All, Getting Started

How Many Megapixels is Enough?

Posted on 05-08-2019
Written by digiDirect

 

People often evaluate a camera’s quality by looking at how many megapixels it has, being under the impression that a camera with more megapixels is automatically superior than one with less. This isn’t necessarily the case – and you may not need as many megapixels as the photographer next to you. Join digiDirect as we outline how many megapixels you need for your purposes, as well as why you can’t measure a camera’s quality by megapixels alone.

Pixel Size vs. Megapixels

One megapixel (commonly abbreviated to MP) is one million pixels. Megapixels are a way to measure quantity and have little to do with quality.  Basically, what this means is that you need a certain number of megapixels in your photography depending on how you want to use or share your images. Your camera's quality factors in many things like the image sensor design, optics, engineering, firmware and pixels. The centre of your camera contains an image sensor, and this sensor has an array of pixels. The pixels act a little like buckets that collect light.

The image sensor can come in different sizes, and the larger the image sensor, the larger the pixels can be. Larger image sensors are also able to collect more light. The more light they collect, the cleaner and clearer the photograph, and the less noise it will have.

You can get a rough idea of the camera's image sensor's size by looking at the lens' diameter. For example, an eight-megapixel camera on a smartphone crams eight million pixels into a tiny sensor that is about as big as a baby aspirin. In contrast, a larger sensor camera with the same number of pixels would mean that each pixel is physically larger. This would allow the pixels to catch and hold more light without letting it blur into other pixels and cause noise. Now, realistically a larger sensor camera these days would have more than 8 megapixels, but it illustrates the point.

Phone pixel sizes are starting to undergo a shift. The newer smartphones have slightly larger pixel sizes and are capable of producing higher quality photography. The iPhone 7 features a pixel size of 1.22 microns per pixel, and the Samsung Galaxy S7 features a pixel size of 1.4 microns per pixel. This brings their size to roughly that of many point-and-shoot camera models.

Mirrorless cameras, advanced compacts and professional or semiprofessional DSLRs come with even larger sensors. The most common sizes are APS-C (about 22mm x 15mm) and full frame (36mm x 24mm). It's safe to say that if everything else is the same except sensor size, an 8 MP DSLR will give you a superior image than if you shot it with an 8 MP compact camera. Similarly, the compact camera will give you better images than you'd be able to capture on a smartphone.  



While smartphone image quality has been steadily improving, smartphone cameras still feature significantly smaller image sensors than dedicated cameras
 

Where Megapixels Matter

Megapixels are still important, however, when we come to look at image size. How big do you want your final photograph to be? Basically, you need a camera or a smartphone with enough megapixels to support your desired final image size. This is especially important if you want to print out your photographs, as image size is much more important in print format than if purely being viewed digitally.

The overall quality of the printed picture depends directly on having enough data or pixels to create a clean, bright and defined picture. To help you understand this in a more in-depth way, we’ve covered how many megapixels you need for different photo mediums:

Prints 

Most people understand that the format that requires the highest resolution is prints. If you're not sure how many megapixels you need to get a sharp and clear print, there is a simple formula you can use to get an exact number of requisite megapixels.   

Megapixel count becomes much more important when making prints


The first thing to understand is that for a picture to be of sufficient quality in print form, it generally needs to have 300 pixels per inch (PPI). With that in mind, determine how large your physical print will be in inches. Let’s use 8x10 inches as an example (slightly smaller than A4). Because we know it is 8 inches by 10 inches, and we know we need 300 pixels per inch, how do we determine the length and height in pixels? Simply by multiplying the length and width by 300 each! That gives us a figure of 2400 pixels by 3000 pixels. So we know that the picture we take with our camera has to be 2400 pixels by 3000 pixels in order to be of sufficient quality to print out at 8 inch x 10 inch size.

But how do we convert that to megapixels? We simply need to determine the total number of pixels in the image - i.e. we need to know the area in pixels. Remembering back to high school, we can calculate the area by multiplying the length by the height. So we multiply 2400 pixels x 3000 pixels, giving us a total of 7.2 million pixels. Finally, one megapixel is one million pixels, so if we divide that number by one million, we’ll get the required number of megapixels. In this case, that results in 7.2 megapixels. So this means that as long as the photo is taken on a camera with 7.2 megapixels or more, it will be of sufficient quality to print at 8 x 10 inch size.

That sounds complicated when written out, but it’s actually quite simple. To recap:

1) Determine how large you want the print to be in inches

2) Multiply the length and height (in inches) each by 300 to convert the distances to pixels

3) Multiply length x height, and then divide the resulting number by 1 million

That’s how many megapixels you need! 

Desired Print Size
(in inches)
Megapixels Required
(for 300 PPI print)
6x4 2.2 MP
5x7 3.2 MP
8x10 7.2 MP
11x14 13.9 MP
16x20 28.8 MP

Digital Photographs

If you never plan to print out your pictures and you want to use them exclusively online (like on social media), you'll need fewer megapixels. This is because online viewing requires less resolution than physical printing. The magic number for online viewing is 72 pixels per inch, as opposed to 300 PPI for printing. So the resolution for online photos is less than a third of that required for print, which means that almost any modern-day camera will take images of sufficient quality for online viewing.

As an example, one of the largest photo sizes you’ll find on social media is the Facebook cover photo. As of Aug 2019, Facebook recommends your image be 1640 pixels by 720 pixels. Using our formula, that means we only need a camera that has 1.2 MP in order to be of sufficient quality (1670 x 720 = 1 202 400 pixels. 1 202 400/1 000 000 = 1.2 MP). This makes a smartphone perfectly capable of producing photos to use online.


