Digigraphica

Picking the Right Digital Camera

Megapixels Come First

Dan Knight - July 2002, updated Jan. 2008

Once you decide you want or need a digital camera, the first issue you should address is megapixels (MP). A pixel is a single point on your screen or in your image. The number of pixels in an image determines how big you can make it without losing quality.

But instead of starting with megapixels, we need to go back a step and ask, "What's the largest print you ever expect to make from your digital camera?" If you want a crisp 8x10, you'll need more pixels than you would to create a sharp 4x6. And with photo quality inkjet printers, it's increasingly likely that you'll be printing an 8x10 now and then.

Once you've determined the maximum image size, you need to determine how many dots per inch (dpi) will provide the sharpness you need. For general work on an inkjet printer, I've found that 180-200 dpi is excellent, although if you're working for high quality magazine or art book output, you should probably be working in the 250-300 dpi range. (Don't confuse print resolution with printer resolution. Most color printers today work anywhere from 300 dpi to 720 dpi. As long as this number is at least 40% higher than your print resolution, you don't need to worry about it.)

Let's look at how many pixels some common print sizes need:

size       180 dpi          200 dpi          250 dpi   
4x6     720x1080  0.78   800x1200  0.96  1000x1500  1.5
5x7     900x1260  1.21  1000x1400  1.4   1250x1750  2.2
6x9    1080x1620  1.75  1200x1800  2.2   1500x2250  3.4
8x10   1440x1800  2.6   1600x2000  3.2   2000x2500  5.0
8x12   1440x2160  3.1   1600x2400  3.8   2000x3000  6.0
11x14  1980x2520  5.0   2200x2800  6.2   2750x3500  9.6
11x17  1980x3060  6.1   2200x3400  7.5   2750x4250 11.7
12x18  2160x3240  7.0   2400x3600  8.6   3000x4500 13.5
16x20  2880x3600 10.3   3200x4000 12.8   4000x5000 20.0

There's a little leeway here, but even a 2 MP camera should be adequate for top quality prints up to 4x6 - even in high quality print publications! For the average home user with a color inkjet printer, entry-level 1.3 MP cameras did fine at 5x7 and 2 MP cameras can produce a sharp 6x9 - but you really want a 3 MP camera to get that nice sharp 8x10.

If you plan on going larger than that, keep in mind that larger prints are generally viewed from a bit farther away, so you can use the 180 dpi column as your guide for 11x14 and 11x17. That 5 MP digicam can produce a very nice 11x14, and 6 MP cameras can produce very nice 12x18 prints. But if you want to go to 16x20s, they're a bit out of your reach at 5-6 MB unless you resort to sharpening your image in Photoshop. This is where 8 MP and better cameras come into play.

Online Images

What about images for the Web? Compared with even a 4x6 print, Web images are tiny. Even a high resolution 1280x1024 screen is just 1.2 MP, and since your pictures will tend to be a lot less than full screen, a sub-megapixel cameras could be adequate if all you need is Web output (then again, most sub-megapixel cameras, such as those built into mobile phones, have so many other compromises that you'll want a better camera).

Don't be afraid to get a camera with more pixels than you need, either. That will give you room to crop and manipulate the print with minimal loss of detail. Remember, you can always make a picture smaller, but you can't put in detail that wasn't there to begin with.

That said, there are a couple of drawbacks to excessive megapixels. The first is that the images take up more storage space on your memory card and hard drive - and take longer to write to your memory card. The second is that especially with smaller point-and-shoot digicams dividing a small image sensor into more and more pixels means more unwanted noise in your images.

Based on all this, I usually recommended that most of my customers start by looking at 3 MP cameras, and five years after writing this, I almost always shoot my 5 MP and 8 MP digicams at the 3 MP setting.

Go to Picking a Type of Digicam.

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