Understanding Image Resolution
Learn about resolution for imagery and video.
WHAT IS IMAGE RESOLUTION?
Firstly, within computers, resolution refers to the number of pixels inside a display or image. So you may ask what is a pixel? A pixel is the basic unit of colour on a computer display, these are basically small tiny coloured squares.
Every 3D Animation or Rendering has a dimension of the number of pixels on a horizontal and vertical axis, basically how tall and wide they are. This is an important specification of image quality, because the sharpness of the image depends on the resolution. The same pixel image will be sharper on a smaller display and gradually lose its sharpness as the larger the screens. This is because the same amount of pixels is being spread across a larger area. If a 3D Rendering is too low in resolution, you will see the squares and the image will look grainy or blury.
Clients clearly want high resolution for good quality images. But the higher the resolution, the longer it takes to process and work on for final production, and the more computer power is needed. So there is no need to get something that is prepared for a billboard if you are only going to use it on a computer screen.
WHAT IMAGE RESOLUTION DO YOU REQUIRE?
UNDERSTANDING IMAGE RESOLUTION FOR PRINT
One of the most confusing things for anyone that does not know what they are doing is preparing an image for print. Image scale, DPI refers to the dots per inch for a printer. Nowadays, we refer to these as pixels per inch or PPI, as technology has advanced with digital media.
UNDERSTANDING IMAGE RESOLUTION FOR THE WEB
When creating and optimizing images for your website it is essential that you create the correct size images, because the larger they are the longer your website will take to load. This is a negative for search engine optimisation. So if you are hunting for those Google clicks, make the correct size images. If your image is being displayed at 700 x 500 @72 PPI then it does not make sense to show it at 4000 x 2850 @ 300 DPI.
Below, we have broken down the resolutions needed for typically desired sizes for optimal quality at 300 DPI.
| PHYSICAL IMAGE SIZE (INCHES | IMAGE SIZE IN PIXELS @72 PPI (IDEAL FOR WEB) | IMAGE SIZE @ 300 PPI (IDEAL FOR PRINT) |
|---|---|---|
| 4″ x 6″ | 334×432 | 1391×1800 |
| 5″ x 7″ | 360×466 | 1500×1941 |
| 8″ x 10″ | 576×745 | 2400×3106 |
| 8.5″ x 11″ | 612×792 | 2550×3300 |
| 11″ x 14.235″ | 792×1025 | 3300×4271 |
| 18.544″ x 24″ | 1335×1728 | 5563×7200 |
CREATING BILLBOARDS & EXTREMELY HIGH RESOLUTION IMAGES
When creating images for billboards there are few factors that should be taken in to consideration:
Billboards are usually viewed from a distance, therefore creating the image at 72000 x 93182 at 300 PPI is not practical for a couple of reasons:
- Post processing software such as Photoshop may run out of memory at such size. You will need a seriously expensive computer.
- The final file size will be around 25gb.
So what is the best practice for such large-scale printing projects?
The answer to this is to work at a large PPI and scale back when ready to print.
So to begin with your would create an image in high resolution such as 8000 x 8000 at 400 PPI. This would give you a good quality at 20″ x 20″. Once the image is finalised you scale the PPI from 400 to 40.
This image will now be suitable for 20″ x 20″ at 40 PPI, an example resolution for billboard sized images.
UNDERSTANDING IMAGE RESOLUTION FOR 2D & 3D ANIMATION
If you think about what is said above. animations work just the same, but instead of a still image with pixels in it, an animation is built up of multiple images to make a video, usually about 25-60 frames, or images, per second. Therefore this is a big factor of the quality and cost of an animation. Pixels greatly effect how far you are able to zoom into the image. If you blow it up too much it will become pixilated and no longer clear.
So what resolution do you require? Picking the resolution based on the display or screen is the best option. Firstly, normal computer screens are usually HD (high definition) 1920 x 1080. Secondly, today the standard television is UHD (ultra high definition) 4k (3840 x 2160). Finally, there are larger screens but these are less common coming in at 8k.
STANDARD VIDEO RESOLUTION
- 720p (web or old tv)
- 1080p (web or high definition tv)
- 4k (current standard ultra high definition)
- 8k (the new ultra high definition)
THE EFFECTS OF RESOLUTION ON RENDER TIMES
As we said above, choosing the correct resolution of your animations is essential to render times, because every time the res of an image doubles the surface area quadruples. Likewise, render times and file sizes go up at least fourfold. These relationships are relevant to video, as the render times are already very long. It is always best to clarify this at the start of a project to avoid any confusion from either party.