Color Temperature: Is It Warm Enough For You? ~

At first blush, there doesn't seem to be any obvious connection between temperature -- how warm or cold it is -- and color. So why is it that we photographers so freely throw around the term color temperature? Sounds like it must be something important, and in fact, it is.

The term itself comes to us from physics, and refers to black-body radiation; essentially, as a black body is heated, it glows in a color specific to that temperature, which is always measured in degrees Kelvin (K). In practical terms, any source of light will radiate at a particular color temperature, producing a predictable color in the visible spectrum. The chart on the left illustrates some examples. Traditional incandescent lightbulbs radiate at around 3000K, which is why their color is markedly yellow-orange. Fluorescent lamps, and some modern cool-white lightbulbs will radiate at much higher temperatures, above 6000K, and so will have a more bluish color to them. This has always been important to us in photography, as most color films were designed to "see"and record light in a normal daylight range, which is typically between 5000 - 6000K, and if the sources of light illuminating our photos varied from that, it resulted in images that didn't look natural. You've probably seen pictures that were either very yellow, or unnaturally blue-green. That's why.

Of course, painters and photographers have always confused the issue by defining colors, or color-casts, as being "warm" or "cool". This is almost certainly because we looked at a glowing fire, felt its warmth, and recognized the color it gave to anything it illuminated as a "warm" glow. And yet, the actual color temperature is at the cooler end of the spectrum, as you can see from the chart above. And those very high temperatures, above 6000K, are decidedly "cool" in appearance.

With color film, we used filters over the lens to add a compensating color in order to produce images that looked natural and daylight-balanced, or at least made sure to use light sources that were daylight-balanced. Most electronic flash units were fairly well color-balanced, or slightly biased to the "cool" end of the spectrum, which could easily be further improved in the printing process. Digital cameras can control for a wide range of color environments with their built-in white balance pre-sets, or the ability to  set a custom white-balance for a particular shooting environment. (This was covered in my last blog post; take a look).

Like so much in photography, color can be a very subjective thing; what looks pleasing to one may look odd to some one else.  But there are times when we need to work with objective, agreed-upon standards, too; and the best example of this is when we make shade-matching images for the dental lab. An understanding of color temperature, and control of the digital camera, is part of what makes it work successfully.

Are you getting good results with you color images, or still something of a challenge? Let's have a nice warm conversation.

Later amigos!

Dave

And now, a word about White Balance....

My last post here (I think I must be on a summer hiatus?) discussed Picture Style; the differences among them, and which of them was most appropriate for intraoral imaging. Now I'd like to take a closer look at White Balance, which can just as easily be a source of some confusion for the non-professional shooter.

White balance (sometimes called gray balance, or color balance; all the same thing) refers to the process of removing an unwanted or unnatural color cast in a scene so that objects that appear white to our eyes will look white in the photograph. Our eyes are great compensators and will correct for environmental conditions, reflections, color temperature, and so on, but unless we make those  adjustments in our camera, we'll get poor color images that are difficult to correct in post-processing. This is much easier to do with digital cameras than when we were all using film and our options were much more limited.

Here's a good example of that. Viewed individually, we may not see anything terribly "wrong" with any of the pictures of this lady with a guitar, but side-by-side we can make a more critical assessment. While the image in the middle has more natural and neutral tones, the one on the left is distinctly "warm" (strongly tending towards the reds and yellows) and the one on the right appears distinctly "cool" (tending more towards the blues and greens).

Now let's look at how we control for this in the camera settings:

AWB: Auto White Balance; this mode calculates an average color temperature for an entire scene. While I often find this problematic in a scene that has multiple sources of light, each with its own strong influence, it works well with one dominant light source -- as when we are shooting intraoral images using a ringflash. I typically use this mode for exactly that reason. In the sample above, and in the following, the color chart on the left was shot using available, natural daylight. The ones on the right are shot using on-camera flash.

DAYLIGHT: usually useful for making available-light exposures on bright, sunny days. (Since I live in Oregon, I probably don't get to use this one very much!)

SHADE: open shady areas on an otherwise sunny day with blue sky will tend to shoot somewhat cool, so this mode adds more reds and yellows to the scene.

CLOUDY: This may be a bit more Oregonian (maybe with a little rain?).  Here, too, the thought is that cloudy days produce cooler exposures, so this warms it up a little. You can certainly use this anytime on a sunny day if you like a slightly warmer touch to your pictures. Everything is worth experimenting with.

TUNGSTEN: Have you ever seen old photographs that were taken indoors, and they all look intensely yellow? That's because color film was usually "Daylight" balanced, and common light bulbs -- tungsten bulbs -- produce a low color temperature, yellow-orange color cast. This camera setting compensates for that.

FLUORESCENT: Traditionally, fluorescent lighting was distinctly magenta-blue, in the same way that tungsten lighting is distinctly yellow. However, most modern fluorescent bulbs are now designed to produce a more natural color balance.

