sRGB VS RGB

[phatkid77]

quick shots from last nite

RGB (what ive been shooting in)


sRGB


i think the latter looks more saturated??

phats

[jfrancho]

I don't have time to go into it right now, but it appears that you are assigning profiles to images, rather than converting. NEVER assign! ALWAYS convert! Seriously, I'll come back to this post later this evening, and explain further.

[ohenry]

For the web, convert your files to sRGB. Adobe RGB is a wider gamut color space and good for editing and even print but will look flat when displayed on the web or in a program that is not color space aware.

[jfrancho]

OK. You have three basic areas of the workflow: capture space, working space, and destination space. If you are using raw format, capture space won't be relevant, since you can just assign you working space in the raw converter.

If you're in jpg mode, then the default is sRGB. sRGB is a web friendly color space designed for monitor displays. It's got a good range of colors, and since most uncalibrated monitors are targeting that output, your pictures will display somewhat close to the way you intend. By somewhat close, I mean blue will be blue, red will be red, but the contrast (white point) and brightness (black point) might be off a bit. Chances are, the uncalibrated monitor will look a little cooler in color cast due to a slightly high target temp. like 9300 K. But it's close enough.

Back to the camera capture mode. Some cameras have the option of using a wider colorspace, Adobe RGB. This has a wider gamut than sRGB, meaning all the colors available in sRGB are contained in the Adobe RGB colorspace. All that, and then some - particularly in the saturated reds and blues. If you want to get into this advanced color management, I suggest you invest in a monitor calibration software/hardware bundle. B&H has a pile of them. Look for something in the $200-300 range and make sure it uses measured luminance. Remember that variable contrast and brightness I mentioned - this'll fix that on your monitor.

Short of calibrating your monitor, if you have Photoshop, you can use Adobe Gamma to get your monitor in the ballpark. Go to the Control Panel to run the wizard, and follow the instructions.

OK, you have a calibrated monitor and you're still wondering what capture workspace to set your camera at. If you are going to do anything more than crop and resize your images - tasks like color correct, sharpen, tone, touch-up, reduce noise come to mind - then I recommend using a wide gamut workspace. Adobe RGB, or aRGB for short fits that bill. If you are using raw format, there are even larger gamut color spaces, but save those for when you are more comfortable with color management.

While we're on the topic of raw, jpg and color, let's address color depth. If you are going to shoot in raw, make sure your output color depth is set to 16 bits per channel and save as a psd file. This will ensure that you extract every bit of color data from that raw file. If you are shooting in jpg mode, and using Adobe RGB, you will want to convert to 16 bits per channel by using Image > Mode > 16 bits/Channel. This will allow extremely sensitive editing, and reduce posturization in the final output. It's also a good idea to File > Save As... and choose psd. Consider this psd (either from raw converter or the jpg) you digital negative. Forget what everyone else says about raw being a "neg" - the analogy doesn't really work. You can edit this and retain the final version for cropping, reprints, different sizes for websites, etc. later.

If all you are going to is crop and resize, then choose sRGB. It'll save you the step of converting to the destination space. This called early binding to the destination space. It is absolutely fail safe. You can't get your colors messed up.

So at this point, you've decided these are wedding pics, and you want the most color possible for your pics. Well not so fast, most print services require files be sent converted to sRGB. So, in the end, you aren't gaining any overall color, but while you editing, you have a much larger pallet of color to work with, and that larger pallet will result in smoother edits.

After you are done editing and you are ready to switch to your destination space, or sRGB, go to Edit > Convert to Profile... and choose sRGB as the convert to space. Then you can (and this is the same for the raw workflow, or jpg workflow) use Image > Mode > 8 bits/channel to reduce the bit depth, and File Save As... a jpg. Use Quality 12 for this step.

So, either set the camera to sRGB and forget it. Or, take advantage of the wide gamut colorspaces available.

Review:

For jpg workflow:
Set camera to Adobe RGB
Set Photoshop working color space to Adobe RGB
Convert jpgs to 16 bpc
Edit
Save as a psd
Convert to sRGB
Convert to 8 bpc
Save as jpg.

