Lately I have been finishing my underwater images in Photoshop, as Lightroom does not offer the amount of color correction control I waned.

However, reimporting my corrected images into Lightroom, the black point RGB numbers were not  consistent with my Photoshop RGB numbers.

My normal workflow is:-

1. Import my RAW underwater images into Lightroom and optimize them as far as possible.
2. Open the image into Photoshop with the Lightroom adjustments.
3. Do a final colour correction in Photoshop using a Curves Adjustment layer and  RGB numbers. Using “Color Correction by the numbers” tends to give the image more punch, with blacks set to 12:12:12 (5%  black) and whites to 243:243:243 (5% white). (This technique is explained in detail in Photoshop CS4 – Color Correction by Taz Telly on Lynda.com.)
4. Save the Photoshop modified image with layer modifications in TIF format.
5. Import the modified TIF file back into Lightroom.
6. Knowing the final RGB numbers in the modified TIF file, do a final adjustment to the original RAW file in Lightroom, to get the RAW and TIF images as close as possible.

When I set my blacks and whites to 5% in Photoshop and imported the images back into Lightroom, I noticed the blacks were not 5% black.

I was stumped on this for a while until I did a bit of experimenting to figure out what was going on.

Figure 1 – RGB1998 Test pattern.

Creating the test pattern in Figure 1 using a RGB1998 colour profile, the RGB 12:12:12 (5% black) in Photoshop measured 2.2% black in Lightroom.

Likewise the RGB 243:243:243 (5% white) in Photoshop measured 4.6% white in Lightroom.

What is Happening?

To fit in as many colors as possible, Lightroom uses the Melissa RGB color space (named after one of the Lightroom team members), which approximates the ProPhoto RGB profile, and is larger than the RGB1998 and sRGB profiles.

When my Lightroom image is exported to Photoshop, the image is converted to my RGB1998 working color space, which alters the black point.

This means:

1. If I have an image in Lightroom that I want to adjust for 5% black in the working RGB1998 color space, I need to set the black points in lightroom to 2.2%.
2. If I have an image in Lightroom that I want to adjust for 5% white in the working RGB1998 color space, I can use the Lightroom setting as 95.4% is close enough to what I want.

]]> http://www.carlchapman.com/workflow/colour-management/lightroom-rgb-percentage-vs-photoshop-rgb-numbers/feed/ 0 http://www.carlchapman.com/workflow/software/photoshop-cs4-bug-color-sampler-to-curves-shortcut-in-windows/ http://www.carlchapman.com/workflow/software/photoshop-cs4-bug-color-sampler-to-curves-shortcut-in-windows/#comments Sun, 11 Oct 2009 10:35:54 +0000 Carl http://www.carlchapman.com/blog/?p=611 I was doing some color correction recently and noticed there is a bug in the Windows version of Photoshop CS4 when using the color sampler tool shortcut that places a point on the Curves Adjustment layer.

Using the colour sampler tool in Photoshop CS4 you can select a point on an image, which places a marker and allows you to read the RGB relevant numbers on the info palette. If the curves tool is open and you CTRL -SHIFT select the marker again, the point is placed on the individual Red, Green, and Blue curves that relate to the colors of the marker.

This should also work when you are using the Curves Adjustment layer, and I have watched people use this shortcut on Mac machines without problem.

However it does not appear to work for the Windows version of Photoshop CS4. Nothing seems to happen when you use the CTRL-SHIFT select function when the Curves Adjustment layer is selected.

• Initial Problem description.
• Fix Details.

Going to the browser configuration menu (see my previous post Firefox V3 Browser Colour Management), I notice the gfx.color_management.enabled element has been removed.  Now only gfx.color_management_rendering_intent and gfx.color_management.mode are listed.

Using the default setting of management.mode =1 from the upgrade (new browser default is 2), I get the following result:-

Image 1

Notice how version 3 (right) displayed the color profiles correctly, but now version 3.5  (left) is not displaying e-sRGB and YCC-RGB correctly. The GBR and Adobe 1998 segments are displayed correctly.

I have looked around the web and apparently the reason for this change is that Firefox 3.5 no longer supports ICC Version 4.

I have ended up configuring my browser with the options:-

• gfx.color_management.mode = 2  (Color management applied only to tagged images.)
• gfx.color_management_rendering_intent = -1  (Use embedded intent)

For more information on these settings see the Mozilla developer forum – ICC color correction in Firefox.

I am traveling at the moment, so do not have the benefit of my large screen, but am running my colour profiled laptop using a Windows XP Pro platform.

I checked a favorite page on CNET that has a number of test images. The Browser displays the images as being color managed, but it is like the profiles are being displayed incorrectly.

I viewed the CNET images in three different browsers. Left browser is Firefox with color management enabled, center is Chrome, and right is Safari 4.

Both Firefox and Safari display as colour managed browsers, but the Safari browser is displaying the profiles of the top and bottom image differently, where Firefox is displaying the profiles correctly.

This is quite confusing as some tests  on the David Harradine  Image test page, and directly viewing images from the drive in safari4 are OK.

