Wrong Quality Assumptions When Looking at an Image at 100-Percent Zoom

Wrong Quality Assumptions When Looking at an Image at 100-Percent Zoom

Have you had cases when someone looks at a photo at 100 percent and says it looks bad, but when you check it yourself, it's just fine? Is it possible that both are correct?

History of Zoom

In the past, pieces of art were viewed in their natural habitat: their tangible versions. Whether it's a beautiful ring, a gorgeous painting, an impressive wood carving, or a magnificent old building, it always looks good when you normally engage with it. By "normally," I mean the common situations when you happen to see such an artifact. If you go closer to a building and look at the details of its walls from 10 inches, you will see lots of imperfections. The same goes if you look closely at a big painting. The less the imperfections at closer levels, the higher the overall visual quality of the object is. Usually, even if imperfections seem a lot from a small viewing distance, they rarely affect the image and impression.

There are lots of similarities with digital content. Normally, you look at them at a certain distance, and even if you zoom in and see imperfections, they may not be noticeable otherwise. We, as visual craftsmen (as well as some sophisticated clients), tend to zoom in on graphics to see how good the detail is. Many times, people change their overall opinion about a visual piece of art based on the zoomed version, which is a different story. In order to be fair, we usually zoom at 100 percent. There is an assumption that 100-percent zoom is fine, while more is too much of a test. How is it possible to have different and at the same time, correct quality conclusions when zooming 100 percent of the same image?

How Does a 100-Percent Zoom Work?

Not all zooms are the same. If we are talking about looking closely at a physical object with our own eyes, our "zoom levels" will be identical, but with digital content, the zoom function is stolen by the media we're viewing the graphic with, the displays. When you tell an application to show a 100-percent zoom of visual content, it will base the final result off of the number of pixels on your screen. As screens differ in sizes, the functionality that shows you a 100-percent zoom representation will have different results on different devices.

In the following example, there is an image of size 3,888 by 2,592 pixels. It's a shot from the days when 10 megapixels was a normal image size. Let's have a laptop with a screen resolution of 1,024 by 768 and a 5K monitor with a resolution of 5,120 by 2,880 pixels. On both displays, we open the image in Photoshop or similar software, and we zoom in at 100 percent. The results will be quite different.

Comparison between 100% zoom on different screens

The red rectangle shows what would be visible on a 1,024 by 768 screen, while the blue one is an approximation of a 5K display

The smaller screen will show the following:

Approximation of the 100% zoom on a 1024 by 768 screen

Conclusion

Zooming at 100 percent was a thing when most displays were similar. With today's diversity, 100-percent zoom is only a number that has nothing to do with the quality judgment of a visual. If you want to deliver quality results, simulate the view of the final media your work will be displayed on. The fact something looks detailed on a small screen doesn't mean it will be as detailed or good on a large screen for the reasons presented above or vice versa.

Another Possible Conclusion

You don't have enough money for a 40-megapixel stills camera or an 8K video camera? Do not worry. Just tell your clients to get bigger displays and higher-density mobile devices, and your visuals will look great at 100 percent. No full screen allowed.

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15 Comments

Colin Shawhan's picture

This is very true, and very similar to what we would do in the audio mixing world before committing to a final mix -sample it on some crappy speakers to see how it sounds. A lot of studios keep a junk set of speakers, or an old boom-box, precisely for this purpose.

A well-processed photo should make a good impression on anything, but someone with a 5k display will have to understand that blowing up the jpg from Facebook is going to yield garbage. Everything from Facebook is compressed muckity-muck!

It does look okay on a smart phone, though.

Typically, I find photos that work on both high-end displays and your sister-in-law's smart phone are well composed, interesting subjects with good solid contrast, etc. In a way, it's easier to learn the basics of shooting when you have to deal with these limitations, as those of us who shot on 4 mpx cameras in 1998 learned to do, back when to "share" it with your friend you had to burn a CD!!

