Professional Photography : color

Color Management in Windows Vista vs. Mac OS X

Eileen Fritsch — Mon, 23 Nov 2009 14:01:00 GMT

I am a cross-platform kind of guy. I have my wonderful black MacBook as well a Dell desktop running Windows Vista Professional. When I teach a class on color-management or other aspects of photography, I always like to know which platform each photographer is using.

In most cases, the photographer’s operating system of choice has to do with experiential history—whichever platform the photographer first started using is what they have continued to use. Sometimes I hear about photographers who have switched from OS X to Windows and vice versa.

One reason I use both operating systems is because I frequently get questions about how Windows integrates color-management differently than Mac OS X. Different versions of Windows handle color management differently, So let’s focus first on Windows Vista.

Storing Profiles in Windows Vista: In Vista, the ICC profiles for your displays, scanners, cameras, and printer/media combinations are stored in the Windows/System32/Spool/Drivers/Color directory. If you haven’t done so yet, you might want to make a shortcut on your desktop to the contents of the directory.

One of my favorite color-management features of Windows is that if you acquire a profile from an outside source (either by downloading one from a website or having one sent to you via e-mail), you can easily copy the profile into the proper directory.

Simply right-click on the profile and select Install Profile. This simple process will copy the profile into the Windows/System32/Spool/Drivers/Color directory where it will be available for ICC-aware applications such as Photoshop and Lightroom. Mac OS X does not have this feature. If you are wondering where profiles reside in OS X they are located in you Library/ColorSync/Profiles directory for either the root or user level.

Display Calibration: When you calibrate and profile your display for color-accurate editing, you should know that one of the trickier things about Windows is that the video card driver must support a software rewrite of the default gamma tables in the video card LUT (Look Up Table).

X-Rite has a tool to test this. Click here to check it out.

If your video card does not support modifiable video LUT's then you may have to upgrade or downgrade your video card driver, or even possibly purchase a new video card. This is common on many older laptop PCs.

Mac OS X works on a totally different premise and ColorSync can use a table in the display profile to load the calibration data to the video card.

Windows Color Systems: One of the biggest changes in Microsoft color management was the introduction of WCS or Windows Color System for Vista. This was introduced during the development of Vista. This initiative was a collaboration with Canon, and uses Kyuanos technology developed by Canon. WCS is very powerful and has a host of totally new features designed to evolve color in the OS.

We’ll talk about some of these improvements in more detail in a separate post, but some of the benefits of the Windows Color System include a completely revamped color infrastructure and translation engine called CITE, an enhanced color-processing pipeline that supports greater bit depths and multiple color channels, and support for scRGB (a wide gamut RGB space developed by Microsoft and HP). Most notably, Windows Color System provides an improved user experience through a centralized color control panel.

Where Vista Still Lags Behind Mac OS X: The biggest issue with color management in Windows Vista is the lack of integration of the display profile into every application.

One of the beauties of Mac OS X is that every application uses the display profile to render color. This means that if an image has an embedded profile, OS X will convert the color data and give you the correct appearance on your screen. Your images will look the same whether you are viewing them in Photoshop, Preview, Safari, and Mail.

This is not true for Windows Vista. In Vista, applications need to be ICC aware to accurately display color images that have been created and saved in color spaces other than sRGB.

This means that images that you have edited and stored in the Adobe RGB or ProPhoto color spaces will look different in Internet Explorer, Outlook, or Microsoft Picture Viewer than when you edited them in Photoshop or Lightroom.

For more information on photography and color at Microsoft visit www.microsoft.com/prophoto and www.microsoft.com/whdc/device/display/color/WCS.mspx

Marc Aguilera is a part-time professional photographer and Photography and Digital Workflow instructor for University of California San Diego Extension. He is also an Apple Certified Professional in Color Management and Apple Certified Pro Trainer. He is a color expert for X-Rite's Color Services division and speaks on behalf of the creative community at AIGA's HOW Conference and at the PIA/GATF Color Conference each year. He has a BA degree in Visual Arts from Univeristy of California-San Diego. You can reach him through his blog at http://www.colorcritical.com.

