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Welcome to Dijemeric Visualizations

Where photography and mathematics intersect with some photography, some math, some math of photography, and an occasional tutorial.

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Tuesday, September 20, 2011

Correcting Color Casts in Photoshop

1) duplicate the original layer, in this example a scenic with a strong red cast

2) Apply Filter>Blur>Average to get ...

 ... a layer of just one color - the color cast with RGB values of 123:108:118

 3) Invert the color layer ...

... to get the complementary (opposite) color with RGB values of 114:148:138

4) Blend Color mode

5) Change opacity to 10-40%

6) If it looks 'flat' add a bit of saturation.  As this looks ok to me, I did not add any saturation.   Compare the color cast removed version (this one) with the original in step 1 above.

Based on a presentation to the Berkeley Camera Club by Bernadette Talbot 
A nice YouTube 'how to' by Tim Grey at

Wednesday, September 07, 2011

Sweet stuff - Time Lapse Photo-microscopy With an iPad 2

Sugar dissolves in water, right? Coffee drinkers know that and some who drink tea do too, but what happens if you put in more sugar than the water can hold? Place a few crystals of sugar on a microscope slide. Add a small drop of water and watch. If you are patient, you will see that at first the crystals dissolve rapidly, then the process slows and eventually seems to stop. As the water surrounding the sugar crystals hold more sugar molecules, the water becomes saturated. As molecules of sugar leave the surface of a crystal more molecules in the water return to the surface of the crystal. When the rates are equal, the water can hold no greater concentration and the crystals stop dissolving.

What if you put just one crystal into a drop of water? Or what if you added even more water to the saturated solution? To find out, watch the video.