Statistical Blending

You can use statistical blending to render high dynamic range images, to reduce noise, or to create multiple exposure effects in Photoshop (CS4 extended edition). All these techniques require that you have multiple images to start with. For HDR images, you need different exposures of the same subject from a stationary viewpoint. The same is true for noise reduction, only the exposures should be identical. Multiple exposure effects can use any number of different images, all of the same dimensions. In each case, you start by stacking all the images into layers, selecting all layers, and converting them into a smart object. Then you use the Layer > Smart Objects > Stack Mode functions Mean or Median to create a statistical combination of all the images, which you can rasterize. Details after the break.

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Worthy of 16-bit Printing

Is there really any difference between printing with 8-bits per channel and printing with 16-bits per channel? I’m not sure yet, but I’ve been dealing with a photo that could reveal the difference. It has some very fine, continuous gradations–exactly the sort of thing that Epson says is worthy of 16-bit printing on the 9900.

Evening light

Evening light (Alma de la Serra, 2009)

I’ve been printing this on Hahnemühle Photo Rag (HPR), an exquisitely unforgiving paper. I reveals every glitch–which is to say, it’s a fantastic paper, capable of recording the finest nuances. I’ve been printing this 16-bit/channel image in 16-bit/channel resolution, and have been very gratified with the results.

Dust has been the only problem. Ink on HPR will not bleed into the gaps left by tiny particles, nor does it have a texture that will hide specks. This particular image really shows such flaws. I throw out about a third of the prints, looking for perfection. Nothing else will do. I haven’t had this problem with other papers–but maybe I’ve just been lucky, or there’s more static charge on HPR. In going digital, photography has not left dust behind.

Incidentally, this is a high dynamic range image, a composite of 5 images. I used qtpfsgui to composite and tonemap the image and finished the processing in Photoshop CS4. Qtpfsgui/ Luminance HDR is an open source application for HDR workflow. It doesn’t have the bells and whistles of Photomatix or Photoshop, but it gets the job done, once you grok the interface.

This print and a few others by Alma de la Serra will be on view at Transistor over the coming weeks.