Bit Depth Basics: More Than a Numbers Game

Eileen Fritsch — Wed, 29 Jul 2009 18:58:00 GMT

By David Saffir

One of the most under-appreciated features of newer-model DSLRs is their ability to capture images with greater bit depth. Bit depth is a way of quantifying the amount of color information in each recorded pixel. It is also a key component of high-level image quality. In this post, we’ll look first at the numbers. Then, we’ll talk about what these numbers mean in terms of dynamic range, color fidelity, and highlight/shadow detail. These are key attributes that influence the quality of the final print.

Not long ago, most cameras functioned in 8-bit mode. Then the higher-end DSLRs became capable of using 12-bit capture. Now they are up to 14-bit, which is a huge benefit to photographers. If you don’t understand bit depth, these may sound like incremental improvements. But they are actually exponential improvements.

To see what I mean, let’s start with a brief review of the numbers. It is simple but non-intuitive:

· There are three primary colors (or color channels) in each captured digital image: red, green, and blue.

· Bit depth describes the number of tone gradations (or intensities of color) provided in each pixel. Most digital images are captured and/or stored in 8-bit, 12-bit, 14-bit, or 16-bit mode.

§ An 8-bit image has 256 tone gradations in each of the three color channels;

§ A 12-bit image has 4,096 tone gradations in each color channel;

§ A 14-bit image has 16,384 tone gradations in each color channel; and

§ A 16-bit image has 65,536 tone gradation in each color channel.

Another way to look at the depth of an image file: A 16-bit image file is twice as big as an 8-bit file.

The major benefit of working with high-bit images is increased dynamic range— the range of tones and detail that the camera can record from the darkest dark to lightest light.

One software company, DXO, now provides public access to its database on camera performance. Here are some examples of the differences between 12-bit, 14-bit, and 16-bit capture:

· The Nikon D2X captures images in 12-bit mode when shooting in RAW format; its dynamic range is rated at 10.9.

· The Nikon D3 captures in 14-bit mode; its dynamic range is rated at 12.2.

Dynamic range is measured like f/stops: an increase of one step is a doubling of dynamic range. That’s a big, big difference.

There is also a noticeable upside in image editing, and in the appearance of the final print.

Figure 1 above is a screen shot of a 16-bit image being edited. Note that the histogram is smooth and even, and shows no breaks or lines.

Figure 2 above shows a screen shot of an 8-bit version of the same image. Note the white lines running vertically in this histogram. These are sometimes called drop-outs, and they show information that is lost when the image is edited . These losses can result in color distortions, posterization, color aliasing, and more.

We lose information every time we edit or manipulate an image. So, the more image information we have to start with, the more information that is available to us as we progress in our workflow.

It pays to set up your workflow to protect as much image information as you can for as long in the process as possible. Most printer drivers can handle high-bit images without difficulty. In my own workflow, I only use 8-bit images for web publishing, e-mail, and the like.

Image-editing programs such as Adobe Photoshop Lightroom are now set up to use high-bit images. And Adobe Camera RAW and Photoshop provide pretty much the same editing tools for 8-bit images and high-bit images, making workflow choices easier for the photographer. This is all good news for those of us who love creating the most detailed and beautiful prints possible.

What’s re-complicating printing workflows right now is the fact that Adobe Photoshop Lightroom uses a bigger color space—ProPhoto RGB instead of Adobe RGB. But we’ll leave a discussion of printing through Lightroom to a future post.

If you have any specific questions about bit depth, I would welcome your comments.

Choosing the Right Color Space

Eileen Fritsch — Sun, 01 Mar 2009 20:03:00 GMT

By Jon Canfield

One area of contention among digital enthusiasts is the choice of color space for doing editing work. Almost every camera gives you the option of sRGB or Adobe RGB at capture. sRGB is a good choice for JPEG capture, especially if you intend to place your images online. It’s a standard that is safe for most situations and displays. But is it appropriate for printing? That depends a bit on your printer and your workflow.Most of the better inkjet photo printers support a color space closer in size to Adobe RGB. Some of the newest printers are capable of printing colors outside of Adobe RGB as well, which makes ProPhoto a consideration.

