when you stay in 16bit and output to a device that supports true 16bit bandwidth or are going to CMYK separations.
 
Correct, yes.

But since it doesn't take up any extra disk space, I think it's better to retain the option rather than assuming you'll never need to print CMYK.

However that's probably just me secretly thinking I'll get famous one day and my back catalogue will be worth summink ;)
 
LOL, those of us with the half-empty glass just keep the raw file instead.
 
As do I, but I typically spend half an hour processing each image and since I'd rather not have to repeat the thirty minutes of 'fun' I also keep the PSD.

The price of disk space is less of a burden than the time it would take to do it all again (assuming I could even remember exactly what I did, and that future versions of Photoshop worked in the same way, with the same tools).
 
In January's Digital Camera magazine (Issue 55), they say set your camera and photoshop to Adobe 1998 RGB and never sRGB. They say the s = stupid! They do also say you will have to convert it to sRGB for web use, which is just what advice has already been given here, so well done TP people, once again.

Now, if I only knew how to check...........:LOL:
 
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