For raw:
Set converter to 16 bpc, aRGB
Edit
Save as psd
Convert to sRGB
Convert to 8bpc
Save as jpg

For simple sRGB (Early Binding)
Set camera or raw converter to sRGB
Edit - make sure you convert to 16 bpc
Convert to 8 bpc
Save as jpg

[CogSci]

Thank you very much for the excellent explanation!
I have just one more question:
Which profile do you recommend to use for calibrating the monitor, sRGB (to see how the photo looks on the client's monitor, or in print) or aRGB (for editing in this color space)?

Best regards,
Klaus

[jfrancho]

When you calibrate the monitor, you'll be creating a custom profile for that monitor. The software should automatically apply it to the video output settings. That custom monitor profile will describe how the monitor will display the colors. The colorspace used in your image file describes the colors used. Make sense? So, you'll set your driver up to the default (for Windows its already sRGB) and the run your calibration tool, and create a profile that modifies the driver output. The tool should apply this to the video output itself. I use a Spyder2 Pro kit, and it uses a program called Profile Loader.

[CogSci]

Thank you very much for enlightening me! I finally got it. The whole picture ... not so complicated after all!

Best regards,
Klaus

[Jason Hermann]

Originally Posted by CogSci

Thank you very much for enlightening me! I finally got it. The whole picture ... not so complicated after all!

I second that Thankyou very much jfrancho.
Jay

[Waleed]

[grsphoto]

jfrancho

Excellent explanation

I have to question: "you will want to convert to 16 bits per channel by using Image > Mode > 16 bits/Channel. "

If you start with a 8 bit file ( jpg) and are just doing minor tweaks ( levels?) what real value is there in going to 16 bit?

It makes sense to me if you are shooting raw ( 12 bit) and working in 16 bit mode ( my preferred workflow)

Your thoughts?

Glenn

[jfrancho]

The difference is probably negligible in most images, but if you are applying a curve or adjustment with levels, by converting to 16 bits per channel, you will get more sensitivity and smoother transitions. Find a picture with a vast expanse of blue sky. Run a moderate S curve on it in 8 bpc mode, and take a snapshot. Roll back to the original and do the same edit after converting to 16 bit mode. Zooming in at 100% will reveal the difference. Many times it won't matter, but it is a simple step and can prevent problems down the road.

[Colby]

Jfrancho
Thank you for you clear and concise explanation of sRGB vs. Adobe RGB. It answered questions that I have had. The workflow information is also great.
Thanks and see you in your pictures
Colby

[KellyL]

Being a hands on, visual learner, I am going to have to read through this a few times before I fully comprehend. I find color spaces confusing and my schema is narrow. Thanks for the input on this topic, John.

[jfrancho]

You are all welcome. I do need to revisit one of my comments:

The software should automatically apply it to the video output settings.

I was speaking from a Photoshop perspective. If you are a Canon user, and like DPP for raw conversion (I do ), then you need to set the profile that you created with your calibration device in the Preferences. If you are not using a calibration device to create a custom display profile, then set it to monitor sRGB. I really have no experience with other camera OEM software, so mileage may vary with other software.

Also, using multiple monitors on a Windows system opens up a whole new can of worms, but that's for another post, and another poster.

[Paul Shields]

Great explanations jfrancho. This is such a common problem and I've been caught out in the past not realising the differences between assigning and converting. It makes such a big difference when posting on the net.

[jfrancho]

It's a terrible topic to try to overcome on a web forum - there are so many branches to each person's personal work flow and there really isn't one bulletproof color management system that fits all. What I posted above is distilled from many great web sites, like Cambridge in Color, Luminous Landscape, this and other forums, and Real World Color Management, along with my own trials and tribulations of images with dorked up color.

This info can be used as a general guideline on how to handle color management, but the best solutions come from explaining the specific work flow, equipment, and intended output. This pretty much covers web presentation and getting files ready for large consumer print services, like Mpix. It gets quite a bit more complicated for press - a topic that I've only begun to scratch the surface of.

