The Retina Display Fallacy

Introduction | Looking at Photos at 100% (Original Size) and at 50% | Conclusions

On this page, I would like to write about what I call the "Apple Retina display fallacy," which I fell for - and which made it somewhat complicated for me to assess the sharpness of my Leica X Vario (or any other camera).

For those who do not want to wade through this page: Images and photos displayed at 100% size (original size) may look much more fuzzy on a Retina display than they actually are. So be careful in judging their sharpness without making comparisons.

Introduction

In 2012, I bought a 15" Apple MacBook Pro with Retina display (and in 2013 for my wife, too; I still have a "normal" display, an external monitor, in my household, but I use it rarely...). And as I mentioned elsewhere, I bought a Leica X Vario in July 2013. As I was used to, I looked at my photos in 100% size to judge their sharpness. However, despite all the high praise for the lens that I read all over, I was not enthusiastic about what I saw - also not when I looked at some X Vario photos in original size from other photographers. I also compared my X Vario photos with photos taken with my Ricoh GXR A16 and found those to be sharper - at least at the center. At the end of 2013, I bought a Ricoh GR and came to the same conclusion for this camera.

So what was wrong with the X Vario - or were there other causes for the fuzzy photos? I found out that one reason for the fuzziness of the X Vario photos (and also other photos) was that I viewed them on an Apple Mac Book Pro with Retina display.

The Apple Retina Display

Let me explain the Apple Retina display by quoting the respective Wikipedia article:

"Retina display" is a brand name used by Apple for liquid crystal displays that have a pixel density high enough that the human eye is unable to discern individual pixels at a typical viewing distance. ...
When an Apple product has a Retina display, each user interface widget is doubled in width and height to compensate for the smaller pixels. Apple calls this mode HiDPI mode. ... In practice, thus far Apple has converted a device's display to Retina by doubling the number of pixels in each direction, quadrupling the total resolution. This increase, combined with the size-doubling of the user interface, creates a sharper interface at the same physical dimensions.
Typical resolutions are: 326 PPI for the smallest devices (iPhone, iPod Touch, and iPad Mini with Retina display), 264 PPI for mid-sized devices (iPad third generation and onwards, including iPad Air), and 220 PPI for larger devices (MacBook Pro)

So, how can an application on a computer with a Retina display handle images and photos? Here are some possible approaches:

Use 4 pixels to display a "standard" pixel to maintain the image's original size; you can either
- interpolate the image > this leads to a somewhat fuzzy look
- or not interpolate the image (that is, simply quadruple the pixels) > this leads to a "pixelated" and also somewhat fuzzy look and is typically the approach used by applications that are not adapted to the Retina display
Use 1 pixel to display a "standard" pixel > this cuts the size of the image in each direction in half (1/4 of the area), but makes the image appear very sharp

Browsers are usually adapted to the Retina display, but the myriads of images on the Internet are not (apart from those on the Apple Website...). They therefore use a "mixed" strategy and display images on the Internet differently from their user interface and from text: They quadruple the image pixels (thus maintaining their size) and adapt the remainder (UI, text, etc.) to the Retina display. They may use either of the two first approaches (interpolate or simply quadruple).

Now let's see what some applications that I use for displaying images do with images.

Looking at Photos at 100% (Original Size) and at 50%

100 % Size (Original Size)

A lot of people maintain that you should never view photos at 100% size (one image pixel corresponds to one screen pixel), you should print them for "real" judgment, instead. Using digital cameras since 1996, I know that photos look fuzzy when you view them at 100%. Nevertheless, only in this view mode you can reliably spot problems such as fuzzy corners or compare different cameras.

In addition, some applications, including browsers, offer an "100% size" (or "original size") view so that you inevitably come across 100% views, possibly without thinking much about what that means...

So, the interesting question for me - one that I have neglected so far - is: What do certain applications do when you look at photos in 100% or "original size" (which I equate to 100%...) on a computer with a Retina display?

Above, I listed some possible approaches, and here are the answers for the applications that I use to display photos:

Adobe Photoshop 11 (12)*: Quadruples the pixels to keep the original size, no interpolation
=> results in a somewhat "pixelated" and fuzzy look
GraphicConverter 9: Displays pixels in 1:1 fashion thereby showing photos in half size
=> cuts the size of the image in each direction in half (1/4 of the area), but makes the image appear very sharp
Preview ("Vorschau"): Quadruples the pixels to keep the original size; there does not seem to be any form of interpolation (I am not quite sure about this)
=> results in a somewhat "pixelated" and fuzzy look
Apple Safari: Quadruples the pixels to keep the original size, uses interpolation
=> leads to a somewhat fuzzy look since the image is actually "blown up" (to its "original" size on "normal" displays)
Mozilla Firefox: Quadruples the pixels to keep the original size, no interpolation
=> results in a somewhat "pixelated" and fuzzy look

*) The application has not been adapted to Retina display, meaning that the whole user interface looks pixelated.

I mention the two browsers Safari and Firefox, because I often download photos and then click the magnifier to view the photos in "original/100% size". This step typically leads to disappointing look of the photos. The same holds true if you select "original size" in Apple's "Preview" application.

I only realized what Photoshop Elements does, when I displayed a couple of photos in GraphicConverter 9 at 100%. While the photos appear much smaller in this view in GraphicConverter, they also look much sharper. This increase in "apparent" sharpness is not only due to the downscaling but also because the "pixelation" effect is no longer visible.

Using my external monitor, I looked at photos from different cameras at 100%, that is, with one image pixel being represented as one screen pixel. The impression that you get of the photos is quite different here, because you clearly see the pixel matrix. But subjectively, the images appear sharper than when being interpolated or pixel-quadrupled on a Retina display. But this may only be my subjective impression...

50% Size

Digital photos typically look much better when viewed at 50%, but this may depend on the software that you use and how it scales images down. With "normal" displays, photos looked good in Adobe Photoshop Elements when they were scaled down to 50%. This is, however, not the case when using Photoshop Elements on a Retina display. There I can clearly recognize the 2*2 pixels, and the photos still look "pixelated."

Scaled Photos

Finally, applications may scale images and photos to different sizes (window size, screen size, etc.). This can be done using various approaches and may lead to quite different results. I therefore will not discuss the issue of scaled photos here.

Why Do I Not Show Any Examples?

Showing examples is difficult for a number reasons:

The examples look different of "normal" displays and Retina displays
Browsers blow the images up and make them look fuzzy - but this page communicates through a Web browser...
Screen shots are blown up to double size when done on a Retina display. They need to be downscaled (50%) for use in a browser (which may introduce unwanted effects)

I may reconsider my decision and publish some examples in the future, though...

Conclusions

Photos shown at 100% (or original size) always look somewhat fuzzy, but there are differences. On "normal" displays photos taken with larger sensor cameras look quite OK. Most important is that you use this view to compare cameras or look for certain deficiencies in the images (for example, fuzzy corners) but do not make "absolute" judgments about a camera's and lens's sharpness.

On a Retina display, however, you may be a little shocked how fuzzy your photos look at 100%. Therefore, it is important here to have comparison photos taken by other photographers or with other cameras to make judgments about the quality of your camera or lens.