Topic awaiting preservation: Newbie help needed with RGB colour management (Page 1 of 1)

I'm tyring to get Adobe Photoshop 5.5 set up to convert my downloaded pictures from my Canon camera (A70) into Adobe RGB. (All the books seem to recommend using Adobe RGB rather than sRGB). I've hunted high and low but can't find any advice as to what input settings I should use for my camera. Canon is not listed in any of the options. There's nothing in the camera spec to say what type of RGB it uses. If I have "none" as the input and then press "convert" the photos all darken and have a somewhat red cast. The best results seem to be obtained by using the sRGB input. Am I doing the right thing? Also how do I adjust the input for my scanner (Hewlett Packard 5370C). Your advice would be much appreciated.

Hello and welcome to the Asylum dahliarose
Football on the TV in 2 minutes so I'll just lash in a quick suggestion;
In Photoshop, with the imported photograph open, go to Image>Mode and select RGB colour. Is that it?
I know nothing of scanners sorry

::tao:::: ::cell::
"Those who look for monsters should look to it that they do not become monsters.
For when you gaze long into the abyss, the abyss also gazes into you"

Thanks for the reply. Image Mode is not the solution. The problem is trying to decide how to import my files in the fist place. I've change the work space to Adobe RGB as recommended in the books I've been reading. When I try and open a new file from my camera I get a message saying "This RGB image does not have an embedded profile. Specify desired input conversion." There is a long list which inclues sRGB, Adobe RGB, Apple RBG, Color Match RGB, Wide Gamut RGB, etc. How do I know which one to choose? There are two Hewlett Packard IIc scanners listed which I presume are high-end professional scanners but not my more humble home scanner.

Basically it all depends of what you want to do with your images


A friend of mine already answered such a question, here's what he said :

quote:

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Adobe RGB is only good if you are editing your photos in Adobe. Most other Windows software and devices (printers) prefer to see a sRGB image for colour matching. Also the same applies to print labs (non-professional) and instant print booths, better results will be obtained with sRGB.

Publishing pictures to the web is also better in sRGB, also sending picture discs to friends are better in sRGB. It all depends on what you are going to do with the pictures you take which colour profile will suit you best.

Adobe RGB has a wider colour space than sRGB, quote Adobe: "The larger the RGB working space, the farther apart each color value would be from its nearest neighbor." which comes down to Adobe RGB has a broader range of colours. This means that your images are truer in colour shading but the difference is very difficult to see with the naked eye. If you are taking pictures with the intent to only edit/print in Adobe applications then Adobe RGB is your preference.

Adobe RGB images straight out of the camera will look less colourful/contrasted than sRGB images when viewed in standard Windows applications. The same applies to printing these images using Standard printer profiles which expect/prefer to see an sRGB image.

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It should help

----
If wishes were fishes, we'd all cast nets.



(Edited by Moon Shadow on 02-27-2005 16:19)

Let me see if I understand this dahliarose, I am a Tao of little brain so excuse me if I state the obvious or repeat things. I am not familiar with PS 5.5 as I use PS7 so I'm hoping there is not too much difference in this procedure.
When I am editing digital photographs (I use a Fuji S304) I first transfer them from my camera to my computer using the software that comes with the camera. This saves the images as JPEG's. I then open the image in PS.
I assume that you are having difficulty loading the photos into PS from a folder on your computer, and not straight from the camera?
After reading the info below* I see that the A70 saves as JPEG only (some DC's also give you the option to save to disk as a TIFF or in RAW format).
*info below
relevent forum discussion
Ken Rockwell
DPReview
You are saving the photos from the A70 to your hard drive as JPEG's aren't you?
Good luck let us know how you get on. I'm sure there is something we should be able to do to sort this out

::tao:::: ::cell::
"Those who look for monsters should look to it that they do not become monsters.
For when you gaze long into the abyss, the abyss also gazes into you"

Some good info here also.

http://epaperpress.com/psphoto/index.html

If you want to learn Color Management, http://computer-darkroom.com/home.htm is a very good place to begin with.
You should look in your camera manual to see what color mode it uses. I bet sRGB.
I'm wondering if PS5.5 can see the exif info. seel in file>file info.
If the files are untagged, you may try image>apply sRGb profile, then ImageConvert to AdobeRGB.

Pierre Courtejoie

Thank you everyone for the advice and the useful web links. Further to Tao's posting I thought I would just confirm that all my images are saved onto my hard disc as superfine JPEGs. The camera manual does not say anywhere what colour mode the camera uses. The JPEGs are in the Exif 2.2 format (also known as Exit Print) which is "a standard for enhancing the communication between digital cameras and printers". I don't want to print my photos out at home. I take them on a CD to the local specialist camera shop. I guess I would need to check which RGB mode they use to print their photos. I'm not interested in publishing photos on the web - I just want to get the highest quality prints which is why Adobe RGB was recommended. Pierre, I don't have an option in the image menu to "apply sRGB profile" with PS5.5. I've just discovered on the PS5.5 help menu that most scanners are adopting sRGB as the default setting so I presume that is what my scanner uses and probably my camera too.

dahliarose

As MoonShadow said, "it all depends of what you want to do with your images".