Tihomir Lazarov's picture

The problem here is when you have a 20-30 megapixel file and someone views it at 100% on a 1024x768 display all the defects are visible on the lower resolution screen way more than on a high resolution one. If you shot on a 4 megapixel camera the shot may look great at 100% on a 1024x768 screen though (less "zoomed-in").

Otherwise I agree with your explanation of the quality-assessment of any audible or visible product using different devices and how it has to be very very well balanced.

The one use for 100% zoom I have is when you have taken several shots in a row and want to decide which one you want to edit. I zoom in to select the sharpest or clearest image with the highest amount of detail. Very useful in bird photography. But overall I agree, we are talking about images and the emotions they invoke, not reviewing CAT Scans.

Tihomir Lazarov's picture

Yes, that's a very accurate use of 100% zoom. I use it for that too.

Jon Wolding's picture

I have a lot of problems with clients previewing attached full-res images on Gmail (and other email clients, I assume)... the previews of the full-res images are often terribly compressed.

Tihomir Lazarov's picture

That is why I am always sending a ZIP archive.

I myself zoom out all the time to make sure the big picture still looks good. Sometimes, something looks fine zoom at 100%, but looks funky viewed normally. For example, it's a problem with certain types of noise reduction: looks good from close, still detailed, etc. But when seeing the image fully, you realize certain areas are kinda blotchy.

Tihomir Lazarov's picture

That is true. Overretouching also can make the normally viewed image look bad.

The only reason zooming 100% (or even (opposite of odd) multiples 200%, 400% and fractions 50%, 25%) is useful is to avoid any misrepresentation of pixels by minimizing phenomenons like aliasing and moiré caused by 2 pixel grids (the one of the photo and the physical one from the screen) overlapping in an uneven way. The most common artifact related to this is "digital" banding. It's digital if you see it on uneven multiples/fractions of 100% and doesn't translate in print. But that's basically it. Mainly because most people won't look at your images at those "perfect" zoom numbers. So if the banding shows at other zoom levels, you need to fix it anyway. So in the end, your image needs to be ok at all zoom levels. :D

Pawel Paoro Witkowski's picture

When you not zoom 100% a preview of an image is displayed. To make things faster for preview and working with photos there is some optimisation done leading to not look perfect. This means that you probably should not check photo sharpness not on 100% zoom, it should help you identify overall image structure. You will then prepare later on a size for the medium it will be shown on. Simple as that.

Krzysztof Kurzaj's picture

I could never understand obsession people have with pixel peeping and, what comes with that, viewing pictures at 100% zoom or 200% or so. Outside of convenience during editing/retouching zooming photos on a computer screen makes completely no sense to me unless that 100% actually fits on the monitor. Given 4K monitor has resolution of about 8.5 megapixel it is virtually never the case with files from modern cameras.

While there are many theories how photo prints and images in general should be viewed a good approximation is a diagonal rule where viewing distance should be about the same as diagonal of the viewing image. While viewing from a longer distance is still acceptable it is not recommended to shorten this distance as borders of the image will start significantly falling out of peripheral vision.

Zooming in on images is a perversion made possible by digital technology. As natural as it seems to be for digital images it is quite weird when executed with photo prints. If you hold a photo print do we tend to actually stick our noses in the paper to check sharpness or grain? It feels almost stupid doesn't it? A print is meant to be viewed as a single piece from the most comfortable distance.

Tihomir Lazarov's picture

I absolutely agree with the unnecessary problem the digital technology created.

Nah man, corner sharpness of my lens wide open at 200% zoom is the maening of life!!!!! I never even want my corners to be sharp wide open, but this lens better do that when I'm shooting an image of a wall at my house for testing, or the internet is going to know!!!!!

The whole article is kind of there in the name: 100% zoom means 1:1 representation of pixels. If people didn't think that is what 100% zoom means, what were tehy thinking exactly? I really cannot get any other interpretation.

Tihomir Lazarov's picture

But many don't get into an account that 100% doesn't look the same on all devices. It looks one way on a 1024x768 screen and quite differently on a 5K one. With physical prints you have the same 100% for everybody and there's no need (and it's hard) to pixel peep there. Digital makes the process different from the natural handling of physical graphics.