Photos that will primarily be used only in digital mediums have a lower megapixel requirement
 

Using Excess Megapixels in Order to Crop

As you’ve gathered by now, you don’t actually need a huge amount of megapixels in order to post online or make small prints. However, a higher megapixel count can become much more useful when you start to crop into your photos. Maybe the picture you took includes extra space around the subject that is not required, and you’d rather crop in tighter on the subject. If you started with a 20 MP image but cropped in 50%, you would be left with a 10 MP image. While a 50% crop might be considered a bit severe by some, generally speaking you want to have the flexibility to do some amount of cropping on your images if required without destroying the image quality. For this reason, you’ll want to have a significantly more megapixels at your disposal than the bare minimum.




Having excess megapixels provides more flexibility to crop your images while still retaining high picture quality 

Having Too Many Megapixels

On the other hand, having too many megapixels can have some detrimental effects as well. One of the most common examples in in low light performance. At the beginning of this article we discussed the size of the pixels on your image sensor. Remember we said that the larger the pixel, the better it can capture light. This means that, on two sensors of the same size, the sensor with less megapixels will by necessity have physically larger pixels than the sensor with more megapixels, and therefore will theoretically have better low light performance. An example of this is the Sony A7S II and A7R IV. Both are full frame cameras, but the A7S II has only 12 MP, while the A7R IV has 61 MP. As a result, the A7S II's much larger pixels provides that camera with superior low-light performance, at the expense of resolution.


The Sony A7 lineup contains a range of cameras that all have the same sensor size (full frame) but have quite different sensor resolutions (megapixel count)

But don’t throw out all your high resolution cameras just yet. There are many other factors that can influence low light performance, such as image processor, type of sensor, and so on. As such, it’s not a guarantee that a lower resolution sensor will outperform a same-sized higher resolution sensor in low light, and in fact there are a great many exceptions to this rule. But it is something to keep in mind.

Another common issue with a high megapixel sensor is that more megapixels means that more data is stored, meaning the resulting pictures have larger file sizes. This means you’ll have to plan for larger memory card capacities and hard drive space to store the same amount of photos. While this may not be critical as the cost of storage continues to decrease, but suffice to say a happy snapper probably doesn’t need every photo to be 50 MB in size!

How Many Megapixels Do You Need

After all these calculations and considerations, we still haven’t answered how many megapixels you actually need. Generally speaking, each person will fall into one of three broad categories  based on photographic skill and/or interest; casual, enthusiast and professional. While these are rough guidelines and will vary from person to person, below we’ve outlined the megapixel requirements typically seen by each level of photographer.

Casual Photographer

For the casual photographer or someone who's just starting out, bigger isn't always better in terms of megapixels. You're most likely going to take your photos and upload them to your computer or device so you can share them. For prints, you’re likely to print off standard 6x4 inch prints. If this is the case, you really don't need to be too concerned about the megapixel resolution of your camera. Most modern cameras fall somewhere between 16 MP and 60 MP, all of which are more than sufficient to meet your needs. You should base your camera buying decisions on other features beyond sensor resolution.

Entusiast Photographer

The enthusiast photographer goes beyond just happy snaps and tends to make efforts to continually learn more about photography and improve their skills. As such, they are more likely to display their shots around their home, office or studio. This means they will want sufficient resolution in order to allow them to make larger prints. While in a pinch they also can likely get away with any current camera on the market, they may want to make a point to look at a camera with at least 20 - 25 MP of resolution in order to accommodate for the potential to crop their photos while still retaining enough information for larger prints.

Professional Photographer 

Professional photographers don’t only take pictures for personal use, they are also frequently delivering images to clients. The needs of these clients can vary wildly and they are more likely to require high resolution images in order to print in a variety of situations. These may include wedding albums, fine art prints, or even magazine or billboard advertisements. The professional photographer needs to always be able to provide their clients with images of sufficient resolution to fill their needs, so they will want to err on the side of a higher resolution camera in order to ensure that. Full frame cameras with higher resolutions, like the 30 MP Canon 5D Mark IV, 45 MP Nikon Z7, or even the 61 MP Sony A7R IV may be desired. This will require the professional photographer to work with larger memory cards and have more storage space for their files.


Photographers of different skill levels will have differing megapixel requirements

Other Factors   

That’s the bulk of what you need to know about megapixel requirements, but there are a few final grab-bag points.

  • Frames Per Second - If shooting sports or action photography, you’ll typically utilise fast burst shooting sequences in order capture the action. Because a higher resolution camera will capture more data with each image, higher resolution cameras generally have slower burst shooting capabilities. However, this is not always true - for example the 61 MP Sony A7R IV can shoot at 10 fps at full resolution.
  • Lens Quality – Your camera is only as good as its lens. You can capture all the resolution you want, but if the image is coming through a low quality lens, that resolution won’t translate into higher detail. When shooting with a high resolution camera you’ll want to ensure you are using high quality lenses that can resolve at a sufficient quality to match the quality of your sensor.

 

Contact digiDirect Today!

Do you know how many megapixels you need to render high-quality photographs? If you are not sure or you still have questions or concerns, reach out and get in touch with us! Our staff are on-hand and ready to answer any questions you may have and help you choose the best camera to suit your needs. 

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