The color profiles are used by PhotoShop to determine how much of the color space PhotoShop will use for editing the image. The reason PhotoShop is telling you that there is no Color Profile associated with the image is that when the image is created on your hard drive by the camera or your scanner, there is no color profile associated with it. When you read the image into PhotoShop, it will associate a color profile with the image. The camera is probably using sRGB color space. You may be able to choose the color space used by the scanner.

The printer will convert the images to CYMK color space before printing them. Because you are associating an RGB color space with the images, you may notice a dramatic drop in saturation when the photographs are printed. The amount of shift in saturation will depend on what colors are used in the image.

You can get an idea of how much shift you will see by changing the mode of the image to CYMK in PhotoShop. There is also a Gamut setting (I think it is under the Windows menu. I don't have PS5.5 up right now). This setting will highlight any areas of the image that are outside the CYMK color space. If there are areas outside the CYMK color space you may want to change the colors used in those areas to a color inside the CYMK color space rather than allow PhotoShop or the printer to do it automatically.

If your scanner will create images in a CYMK mode you will be better off doing that than creating RGB images and converting them to CYMK. The images you create this way will look more like the original than if you create an RGB image and convert it to CYMK.

All automated color space conversions will cause some loss of color clarity in your images. You should avoid them when ever possible.

Since your intent is to print the pictures you are taking with the camera, using the widest range of RGB will help to reduce some of the loss of color clarity when you convert to CYMK so you are probably better off selecting the Adobe RGB when you read them into PhotoShop.

The best thing is to experiment with various settings while taking a couple of your images through the process of moving them from the camera or scanner to the computer, manipulate with PhotoShop and then take them to the printer. Playing with a range of settings for each step in this process will result in printing twenty to thirty different images which you can compare to each other and determine for yourself which methods produce the results you want.



.

-- not necessarily stoned... just beautiful.

Hyperbole, Thank you for the advice. I think as you say it is best to experiment with different settings and see which one works best. I shall get some prints done in sRGB and some in Adobe RGB and see if I can notice any difference. I've now been told by Hewlett Packard that my scanner uses sRGB colour space and I'm pretty certain that my camera also uses sRGB though I've not yet had a reply from Canon. Hewlett Packard have referred me to the following URL which other readers might find helpful:

http://www.answers.com/main/ntquery;jsessionid=15hp4d9pbnhe4?method=4&dsid=2222&dekey=SRGB+color+space&gwp=8&curtab=2222_1&sbid=lc04b


I'm somewhat confused about your comments on CYMK. I used to work in publishing and so I have a reasonable understanding of the four-colour (ie, CYMK) printing process which is used to produce newspapers, books and magazines. I'm only producing amateur family snapshots and am not intending to have any of my prints published so presumably your comments about CYMK don't apply to me. I'm producing jpeg images on my camera which I transfer to a computer. I'm not working with transparencies which have to be converted into four-colour separations. The photographic labs must surely all work in RGB. My local photographic shop uses an AGFA machine which apparently cost about twice as much as the machines used by Boots, Tescos and other high-street stores. This machine has an in-built computer which they tell me has a very sophisticated mechanism for colour management and produces very high-quality prints. I shall experiment with a few sample photos and see how I get on.

dahliarose

dahliarose,

I was probably a little sloppy in my terminology. I was using RGB to refer to additive color space and CYMK to refer to subtractive color space.

When you look at an image on the screen, you are viewing the colors in an additive color space, in this case RGB. The Red, Green, and Blue phosphors of the screen are excited to create bursts of light which add together to create the various colors you see. When you take that image to any kind of print (be it newspaper, magazine or photograph) you are converting the image to a subtractive color space. That space is most commonly CYM or CYMK. The subtractive color space is created by adding inks, or emulsions to the surface of the paper which will filter out the light being reflected by the (white) paper.

Even if your photographic lab is willing to accept a disk with the image stored in RGB, they will at some point have to convert the image from an additive color space to a subtractive color space in order to put the image on the paper.

RGB can show colors that are not available to you in CYM. There are colors (not as many) in CYM which cannot be created using RGB. When you convert from one color space to the other the colors that are out side the space you are converting to will be shifted into the new color space. How they get shifted depends on how the programmer who set up the conversion program decided to shift them. Usually they will be shifted to the nearest color in the new space. (Nearest is usually determined by vector subtraction to create the shortest shift).

