iPad 3's Higher Resolution
Yes, the iPad 3's higher resolution screen should be a thing to see — literally. I haven't yet, so I can't offer any first hand reports. I can, however, address a few issues relative to LensWork Extended and our strategy for this new device.
Because we choose to publish in the scalable PDF format, one of the advantages we have is that there is no native "screen resolution size" for a PDF. The page is scalable — which means literally that it can accommodate itself to any display size. Sort of. Let me explain just a bit. This might also explain why we are so committed to PDF as the format of choice for our publications.
There are several areas of concern in this discussion of scaling PDFs for display, each with its own rationale.
Unlike web pages, PDFs are constructed on fixed page dynamics. A PDF can be scaled up in size (or down), but in all cases the resulting display is still based on the display of discreet page units. Just as in a printed book, the aspect ratio of a PDF page is fixed when it is created. This is why we produce two portable versions of LensWork Extended. The iPad version is based on a 4:3 aspect ratio. Android displays can vary a bit, but they are all pretty close to 16:10 aspect ratio. We produce the two versions of LensWork Extended so readers will have an experience that fills their screen — if not perfectly, then darned close to a perfect fit. This has nothing to do with the image resolution, but is a fundamental factor when publishing for a portable device. So, PDF pages are a fixed aspect ratio, but not a fixed size.
Fonts and Vector Graphics
Unlike text in a Photoshop image, all the text (fonts) in a PDF are vector graphics. Vector graphic components can scale up and down in size without degrading. So, as the pages in a PDF document are scaled up or down in size to fit the screen resolution, the text always remains sharp and clear no matter what scale size you are using to view the page. Text in our PDF documents will always look sharp and clear no matter the resolution of the device you are using.
Rasterized Images — e.g., Photographs
Rasterized images (all photographs are rasterized images) are another matter. On a web page, the images are displayed according to their actual pixel dimensions. For example, here is a screen shot of a recent image from this blog.
You can see from the information box at the right that the image is 603px wide. Because my monitor displays visual data at the rate of 96 pixels per inch, when I measure the size of the image on my screen with a ruler, it measures 6.33" wide (603px/96ppi=6.33in) . If your monitor displays at 72 pixels per inch, you would measure 8.37". All well and good.
But, these images cannot be scaled without problems — especially they cannot be scaled larger. Doing so, in a web browser for example, will make a larger image (and text), but the quality of the image will degrade as the pixel density of the image on the screen drops to a lower density than the native pixel density of your monitor. That is to say, you'll decrease the pixel density from, say 96ppi down to something less than this, thereby forcing each pixel in the image to cover more than one pixel on the screen. This is known colloquially as "pixelization" and appears as a "blocky," rough-edged artifact that reduces detail and blurs the image.
Essentially, the best approach is to always have enough pixels in the image to match the pixel dimension in the display. For an iPad 1 or 2, because the display is 1024x768, and image that is 1024x768 will fill the screen, pixel for pixel — each pixel in the image creating a single pixel on the display. What you see is limited to the pixel density of the display.
Enter the iPad 3 display challenge
So, what happens when you display a 1024x768 image on the new Retina display of an iPad 3? The engineers have two choices. They can either display the image using one pixel in the image to cover one pixel in the display, or they can stretch the image to the 1024 pixels in the image cover all 2048 in the Retina display. In the first strategy, the image will look very "Retina sharp" but it won't fill the screen; it will be small. In the second strategy, the image will fill the screen, but won't look as sharp as an image created at full "Retina screen" resolution. It will start to degrade like the example above — not as dramatically, but visibly.
LensWork Extended already has additional resolution
Because LensWork Extended is created as scalable PDF pages, what you see is scaled to fit the monitor size. It will fill the available display size even if that means scaling up or down to make it fit. Scaling down is never a problem; scaling up can be if it forces images to drop below the pixel density of the native display device.
From the very beginning, we've design LensWork Extended to include more resolution than any display was capable of. In essence, LensWork Extended is always scaled down — on purpose — to fit the display. You may not be aware of this, but it's a feature we built in with every PDF we publish. We did so specifically so our readers could zoom in on an image without pixelization occurring. As they zoom in, there is no pixelization until you reach the threshold where the zoom factor exceeds the resolution of your display device. It's a neat trick that allows higher quality images even if a reader wants a closer look to see details.
We produce two different resolutions of LensWork Extended — the Disc Edition and the Online Edition are at 2,667x 1666 — already higher than the Retina display; our current iPad Edition (1250x1666) and the Android Edition (2000x 1666) are a bit less. Even so, as you can see, our existing iPad Edition already exceeds the resolution of both iPad 1 and iPad 2 screens. These files viewed on a new iPad 3 will look far better than you might expect because of this additional resolution. Our iPad Edition PDFs are still a bit shy of a full resolution Retina display, but will be far better than if this additional resolution were not part of our strategy.
Will an increase from 1250 to 2048 make a difference in the Retina display? Possibly; we're not sure yet. We're now looking into an increase in resolution for the iPad 3 and whether or not there is any visible advantage to doing so. The additional resolution will require a sizable increase in file size that may cramp some users with limited storage. Downloads will take longer and page flips might be slower. They certainly would be for people who choose not to upgrade to the iPad 3. If there isn't enough visible payoff over our already higher resolution PDFs, we probably won't increase the resolution. If, on the other hand, the differences are visible and important, we might consider it. We'll keep you posted.