Camera Sensors, Megapixels and How They Affect Post-Production Results

LESSON 3:BEFORE THE CAPTURE

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We are excited to share a guest article from Ontario-based commercial photographer Gerry Kingsley:

In this article I’d like to talk about the difference between sensor types, sizes, megapixels and how they affect post-production, while keeping the technicalities to a minimum.

Sensors

Sensors today come in a few different types and various sizes. The two most common types are CCD and CMOS. While other sensor types do exist, we won’t be mentioning them as the likeliness of anyone reading this using one is very slim.

CCD or Charge-Coupled Device sensors were the first type used for digital cameras, while CMOS or Complementary Metal-Oxide-Semiconductor sensors are the newest (not really all that new but newer) type of sensors used in digital camera technology.

The difference between CMOS and CCD is in the way the sensor captures and converts light into a digital image.

CCD sensors filter light particles through a single node converting the particles into electrical charges at the same time, while CMOS sensors convert each particle individually. Since CCD sensors charge the light particles all at the same time, they use a considerable amount of energy compared to CMOS sensors (i.e. affecting things like battery life, prone to overheating, poor performance in low light, slow processing).

CMOS sensors were initially introduced as an alternative to the CCD type because they offered much cheaper manufacturing costs, better data throughout and lower energy consumption. CMOS sensors have all but replaced CCDs today.

Because of the obsolescence of CCD sensors, we won’t be going into the specific pros and cons as they both can produce great image quality and both have advantages and disadvantages. CCD sensors are still used in some medium format cameras, but they too are slowly transitioning to CMOS sensors.

Rather than debating which is the better of the two, we’ll keep the topic focused on how sensor sizes and megapixels affect post-production.

Megapixels

There are many articles on the web which discuss “the megapixel myth”, talking about whether or not more megapixels means better image quality. Over the years manufactures raced to top one another by increasing the amount of megapixels in their camera bodies, “one-upping” their competitors. This increased sales because everyone automatically assumed the bigger the number meant the better the quality.

This however is not always true.

We’ve all seen the ads for the new iPhone and Android devices sporting larger and larger megapixel cameras year after year, or a hot new point-and-shoot with 20 megapixels. Does that mean a 20 megapixel point and shoot is just as good as a 20 megapixel full frame pro DSLR?

To better understand this, let’s first look at the sizes of the most common sensors on the market today:

• Medium Format = 50.7 x 39mm (Kodak)
• Full Frame = 36mm x 24mm
• ASP-H = 28.1mm x 18.7mm (Canon)
• ASP-C = 23.6mm x 15.8mm (Nikon, Sony etc..)
• ASP-C = 22.2 x14.8mm (Canon)
• Four Thirds = 17.3mm x 13mm (mirrorless)
• 1/1.7IN = 7.6mm x 5.7mm (compact cameras)
• 1.2.3IN = 5.7mm x 4.2mm (compact cameras)

As you can see there is a huge size difference between 1 2/3in and full frame. The two black rectangles below represent the size difference between a full frame 36 x 24 mm sensor (left) and a 5.7 x 4.2 mm sensor (right) found most commonly in compact cameras and smartphones.

RA_sensors_GKingsley

If both sensors can produce images at 20 megapixels, which one will be better quality?

Well, the smaller sensor, even though being the same advertised megapixel count, takes in less light and captures less information. Therefore in order to produce the same megapixel count as the full frame sensor, the camera needs to simulate it by effectively “blowing up” the image to the pre-engineered megapixel sizes using its internal processor. This in turn results in more pixelated and distorted images most noticeable when viewing them at 100%.

It’s important to understand that in order for a high-megapixel-count sensor to produce a higher quality and more detailed image, size really does matter. This doesn’t mean you can’t take a good quality image with a smaller sensor, but the bigger sensors will always yield the best quality and the highest possible detail.

How many megapixels you need and what size sensor you will want to shoot with, will be determined by the type of photography you specialize in as well as your personal preference.

Looking at the new technology today we’re seeing huge improvements in sensor technology across the board, most notably in the medium format and full frame CMOS sensors. Look at Phase One cameras, for example – the larger sensor size in these cameras has the ability to filter more light and thus capture more information, which gives them a huge advantage when highly detailed images are needed.

Post-Production

Looking at an image straight out of camera (SOOC) shot with a Nikon D810 at f/4.5, we can see a lot of detail even at 100% zoom:

RA_sensors_eye_photo_GKingsley

RA_sensors_eye_closeup_GKingsley

And this is the same shot zoomed in at 457% on a computer screen, just a couple of steps before seeing the individual pixels:

RA_sensors_eye_closeup_2_GKingsley

Working with this much detail can provide better results because you can achieve clarity and retouching ability not attainable when working with files created using a smaller sensor.

These newer higher detailed RAW files allow us to push and pull highlights and shadows without affecting the overall quality. Also, these large sensors are better able to process colors and toning straight out of camera with smoother gradients between highlights and shadows minimizing distortions and color banding. Even with an image that is severely underexposed, it is possible to recover it to the correct exposure in a Raw Converter without losing much detail or compromising the quality. This wouldn’t be possible on an older 12-megapixel sensor, for example.

Having said that, it’s important to take note that if your work is mainly going to be posted online then it might not be necessary for you to make the leap to the biggest sensor you can find. Medium formats are still in excess of 15k$+ for an entry level set-up.

To put it into perspective, let’s say your client wants you to produce images for his website and the largest image will ever be viewed at 1080 pixels, that means your 36 megapixel+ image will only ever be viewed at 2 megapixels (1920 x 1080 = 2,073,600 pixels, effectively). Therefore, having the largest sensor might be great, but it might not actually be necessary.

As always, it comes down to individual professional needs. My suggestion is before going out and buying the latest and greatest body, be sure to weigh the cost versus the benefits.

Gerry is commercial photographer whose work focuses on advertising, fashion, beauty and portraiture as well as travel. Since 2008, he has been published internationally for his dramatic photojournalism and creative adventure travel work. His photography has taken him to countries such as Kenya, Ireland, Dominican Republic, the United States and all across Canada.
www.gerrykingsley.com

 

 

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