Controlling Digital Grain
Keep The Appearance Of
Grain Under Control In Your Photos By
Rob Sheppard
In
the last issue, we started looking at grain from a digital perspective. Visually,
"noise" in a digital
image file creates the same sort
of effect as film grain. Regardless of the way it got into your photo, the irregular
speckled pattern of anything that looks like grain can be a problem.
Unfortunately, we often inadvertently enhance this grain while working on a photo
in the computer. There hasn't been a lot of advice on how to control it, so here
are 10 ways you can work to reduce grain.
1 Use fine-grained films whenever you can. Slower films equal
smaller and less noticeable grain. The best are those with a film speed in the
ISO 100 range.
2 Minimize
sensor noise. You have no control over the sensor itself (more expensive digital
cameras often better control noise). However, if you shoot in bright light and
restrict the use of higher ISO numbers (e.g., an ISO equivalent of 400), you'll
minimize the noise in the image from the sensor.
3 Be sure you have enough exposure. Underexposure for both film
and digital cameras can cause grain/noise problems. This is especially a problem
in low light and when shooting light or bright subjects (including backlight).
Check your LCD monitor. Add exposure or use a flash, if needed.
4 Buy the best scanner you can. Avoid the really low-priced units
as they tend to pick up a lot of noise in the dark areas of an image.
5 Use JPEG (a compression format) sparingly. Never try to cram as many photos on a memory card as you can-buy a larger card.
Set your camera to its highest-quality compression even though that means larger
file sizes.
6 Be careful to avoid
overprocessing an image's color in an image-processing program. This often
leads to increased digital grain.
7 Realize
that out-of-focus areas and large expanses of one tone (such as sky) emphasize
grain. If necessary, select the sharp areas to separate them from the rest
of the photo before sharpening the image. Never sharpen out-of-focus or plain-sky
areas.
8 Avoid oversharpening of
a photo. Sharpen only the sharp parts of your photo.
9 Be sure you have the correct image file size for your print needs. Avoid forcing a low-megabyte file or low-megapixel image to be a big print.
10 Try Visual Infinity's Grain Surgery
plug-in, (877) 596-0931, www.visinf.com. This
program offers a high degree of control over grain effects. You choose the amount
and way the grain is dealt with (removing grain digitally also can affect the
sharpness of an image).
You'll never completely eliminate grain with
standard photographic procedures at this point in time. Sometimes grain can be
interesting and even add to the sharpness of a photo. However, it can be controlled
with the steps listed here.
