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What is a Megapixel?

“Megapixel” is a camera manufacturer’s favorite word.

For a newbie photographer too, the word has immense significance. I am not going to go too deep into what professionals think because opinions are beyond the purview of this discussion.

The fact remains that megapixels do matter.

You need a sufficient amount of megapixel to produce a good print and for that matter even to share an image online with your friends and loved ones.

But there is more to megapixel than that. It has wider connotations and deeper ramifications. These days camera manufacturers are going head over heels trying to promote megapixels of their new camera sensors. Some of that is meaningful. Some of it is baseless propaganda. There is a limit to how much megapixel is necessary.

Let’s start from the very beginning.

Megapixel Definition

  • What is a Megapixel? A Megapixels refers to a cluster of pixels.
  • How many exactly? Well, one million. So one megapixel is one million tiny individual pixels.

If a full-frame camera has, for example, 22 megapixels; that is 22 million pixels. That is a lot of tiny pixels packed on to a small sensor surface.

What are Pixels?

That invariably leads to this question: What are pixels? Pixels are Picture Elements, the tiniest element that is controllable on the sensor.

Each digital image that you see on a computer screen is made up of millions of these tiny pixels.

Each tiny pixel is a light sensitive photodiode. They have a small space to capture the photons in the light. On top of that, the individual pixels also have microfilters. These filters will absorb either red, blue or green light and reflect every other wavelength of light. At the bottom of the pixel, a wiring connects it to the image processor.

Pixels, in fact, are what make up the surface of the digital sensor. They play an important role in the print size of your images.

What is Resolution?

We often hear the term resolution when discussing photography. Resolution denotes the number of pixels that are there on an image. Pixels are the tiny dots that make up an image.

The higher the number of pixels, the greater is the resolution. Also,  the amount of detail in the image is better too.

A higher resolution is also ideal when printing large images. The standard for printing is 300 dpi. Though dpi (dots per inch) and ppi (pixels per inch) are not the same things they are sometimes considered the same and therefore higher concentration of dots (or pixels) means the image is going to appear sharper, detailed and continuous (not pixelated).

Professionals look for cameras that have a larger resolution. This gives them the ability to crop if required and still be able to print large. It is pertinent to note that resolution is measured in megapixels. One megapixel is equal to one million pixels.

Megapixels and Print Sizes

How to Determine Print Sizes from Digital Cameras

There is no standard print resolution that will work for all print sizes. For small 4 x 6″ postcard sized prints the standard printing resolution is 300 DPI. That is 300 dots per inch.

Conversely, for a large billboard, the printing resolution could very well be 50 DPI or much less. Here dots and pixels are loosely considered the same. They are not the same though. But for the sake of understanding, this concept let’s say that they are.

What is a Pixel and How Many Do You Need?
Large Format Printing: What is a pixel and how many do you need? For indoors wall hanging photos aim for 300 DPI (dots per inch), for outdoor billboards (seen from far) less DPI are ok.

Now, the maximum size that you can print an image to will depend on the number of megapixels on your pictures. This is where quantity does matter. The more the megapixels your images have larger the size you can print.

It may appear though I am suggesting that you opt for a higher resolution camera. I am not. Read the rest of this discussion before you make up your mind.

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Formula to Determine Print Size from Image Resolution

This is the formula to determine the number of megapixels required for a 5 x 7″ print at 300 DPI.

5 x 300 x 7 x 300 / 1,000,000 = 3.15 Megapixels.

Surprised? Wondering why you fell for that gimmicky ad that promised a 30-megapixel sensor when all you needed was merely 3.15 megapixels to make a decent print? Don’t feel that bad. After all, your high-resolution camera has some other advantages as well.

MegapixelResolutionPrint Size at 300 DPI
42 MP7952 x 530 Pixel20 x 30 Inch
30.4 MP6720 x 4480 Pixel16 x 24 Inch
24.3 MP6016 x 4016 Pixel16 x 20 Inch
20.1 MP5456 x 3632 Pixel11 x 14 Inch

Purpose of the Print

Small Prints (High DPI)

The purpose of the print determines the resolution that you need. Let’s say that you need to print a couple of your vacation photos with your significant other. A mere 5 x 7″ size is what you are looking for. These prints will be seen from a distance of about arm’s length. Which means a minimum resolution of 300 DPI is necessary to ensure a homogenous image.

