I get asked how many megapixels do I need for a specific print size quite often. It's a common question and it seems to be a source of confusion and frustration for many people.
The truth is that most modern cameras have enough megapixels to cover the print sizes most people would want, so my admittedly cheeky answer is if you have to ask, don't worry about it.
But this question seems to keep coming up. In the last few weeks I've heard:
- How big a print can I make with my camera?
- If I want to make an X size print, how many megapixels do I need?
- Can I make A3 prints with my camera? (A3 is roughly equivalent to tabloid)
So, the short (and more polite) answer is if you bought your camera in the last few years, don't worry. You have enough megapixels for an A3 photograph, and probably even higher.
The long answer is, of course, it depends.
It's important to understand that the quality of a print is not based purely on how many megapixels your camera sensor has. Many factors influence the quality of a final print, such as:
- Lens quality
- Digital Noise (from high ISO)
- Sensor dust
- Sensor size (or more accurately, pixel size) Post-processing (I use Apple Aperture for most of my work)
- Ink and paper choice
As an example, I have printed photographs from my very old 6 megapixel Nikon D70s at 16" x 16" that look amazing. And this is a 10 year old camera! But I have also printed photographs from the same camera at 5" x 7" that look pretty average.
Megapixels definitely are not the be all, end all of print quality.
Another point to consider is viewing distance. You can expect the viewer to hold a 5x7 print and look at it up close, but you wouldn't expect them to do the same with a 40 inch one. Bigger prints are usually framed and hanging from a wall, where the viewing distance is a meter or more. Resolution is not as critical in this case. Think of a billboard up in the roof of a building. If you got close enough to it, say 30 cms (the size of a standard school ruler), you'll see the photograph is highly pixelated and blurry, but from farther away (the appropriate viewing distance), it looks fine. Consider the viewing distance when deciding on the print size and how many megapixels you might need.
So how many megapixels do I need then?
OK, if you want details, here we go. All things being equal, the table below will give you an idea of the maximum print sizes you can make from a given camera's megapixels.
File sizes are based on a 12 bits/pixel RAW file. Hi-Res Print are based on 300dpi, which is roughly the standard for "photo quality" prints. Normal Print sizes will give you a good print if you start with a good file to begin with.
|MP||RESOLUTION||FILE SIZE||HI-RES PRINT||NORMAL PRINT|
|2||1600x1200||~ 2MB||5" x 4" (13cm x 10cm)||10" x 8" (27cm x 20cm)|
|3||2048x1536||~ 3MB||7" x 5" (17cm x 13cm)||13" x 10" (35cm x 26cm)|
|5||2560x1920||~ 6MB||8" x 6" (21cm x 16 cm)||17" x 13" (43cm x 32cm)|
|6||2816x2112||~ 8MB||9" x 7" (24cm x 18cm)||19" x 14" (48cm x 36cm)|
|8||3264x2468||~ 12MB||11" x 8" (28cm x 21 cm)||21" x 16" (55cm x 42 cm)|
|12||4000x3000||~ 18MB||13" x 10" (34cm x 25cm)||26" x 20" (68cm x 50cm)|
|24||6048x4032||~36MB||20" x 13" (51cm x 34cm)||40" x 27" (100cm x 68cm)|
In summary, if you have 5 megapixels (photos from your iPhone 4 for example) you can print 8X10 with pretty decent quality (assuming a well exposed and sharp file).
If you have 10 megapixels you can print an A3 size photograph at photo quality. Most modern cameras have at least 10 megapixels.
See? Unless you're planning to make huge prints, don't worry about how many megapixels you need!