[m1ks]

Hi J,
I'm a relative newcomer to Photocamel having found it via Dpreview.
That aside, you seem very knowledgeable regarding profiles and suchlike and I have a problem understanding this, i'll explain my situation.
(FWIW i've had several people babble at me on DP and really cannot make head nor tail of their responses and don't feel they really understand me).
OK, I have a pantone Huey with which I calibrated my monitor, all straightforward and Ok so far, it created a custom profile as one would expect.
When I open a converted RAW, (Tiff or Jpeg), in CS it asks me if I want to leave the profile as captured (I shoot in aRGB), ignore, or assign the custom profile, (calibrated profile).
If I assign the cal prof, the image looks OK and prints looking near enough like the 'seen on screen' version.
If I assign the working prof aRGB, the colours are more muted than print.
I understand the colour gamut issue re sRGB for web etc and aRGB for editing and for images to print i've set to calib prof.
I've had many many people say i should not assign the calib prof when opening my images and should use aRGB or sRGB instead, (this is where my brain goes whooooaa there boy and shuts down), none of the posters have given an understandable reason for this.
Could you please advise me if i'm OK to assign the calib prof upon opening an image or if I should be using a / s RGB and why this takes me from prints which look 'matched' when using the calib prof and 'off colour' when not.

I hope this makes sense and await your reply.

Mike

[jfrancho]

If you shot in raw mode, color space in camera doesn't matter that much. You will assign what working color space when you convert to TIFF. The reason Photoshop is asking what to when opening the image is caused by your color management preferences. You will want to change these. Ctrl-Shift-K should bring up the Color Settings dialog, and you will want to set them up like this:



This will preserve the color data as encoded by the camera, or as specified in the raw converter.

Never assign profiles. The only time this ever happens is when the file has no color space info, and you have to guess at the right color space. This shouldn't ever happen if you are working with your own images. Assign the wrong profile to an image made in another profile, and the colors will be skewed. It is perfectly acceptable to convert from one profile, like Adobe RGB to sRGB. I prefer to do this conversion in 16 bit/channel mode. Here is the Convert to profile dialog, for reference:



Assigning the profile created by the Huey is totally unpredictable, and may work once, but I don't expect consistent results. Never, ever do this.

Remember, the Huey is a profiling device that describes and correct the color behavior of the monitor. The "profile" created by this may seem to be a working color space, but really isn't as comprehensive as even a small gamut color space like sRGB.

The "working color space" is your pallet of colors with which you can use in your image file while editing.

"Color Depth" refers to the number gradations there are in each channel. It's measured in bits/channel. There are three channels - R, G, and B - so and 8 bit/channel JPEG contains 24 bits of color data. 16 bit/channel offers much more sensitivity when editing, and therefore is the preferred output from RAW conversion when there will be some processing in Photoshop. Unfortunately, JPEG doesn't support 16 bit/channel images, so files have to be converted to 8 bit/channel before saving in this format and shared on the web. Do this LAST in your work flow.

Lastly, as explained above, sRGB is the required output for close to correct color rendition on the web. Many print services also require files be converted to this color space for printing.

For more information on processing image files, color spaces, color depth, and how all this relates to work flow see these other posts:

http://www.photocamel.com/forum/imag...harpening.html
http://www.photocamel.com/forum/imag...ts-images.html

Also be sure to explore the informative links in my post above.

[happusa]

Jfrancho - have a karma for this one!!! Fantastic info. Thanks

[m1ks]

Also be sure to explore the informative links in my post above.[/quote]

A huge thankyou to you for taking the time to explain this in a clear and concise manner, I really do appreciate it, this is the most comprehensive explanation I have ever received and can only assume that previous posters on the subject either weren't sure or simply didn't know themselves but that only added to my confusion on the subject.
I will ask one more thing however, , Do I need to adjust the profile assigned to the printer, (which I believe is currently the Huey), or leave it alone.

Thanks in advance for this and thanks immensely for the previous post.

Mike