When converting from RGB to CYM many of the vibrant colors you see will be shifted to a more muted color. There will be a loss of saturation because many of the more vibrant colors in RGB are outside the CYM color space. These are called "out of gamut" colors.

When I want to print an image, I would rather look at the image in PhotoShop and shift the out of gamut colors to another color that is in gamut myself than allow someone else to pick the new colors for me. I have had the experience of sending an RGB image to a printer and letting them do an automatic conversion from RGB to CYMK. The image came out muted and desaturated. After I saw what happened, I took the image back into PhotoShop, converted it to CYMK and chose a couple of different colors. I took a vibrant pink to a different shade of vibrant pink and a pastel blue to a different shade of pastel blue. The image looked essentially the way I wanted it to, but this time when the printer printed the image there was no shift in the saturation and the image on paper looked very close to the image I had created in PhotoShop.

This is a long way of saying "Yes, I think my comments about CYMK do apply to you."

Good luck. I'm glad you are going to try a couple of experiments to find out which method works best for you.



.

-- not necessarily stoned... just beautiful.

Excellent information Hyperbole. Again the knowledge base here... astounds.

I've just spent a few weeks looking into this very thing. ...the type & make of printers being used by local outlets... type of paper etc. some email chat... some in person. Again reading and re-reading "professional photoshop 5" The classic guide to color correction by Dan Margulus. (Thank you VP)

While some of the info in the book might be outdated a bit, there's a lot of solid basic info on things like sRGB.

quote:

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sRGB is a standard suggested by Micro-Soft and Hewlett-Packard, with the fanciful idea of someday having everybody who accesses the Web see precisely the same colors, regardless of what monitor they use.


In May 1998, as Photoshop 5.0 shipped, one of its top color architects wrote as follows about his program's new default: "Actually, sRGB is only recommended for those that don't better (or never do anything other than Web work)."

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A couple of things I learnt along the way. Don't count on the person running the machine to necessarily know a whole lot ... if anything more than you. I was talking (in person) to this one fella... asking about the sRGB RGB... and just as I was about to ask about the conversion to CYMK he blurts out something like... ".... Oh ya.... and then there's that C M K...ah CKMY... I don't know...can never remember what that stuff's about. I just run the machine."

That was pretty scarey.

Some other useful (to me at least) information I gleaned along the way.

If you're scanning actual photographs and then burn the images to CD and then take that CD in to have hard copies printed from the CD, you can save them out as TIFF's. If however you want to upload those same images to the outlets site and have them printed... you can only upload jpegs... because of the difference in file size.

Also... ( now this is from film taken in for developing) all outlets seemed more than willing
at no charge, to SCAN & burn an additional CD at what this outlet calls "Expert resolution: 4523 x 3023 pixels" allowing you to see and thus work with a whole lot of pixels. =) The "Consumer resolution: (is) 1536 x 1024 pixels" and in the middle "Professional resolution: 3072 x 2048 pixels"
These of course are 'single images.'

I thought that was quite accomadating.

Now a question I didn't get around to asking and you've sort of answered it up there^ is:

Does it make sense to burn to CD and then have printed a CYMK color bar or color wheel (using PS) which in my little pea-brain sees this a point of reference for at least that specific printer (outlets)?

Make sense?

Again... thanx for the info... when it comes to this technical stuff you, JKM, Steve and that WARJ. fella and others I've missed... make this old guy's head hurt. Really REALLY HURT! I'm gonna have to pad the wall.

NoJive,

I like the idea of creating a color bar and having the photo lab print it. In fact, I would create two color bars one in CYMK and one in RGB and have the lab print both. It would be instructive to see how they compare.

If they could print both on the same sheet so you can compare the two results side-by-side that would be great.



.

-- not necessarily stoned... just beautiful.

I understand the differences between RGB and CYMK but I'm still somewhat confused about this issue. When I look at the properties of my Hewlett Packard DeskJet printer it clearly states that the machine uses an sRGB colour space. As I was unable to get an answer from my camera shop about the spec of their Agfa machine I checked out the Agfa website:

http://www.agfaphoto.com/en-GB/photo-processing/index.html

On searching the website for RGB I came across the specs for some Agfa photoprocessing machines which state that the exposure used is "RGB laser 400 ppi". I also found the following webpage which explains the RGB laser printing process:

http://www.gammaphoto.com/tech_lambda.html

Here it clearly states that files should be in RGB format. If they are in CYMK they have to be converted to RGB and the company prefers to do their own conversion. All this suggests to me that for my purposes, using the high-quality Agfa machine in my local camera shop, I should supply my photos in RGB format to get the best possible results. Presumably the photoprocessing machines used by other companies will have different specs so it would all depend on the type of machine used by your local high-street shop.

dahliarose

Yes, I understand that many printers these days are expecting RGB input. This would include your HP, the Lambda Digital Photographic Printing System on the web site you pointed out, and possibly the AGFA at your photo-lab.