If I view my images on iStockPhoto they are displayed OK in Safari4, however if I view my images on Alamy or Photoshelter they are not displaying correctly in Safari 4, where they used to display OK in Safari3.

The images on all of these test sites display correctly in my color managed Firefox browser.

It seems like one of the methods for determining colour profiles has been removed in Safari 4.

I am not exactly sure what the error is, but would be interested in anyones comments.

The Problem

I was recently scanning some images using my CanoscanFS4000US slide scanner (Canonscan FS4000US ICC profile).  After scanning the images and assigning the custom profile, a number of slides were exhibiting saturated highlights.

Figure 1 – Saturated highlights

Figure 1 shows the ear of a Koala bear. You can see an area of red pixels around the bright centre of the ear.

I had not seen this in the past and it had me confused for a while, as I thought using a custom profile was supposed to correct this.

With a little investigation I was able to determine my problem was the scanner settings.

Scanner Settings

The Canoscan FS4000US scanner has a number of user configurable settings such as Exposure, Dust Removal, Focus, Colour Matching and Gamma.

I set the gamma to 2.2 and turned off all the auto settings.

Figure 2 – Exposure setting options.

The Auto Gain checkbox was left checked (ON), thinking this was an additional function to the exposure setting.

I then scanned one of my Wolf Faust (www.targets.coloraid.de) IT8 Provia 35mm transparency targets.

Figure 3 – IT8 target with Auto Gain ON.

Checking the scan results, a number of the light colored boxes are blown out/bright white (Figure 3).  Deselecting the Auto Gain checkbox (OFF), and using a zero exposure (EV0), rescanning the target produced the same result.

As EV0 was causing saturation, I decided to try EV-1. (Unfortunately the manual exposure setting for this scanner only works in +/- 1 steps.)

Figure 4 – IT8 target with Auto Gain OFF and EV -1.

Rescanning the IT8 target with Auto Gain OFF and EV-1, Figure 4 was a bit darker as expected, but the lighter squares showed some colour and detail. I also checked the blacks in the bottom row to make sure each was still distinguishable and they were not saturating.

Rescanning the target with Auto Gain ON and EV-1, I got the same blown out image as Figure 3. From this I can only deduce that the Auto Gain function overrides and disables any manual exposure setting.

Assigning the Profiles

I created separate ICC profiles from the IT8 target with Auto Gain ON and OFF, and assigned them to copies of the scanned image in Photoshop.

Figure 5 – Basic scanned image.

Figure 5 shows the scanned results for the same transparency. The left image was scanned with Auto Gain ON and EV-1. The right image is scanned with Auto Gain OFF and EV-1, and is darker as expected. At this point there are no signs of highlight saturation.

Figure 6 – Applying the ICC profiles.

The ICC profile generated with Auto Gain ON  and EV-1 was assigned to the left image in Figure 6, and the profile generated with Auto Gain OFF and  EV-1 assigned to the right image. Notice that in assigning the profiles to each image, the mid tones and colour casts where also automatically corrected. (There is still a slight red colour cast, but this can be improved later in the workflow process.)

Figure 7 – Close up view of highlights.

Zooming in on the ear in Figure 7, the area of red pixels formed from saturation can be seen around the bright area in the left image, but the image on the right is showing no saturation and significantly more detail.

Figure 8 – 3D view of compressed and uncompressed ICC profile.

The effect of Auto Gain compression on the pixels can also be demonstrated in viewing the ICC profile with the Chromix ColorThink software in Figure 8. The solid profile is the same for Auto Gain ON EV0, Auto Gain OFF EV0, and Auto Gain ON EV-1. The wireframe shows the profile for Auto Gain OFF EV-1.

Conclusion

A couple of important things I have learned in this little experiment are:-

1. Turn off ALL your scanner Auto settings when doing a scan. Using manual settings can make image correction easier and more accurate.
2. Be careful when profiling a scanner. Look for blown out highlights or saturated blacks in your target scans. You may have to fine tune the manual settings to get the best results.

]]> http://www.carlchapman.com/workflow/colour-management/scanner-settings/feed/ 0 http://www.carlchapman.com/workflow/colour-management/canoscan-fs4000us/ http://www.carlchapman.com/workflow/colour-management/canoscan-fs4000us/#comments Wed, 24 Dec 2008 05:51:55 +0000 Carl http://blog.carlchapman.com/?p=162 I decided to get serious about profiling my Canoscan FS4000US slider scanner, due to having several years of slides from the period before my switch to digital.

My Canoscan FS4000US scanner is a couple of years old now (costing around $1500AUD when new), but provides high resolution images from slides and negatives.

For years I have wondered about what profiles to apply to my scanned slides. I tried hunting around on the web to see if there was some kind of boxed ICC profile available, but could not find anything.

For a while now my standard procedure has been to import the images from the scanner into Photoshop, assign the sRGB profile, and then convert to my default workspace profile of AdobeRGB. I have tried assigning AdobeRGB profiles directly to the scanned images, but it resulted in over saturated images.

Noticing my images were slightly washed out after conversion, I began to question how much color information has been distorted in the workflow process.

