What is the resolution of the human eye?
Let’s step back for a second and try to answer what is apparently a very common question: what is the resolution of the human eye? The answer, in short, is that it’s very difficult to provide an accurate answer! Of course, due to the complexity of the human eye and the way in which it works, there isn’t a straightforward and simple answer.
According to the presentation by the Joint Technical Meeting based at the University of Salford in March 2007, it has been estimated that human vision resolution is the equivalent of 576 megapixels (24,000 x 24,000 pixels) – which is about 10 times the resolution of a 2K projected image, and 5.85 times a 4K image. (For a good explanation of it all, see http://www.clarkvision.com/imagedetail/eye-resolution.html). And of course the human eye sees more than 10 million different colors and shades...
What does this mean in general, and what about 4K in Healthcare?
Back in 2010, I interviewed Michael Karagosian about 4K and resolution. Michael has been involved with digital cinema since the beginning, and what I discovered is that resolution isn’t actually the most important aspect of a picture. There are a number of other elements that help to determine the quality of the image. Michael had a hierarchy for picture quality, which puts color and contrast above resolution. The colors and the contrast provide a better image quality than the resolution just on its own. These are the things that we notice first. Is the color right? Is the contrast right? Are the blacks really black? ...
Detail-rich, color-correct images
In the operating room (OR), it’s vital that the staff be able to determine the smallest detail. 4K not only brings better resolution to the screen, but a wider color gamut in which black is black – which leads to more detail-rich, color-correct images for better differentiation between tissue types amongst other things.
More information in one place
More complex procedures in the OR require different types of imaging – and this is where 4K is also of benefit, because it can show multiple modalities on one screen without the risk of losing image quality through scaling or distortion.
Higher resolution images also provide the ability to display more user information on a screen at one time – vital signs, patient information, and so on – providing the staff with the information they need in a single place rather than spread out over several places where there is the risk of missing something.
Increased depth perception
When I spoke to Michael in 2010, the other topic we discussed (apart from resolution) was the movie-going experience and whether 4K would help that experience. Michael felt that the premiere movie-going experience is about immersion and, therefore, you are likely to want to be closer to the screen, which in turn means that the resolution becomes important. Although again, brightness will also play an important role.
And although a different sort of immersion is needed in the operating room, it’s still crucial that the surgeon be able to really concentrate on what he/she is looking at and not be distracted by other things or have to wonder whether he is seeing a side-effect of the image or an issue with the patient. The higher resolution image with its color depth helps to do that. In the 4K video, Dr Mathieu D’Hondt mentions this specific requirement.When people see higher resolution images – especially 4K – they often remark that the images almost start to look 3D, even though they’re not, because of this depth of color. This means that when surgeons look at the screen they can see more depth or detail in the image.
We know how important resolution is for close-up work, where you are directly in front of the screen and want to see minute detail – this is why computer screen resolutions continue to improve. Of course, this is also related to the size of the image in question and the size of the screen – 4K has enabled cinemas to make better use of the front row seats, because the quality of the resolution there was improved. Higher resolution in the OR is important because it provides more detail for the surgeon and other medical personnel.
However, in order to get a good image, the whole chain – from camera through processing – has to be in the same quality, i.e. 4K. If there is any variation, the quality of the final image will then be affected. In other words, the 4K end-to-end process, from image acquisition to streaming, presentation and recording, is important.
We should briefly mention that color depth and contrast ratio are also important elements – the better the color depth and the contrast ratio, the more detail the resolution is able to reveal in the final image. The three elements tend to go hand-in-hand.And this is why the use of 4K in Healthcare (as elsewhere) is so exciting for those involved – because it’s really changing the way that people work!
Read more about 4K in the OR: