Camera Resolution

In this video I’m asking the question, ‘Do you need to shoot with a High Resolution?’ If you’re releasing a movie in 4K, should you use a 6K or 8K camera? Or can you simply shoot in 4K? Let’s dive in and see what we can discover.

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Different Between Camera and Picture Resolution

It’s important to understand that camera and screen resolution are two different things. A picture is made up of millions of pixel, whereas a camera sensor is made of millions of photosites.

Screen Pixels

If you look at a screen with a magnifying glass, you’ll see that each pixel has three emitters. These are red, green and blue, which are the primary colours of light. So, each pixel has three colour channels. By varying the brightness between these emitters, each pixel can create thousands of different colours.

The screen resolution is defined by the number of horizontal pixels. So when we say a screen is 4K, it’s approximately 4,000 pixels wide.

Sensor Photosites and Camera Resolution

A camera sensor is covered in photosites. These are tiny cavities that collect light. Photosites only measure brightness, they don’t detect colour. So above each photosite is a coloured element. These filter the light, allowing only one colour into each photosite. The red element only lets in red light and so on. So, each photosite only has one colour channel.

These colour filters are arranged in a pattern across the sensor. This pattern is known as a mosaic. This is a Bayer pattern, which is the most common type of mosaic.

The sensor resolution is defined by the number of horizontal photosites. So when we say a camera is 4K, it’s approximately 4,000 photosites wide. You might also see a camera resolution in megapixels. For example, a 4K camera might also be described as 9 megapixels.

Resolutions

Camera sensors and display screens are defined by their resolutions.

HD (TV)1920 x 1080

DCI 2K (cinema)2048 x 1080

UHD 4K (TV)3840 x 2160

DCI 4K (cinema)4096 x 2160

6K (Z CAM E2-S6G camera)6144 x 4096

6.5K (Arri Alexa 65 camera)6560 x 3100

UHD 8K (TV)7680 x 4320

8K (RED Helium camera)8192 x 3456

12K (BMD URSA Mini Pro camera)12288 x 6480

From Camera Resolution to Picture Resolution

So how do we get from photosites which have a single colour channel to pixels which have three colour channels? And what happens to the resolution during this conversion?

Demosaicing and Resolution

The data from the photosites is converted into pixels through the deBayer or demosaic process. If you’re shooting in a video format, this happens inside the camera. But with some Raw codecs, the demosaic process takes place in your postproduction software.

Now this is the fun bit. According to cinematographer Art Adams, up to 20% of the resolution can be lost when the picture is demosaiced. So, imagine you’ve shoot with a 4K camera. After the photosite data is converted into pixel data, the image resolution is now less than 4K.

Scaling, Cropping and Resolution

So, the demosaic process is the main reason the picture loses resolution. But there are other things we do in postproduction that reduces the resolution.

During the edit, you might want to make a shot tighter by scaling it up. Doing this also lowers the resolution.

You might want to crop the image to change the aspect ratio. Again, you’re dropping the resolution.

If you apply a stabilisation effect, this crops the image slightly as the edges.

So you can see that between the film being shot and mastered for release, there are opportunities to lose resolution.

Reasons for Not Needing a High Camera Resolution

Let’s take a look at some of the reasons why people believe you don’t need a high resolution…

Motion Blur

The first reason is because moving pictures create a certain amount of blur. People say resolution is less important with blurry images. That’s true of course, but not all of the picture has movement all of the time. And sometimes the story demands a simple static shot, which might not have any motion blur.

Too Many Photosites

High resolution cameras have more photosites on their sensor. It’s been said that too many can reduce the quality of the picture. The more photosites you pack onto a sensor, the smaller they need to be. But if the sensor is bigger, then so are the photosites. The larger the photosites the more light they collect during the split second the sensor is exposed.

Both these have the same resolution, but the one on the right is larger. This means the photosites will also be larger. It doesn’t make a huge difference, but larger photosites will improve the dynamic range of the camera.

Do We Need a High Camera Resolution?

So back to the big question we’ve been asking, do we need to shoot with high resolution cameras?

High Quality Distribution

Imagine you’re producing content for TV, cinema or you simply want a high quality 4K release. In my opinion you should shoot in 6K or 8K. Resolution is lost between the camera and the screen, so it’s the only way to guarantee a good quality image.

It’s the same idea if you want to distribution in HD or 2K. I recommend you shoot in 4K to guarantee a good quality picture.

I should also mention that some cameras over-sample. The Sony FX9 is a good example of this. They might record in 4K, but the data is actually coming from a 6K sensor. This can be a good thing if the demosaic process happens in the camera. If you record in a Raw codec, you need to make sure you’re getting the full resolution of the sensor. 

Streaming

If you’re making content for YouTube or a streaming service, shooting in a higher resolution is less necessary. Video streams have to play smoothly over wifi, so the pictures are heavily compressed.

In the technical spec for Netflix it says, ‘Source material must be of a quality that is equal to or greater than that of the chosen Netflix specification.’ So if you want to distribute in 4K on Netflix, the content needs to be shot in 4K or higher. It also says that up-resing is disallowed. This means if you shot in HD, you can’t up-res it to 4K. This is why Netflix don’t approve older Alexa cameras, as these are only 3K. 

On YouTube 4K videos take longer to upload and process. And even when you upload a 4K file, YouTube doesn’t always make it available in 4K.

The Resolution of the Blackmagic URSA Mini Pro 12K

Finally… let’s talk about the Blackmagic URSA Mini Pro 12K. Does anyone need at 12K camera? Let’s look at some practical reasons why you would shoot with such a massive resolution…

You can create camera moves in the edit. If you zoom in and move around, you’ll still have a high res picture. Just be aware, it won’t have the natural look of a real camera move.

The 12K shot can be the wide, then you scale up for the closer shots.

Eventually the screens we watch will be 8K, so you could also say a 12K camera is future proof.

Summary

When you’re choosing a camera for a project, resolution is an important consideration. Think about where you’re going to release your film and what the screening resolution will be.

If you want the best quality, Shoot at a resolution that’s higher than your screening resolution. Or choose a camera that over-samples.

If very high quality isn’t your priority, or the specifications allow it, you can choose a shooting resolution that’s the same as your screening resolution. But avoid shooting in a lower resolution which forces you to up-res the picture.

If you’ve got any questions or suggestions please comment.

Go Further

If you found this useful, check out the rest of my fantastic Camera Training articles:

Return to Cinematography Training page


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