Re: How can you avoid grain in a picture?


Message posted by lone wolf on February 22, 2005 at 17:28:49 PST:

Frank's right about the density of the image, but as always, it depends. For instance, as you push the film, the contrast increases. If the task is to shoot the base from Tikaboo, you need all the contrast you can get, so pushing one stop is not a big deal. [if you don't push, you need to increase the contrast in photoshop, which will amplify the grain.] Red Flag photos are another story. If there is enough light to get close to the 1/(shutter speed) guideline, I shoot Asti 100F at 100. But if the light is low, I push it one stop because I probably won't be getting that much of a contrasty image in the hazy light, and the grain isn't objectional when pushed one stop.

I have some grain reduction examples using image stacking, but can't show them here. Besides stacking, which averages the grain, you need to be very careful how you sharpen the image since it accentuates the grain. I've been experimenting with a program called Iris (free at astrosurf.com) to do sharpening with less grain accentuation. The procedure is a bit complicated, but it consists of color seperation of the RGB image, statistical noise reduced of each color, recombination back to RGB, conversion to LAB, wavelet sharpening on the luminance channel, then replacement of the original luminance channel with the wavelet sharpened channel, then reconversion to RGB. The results are pretty impressive. I plan on doing my next panoramics with this technique.


In Reply to: Re: How can you avoid grain in a picture? posted by Frank Stamm on February 22, 2005 at 17:15:14 PST:

Replies:



[ Discussion Forum Index ] [ FAQ ]