Interview On ICC Profile
Rich Collins
Printing out our own photos is something we all do. But getting results that we are happy with is another matter. While this article is not going to tell us how to do this, (I will deal with this in another Post), we should all have an understanding as to what helps us accomplish this. The famed ICC Profile, which hopeful
ly we've all heard of and most of us are at least minimally familiar with, is a key component in the mix. Here to answer a few critical questions is Ethan Hansen of Dry Creek Photo.
Dry Creek Photo provides printer profiles for the Commercial end of print processors, or Lab, that we, as photographers, use for our enlargements. They have been at this for nearly 6 years and have progressed from providing these free for photographers, which is no longer available, up to the Commercial end where they build profiles for high end commercial clients. But we can still learn a lot from this exclusive Company. Ethan Hansen has given answers to some of the most troubling questions we, as photographers, have wrestled with for a long time. If you wish to read further their site has an excellent read. A link is provided below.
Shooting Outside: Thanks Ethan for being available from your busy daily schedule. We at Shooting Outside really appreciate a professional such as yourself taking the time to help and for doing what you guys do at Dry Creek Photo. I have a few questions for you.
Shooting Outside: What is the primary function of an ICC Profile?
Ethan: The ICC Profile lies at the heart of the entire process. Going one level of abstraction higher, there are two types of color models: Device Independent and Device Dependent. Device-independent color spaces, such as CIELAB or XYZ, model how our eyes see color. A CIELAB (aka LAB) value defines a definite, physical color. In a device-dependent color space the meaning of a given color value, depends on the device in question. This holds true for physical devices including monitors, printers, and cameras as well as for virtual devices such as those modeled by Adobe RGB, sRGB, or other familiar color spaces. Our Intro to color management page at http://www.drycreekphoto.com/Learn/color_management.htm goes into more detail on this topic.
An ICC profile describes how the color values used by a particular device, such as a digital camera or a virtual "device" such as sRGB, map into a device-independent color space such as CIELAB. Using profiles allows different devices to communicate color accurately. The device-independent color space acts as a universal translator; with accurate profiles, the scene your digital camera records is reproduced faithfully on both your monitor and in print. Color-savvy software such as Adobe Photoshop use profiles both to match color to the greatest extent possible and to show the limitations of any step in the process.
Without profiles we go back to the days of color-by-number. A digital image is simply a file full of numbers. Without a profile, the numbers have no direct meaning in terms of color or tone. It took highly skilled digital editors and printers to know what CMYK value gave accurate skin tones on each print stock. It also took many iterations of edit, proof, adjust, reprint, etc. to get decent copy. ICC profiles both automate the process and are more accurate. In many ways the history of color profiling mirrors that of desktop publishing, just 20 years later. You no longer need to be a CMYK wizard to produce superb quality images and prints, just as traditional typesetting skills are not needed to use a word processor.
Shooting Outside: Why is it important to cyclically calibrate a monitor?
Ethan: If your monitor is not accurately calibrated and profiled, there is no way to trust what your eyes see. There are two parts to the process: calibration and profiling. The calibration step attempts to match your monitor to a known standard. Equal amounts of red, green, and blue should add up to a neutral color, white and black points should be accurate, and the gamma curve that defines how one goes from one point to the other is set to a given value. In large part, the profile describes how your monitor deviates from the ideal. It also defines the limits of the color range and any quirks in color or tonal response.
Shooting Outside: Are the ICC profiles that accompany most printers today good enough for a weekend photographer?
Ethan: They are certainly getting better. We still see a general trend, however. The first round of printers made by HP, Canon, or Epson tend to have very similar output behavior. As a given model ramps into higher volume production, we see greater printer-to-printer variability. This may correlate to additional manufacturing lines being brought online, or to other factors. It may well also explain why many early reviews of higher end photo printers tout the accuracy of the canned profiles, while later users see problems. In the end, it comes down to a matter of luck. If your printer is a close clone of the machine(s) the manufacturer characterized, the canned profiles may well suit your needs. If not, you will need a profile made for your specific printer to unlock its full potential.
Shooting Outside: How does one access a profile and what determines the correct profile?
Ethan: Profiles are not used directly. A question we commonly get is "what application do I use to open your profiles." The short answer (aside from RTFM) is you don't. Photoshop or any other good image editing or printing application uses the profile to convert the colors in the image file to the correct values for a particular output device. As to what determines the correct profile, that is harder to answer. A profile is a highly detailed snapshot of how a given device behaved at a given time in the past. If the device still behaves the same way, the profile will still be accurate. If not, a new profile is needed. Ideally, you will reprofile your own devices as needed. A lab should also provide updated profiles as their printers change.
The digital printers used in many photo labs are capable of outstanding accuracy over time. Machines such as Fuji Frontiers, Noritsu QSS, Agfa d-Lab, Durst, Oce LightJet, Chromira, etc. that print on silver halide paper all have densitometers that allow the machine to compensate for changes in chemistry, emulsion batches, etc. A well maintained digital printer has less color drift over the course of a year that the best optical printing lab has between morning and afternoon. That said, there are systematic shifts in the machine output that are not caught by the built-in systems.
We worked extensively with Fuji, Agfa, and Noritsu to determine optimal profiling intervals. In general, after 9 months to a year, the output color shifts will be barely visible to a trained eye under ideal lighting conditions. We recommend our lab customers reprofile their machines on a matching basis. Some choose to profile their machines every 4 to 6 months, while others are comfortable with longer timeframes.
