Who needs high resolution?

Most cameras shoot with sufficiently high resolution to make regular and even medium-sized prints. However, photographers who want to make a large print of one of their photos may discover that the resolution they shot the picture with was too low for the size of the print.

Should you always use the highest resolution setting in your camera? How do you change the resolution of a picture that's already been shot? What is resolution really?

What is resolution?

Resolution is a term that describes the number of pixels in a photo. In a sense, the picture's resolution determines how far we can zoom into a photo and still see the fine detail. The following photos demonstrate this:

The right photo has higher resolution and the left one has the lowest resolution of the group. You can see that it's possible to tell the details apart in the right photo – the hand holding the camera – while the detail in the left photo are blurry.

We don't always need to shoot with the highest resolution. The smaller photos in the example above are just smaller versions of the bigger photos, but it's not as easy to tell the differences between them. So if you require a small-size photo (for a computer icon, for example), high resolution is completely unnecessary and will take up too much room on your hard drive.

If, on the other hand, we won't be able to make a poster-sized print of the blurriest photo in the example, because the resolution is just not high enough.

How is resolution measured?

Resolution is measured in two different ways (both representing essentially the same thing – the number of pixels in a photo):

Megapixels – A Megapixel means 'one million pixels' (see entry in our photograpgy dictionary). Thus a photo with a four Megapixel resolution (4MP) has four million pixels in it.

Photo dimensions – you will also see the resolution of a photo expressed by its width and height. Beyond giving you the resolution, this way of expressing resolution also tells you the photo's proportions – narrow, tall, wide, etc. An 800 by 600 photo is 800 pixels wide and 600 pixels tall (this used to be a common computer screen resolution). The total number of pixels in this case would be 480,000 (800X600), which is like saying 0.48 megapixels.

By the way, a computer screen with an 800 by 600 resolution will take a 0.48 megapixel photo and make it fill the screen. Higher resolution photos will be too large for the screen and the computer will have to make them smaller, so that it can render them. In fact, we won't be able to tell a 10 megapixel photo from a 0.5 megapixel photo displayed on an 800 by 600 screen unless we zoom into the high resolution photo. That's why a photo that looks great on our computer screen may come out too grainy in print.

Screen resolution and when to reduce photo sizes

The photos in the previous demonstration are 67 by 100 (for the highest resolution photo) and 8 by 12 (for the lowest resolution photo). There would be no point in using high-resolution photos if you are planning on displaying them on a computer screen or a website. This will just slow down the loading speed of the page and will not improve the way the photos look.

Which resolution is best for photography?

The best resolution to use really depends on what you intend to do with the photo. In theory, there's not strict correlation between the resolution you shoot with and the size of your prints. You could, in theory, print a photo shot at 1 pixel (yes, one pixel) on a mile-long poster. This will come out as a simple monochromatic poster.

Four megapixels is recommended for a 4 by 6 inch print, but you probably won't find a new four megapixel camera anymore since every new camera can shoot at much higher resolution. Our guess is that whatever camera you currently have can take photos that you can print regular-sized photos from. In fact, you might be needlessly shooting at too high a resolution. So change the default settings on your camera and save room on your memory card!

So when do you need high resolution?

The scenario goes like this: you're going through the photos you just took at your kid's birthday party and you scream – 'we have to hang this photo at grandma's!' You're in luck if you shot those photos at a high resolution. If you didn't, you are probably looking up “increasing photo resolution” in Google only to discover that there's not much you can do.

The lesson - make sure you're shooting at high resolution if you're planning on making large prints of your photos. Shooting at six megapixels will allow you to print beautiful 15 by 20 inch photos.

Another good reason to use high resolution is for photo editing. If you want to only use a part of your photo (i.e. crop your photo) to show the part where your kid is holding a kitty and crop out the rest you will, in essence, be enlarging that portion of the photo which doesn't have as many pixels as the entire photo.

Changing the resolution and camera buying tips

As we mentioned, you can't really improve the photo's quality after you shot it, but you can increase its resolution with a simple piece of software. This software can take a one-pixel photo and turn it into a four-pixel photo. How? By simply increasing its size by a factor of four. The outcome is not that spectacular – the software did not do much more than physically enlarge your photo. It takes two adjacent pixels (a yellow one an a red one, for example) and superimposes an orange pixel in between. This attempts to improve the resolution by means of mathematical interpolation, but does not really increase quality or let you print a worthy photo for grandma's living room.

Some digital cameras on the market claim to have 'interpolated resolution' numbers – a camera would be presented as a four megapixel camera but will claim to have eight 'interpolated pixels'. We recommend that you focus on the actual resolution when buying a new camera, and ignore the 'interpolated pixels' claims.

Reducing a photo's resolution actually works! This will diminish the quality of the photo, but will let you upload photos to a website faster. Photo software oroducts such as Picasa reduce your photos' resolution automatically when uploading them to their servers. This makes uploading them and viewing them online faster. Viewers won't be able to tell the difference unless they try and print your photos.

There are so many software products that can help you increase or decrease photo resolution. We recommend a software called IrfanView that is simple to install and simple to use.