How much difference is there? Figure 1 below shows both sRGB and Adobe RGB spaces, along with the ProPhoto color space. In this figure, the red area is the sRGB color space, green indicates Adobe RGB, and the outside line is ProPhoto.

Figure 1

It’s pretty easy to see that ProPhoto covers just about every imaginable color, so why shouldn’t you just select this color space and be done with it? The main reason you might not choose ProPhoto is that you can have colors in your image that will be significantly out of gamut for your output device.

Let’s take a look at Figure 2 below. This shows the ProPhoto color space as the large area with the new HP Baryte Satin Art Paper on an HP Designjet Z3200 printer as the inside area. The Baryte paper is an excellent media with a large color gamut, but it’s significantly smaller than ProPhoto. So, if you print to this paper you run the risk of having colors that are out of gamut and will need to be mapped to a new color.

Figure 2

But, if we work in Adobe RGB, you can see in Figure 3 below that Baryte actually has colors that can be reproduced outside of this range. You would end up having colors clipped and remapped that weren’t out of range of your printer in the yellow and cyan spectrum.

Figure 3

If you’re working in Photoshop Lightroom, this is a moot point because Lightroom uses ProPhoto as its working color space. Photoshop however gives you the option of selecting a working space.

My recommendation to attendees at my workshops is to use the ProPhoto space if they’re doing their own printing. I’d rather have color in my image that is beyond the paper limits than have colors lost that I could have reproduced.

But, does it matter? After all, as I mentioned at the start of this post, your camera most likely only has sRGB and Adobe RGB as choices. If you’re shooting RAW though, a color space isn’t actually applied until you convert to an image format such as TIFF or PSD. If your image is already in one of these formats, going from Adobe RGB or sRGB to ProPhoto isn’t going to improve your output. It would be like moving a gallon of water from a one-gallon bottle to a five-gallon bottle. You still have a gallon of water.

If you’re not shooting RAW, you’re already giving up quite a bit of image data, so I’d suggest using Adobe RGB to keep as much color information as possible unless you don’t print, or you send your work to an online photo service such as Mpix or Snapfish to be printed. In that case, sRGB will save you a bit of time and give you results that will be as good as you can get from the source files.

Fine-Art Reproduction Part 2: What You Need to Get Started

Eileen Fritsch — Thu, 24 Jul 2008 20:26:00 GMT

By David Saffir

Professional photographers are uniquely qualified to get into the fine-art-reproduction business because the element most critical to success is a quality image capture. Photographers not only have a discerning eye for color and detail, but also tend to have the best capture equipment. For fine-art reproduction, the lens, digital sensor, and software used to process the RAW digital image files have to be pro level, with no compromises.

Specialized Training
Before you invest in any additional equipment, it might be wise to invest first in some training—so you can see for yourself how the fine-art reproduction workflow differs from printing your own photographs. During a good training session, you’ll see why it’s not smart to try to cut corners when it comes to buying quality equipment.

For example, the training should cover specific capture, color control, and printing techniques that have proven to be successful in faithfully reproducing the colors used in the original artwork. This usually requires one to two full days of work, with lessons focused on image capture setup, color management, media selection, image editing and print prep. You also need to understand how the build good relationships with artists and some of the printmaking traditions specific to the art market. Once you’ve been trained, you’ll better understand the rationale behind all the other elements listed below.

The Right Lighting Setup
Digital image capture for fine-art reproduction is based on good old-fashioned copy work. It requires two to four color-corrected lights (strobes or continuous), diffusers or softboxes, a sturdy tripod or studio stand, and a stable copy stand that can support artwork in a range of sizes. You could use continuous lighting using tungsten bulbs, but I don’t recommend it. Even though we can correct color pretty well, a light source that isn’t color-balanced can lead to a number of problems, including excessive time in post-production trying to correct color distortion. It’s better to use color-corrected halogen or fluorescent lights.

