Friday, March 21, 2008

Software Tip: Printing and Dots Per Inch

I had a friend ask a question about printing his digital photos. I thought it would be good to bring the same ideas to you.

Digital photos are made up of tiny little squares of solid color called pixels. This is where the term megapixel comes from, which is a measurement of how many millions of pixels a camera captures in each shot. The more pixels you have in an image, the more detail the image will show.

Therefore, when you go to print your photos, you want to have a lot of pixels packed into the image. The way we refer to how many pixels there are is by pixels per inch (ppi, which is the same as dots per inch).

My basic rule of thumb is if you don't have at least 200 ppi in your photo, you will likely see jagged little edges along the lines in your print. If you want something that will be "picture perfect," then you need at least 300 ppi.

"But wait a minute," you might be thinking, "my camera only said how many megapixels it shoots, not how many pixels per inch the photos will have!" You're right — the amount of ppi is up to you when you go to print a photo.

Let me give you a real-world example. On my Canon 20D I have three different sizes I can select for my photos: large, medium, small. Here are how they differ in megapixels and dimensions (in pixels):

SettingDimensionsMegapixels
Large3504 x 23368.2 MP
Medium2544 x 16964.3 MP
Small1728 x 11522.0 MP


This says that at 200 ppi, the largest I prints I could realistic get from each of the sizes are as follows:

SettingDimensionsLargest Print @ 200ppi
Large3504 x 233611.7" x 17.5"
Medium2544 x 16968.5" x 12.7"
Small1728 x 11525.8" x 8.6"


So in other words, you can print a 11x14 from the large, 8x10 from the medium, and 5x7 from the small setting. Trying to print a 11x14 from the small will result in an image that seems "blocky" and won't look good, but printing a 5x7 from the large will look beautiful and full of detail.

My next post will talk about using the crop tool in your favorite photo editor and how you can crop out a portion of your photo but still make sure it has enough resolution to print well.

Monday, March 17, 2008

Photo Tip: Window Light Portraits

I know it's been a long time since my last post, and I apologize. I hope the simpleness and impact of this tip will make up for it.

Please take a look at my wonderful daughter below:


What a wonderful photo! But if it is simple to do, then what's the secret? All I did was find a window in the house that faces north and place a dark backdrop away from it.

During this time of the year the sunlight will never shine through a north-facing window. But the light sure does, and it creates a wonderful ambient lighting effect.

To maximize this effect, I took a dark quilt and draped it several feet behind her. Here's a shot showing how the window and black backdrop relate spatially to each other:


Because the light hitting my daughter's face is several stops brighter (or, in other words, several times brighter) than the backdrop, the backdrop becomes completely black. And because of the ambient lighting coming through the window, it creates soft shadows as it wraps around her face.

You can do this shot with any kind of camera that has a zoom lens. Just stand several feet from your subject and zoom in. This will isolate him or her against the backdrop and you won't see anything else in the background.

Try it yourself and you will see how easy it is!