TG Daily decided to check out how well Microsoft's HD Photo format compresses pictures. During their tests they found HD Photo offers file size advantages from only 5% to as high as 45% in some cases.
However, they conclude that for now there's little incentive to switch from JPEG to HD Photo as the old format is still good enough for "the average user":
Even on a HD monitor, it was difficult to determine what exact HD Photo compression would reveal the same image quality as the 185 KB JPEG. From our subjective view, parity was reached at 61% compression and a file size of 145 KB, which would translate into a 22% file size advantage for HD Photo in this specific case.
However, this 22% advantage only applies when the image is viewed as a whole. Zoom in those details and you see that HD Photo creates substantially less artifacts than JPEG and is capable of creating smoother color transitions – at the expense of sharpness. We have seen file size advantages from only 5% to about 45% in our tests over the past few days. In that sense, we still believe that HD Photo is just as moody and unpredictable as any other current image format, such as JPEG or PNG.
But HD Photo’s advantages aren’t really revealing themselves on the lower end of the spectrum. Move to HDR imagery and the format shows its strength. Photoshop users can save a 32-bit HDR image in six formats (Photoshop, Large Document Format, OpenEXR, Portable Bit Map, Radiance and TIFF.) In TIFF, our uncompressed 6 megapixel HDR image came in at 73,582 KB. The lossless HD Photo version, which showed no visible differences in quality, even in details and under 16x magnification, saved the image in about half the time and packed the data into only 24,487 KB.
These results clearly suggest that HD Photo’s time may not have come yet. As long as JPEG is simply good enough for the mainstream, there is little incentive to switch from JPEG to HD Photo. However, enthusiasts and professional users can already see what the future may bring and save a boatload of room by using the format. Even in times of Terabyte hard drives, image size matters, especially if we are talking about a difference between 75 MB and 25 MB.