Sunday, July 29, 2012

Basic Terminology, Part 3

This post will quickly round out our look into the basics of image "parameters" - the things you can adjust in a photograph, either in camera, in software post-processing, or both.

I cannot neglect mentioning White Balance and Auto Colour Corrections to end off this discussion. Also, there are several other less encountered, but sometimes important parameters such as Colour Spaces and Colour Models.

White Balance

Camera Accidentally Set for "Tungsten" WB

As you can see, White Balance is one of the most important parameters to get correct from the beginning if your camera will only shoot JPEG, but if you're shooting with RAW files, once again, it will save the day, because you can recover the correct WB, or deliberately select any "wrong" WB using your RAW Conversion software. In fact, that's exactly what I did for this example - I selected "Tungsten" from the list of WB values, which are typically "Daylight", "Shade", "Cloudy", "Tungsten", "Fluorescent", "Flash", or "Automatic". I normally set my camera to "Automatic", and find it's very good at making this decision for me.

If this sounds vaguely familiar, if you're old enough, you might recall when you bought your camera film at the drugstore, you had a choice between "Daylight" or "Tungsten", depending on whether you were going to shoot that role of film outdoors, or indoors with normal incandescent light bulbs. The latter would compensate the colours with a bluish tinge, overcoming the yellow-orange glow produced by incandescent light. If you used "Daylight" film indoors with nothing but household light bulbs, the pictures would turn out with a yellow-orange cast. If you had to use Daylight film indoors, to get the correct colour, you would have to use a flash. Further to this, if you were to use Daylight film indoors under fluorescent lighting, you would end up with a greenish cast, which could be overcome by screwing a "fluorescent filter" onto your lens, or by using a flash. finally, if you had to use Daylight film on a cloudy day, you might end up with a slight purple tinge in the pictures, which you would have to compensate for wit a "Daylight Filter" on your lens. So, you see how easy digital cameras have made this now? You can either select the correct WB from a much broader menu of choices, or simply shoot your camera with Auto-White Balance (AWB) and forget it.

RAW Conversion software offers one more possibility that you can play around with - that is "Manual White Balance". This whole White Balance thing is connected to "Colour Temperature", and when you select from one of the presets discussed above, there is normally a temperature number showing in a box underneath. This number is 4 digits (order of thousands) and represents colour temperature in "Degrees Kelvin", with the lowest numbers being the red, and the highest numbers being the violet ends of the spectrum. By using the software's Manual White balance, you can customize this colour temperature to be exactly what most pleases your eyes, by 'warming" or "cooling" your overall colours.  You might also notice that adjusting the temperature manually could have an influence on how much detail is revealed in the picture, so for example if you slide it a bit warmer, some hidden details might emerge, and keep in mind, by doing this, even though you might end up with a hideous colour cast, (say red), the uncovered detail will still be there if you convert the picture to Black and White by desaturating the colours completely as a next step.

Auto Colour Correction

 Original JPEG from Camera

JPEG With "Auto-Fix" Applied

This is good news if your camera doesn't shoot RAW files. All JPEG Editing Software, even the basic Windows Picture and Fax Viewer that comes with every computer, has a very effective single click "Auto-Fixer". Above, you can see for yourself what a tremendous effect this has on a JPEG file. Quite often, this is all you need to fix up pretty much everything we've been looking at in these three lessons - a pictures Contrast, Saturation, Brightness, Gamma, White Point, Black Point and Colour Temperature can all be fixed with one mouse click! 

This is always the very first thing I do to a JPEG file - try the Auto-Fix (which, by the way, in GIMP is found under Colors > Auto... then there are several different "fixes" that you can apply - if you're a GIMP user, take the time and try them all). I've found over the years that the better quality my camera is, the less change the "Auto-Fix" will have on my JPEGs. So, you might be asking, why is my "from camera" JPEG so bad as seen above from my top of the line EOS 7D? I would say that in this case, it was high noon, with the sun directly overhead, and I didn't have my lens hood on. This usually causes all kinds of problems, no matter how good your camera is. Anyway, the point is, don't think it's "unprofessional" to simply try the "one click solution" first. If the result makes you happy, you can save a load of time, and if you are a professional, time is money.

Colour Space

I'm not going to talk about this at all. There are two Colour Spaces  - RGB and Adobe. With some cameras (like mine) you can select one or the other, and I suppose if you're an Adobe Photoshop user, it's best to select Adobe in your camera. <citation needed>. That's all I can say.

Colour Models

This is where it gets real scientific, and again, I'm not going to spend any time on this. When you're using a RAW Conversion Software, you're bound to run into some of the following terms, which are all Colour models. They are RGB, CMYK, LAB, and HSV, among other lesser known ones. If you want to know more, just search Wikipedia for each of these, or do a general search on Color Models, then try to apply what you've learned in using your software.

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