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January 21, 2008 meeting notes:

We got off to a great start this year with a look at some useful features in Photoshop CS3 and its accompanying Camera Raw software. For those without it, I talked about how you can tear up and posterize your picuture by making adjustments to contrast and color to a common jpeg in its 8-bit-only form. Posterization can be seen by going to Image> Adjustments> Levels and looking at the chart, called a histogram. Normally, you see gradual bumps and valleys with no spikes. But after stretching and squeezing the lighter or darker areas to improve contrast, you can readily see in re-checking a jpeg's histogram the damage done to the photo. This becomes most readily visible as areas in the sky for example that resemble paint-by-number sudden changes in tone instead of smooth gradations. Not good.

To avoid this jpeg problem, a professional photographer once showed several of us in 2006 how to convert, in Photoshop, an 8-bit jpeg to a 16-bit file. You go to Image> Mode then choose 16-bit. Its so easy, a caveman could do it. Compare adjustments yourself as he did when you only have jpeg files with which to work and you will see gradual, though more severe bumps and valleys but little or no spikes and gaps. Neither he nor I can explain how this works since you can't actually add bits, but it just does.

As you remember, raw photo files are unprocessed by the camera. They have more detail stored and ready for your raw-converter software to unlock their potential. Using raw therefore enables a wider exposure latitude for photos shot with too much or not enough light. Graphics SIG attendees have a high interest in using their camera's raw files for day-to-day photography and that is where we plan to spend much of our time this year. Also, two of the DigiCam SIG members have recently acquired the new point-and-shoot raw-file-producing Canon G9.

These and the raw-capable DSLRs many members have now are worthy of going the extra mile to make memories for ourselves and others as they yield a higher "keeper rate". My improving keeper rate is also due to knowing the camera's limits, features, constantly adding to my photographic experience, and using the derriere-saver Adobe Camera Raw or ACR.

We opened some photos and played with the higher-contrast projector to produce some fine, color-balanced, less contrasty results. For fun, I took pictures of some friends' daughter in the Queens contest, part of the Nueces County Junior Livestock Show. The Robstown H.S. event is lit mostly with a very low spotlight. The balancing act here was to use the lowest possible ISO, the widest depth-of field (focused area), and the fastest shutter speed possible to produce the most acceptable photos. Using a low ISO keeps me from having to use any noise-reduction plug-ins which will smooth things out but cause a loss of detail. A wide area in focus helps me keep a moving subject in the right plane, and a fast shutter will ensure 1) I hold the camera steady enough and 2) the subject doesn't blur from her own movement. Its not too hard to fail at any one of these, but sure enough, examining one contestant's series, I experienced all four problems on three successive shots!

To tackle these problems, plus under- and over-exposure I started with the Exposure slider. That takes care of some highlight recovery, though it affects your entire histogram (all values) visible at the top of the screen. But ACR 4 has now added a very specialized slider, Recovery, for us to juggle with Exposure! Another one below it, Fill Light, works on adding light to the shadows to taste. The new Convert to Grayscale checkbox allowed me to try out what some youth are now discovering: black and white photography.

Comparing a "pre-baked" monochrome conversion I did at home, our new creation was adjusted to a just-right contrast and very pleasing to the eye, thanks to the abundant adjustments one can make in ACR. Contrast, shadow and highlight detail are not the only things you can correct with the ACR sliders. I also showed how a slightly out of focus subject or one blurred due to your or the subject's movement can be sharpened more than usual to bring it closer to appearing in focus.

Lastly, ISO 800 requires some Luminance noise correction, usually 10-15 on my slider, and Color Noise I slide to about half whatever Luminance is. These minimal adjustments allow for little appearance of noise or loss of detail.

Tough on software,
Bruce Switalla, Graphics SIG leader
 


 


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