A Good Camera and Lens
I use a Hasselblad H-series camera and a Phase One digital back. I really don’t see any reason to use film for fine-art reproduction unless your client wants to archive an image on film for some reason. With my equipment, I have gotten excellent results with images up to 40 x 60 in. in one frame, and panoramas up to 10 ft. long. It is quite feasible to shoot even larger pieces in one frame. Or, you could shoot the image in quarters and stitch them together in Photoshop. The recently released Phase One/Mamiya medium format combination is interesting, and costs less than competing products. A new Mamiya kit with an 80 mm lens has been reported selling for $10,000. You could use a high-end DSLR, like the Canon Mark II and III-series, or the Nikon D3 series on many pieces of artwork, but successfully reproducing a large painting usually requires the resolution that only a medium-format digital camera can provide. In any case, the cost of acquiring technology is lower and dropping every month. Used equipment is frequently an option as photographers trade in and trade up.

Procedures and Tools for Controlling Color
Reproducing artwork requires processes for controlling color at every step in the process, from capture to output. The more careful you are in controlling color, the less time and materials you’ll waste trying to get your print to match the original. If you’re serious about your digital photography, you probably have already invested in a high-quality monitor and tools for keeping it calibrated so you can accurately preview and edit your images on screen.

The most straightforward way to control color while shooting is to:

Ensure that the target artwork is evenly illuminated from corner to corner and from side to side, within 1/10 of an f-stop;
Shoot at lowest ISO available;
Use RAW capture; and
Include a grey card or white/grey/black target in your shot. (This will be an enormous help when processing the image on your computer.)

Finally, you will want to be able to routinely create accurate custom color profiles for each type of print media you use.

You can use a handheld spectrophotometer (such as the ones made by X-Rite), or an online service (which can be pricey). Or, you can buy a wide-format inkjet printer that has the custom-profiling functionality built-in (such as the HP Designjet Z3100). Being able to obtain accurate color profiles is essential, but that’s only part of the game. In order to efficiently be able to produce a print that looks just like the print you output six months ago, your profiles must be re-created or updated periodically.

A Pro-Model, Pigment-Ink Printer
You’ll need access to a wide-format, wide-gamut printer that can handle a variety of media types, media thicknesses, and roll widths. Most people in the fine-art reproduction business have a printer that can print up to 44 in. wide. Many printmakers use devices that can print up to 60 and 64-in. wide. These wider printers can be used not only to make larger prints, but also to efficiently print higher volumes of smaller prints.

If you don’t yet own a wide-format printer, some studios will rent you access to their printers for a day or half-day. In other areas of the country, you may want to purchase one for yourself. To produce the wide color gamut needed to accurately reproduce fine art, your printer should have at least eight ink channels. In my opinion, having 12 ink channels is better because the color palette and the control provided over color and density is noticeably superior.

It’s also important to be sure that the printer uses pigment inks, instead of dye inks. When used with reputable brands of art papers and canvases, pigment inks can create prints that will last well over 100 years without noticeable fading if they are properly protected and displayed. After you’ve equipped yourself to go into the fine-art reproduction business, the next task is to attract customers. I’ll share a few tips on marketing in my next post.

Improving Print Accuracy

BlogArchive — Wed, 16 Apr 2008 18:25:00 GMT

By Jon Canfield

As photographers, we’re always concerned about how our images are reproduced, either on screen or in print. Sure, we learn about color management and how important it is to calibrate our displays and to use the correct printer profiles for output. But, how many of you have actually checked the accuracy of that output? Are you positive that your printer is giving you the best possible print in any given situation?

Most printers come with quality profiles for the paper that is sold by that company. HP is one of the few that I’ve seen that also offers profiles for popular third party papers as well. For the rest of your output needs, you’ll either need to find profiles, hopefully from the paper maker, or from a user group (Yahoo has groups devoted to almost every brand of printer). Or, if you’re the owner of an HP Designjet Z series printer, you can use the built-in spectrophotometer to make your own. The final option is to spend another $500 to $5,000 to buy the hardware and software needed to create your own profiles.

So, you’ve got the correct profile for your printer and paper, you’ve done your edits in Photoshop on your calibrated display. It’s as good as it’s going to get right? Maybe, maybe not.