Well, the thing is, if you are only going to print occasionally and that too not more than 8 x 11″, then you don’t need a very high-resolution camera. If you are only going to share your images online using a photo portfolio site, any camera will let you shoot good quality, shareable images.

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Large Prints

For Close View

But let’s say that you do want to print large. Really large. Something around 30″ x 40″. For printing this large you will need a pretty high-resolution sensor. Even if you want to view the image from a distance of 3 or 4 feet away, you will need around 40 pixels or higher to make a good image that won’t show up pixelated.

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Another example is a billboard. Billboards are always viewed from large distances; 50″ or more. For printing these big you hardly need 15 – 40 DPI. That means images produced by even a relatively small resolution sensor will be good enough for printing them in large billboard sizes.

Viewing Distance

The recurring thing that comes up in this comparison is the viewing distance.
The greater the viewing distance, the larger is the print you can make with the same sensor.
If the print size remains the same but the viewing distance changes, then you will need a higher or lower resolution sensor depending on whether you walk up to the print or walk away from it to view.

Standard Print Sizes for Images

Examples of Different Cameras / Sensors

Here is a comparison of some of the popular digital cameras that are currently being sold (across different sensor sizes), along with their megapixel resolution and the maximum image size you can print.
Please note that we have selected the largest acceptable size, which is one size larger than the size that is the best. We have considered a minimum distance of 3 feet from the image to viewer’s eyes and that allows slightly more leeway than the best resolution situation.

Canon EOS 5D Mark IV (Full-Frame)

  • 30.4 megapixel (effective) resolution
  • Maximum image resolution 6720 x 4480 pixels
  • Largest print size at 300 DPI – 16 x 24″ (in acceptable resolution)
Canon EOS 5D Mark IV Digital SLR Camera Bundle (Body Only) + Professional Accessory...
  • This Canon Camera Bundle comes complete with All Standard Canon Supplied Accessories and 1-Year Canon USA Limited Warranty...
  • Canon EOS 5D Mark IV 30.4 MP DSLR Camera; 0.4MP Full-Frame CMOS Sensor, DIGIC 6+ Image Processor, 3.2" 1.62m-Dot Touchscreen...
  • 2x SanDisk 64GB Ultra Class 10 SDHC UHS-I Memory Card - Great choice for compact to mid-range point and shoot camera, Twice...
  • Backpack Camera Case, Automatic Speed Light TTL Flash, Red Eye Reduction, Professional 50" tripod, AC/DC Charger, Power...

Nikon D750 (Full-Frame)

  • 24.3 megapixel (effective) resolution
  • Maximum image resolution 6016 x 4016 pixels
  • Largest print size at 300 DPI – 16 x 20″ (in acceptable resolution)
Nikon D750 FX-format Digital SLR Camera Body
  • Full frame 243 megapixel CMOS image sensor and expeed 4 image processor
  • Full HD 60/50/30/25/24p video
  • Built in Wi-Fi connectivity and compatibility with the WT 5a + UT 1 communication unit
  • Shoot up to 65 fps at full resolution frame size (pixels): 1920 x 1080
  • Pro video feature set including: simultaneously record uncompressed and compressed, manually control ISO, shutter speed and...

Sony Alpha a5000 Mirrorless Digital Camera (APS-C Sensor)

  • 20.1 megapixel (effective) resolution
  • Maximum image resolution 5456 x 3632 pixels
  • Largest print size at 300 DPI – 11 x 14″ (in acceptable resolution)
Sony Alpha a5000 Mirrorless Digital Camera with 16-50mm OSS Lens (Black)
  • 20.1 MP Exmor APS-C sensor for great images
  • Mirror less DSLR - Compact Interchangeable Lens camera system
  • Quick Wi-Fi connectivity to smartphones via NFC
  • Model: ILCE5000L/B

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Sony Cyber-shot DSC-RX100 V Digital Camera (1″ Sensor)