Shooting Outside: Have you ever run across a Paper Manufacturer which changes the composition of a photo paper, without updating the profile? In other words how can one be sure they are not using an outdated profile with an updated paper?
Ethan: Epson in particular learned this the hard way. Reformulations of standard paper types 4 or 5 years ago caused headaches for many a photographer. After their travails, most other vendors are reasonably consistent with their papers. This also holds true for the ink manufactured by both Epson and Canon. Some of the smaller third party manufacturers show uncomfortably large variation between ink batches. Paper stocks tend to be more consistent. The majority of the variation we see is caused by the printers rather than the media.
If you don't have a spectrophotometer handy, the easiest way to evaluate whether your profiles are still accurate is to print a test image and compare it to one kept in dark storage from an earlier time. In many cases, a gray step wedge is the all that is needed to see gross output shifts.
Shooting Outside: Color spaces such as sRGB, Adobe RGB & ProPhoto RGB all fall within differing gamuts. When do we know to use one or the other?
Ethan: This is a function of what color space your image originated in. Most low end, consumer point-and-shoot digital cameras record color in kinda-sorta sRGB. Better quality cameras offer at least Adobe RGB range, and the raw output of almost any DSLR is closer to ProPhoto RGB. My preference is to work in the largest color space the image supports. For all the DSLRs we use, this is ProPhoto RGB. Note that it makes no sense, and in fact, degrades image quality to convert an image from a smaller color space such as sRGB to a larger one such as Adobe RGB or ProPhoto. If the output of your camera is closest to sRGB, use it. An alternative is to profile the camera. This is not for the faint hearted, requires reasonably good studio lighting equipment, and is only supported by a few raw file processing applications. For those of use who use camera profiles, however, the benefits are well worth the cost.
Shooting Outside: Color profiles one pays for are good for how long? Your Company Dry Creek Photo provides free profiles. Which ones are better and why?
Ethan: A profile is good until the output of the device the profile is made for changes. Many of the lab profiles on our site get updated because of a machine configuration change or major repair. While the profile on our site are free to download and use, they are paid for by the labs themselves. In my undoubtedly biased opinion, our profiles are second to none in quality. We developed our initial profiling targets and software based on evaluations of -- at the time -- well over a thousand printers. We continually fine-tune the process, and have experience building tens of thousands of profiles. Along with the profiles available on our site, we have made many thousands of profiles for individual photographers, photo labs, printer manufacturers, paper and ink vendors, museums, and oddball industrial applications including t-shirt and CD printers, coffee cups, and aircraft manufacturers (just in case you wondered how the colors on both the inside and outside of various planes were controlled).
Shooting Outside: At some point Dry Creek decided to offer profiles without charge. Can you tell us why?Ethan: We did indeed start by offering free, basic profiles for digital labs in early 2002. At the time, the only printer profiles most photographers had contact with were the lousy ones Epson bundled with printers such as the 1280 and 2000P. The typical experience was to try a profile, see the results sucked, and join the chorus chanting "profiles do not work." Color profiling had been around in one form or another since the late 80's, but did not have an open standard until the mid 90's with Apple's ColorSync. As we made the transition into the digital world, we found ICC profiles invaluable. We built profiles in-house for our own use for some years, but as with many great ideas, the genesis of our color profiling venture arose over late night conversation and beer.The introduction of the Fuji Frontier printer brought high quality digital printing to everyday photo labs. Noritsu, Kodak, and Agfa all followed suit. Our first idea was that it would be wonderful to be able to shoot on a remote location and be able to get reasonably accurate, inexpensive proofs made at a nearby lab. We sent test images to various friends and acquaintances to build a small database of profiles for our own use. The quality of the results were noticed both by said friends and the labs themselves. We then decided to open our offer to the photographic public through several online forums. Our goal was to enable the photographic community at large to experience what color management could provide. At the risk of tooting our own horn, I submit that we succeeded in this task.
We quickly amassed several hundred profiles from labs around the world, and had many more requests pouring in. The onslaught was more than a small company could handle on a no-charge basis, so we called a halt to our experiment. The freebie profiles we built were made from a greatly reduced target -- large enough to be more accurate than a printer's automatic routines could do but far less than what we could achieve with a dedicated effort. We switched to a fee-based profiling service, offering profiles to both labs and individual photographers. While many labs wanted their profiles to be posted on our site, many others decided to either use the profiles internally or to only offer them to select customers. We reluctantly dropped our profiling service for most individual photographers and photo studios, as the tech support demands made the effective hourly wage less than small. Working with most photographers was a joy; the occasional ones who regarded us as a 24-hour hotline for Photoshop, camera, printer, and life support proved unworkable.
We are now working with both selected photo labs and printer companies. By early December, we will re-open our profiling service for both photo labs and printer and media vendors. We continue to work with a number of photographers and photo labs, but not on a general basis.
Thank you Ethan.
Hopefully we all have a better understanding of why ICC Profiles are so important to our getting as close to perfect as we can with our prints both at home and at the lab. Thanks to Ethan Hansen and Dry Creek Photo for their generous time in helping to explain some very important tips. A reminder; Ethan and Dry Creek Photo is not available for questions, but feel free to Comment here with any questions and I'll do my best to point you in the right direction.
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