Anytime I try a new paper, I go to the trouble of printing a test print to verify the quality of the profile for my needs. Many people will use one of their own images, sort of a benchmark, to do this. That’s fine and it gives you a good idea of how the printer does relative to other papers. But I find it useful to use a dedicated test file instead.

The advantage of using a test file is that it stresses all of the critical areas you need to be aware of when printing.
Test-file charts are available from a number of sources, but the two that I’ve found to be the most useful are from Uwe Steinmueller’s Outback Photo site and Scott Martin’s color and black & white charts. You can download these charts for your own use.

The advantage of using a standard chart is in having a known set of values. For example, you can evaluate how well your profile and printer produce gray ramps from white to black, color bars of different hue and intensity, as well as common subjects such as sky, skin tones. If you see problems, you can make adjustments prior to printing to get more accurate results.

Sure, it takes a little time, plus some ink and paper, but the overall time and cost savings can add up if the chart helps you find that your printer isn’t reproducing a particular range of colors as well as it could be.

Color Management in Web Browsers

BlogArchive — Tue, 11 Mar 2008 13:07:00 GMT

By Marc Aguilera

Understanding color management in web browsers is important if you want to directly sell more of your photos and artwork online. You need to know what is and isn't currently possible when it comes to ensuring that your images will consistently look as you intended when you display them in your online gallery.

First of all, know this: All devices produce color differently (we color freaks call it `device dependent color'). Even two of the same devices from the same manufacturer sitting next to each other will look slightly different. This can be hell—especially if you're trying to manage the color of your photographs on the web.

Second, applications can treat color differently. Have you ever wondered why images look a certain way in Photoshop and another way in your email program or the web? It's the same file and on the same computer but it looks different in various applications.

Mac OS X applications built using Aqua (i.e Mail, Preview, Safari, and iPhoto) all use the default display profile and recognize embedded profiles. This means images look the same in the applications

Microsoft applications such Picture Viewer and Outlook don't recognize embedded profiles, so when comparing images in Photoshop and Picture Viewer you will see a difference.

Adobe applications all have a common color architecture and if you synchronize working spaces the color will all look the same—but only in Adobe applications.

Internet Explorer 7 has can recognize embedded profiles in images, but the user has to enable it in preferences.

The current release of Firefox doesn't include support for embedded profiles in images but will do so in future versions.

So no matter what, if you plan to implement a color-managed workflow, your images will look similar in ICC-aware applications but different in everything else.

Secondly, if your display is not calibrated and profiled you will have even more trouble. Color measuring your display is crucial if you want a consistent appearance. (If you don't calibrate your display, you'll simply be experimenting with color rather than managing it.)

Here's how we manage color in at our creative-services agency, encompus:

All of the displays in our studio (5 Macs and 2 Windows) are all calibrated with a spectrophotometer to the same settings - D65 (6500° Kelvin), Gamma 2.2, and 130 cd/m2 Luminance. When we share files and view the displays under similar lighting conditions, these displays all appear similar. Then, the question then becomes one of application implementation.
We run Mac OS 10.4 for design work and Windows XP for web production work.
We all share the same color settings file (.CSF) in our Adobe Applications. sRGB is the working space for our web work and Adobe RGB is working space for our print work.
When a designer prepares an image for the web, we "save for web" via Adobe ImageReady. We embed the ICC profile when we really need to match colors and don't embed the profile when it's not as crucial.
We brief our clients on real-world expectations based on the fact that their customers will be viewing our design work on different browsers and on uncalibrated displays.
When we embed sRGB, it is really only useful for Safari since Safari has color management enabled by default and can recognize an image with an embedded profile. It does not help us with Firefox, unless you're running Firefox 3 Alpha 7 which has an option to use embedded profiles.

The concepts of the ICC (International Color Consortium) are still relatively young. ICC standards were written to be open in terms of implementation, meaning that OS, Applications, and Devices could use ICC profiles differently or not at all.

