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Drones and Camera Sensors

camera sensor and why its important

Well this is a very complicated subject and took me some time to get my head around but I think I have managed to grasp the subject and will attempt to explain what I have understood. Please leave a comment if you think I have any of this wrong. Happy reading and do not forget understanding what benefits the sensor size and the relation to the amount of pixels images may require can assist you when choosing your new camera or drone.

What is a camera sensor?

This is the part of the camera that captures the light coming through your lens each tiny point on the sensor stores one single square colour known as a pixel, therefore when they all join together to create a picture. Types of sensors in today’s digital cameras are mainly CMOS. CCD is an older style that captured good quality images but had higher power consumption. Today’s CMOS sensors have matched or bettered the older CCD style, price points are very similar if not better and these outperform when it comes high-speed capture allowing for burst shooting. CCD and CMOS are not the only types of sensor’s available but when it comes to drones CMOS is the most commonly used, unless that is you drone is carrying a standalone digital camera.

CCD – Charged Coupled Device

CMOS – Complementary Metal Oxide Semiconductor

The Senor make up is quite complicated but from what I can gather it is made from lots of Active Pixel Sensors (APS), which relate to the amount of pixels captured and this is measured in the unit MP (Mega Pixel). The size of the sensor helps to create better quality images but how many you need requires some consideration:

  1. Do you plan on heavily cropping your images?
  2. Do you plan on printing you images?
  3. Do you plan to publish the images online?

Are more megapixel better?

A common way camera manufacturers advertise their cameras is by the amount of megapixels their sensor has and a common belief is the more pixels the better. This is a great marketing plan as every year the sensor has increased the number of pixels and therefore gives the consumer a sense of improvement and the need to upgrade. The thought behind the belief of more pixels are better is, smaller active pixels crammed onto the sensor makes it harder for the eye to distinguish the edges of the pixels in an image therefore creating a clearer picture to the naked eye.

Common image sizes and megapixels to use:

Computer – 2000 x 1000 pixels = 2MegaPixels so to view your image on a computer 2 MP image might be suitable depending on your screen resolution.

Prints – 6×4=2MP, 10×8=6MP, 14×11 or larger = roughly 8MP

Keeping in mind for larger prints they tend to be viewed further away thus allowing the image to be of a lower DPI.

So now we know how many pixels we should have roughly we need to make sure the image is the correct size and understanding Effective resolution should help you decide.

Effective resolution

DPI – Dots per Inch or PPI – Pixels per Inch the common way effective resolution is measure. So for a picture you can target 300 DPI, for a large wall poster you can aim for 150DPI and for images used online about 75DPI should be effective.

To put this into practice the amount of pixels, divided by the DPI relating to your intended display with equal the maximum output size of your image.
E.g. Width 2000 x Height 1000= 2, 000,000MP
So the maximum size a print for 2MP should be was:
2000/300 = 6.67inches and 1000/300 = 3.33inches

Camera Sensor Sizes and Aspect Ratio

The size of a camera sensor helps to identify the image size you camera will output therefore allowing you to understand the maximum size print you can achieved if no cropping is carried out. An aspect ratio can be worked out when you know the Camera Sensor Size and the Sensor size is important as larger sensors tend to capture more light and less noise so your images can be brighter, clearer and sharper. So you may find using a larger camera sensor with less mega pixels will be better than a smaller sensor with more megapixels using the same lens types.

My personal belief is having an understanding of how your camera works can help your final product so I have included in the section below a piece about video resolution as with most cameras and drones they take both still images and capture video footage. I have also included some examples of Sensors on drones and action cameras. Now some of these sensors look the same but cost more money that is because there are other parts that combine to make a camera which affect the image quality like ISO, lens type, lens quality or aperture of the lens. Most of which are all built up together as a point and shoot one camera does all on most drones.

Camera sensor sizes
Note: https://upload.wikimedia.org/wikipedia/commons/e/ec/SensorSizes.png

 

Some of these sizes will differ from manufacturer to manufacturer so please use the above as a guide only.

A square has an aspect ratio of 1:1 even along both edges. A 35mm full frame has an aspect ratio of 36x24mm so if we divide 36mm/24mm= 1.5 crop factor 1.5:1 so 1.5 wider than it is higher. I believe most sensor sizes fit between the 1:1 to 1.5:1 aspect ratio.

 

To work out the crop factor of a camera sensor when the sensor sizes is unknown take the uncropped image size and divide the larger size by the lower size.

 

Missing from the list is the 1” sensor(13.2mm x 8.8mm) found in a lot of point and shoot cameras 13.2/8.8 = 1.5:1 aspect ratio

 

Aspect ratio video resolution
Note – https://commons.wikimedia.org/wiki/File:Aspect_Ratios_and_Resolutions.svg
Video Resolution:

Common sizes used today are 720×1280 HD, 1080×1920 Full HD, 2160×3840 4K.

4K is very memory dependant and the processing power required to post process or edit is high which in the end is more expensive. I aim to shoot most of my drone videos in 4K but before I perform any editing I compress them to 1080 Full HD as this helps speed up the process and most people do not require a 4k format.
 

The DJI Phantom 4 Pro: 1” Sensor 20MP

Image size: 5472pixels/3648pixels = 1.5

Maximum Image size for a print 300dpi:

5472/300 = 18.24 inches

3648/300 = 12.16 inches

The DJI Spark: 1/2.3” Sensor 12MP

Image Size: 3968 pixels x 2976pixels = 1.33

Maximum Image size for a print 300dpi:

3968/300 = 13.23 Inches

2976/300 = 9.92 Inches

DJI OSMO Zenmuse X3: 4/3” Sensor 12MP

Image Size: 4000 x 3000

Zenmuse X5:1/2.3” Sensor 16MP

Image Size: 4608 x 3456

Zenmuse X7: 23.5mm x 15.7mm 25MP

Image Size: 6016 x 4008

Yuneec Typhoon H Plus: 1” Sensor 20MP

Image Size: 5472/3648 = 1.5

Maximum Image size for a print 300dpi:

5472/300 = 18.24 inches

3648/300 = 12.16 inches

DJI Mavic Pro Platinum: 1/2.3” Sensor 12MP

Image Size: 4000 x 3000 = 1.33

Maximum Image size for a print 300dpi:

4000/300 = 13.3 inches

3648/300 = 10.0 inches

GoPro Hero 4 Black: 1/2.3” Sensor

GoPro Hero 5: 1/2.3” Sensor

GoPro Session: 1/3.2” Sensor

 

Sensor size and crop factor – These have an effect on the focal length your lens may provide, this in turn affects the (FOV). A full frame sensor with a full frame lens means your 50mm lens does in fact equal 50mm. Full frame lenses can be used on cropped sensors and vice versa but understanding the crop factor will help because if you use a smaller sensor you will have a cropped effect. This is like having an increase in focal length. E.g. APS-C Sensor with a full frame 50mm lens will have a crop factor of 1.5 so the lens becomes a 75mm equivalent. Full frame sensor cameras and lenses tend to be a lot more expensive but as mentioned you can interchange them.

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