The Big Picture (ACR Super Resolution)

[Chris Kern]

I've been using Topaz Gigapixel for a couple of years now, and have found it quite useful on occasion (albeit less so since Adobe introduced its "super resolution" option), but it has some quirks I find disconcerting.

First, if you have Gigapixel emit a DNG, what you appear to get is not a traditional Linear DNG but the equivalent of a fully-baked TIFF in a DNG container.  Below: the respective file sizes of an RGB raw file (Fuji X-Trans), the 2X enlargement produced by Gigapixel from that raw file, and the 2X enlargement produced by Lightroom from the same raw file:

-rw-r--r--  1 ck  staff    12M Nov  9 18:35 _XT47993.RAF
-rw-r--r--  1 ck  staff   596M Dec 31 16:17 _XT47993-standard-scale-2_00x-gigapixel.dng
-rw-r--r--  1 ck  staff   163M Dec 31 16:21 _XT47993-Enhanced.dng

Although the Adobe super resolution file has been demosaiced (i.e., it's a Linear DNG), it can in some important respects be treated as a raw file—specifically for adjusting white balance and making other color corrections.  As far as I can tell—I'm no expert on this stuff, and am prepared to be proved wrong—the Gigapixel DNG is really just a fully-baked TIFF in DNG's clothing.

More irritating from my perspective is that Gigapixel appears to try to "normalize" the tone curve of any raw image it enlarges by stretching out the tonal values so they cover the full range between black and white.  That may be what the user wants, but I have not found any way to defeat this behavior and I would rather be able to control the image tones myself: when I use Gigapixel, I just want it to rebuild the image with larger linear pixel dimensions and not perform any default "editing" for me.

[digitaldog]

First, if you have Gigapixel emit a DNG, what you appear to get is not a traditional Linear DNG but the equivalent of a fully-baked TIFF in a DNG container. 

If so, that's really dumb and a bit dishonest (giving the impression it's raw simply because of the DNG wrapper). DNG is as I'm sure you know, but many do not, a cousin of TIFF and one can embed a JPEG in it. That's still a JPEG, zero advantage to having it wrapped into a DNG. I wonder how many Gigapixel users think "Wow, a DNG; I've got raw data."
A baked TIFF or JPEG is a baked TIFF or JPEG, no matter how you try to fool people.
At least Adobe is up front about what and when you end up with a Linear DNG.

[dreed]

Now that this seems common, do you bother using teleconverters any more? They introduce their own IQ issues, so better to just "Super Res" and leave the teleconverter at home?

[Chris Kern]

Now that this seems common, do you bother using teleconverters any more? They introduce their own IQ issues, so better to just "Super Res" and leave the teleconverter at home?

I don't know that there is a single, simple answer to that question.  A teleconverter uses an optical approach to project a larger image on the camera sensor.  "Super Resolution" uses a computational approach that reconstructs the captured image with larger pixel dimensions.  The image quality provided by the teleconverter is affected by the optical limitations of the converter and the particular lens attached to it.  The image quality provided by the computational enlargement is limited by the number and variety of the images used to train the neural network to recognize and reconstruct the features in a photograph without producing artifacts.  Which approach works best will probably depend on the way the visual aspects of the subject interact with the characteristics of the enlargement method.

[kers]

i have a 2x Nikon converter and with some lenses (70-200) it does not work very well;  with others (like the 300pf lens) you get clearly more detail.
Much more than you would ever get with software enhancements, that introduce also a lot of false detail.