This concept makes it a nightmare for everyone because although the profile is a standard file type, the uses of a profile all differ depending on application and operating system. At least Apple has taken a huge step forward with Colorsync and Aqua, and Windows Vista has a new color management system called WCS (Windows Color System).

Still, I would prefer that all photographers, designers, and prepress professionals all follow the imperfect ICC color standards than try to invent new ones at this stage.

It really comes down to setting expectations within your devices and with the client. If you're considering selling photos or prints online, you may want to adopt a policy similar to that of the online
art gallery that gives customers seven days to return any artwork they bought that doesn't look like they had expected it to.

Let’s recap :

Calibrate your display to a standard (i.e. D65, G 2.2, Luminance 120 cd/m2). Recalibrate at least once a quarter.
Use sRGB as a working space for your web images. Make sure all your applications do the same (although this can be challenge for some applications).
When you save your images for the web, embed sRGB profiles. For now, they may not look right in Internet Explorer 7 and Firefox, but there will come a time (sooner, rather than later) when all the major browsers will have color management turned on as the default, like Safari.

If you want to learn more about this subject, read Real World Color Management published by Peachpit Press. Better yet, take the X-Rite-sponsored Color Control Freak 08 seminar that I will be teaching at 24 cities throughout the US this spring. We will discuss many of these issues and more. Check out X-rite’s website or contact me directly at encompus.

Frequently Asked Questions about the Gloss Enhancer on HP's Designjet Z3100

BlogArchive — Fri, 21 Sep 2007 13:22:00 GMT

By David Saffir

Any time a pro-model inkjet printer comes out with features radically different from the status quo, questions inevitably arise from photographers anxious to fully understand the true capabilities and benefits of the new features. That’s certainly been the case with the Gloss Enhancer on HP’s Designjet Z3100. Here are just a few of the questions I’ve been asked at some of the trade shows and seminars I’ve attended.

What is the HP gloss enhancer?

It is a clear ink, which when mixed in correct proportions with the other inks on the page, provides a more uniform gloss on the surface of a print, effectively eliminating gloss differential on prints created on glossy or satin papers, and perceived “bronzing” in black and white prints.

Which media can the gloss enhancer be used with?

The gloss enhancer is intended for use on glossy and satin inkjet media. It has no perceptible impact on fine art, watercolor, and similar matte papers.

Is the gloss enhancer like a clear coat or varnish?

No, it is not a clear coat or varnish. The gloss enhancer’s main purpose is to improve the smoothness and gloss appearance of the final print. In my opinion, the gloss enhancer renders prints made on glossy or satin media as smooth and uniform as their darkroom cousins. Personally, I find that the dimensionality and “pop” of the prints is improved, and I find it very pleasing.

Unlike a clearcoat, the gloss enhancer is applied like an ink, and is closely controlled by software. In fact, the gloss enhancer is controlled by its own screening algorithm and it is applied selectively where it is needed. The gloss enhancer is only applied to areas of an image that have an RGB color value of 254,254,254 or lower. Pure white (which has RGB values of 255 in each channel) will not receive the gloss enhancer. (As a practical matter, I set white and black points slightly under max values when using inkjet printers.)

How do I control the use of the gloss enhancer when printing?

The printer driver provides controls that allow you to either: (1) turn the gloss enhancer off; (2) use it only on the inked area (“econo mode”); or (3) use it on the entire page. I recommend turning the gloss enhancer off for making proofs, and using the econo mode for final prints. Applying it to the whole page is usually unnecessary, and wastes a small amount of the enhancer.

What effect does the gloss enhancer have on color?

That’s a good question! If you look closely at a print that has been made using the “whole page” setting for the gloss enhancer, you may perceive a slight change in the white point of the uninked paper. In other words, you will see the gloss enhancer on the unlinked portions of the page, and it seems to reduce the white point to a very small degree. I’m not certain, but I believe that this is the result of increased “glossiness” or reflectance.

In my conversations with HP color scientists and engineers, they indicated that the gloss enhancer has no effect on color rendering in a print. In my own experience, I have made prints from the same color image using gloss enhancer turned on, and turned off – and I can’t discern any significant difference in color between them. Gloss appearance and smoothness – yes; color change – no.