FLASH: Most on-camera flash units produce a color temperature at or above 6000K, which is cooler in tone than standard daylight, so this setting adds some warmth. In practice, I find this usually adds too much warmth, and flashes can vary quite a bit in color temperature as well, so I rarely if ever use this.

These last two settings in your White Balance menu are CUSTOM and, below that, KELVIN setting.  Photographers will frequently "custom balance" their jpeg images to minimize post-production time when shooting a large number of images under the same lighting conditions (think outdoor wedding). This can often improve the overall color quality as well, but intraoral images made with  the macro lens and ringflash cannot be custom white balanced.
And finally, setting an actual Kelvin value can be useful in creating precisely defined color images. This is very useful to commercial photographers.

Since we're on the subject of color, on my next post I'll try to discuss in greater detail some of the broader color issues like color temperature and environmental effects on how we perceive and record color information. In the meantime, play with your camera and experiment with these settings. You can't break anything, and you'll have fun looking at the different results you can end up with.

And post your pictures -- and questions -- right here!

Later, amigos!

Dave

"Picture Style" Setting in the Camera

I was giving a talk recently, going over the many setting options presented in the camera's selection menu, when the question arose as to which "picture style" setting was appropriate for clinical photography. It's a good question, but one that's hard to answer in words alone, so I thought I should try to post an illustration of the differences between them.

I tend to think of it as something similar to choosing the right kind of film for a particular image quality we're looking to get. It's a quick way to select for a set level of sharpness, contrast, color saturation, and color tone, as you can see in the menu. You can go with the default settings in the camera (which I think works fine for our intraoral imaging) or make slight adjustments within them. Digital technology gives us a lot more control over these factors than we ever had before.

The Standard setting, as seen here on the left, has some sharpness applied and usually has a nice, crisp look to it. It's not over-sharpened or over-saturated for most imaging, and is appropriate for clinical applications. I generally use this setting for my dental photography.

The Portrait setting reduces the level of sharpening somewhat, and tone and saturation are thought to be more complimentary to skin tones in general portrait photography. You can experiment with it, but I never use this setting in my clinical work.

The Landscape setting increases the level of sharpening, tone, and saturation. This usually is seen in more vivid blues and greens in the image, which landscape photographers sometimes prefer, but I think is too much for general clinical imaging.

The Neutral setting doesn't have any sharpening applied, and can look a little flat. The idea is that you're going to apply some processing yourself in imaging software, but not such a good idea if you're shooting jpeg files.

The Faithful setting is almost the same as Neutral, but can achieve somewhat better color results when you're shooting under ideal daylight (approx. 5200 degrees K) conditions.

And, of course, you can choose to shoot a black & white image by selecting the Monochrome setting. You can even control for filter effects in this setting, so it's fun to play around with, but remember that an image shot in Monochrome has no color information at all and can't be converted into a color file later on, so don't use this in the clinic!

There are further selection options in the Picture Style menu that let you create your own custom-made style. Like everything else with your digital camera, it can be fun to experiment with these. But when you just need to get some work done, go ahead and set it on Standard. You'll get fine results.

And now that we're getting some nice Spring weather, take that camera out this weekend and have fun!

Later amigos (oh, and Feliz Cinco de Mayo!)

Dave

40 ... And Counting!

We count down our time in decades, I guess because we have ten fingers. This is what I'm counting down now. A simple reflection: It was in the spring of 1973 that I apprenticed at a portrait studio in Cheyenne Wyoming, and am proud to look back on a career in professional photography that has spanned, for better or worse, these four decades.
Thousands, certainly, of portraits; many hundreds of commercial assignments, and more weddings than I care to count. But what I remember most clearly are those first couple years at that studio, living and breathing photography every hour of every day, and acquiring the skills and techniques that I would continue to hone in studios and darkrooms for many years.
Mercifully, there aren't many pictures of me from those days, but of the few I can still find (and admit to) this one by my friend and classmate Terry McCarthy is the one I most enjoy sharing. And that was my dad's Nikon Photomic F.  That was one sweet camera!

My own humble little possession when I began was this Nikkormat FTN and a plain old 50mm lens, which I bought used in Casper Wyoming for about a hundred bucks. I think I must have run a million rolls of film through it; in any event I completely wore it out and gave it an honorable retirement. I was addicted to Tri-X (and Edwal FG-7) along with venerable Ektachrome 64.

We had large-format cameras of all sorts at that studio, and medium-format ones as well. All these were new and wondrous to me, portals to incredible worlds of art and creativity. Eventually I saved up all my nickels and dimes and bought this Mamiya RB 67 and a couple lenses.  I had that baby for years too, and even wore that one out. I guess I'm a little hard on my gear, but then again, these are tools, not art objects. I sometimes wish I still had them, but it's mostly digital now and that technology has taken my career to entirely new places. No regrets.

Would I do it all over again? In a heartbeat! Photography has taken me to fascinating places, to meet incredible artists, and work with wonderful people.  And it brought me here.

My favorite writer Douglas Adams once wrote, "I may not have gone where I intended to go, but I think I ended up where I intended to be".

Amen, brother.