Producing the scanner ICC profile

The first step was to purchase a couple of IT-8 slide targets from Wolf Faust (www.targets.coloraid.de). They were well priced, supplied very promptly, and good quality. Wolf has lots of interesting stuff on his main site www.coloraid.de about color management.

To produce the profile, I then downloaded and purchased the Profile Mechanic software from Digital Light and Color, which made the process of generating a profile very easy, and gave me the ICC profile required.

The generated profile is specific to the individual scanner, settings used, and the type of film the images are shot on. Most of my work was on Fujichrome Velvia100 and Provia slide film. I generated profiles for both, and even though they are generated for my scanner specifically, I have made them available for people to play with.

• Velvia and Provia ICC Profiles ( 6.4 MB zip file) – Updated 10 Jan 09 for high accuracy and better highlights (Settings:- Auto gain off, exposure -1, Screen Gamma 2.2)

Using the ColorThink software from Chromix, and comparing the new profiles to  the AdobeRGB and sRGB profiles, the scanner profile was surprisingly large.

The profile comparison above is for a Provia transparency slide, scanned at a gamma of 2.2.

The real world result

Scanning a sunset image, I assigned the CanonscanFS4000US provia profile, converted it to AdodeRGB, and then used the curves option in Photoshop to bring up the highlights.

The curves screen shows the pixel input is distributed from 0 to 207.

Assigning a sRGB profile to a copy of the original image, and converting to AdobeRGB, the curves screen shows a gap in the area of darks and highlights.

Using the curves tool to bring up the darks and highlights, the input pixels were distributed between 10 and 222.

Therefore the dynamic range of pixels is about the same in both images.

A closer inspection of the curves graphs show more pixel information in the shadows region of the curve for the ICC profiled image. This produces a more natural and correct result compared to the original scanned image.

I am now in the lengthy process of going through my slides and reprocessing them using the correct scanner ICC profile.

Went for a dive the other day on the Quicksilver vessel Silversonic out of Port Douglas.

The visibility was a little hazy after the series of storms we have been having, but managed to grab a couple of shots new species for my collection:- Volitans lionfish and Minor Notodoris nudibranch.

But I was more intrigued by some pictures of Anemonefish from a previous trip.

I had taken a couple of pictures of different species of anemomefish, and noticed that the white stripes came out with a blue hue (see image). The pictures were shot on a Canon PowerShot A650IS using the in-camera underwater colour profile.

I had done quite a bit of playing with the images and could not work out why the white stripes appeared blue, even when flash and colour management calibration was used.

During this last trip I paid more attention to looking at the anemonefish in greater detail, and to my surprise the white stripes actually have a blue hue to the naked eye.

I have also noticed the highlights in the A650 tend to blow out a little underwater. The files are saved as 8 bit JPG, so unfortunatley no information can be required from the highlights. Shooting in RAW would get around this, and I am keen to get my hands on the new Canon G10 and give that a try in RAW mode. Unfortunatley the advance models of the housings are all sold out, and it will be another month before they are available.

For interest, I decided to compare the canned profile with the Spyder 2 colorimeter profile using the Chromix ColorThink software.

The 2D view of the profiles show the canned and measured profiles follow each other quite well, except in the area of blue to red transition. It also shows they are off-set slightly.

Investigating the 3D view (canned profile in solid, measured profile in wireframe), shows the reason for the offset is that the white point has a different placement in two profiles. Rotating the 3D view I  checked the black points and they located in the same place.

Conclusion:- The canned profile will probably do for the everyday computer user, but anyone serious about colour accuracy and management should be profiling their monitor.

Ideally I would have liked to purchase an Eizo screen, but they aren’t within my budget just yet, so I looked at various screens available around town.

Settled on a Samsung 2243BXW due to price, and the fact that Samsung is one of the four companies that make all of the LCD monitors in the world.

The thing that I like about the screen is the 300 cd/m2 brightness. This blows away my laptop, and interestingly this does not seem to be a specification typically listed with laptops.

The first thing I did on setup, was color calibrate the monitor using the Pantone Spyder2 to compare it with my HP laptop.  After some experimenting I discovered Windows does not support ICC profiles on multiple screens, unless separate video cards are used.

The other thing I noticed is that there is a very narrow viewing angle (around 5 degrees) for the correct colour viewing. Moving slightly to either side (or up and down) and a red hue begins to appear at the edges.

After calibrating the screen, I checked the ICC profile using Chromix ColorThink software. This software is brilliant for understanding color issues, allowing visual 2D and 3D rendering and comparison of color profiles.

Results of the calibration show the Samsung 2243BWX screen has a color profile that approximates sRGB. (The Eizo screens quote 95-98% of AdobeRGB1998).

The other result is that the laptop screen gamut is smaller than sRGB, and this explains why images viewed on a laptop in a non-color managed environment appear faded. (I have had a couple of friends confine this effect on different laptop brands.)

This raises an interesting question – If LCD monitors can produce sRGB, why do laptops have a smaller gamut, when they are effectively the same thing?

The conclusion – The Samsung 2243BWX will do me for now, but when I get the funds together, will be upgrading to an Eizo monitor.