Does use of the gloss enhancer change the dry time for a print?

Not in any significant degree, at least on HP media. Some users tell me they have noticed increased dry times when using third-party media. I use many types of papers, but I haven’t had this problem. I suspect some of these issues may be related to using printer-managed color with third-party media, instead of creating a custom profile for the job at hand.

Does use of the gloss enhancer improve print durability?

I don’t have hard information on this topic. First, on HP media the prints are highly water and damage resistant --even without the gloss enhancer. Prints made with HP Vivera inks are highly water resistant, even under running water. Using the gloss enhancer, my personal impression is that prints seem to be more water and scratch-resistant, but I’m not sure how one would go about quantifiably measuring these properties.

Does it make sense for photographers to use the gloss enhancer?

In a word, yes. I see little or no downside, and the benefits in terms of print appearance are significant. I use it consistently. I recommend it to all of my printmaking customers, and so far, none have told me that they prefer not to use it.

In my opinion, the HP Professional Satin photo paper combined with the Z3100 Vivera inkset (including gloss enhancer) provide the best-quality pigment-based photographic prints I have ever seen.

If you have tried the gloss enhancer, I’d be interested in hearing more about your own experiences and observations. And if you have any other questions about it, please feel free to ask.

JPEG or RAW: Which Should You Choose?

BlogArchive — Tue, 24 Jul 2007 13:06:00 GMT

By David Saffir

Decisions made during image capture can have a significant impact on post-production costs and the quality of the finished prints. Two of the most important decisions we make during image capture are which file format and color space to use. Many cameras, particularly DSLRs, allow us to capture images either as JPEG, TIFF, or RAW files. They also allow us to choose to work in the sRGB, the Adobe 98 RGB, or a custom color space.

In terms of cost and quality, the Great Divide lies between JPEG and RAW file capture. It’s easy to understand why many photographers would naturally gravitate toward JPEGs. JPEGs are a compressed file format that reduces file size and increases rate of capture. JPEGs are fast, and in some ways more convenient in terms of storage and computing power. With modern in-camera automatic exposure and color correction, JPEGs can deliver good image quality.

But JPEGs have some important limitations. For example, in a recent article in Photo Techniques magazine, Timothy Edberg noted that the cameras he tested produced images with at least one f-stop less dynamic range in a JPEG file compared to a RAW capture. This makes sense, as an 8-bit JPEG digital capture uses lossy compression. A RAW file typically uses no compression, or lossless compression.

Additionally, an 8-bit JPEG file contains about 256 tones per color channel and a RAW file shot in 14-bit contains just over 16,000 tones. A 16-bit file RAW file has over 65,000 tones per channel. In color editing and in the final print, this can make a huge difference in the appearance of intense colors, such as open skies.

Not only that, but the default setting for JPEG capture is the sRGB color space. This color space is fine for digital images that will only be viewed on a computer display, but sRGB is not ideal for printing. The Adobe 98 RGB color space is significantly larger.

JPEGs also aren’t as versatile as RAW files. RAW files are very flexible, while JPEGs are pretty much locked in. With RAW files, it is much easier to correct color casts or make adjustments in certain colors or the overall color temperature, color balance, exposure, and contrast/levels.

Color artifacts and distortion in details will also be visible much sooner in a JPEG file than in the RAW. The distortions may show up in high-contrast transitions first, but can appear anywhere in the image.

Some photographers object to using RAW capture because it produces “big files” and slows the computer. Given the improvements in computer hardware and falling costs of memory and hard drives, it just doesn’t make sense to accept the limitations of JPEG capture for most uses.

Conclusion: JPEGs are fine if you plan to go straight from the camera to publication. You’ll probably want to use RAW if you plan to edit your images post-shoot.

You can find more details on the basics of RAW file processing in my book Mastering Digital Color published by Thomson Publishing.

Orange Roses and Green Skin

BlogArchive — Wed, 25 Apr 2007 13:53:00 GMT

By Jon Canfield

I’m always surprised when a pro photographer gives me a blank look when I ask about their color management practices. This usually comes up when they’ve sent an image or group of images to me to print for an exhibition or limited edition and the colors are obviously off in tone.

