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BIRDS AS ART ON-LINE Bulletin #92 November 15, 2002


BOSQUE IPTs & THANKSGIVING   I am flying to Bosque this Saturday for the eighth straight year since Elaine's death on November 20, 1994.  Each trip is somewhat of a pilgrimage to her memory and the wonderful years that we had together.  The three IPTs have filled nicely, though for the first time in years they have not sold out.  There are three openings on the NOV 18-20 IPT (hurry!), five spots left on the middle one--NOV 24-26, and room for just two photographers on the NOV 30-DEC 2 IPT.  Having 26 folks join me in New Mexico for fun, instruction, and simply wondrous photography in spite of the poor economy is most gratifying.



When the sunrise in the east looks like a dud, position yourself so that the birds are in front of the southern or western sky where the light often ranges from pink to purple on dead-clear mornings.  This works great for flocks either on the water or in flight...

As many of you know, I have, for the past several years, hosted a Thanksgiving Day Buffet lunch at the historic Val Verde Steakhouse in Socorro for photographers and friends.  The food is incredibly good, with tons of turkey and stuffing and yams and all the fixings as well as table-fuls of great desserts.  This year we will meet at 12:30 pm.  All are invited.  Bring 70mm dupes or small prints to show off.   I hope that you can join us.

TIM GREY'S DDQ  Tim Grey, who works for George Lepp,  publishes an almost-daily question and answer e-mail service called Digital Darkroom Questions (DDQ), which provides a forum for photographers to have their questions related to the digital darkroom answered, and to learn from questions asked by other readers. For more information, or to add your e-mail address to the list, visit"  Simply put, Tim's range of knowledge is incredible.. 

Here is a Q&A that I found extremely helpful.

Q:  I would be most grateful if you would explain the rationale for choosing  specific settings for radius and threshold in unsharp mask. 

The Unsharp Mask filter produces a visual sharpening effect by increasing contrast along edges in your image. Edges are determined based on where contrast already exists, and that contrast is enhanced with Unsharp Mask to increase the apparent sharpness. It is important to understand that your image isn't actually getting sharper. You can't take an out of focus image and make it look sharp. The Unsharp Mask filter is rather a tool for optimizing the apparent sharpness of an image, and to compensate for the loss of sharpness that is a natural result of digital capture and particularly film scanning.

The radius setting determines how far out from each pixel the filter will look for contrast. A very high setting means the filter will look very far, resulting an extreme halo effects in your image that are generally very undesirable. Therefore, the radius setting is the most important one in terms of image quality, and generally should be kept relatively low. I generally recommend a value of 1.0 to 1.5 for images that will be output around 300 dpi. However, the optimal setting will vary from image to image based on specific content, so you'll want to fine-tune it accordingly.

The threshold setting determines how much contrast must exist between two pixels for them to be considered an edge. The higher the setting, the more difference must exist before additional contrast is introduced in a particular area. The threshold setting can therefore be used to mitigate excessive sharpening. It is particularly useful in helping to eliminate noise and to avoid over-sharpening images that have areas you don't want to over-emphasize. Portraits are a perfect example. You want a nice sharp image, but you don't want to over-emphasize each pore on the model's face. Increasing the threshold will provide the solution.

The question then becomes how to determine the best settings based on this rationale. Generally speaking I do recommend some very basic parameters that help simplify the process for photographers. You can set the radius to 1.0 or 1.5, and pretty much leave it there. You can then put the threshold at 4 for most images, increasing it to 8 or so for portraits. Then you simply adjust the amount to suit the image, generally setting it somewhere between 75 and 125.

If you want to be a bit more detailed, you can set the amount to about 100 and threshold to 0, then adjust the radius to determine the best value based on when haloes start to appear in the image. Once that setting is in place, fine-tune the amount to perfect the sharpening, and finally increase the threshold as needed to help eliminate noise and avoid over-sharpening.

Many favor the use of a very high amount and very low radius setting for digital captures. Because images captured digitally don't have grain and are generally more sharp to begin with, this is a good strategy. The net result is to increase contrast more significantly at edges, but not "look" as far from each pixel to find those edges. Typical values in this scenario might be 0.4 to 0.6 for radius and 300 to 500 for amount. 


Still cannot get to the washing machine.  Please order your calendar(s) today.  They make great gifts!  Click here for details:



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