Yesterday I visited my local Apple store and the staff and I did a direct comparison of a standard iMac and the 5K iMac using the same images on both computers utilizing two flash drives that I brought into the store for this purpose. This was not the best set of circumstances for such a direct comparison. The store was overwhelmed and packed with customers at 6 PM on a Friday evening, and I therefore didn't have the luxury of a calm environment. The comparison lasted for about 15 minutes, after which other customers wanted to look at the regular iMac.
There were several other serious photographers in the store at the time also looking at the 5K iMac. We all expected to see a huge difference and to be impressed given the over-the-top language used in reviews. (PC Magazine: "The Retina 5K display isn't just good, it's overwhelming. . .(and) dazzling.")
The assessment of everyone, including the Apple sales staff, was that this was not the case. We were all surprised at the small difference between the two displays, and were generally underwhelmed. The difference between a standard iMac display and the 5K display is subtle enough that you actually have to look carefully, indeed very carefully, to see it. In the store, there was unanimous agreement on that point.
That was also revealed when an apple salesperson came over to demonstrate the improvement in the 5K display. In order to do that he used a web page from the Apple site and blew it way up, probably at a magnification level of 700% to 1000%. At such a huge magnification level, the font was better defined and crisper on the 5K display, but broke up on the regular iMac display. While this did show the difference it also underscores how small the difference actually is and what is necessary to demonstrate it. It also was a completely impractical way to demonstrate the difference in the two displays. No one ever blows up a website to that degree, and if that is what is necessary to demonstrate the difference in the two displays, then, as a practical matter, there is little difference.
My conclusion is that the reviews of the 5K retina display could best be compared to reviews of expensive audio equipment in high-end audio magazines. Reviewers will use over-the-top language to describe what are in fact very small improvements in sound quality and which only an audiophile can hear in any case, or even care about.
What is even more difficult is to quantify the level of improvement, whether it is the visual improvement in a display, or the audible improvement in high-end speakers. What is a 5% improvement to one person can be a 200% improvement to another.
BOTTOM LINE -- With that disclaimer, I would describe the subjective improvement in the 5K display as being 20% or less as compared with a standard iMac display. It is at most a subjective improvement of about 20%, and in my first draft of this posting, I said it was 15% or less. You really have to look closely and carefully to see the difference. However, note my use of "subjective" -- I'm describing the actual improvement as seen on the screen, not the theoretical improvement based on the number of pixels. And subjective is just that – what I would describe as a 20% or less improvement someone else might describe as a 500% improvement.
On the positive side, the direct comparison did demonstrate that you will see slightly more detail in high megapixel sharpened images on the 5K display as compared with a regular iMac display. I didn't have time, in the crowded store, to compare raw images, but I doubt that raw unsharpened images would reveal a greater level of detail and justify the purchase of the 5K display.
I also compared 4K video taken with the new Sony 4K camcorder. This is the first camcorder I have ever owned and my knowledge of video is minimal. With that disclaimer, I would say that the differences were even more subtle. The 4K video on the 5K display appeared to be smoother but not necessarily more detailed.
In conclusion, my bottom line is to convey a clear warning. Don't be influenced by the over-the-top reviews, that in my opinion are greatly exaggerated. That was the conclusion of all of the photographers who watched the comparison. Those in the store all thought the actual difference is very subtle.
I'd be interested in the opinion of others in the forum if you visit an Apple store and perform your own direct comparison using your own high-resolution images on a regular iMac and a 5K iMac. You need not be guided by my opinion, or the opinion of anyone else in the forum. Visit an Apple store, perform your own test with your own images using two flash drives, and judge for yourself. I can't emphasize that point strongly enough -- don't make a decision as to buying it based on the reviews, or my opinion, or the opinion of anyone else, particularly if they appear to be just setting it up and proclaiming it as the best display ever based on the "wow" factor. The only valid comparison is a side-by-side comparison of the regular versus 5K iMacs, using identical images on both.
Footnote: The basis for the comparison were high megapixel images taken with a Canon 1DS Mark II, mk III, or a Canon 5D Mk III. These were not raw images, but rather images that have been sharpened to demonstrate the difference in the two displays. The image that most clearly demonstrated the difference was a rain forest image with a very high level of detail. For the purpose of this demonstration, I took the raw image, applied capture sharpening in light room, ramped up the clarity to 30, and then exported it as a tiff image, resized to both 16x20 and 20x30, with output sharpening for both print and screen set to high. At 20 x30 that resulted in a 320 MB image. I also used other images that have been sharpened for printing in Photoshop, including one digital scan of a highly detailed 4x5 large format Velvia transparency. The rainforest image showed the difference the most clearly. Other high MB images did not, and the difference was barely visible.