The conversation often goes something like this:

Me: “The color balance on these images is off. When was the last time you calibrated your display?”

Client: “What’s that?”

Me: “Have you ever run a utility to make your monitor more accurate?”

Client: “No, I just adjust the monitor until it matches the print”

And there is the problem – they’ve done a calibration of sorts, but it’s exactly the wrong kind. The only time colors will ever match is on their printer and monitor combination. When viewing other images, or when sending images out, it’s a crap shoot on what things will look like.

Color management used to be considered black magic by many of us. The software methods were unreliable and the hardware was expensive and hard to use. That’s all changed, and for the better (except for the software method which is still unreliable).

With hardware devices starting at $60 or so, there is no reason your monitor shouldn’t be displaying accurate color. Yes, you can spend more for an advanced calibration that provides more control over the process. But unless you plan to create printer profiles, you’ll only be investing less than $250.

If you’re a working pro, that investment is quickly repaid in reduced editing and correcting time at the computer. If you’re an amateur, you’re still going to reap the benefits of color correctness, and save time and money when you print.

As a sign of just how mainstream color management is becoming, the HP Designjet Z2100 and Z3100 printers now include built-in color calibration and profiling hardware to ensure accurate color reproduction. The time and cost savings of this feature is tremendous, and the improved accuracy of prints is obvious. For even more control, and adding the ability to calibrate your monitor, the HP Advanced Profiling Solution also includes hardware to calibrate your display.

Regardless of your skill level, if you enjoy printing, editing or even just viewing images, a calibrated display should be considered mandatory. Why not try it and see?

The Importance of Being Calibrated

Eileen Fritsch — Tue, 31 Oct 2006 20:45:00 GMT

[MarcAguileraBio]

I am essentially lazy. I want to take great pictures at the start, then immediately go to print or the web with very little post production. That’s why I’m a digital purist and use color management to simplify my digital experience.

When I shot film, I looked for great light and always made sure I captured exposure that would produce a good negative or transparency. I was hard on myself if I had to rely on post processing to fix my mistakes. Even in the darkroom I liked to use the same few contrast filters for black and white printing. I was a film purist then and am a digital purist now.

As such, I have a mantra that really helps in dealing with digital imaging and printing: “Be Calibrated.”

Calibration is simply: To change the state of a device to conform to a known specification. It’s similar to a car tune up in which a mechanic checks how an engine is currently running, then makes the necessary changes to make the engine operate as it was designed to.

In the digital photographic workflow, I calibrate at every step. I calibrate my monitors with the Gretag Macbeth i1 to conform to a known luminance, gamma, and color temperature. When I shoot with my Nikon D200, I make sure I have calibrated to a known white point. I do this by setting a custom white point with a Gretag Macbeth White Balance Card.

Most importantly, when I print to my HP Designjet 130 and 90 I make sure that I use the “Automatic Closed Loop Color Calibration” feature on the printers. To see if there has been a drift in performance (which is a signal to re-calibrate), I send a copy of the test file shown here and compare it with a previous version. If the appearance of the colors has changed, I re-calibrate.

In every city in which I teach the Color without Limits seminar, one of the questions I hear most often is, “How often do I need to calibrate?” My answer is simple: “I re-calibrate only if I see a drift.”

A certain amount of drift occurs in all printers (and other digital color devices), no matter who makes them. Densities (and sometimes even hues) can change over time or when a new ink cartridge or printhead is installed.

It’s important to check for drift every time you set out to do a print run. Whenever I print, the first thing I do is print my test file. If it looks good, I am good to go. If it looks different than my last test print, I restart the calibration process.

Consistency is essential to managing color. Being calibrated means I can rest assured I will remain consistent.

The importance of being calibrated is that if I am calibrated, I have a better chance that my profile will produce satisfactory results.

Like I said, I am lazy. Really I am. I want to take great pictures and then make great prints with as little time in my digital darkroom as possible. So go on, be calibrated and I bet it will change your workflow forever.