And, Yes, for those printers you want to give them an RGB file as input because they won't know how to interpret the data in a CYMK file.

And, Yes, Gamma Photo states specifically that they want to receive RGB file and if a customer gives them a CYMK file they want to do the conversion to RGB themselves. I interpret that to mean that if someone creates a CYMK file (possibly because that is what they are used to working with and don't feel comfortable with RGB), Gamma wants to use their professional expertise to convert the CYMK to RGB so that they can match the colors as closely as possible when doing the conversion rather than letting a computer pick the new colors for the image. The web page doesn't say so, but I assume Gamma will also charge for this service.

HOWEVER, when you send the RGB file to the printer, at some point no matter what method is used to fix the pigments to the paper, you have switched the image from an additive color space to a subtractive color space. Usually this means converting from the three additive colors Red, Green, and Blue to the three subtractive colors Cyan, Magenta, and Yellow. Most printing processes also throw in Black because it is not really possible to create black by using Cyan, Magenta, and Black because the dies we use in the inks are not creating pure colors .....

When you convert from any color space defined by three colors to another color space defined by three or four colors there [i]is[/] going to be some kind of loss in the color information stored in your image. If your photo-lab is using a machine that defined its color space with many colors it is possible to convert from RGB to the printer's color space and have little loss of color information. Again, however, you have to have a number of colors defining the color space that approaches infinity to be able to do this and most printer manufacturers use only a small number of colors to define the color space. I think I have heard of printers that use up to six colors to define the color space, but six is still pretty short of infinity.

Enough discussion of theory. What I am saying that you need to do is look at your images in PhotoShop and check to see if any of the colors used are out of gamut for the CYMK color space. If they are then you will want to edit the image to move those colors back into the CYMK gamut. After you have done that, you will create an RGB file of the image, take it to the lab and they will give the RGB file to the printer which will convert the RGBs to CYMK and create an image on paper for you.

If you do not do this, you will find that in at least some of your images, there will be color shifting and you will see a loss of saturation in the resulting print. Editing the image in PhotoShop and correcting any out of gamut colors will help you avoid this.

Try the experiment that NoJive suggested above: Create two images in Photo shop. One is the entire spectrum (or gamut) of RGB colors the other the entire spectrum of CYMK colors. Create both files as RGB files and take them to your photo-lab. Ask them if they can print the two images side-by-side on the same sheet of paper and then compare the two spectra to the images on your computer screen. If you don't see any major difference, you don't have anything to worry about. I suspect that you will see some noticeable difference in the RGB color spectrum.

You are absolutely correct that the process of getting image to print varies for each and every printer you may use and I'm sure that any experience you may have with your photo-lab would be different than the experience I would have with my printer. This is the reason it is a good idea to run several example prints to the printer before you have a job that you have to get right. Talk to the printer about the things they can do to help you and about their understanding of the printing process. The printer is a specialist, just as you and I are, and has a very deep understanding of how to run his machines, but may have a very limited understanding of any part of the process outside his area of expertise.

You can learn a lot about the process by talking to the printer. If you are having difficulty understanding each other, it is best to find someone you can talk with and each of you may learn from the other.




.

-- not necessarily stoned... just beautiful.

Hyperbole

Many thanks for the comprehensive and helpful explanation. I think I now finally understand the processes involved. When I compare my printed photos with the same images in PS on my LCD monitor I can see that there is some loss of colour, especially with the deep reds and blues, but the results I'm getting from the photo lab are very good. Some of my reds were too strong anyway so they've benefited from being toned down. (This may of course be because my monitor is not calibrated correctly but that seems to be yet another problem entirely!) I'm still trying to get to grips with the basics in PS and I haven't yet mastered the art of colour correction using curves, levels and channels so for the moment I'm probably best letting the photo lab make the adjustments for me. As an experiment I did try converting two images into CYMK and getting prints made. These two images both had very strong reds and blues when viewed on my monitor as RGB files and when I ran the gamut warning large areas were highlighted. The resulting prints from the photo lab from my home-made CYMK conversions were very poor compared to the RGB files which they converted for me so I can see that it would be best to let the photo lab do the conversions. I think as you say it would be an interesting experiment to create two images showing the entire spectrum of RGB and CYMK colours and get these printed as a comparison. I'm not quite sure how to go about doing this at the moment (as I said I'm a complete beginner) but I shall experiment and see what I can come up with. I thought I was asking a simple question. I never realised that the subject was quite so complicated!

dahliarose