  • 20.1 megapixel (effective) resolution
  • Maximum image resolution 5472 x 3648 pixels
  • Largest print size at 300 DPI – 11 x 14″ (in acceptable resolution)
Sony Cyber-Shot DSC-RX100 V 20.1 MP Digital Still Camera with 3" OLED, flip Screen,...
  • ELECTRONIC VIEW FINDER: retractable Tru-Finder EVF provides sharp resolution, bright self-illumination, and high contrast to...
  • AUTO FOCUS: World’s fastest (0.05 sec.) hybrid AF system (contrast + phase) which is great for action and wildlife...
  • AF DETECTION: The most comprehensive phase detection coverage in a compact camera utilizing 315 Auto Focus points
  • SHOOTING SPEED: World’s fastest continuous shooting speed at 24fps3 w/ autofocus and auto exposure tracking to ensure...
  • IMAGE SENSOR: 20.1 megapixel 1" Exmor RS stacked back illuminated CMOS sensor w/ DRAM for outstanding image quality and...

Sony alpha a7R II Mirrorless Digital Camera (Full-Frame)

  • 42 megapixel (effective) resolution
  • Maximum image resolution 7952 x 5304 pixels
  • Largest print size at 300 DPI – 20 x 30″ (in acceptable resolution)
Sony a7R II Full-Frame Mirrorless Interchangeable Lens Camera, Body Only (Black)...
  • World’s first Full-frame 5-axis in-body image stabilization optimized for 42.4MP full-frame, 4K movie recording with full...
  • 2.4-million dot XGA OLED Tru-Finder w/ZEISS T- coating, connectivity to smartphones via Wi-Fi and NFC w/camera apps, Fast...
  • Shutter vibration suppression, curtain shutter, silent shutter, Resolution meets sensitivity 42.4MP up to ISO 102,400/4K up...
  • Fast Hybrid AF with 399 focal plane phase-detection AF points and sensor is 35 mm full-frame (35.9 x 24.0 mm), Exmor R CMOS...
  • Inside box: Rechargeable Battery NP-FW50; Cable Protector; AC Adapter AC-UUD11; Battery Charger BC-VW1; Shoulder strap; Body...

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Canon PowerShot SX620 HS digital camera (1/2.3″ Sensor)

  • 20.2 megapixel (effective) resolution
  • Maximum image resolution 5184 x 3888 pixels
  • Largest print size at 300 DPI – 16 x 20″ (in acceptable resolution)
Canon PowerShot SX620 Digital Camera w/25x Optical Zoom - Wi-Fi & NFC Enabled (Black)
  • Powerful 25x Optical Zoom with Intelligent IS helps optimize image stabilization for virtually shake free images
  • Built in Wi Fi* and NFC** allows for easy sharing and transferring of images and videos. Maximum f/number : f/3.2 f/6.6....
  • 20.2 Megapixel*** CMOS sensor with DIGIC 4+ Image Processor helps deliver stunning image quality even in low light. Auto zoom...
  • Capture spectacular 1080p Full HD video. Focusing Range : 1 centimeter (0.4 Inches) infinity (W), 1.0 meter (3.3feet)...
  • Large 3.0 inch (approximately 922,000 dots) LCD allows easy viewing even from a wide angle. Battery life: Approx. 295 shots,...

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Sony alpha a6500 Mirrorless Digital Camera (APS-C Sensor)

  • 24.2 megapixel (effective) resolution
  • Maximum image resolution 6000 x 4000 pixels
  • Largest print size at 300 DPI – 16 x 20″ (in acceptable resolution)

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Sony Alpha a6500 Mirrorless Digital Camera w/ 2.95" LCD (Body Only)
  • 24.2MP APS-C Exmor sensor w/ advanced processing up to ISO 51.200
  • Wide 425 phase detection AF points, Fast 0.05 sec. AF acquisition
  • 5-axis in-body image stabilization steadies every lens. Silent Shooting. Noise Reduction :Long exposure NR: On/Off, available...
  • 11fps continuous shooting to 269 frames at 24.2MP w/ AE/AF tracking
  • 4K movie w/ 2.4x oversampling4, full pixel readout, no pixel binning

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  • Rajib is an avid travel photographer and an overall shutterbug. He loves to test and review new photography gear. He has been writing about cameras and lenses for over 10 years now. You can consider him as your "master guide" here at PhotoWorkout.

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