Dave

(Color) Space ... The Final Frontier ~

There are few subjects in photography less well-understood by the average shooter. Color Space. Or Gamut. It's an understanding of the range of colors a given device, like a camera, can "see" and record, or what a printer may be able to produce. Obviously you don't need to be an expert on color (I certainly don't claim to be) to be a good photographer, but since our digital cameras want us to make a decision on which color space to shoot in, we should try to distill down a few of the essentials here to better understand what we're doing.

In other words, what on earth is the difference between using sRGB and Adobe RGB??

Most of what we shoot will be viewed on a monitor, either as we share our photos or post them to a website. This world sees in sRGB; shooting in this mode generally reproduces better saturation, particularly in the reds (at one end of the spectrum) and the deep violets (at the other). But why? Isn't Adobe RGB a larger color space?
Technically yes, it is, but it doesn't actually make more colors, it spreads those colors over a wider area. Since our monitor "sees" these colors in the smaller, more compressed sRGB space, those reds and violets get "cut off" and the program we're viewing the image in has to figure out on its own what those colors are. As a result, you end up with images that, by comparison, looked a bit washed-out. The reds don't pop, everything can look a little flat.

Alright, so when do we use Adobe RGB? I have usually recommended this to dentists who were shooting for high-quality shade matching, and working with labs that were using software which took advantage of this color gamut. It's also preferred when you're making custom prints and likewise are familiar with the imaging and printing software involved; typically you'd be shooting RAW files to fully take advantage of this. (A topic for a new blog post!). So, as I've always said, there's no more effective tool than communication. Work with your lab to see how they would prefer the image files you send them.

Are you getting the color quality you want in all your shots? You might not be, and maybe it's because you're not shooting in the appropriate color space. Check it out.

And let me know. I'd love to hear what's been working for you!

later, amigos!         Dave                      dhutt@dmddigitalphoto.com

Keeping Your Photos Safe, Safer, Safest ~

As a photographer, I know of one particularly scary horror story: a crashed hard drive, photos not backed up anywhere, photos gone...forever. In the past, we had been meticulous to the point of obsession about the care and archiving of our negatives. We had to be; they were our bread and butter. We don't use negatives much any more, but instead we have digital files. And I'm afraid too many of us have become complacent about how we consider their long-term care. Any good computer you buy these days will have at least a half-terabyte (500 Gb) of hard drive space, so it's easy to save our photos there with little concern to running out of room for them. But room isn't the issue. Just ask anyone who has lived through that crashed hard drive horror story.

So, let's talk about some good digital archiving strategies. In the not-so-distant past, we commonly burned our files to CD's (and later, DVD's) to store them. They stacked pretty easily on our bookshelves. But even back in the day there were suspicions about the long-term stability of this media. And -- have you looked at new computers these days? Solid-state is the state-of-the-art, due to greater speed and efficiency; this means no more optical drives for CD's (unless you buy additional hardware. Blech!) So I don't look at this media as a good solution any more. 

Besides, they don't have a lot of capacity. A CD only holds around 750 Mb of data, a DVD around 3Gb. Your typical thumb drive? Easily 8, 16, 32 Gb's. I recently saw a 64Gb thumb drive on Amazon for around $30! I use these all the time to upload everything from entire folders to my Keynote programs. They're especially good if you need to share those files, too, since the USB port is universal. So yes, these are good solutions. But.....

They are not the best alternative, mainly because the very quality that makes them so convenient also makes them vulnerable: if they're easy to carry around, they're easy to lose. What you'll find every photographer relying on are external hard drives. They're stable, have high capacity, and can easily be transported. Plus, they're fairly inexpensive. I use several. As a Mac guy, I have a large (1Tb) external HD dedicated to Time Machine, which keeps my computer's entire content continually backed up. Additionally, I use portable HD's to upload all my photos, Keynote programs, Word documents and other data in a way that makes it easy for me to retrieve them later on when I need to work with them. Since I know that all my important data is redundantly stored (on thumb drives, on Time Machine, and on portable HD's) I can confidently delete them off of my computer's hard drive and not take up space there. 

Yeah, it would definitely be a drag if my computer hard drive crashed. Those are never inexpensive events. But losing my data? Never. I sleep well at night.

Your thoughts? Let's archive them here!

dhutt@dmddigitalphoto.com

Accurate Color ~

As a commercial photographer and printer, I have always taken color very, very seriously. Capturing it on film, in a print, or in a digital image requires precision on many levels.
This is all the more critical in shade-matching, where we convey color information to the dental lab. Using digital technology, this task is much more reliable and accessible. Quality camera equipment -- a good digital SLR camera, macro lens, twin-light flash source  -- makes this possible. Other essential tools are the grey neutralizing tab and a reliable shade tab.

Dr. Dave and I normally shoot RAW files, and this totally unposed (!) picture shows the software we use to process them. But since most labs require jpeg images (they're a lot easier to email and work with) it's good to know that critical color accuracy is just as reliable with these.

Are you getting the color results you need? I might not be rosy, but I'm all ears!

Later!

dhutt@dmddigitalphoto.com