I had occasion to browse the posts from another forum who seemed to be concerned with a process called upsampling in order to have enough pixels for a very large print.
There were offerings of advice, all well intentioned and widely varied.
Each one promoted his favorite application to do the job.

One advanced a theory from his program that is adds noise to the upsample algorithm to prevent a plastic look!
That one was called "Blowup", according to the posting person.

Another used Genuine Fractals, with great results, (which is true)

Another suggested, Perfect Resize.

.... Finally, a well known and well respected photographer poked his two cents in and told them that he uses Qimage for this job, and has been for years.
I didn't ask permission to paste or quote, but to paraphrase, he was saying, Try Qimage and actually make some test prints and use your eyes!

So, just for fun, I took an embedded Jpg from inside a raw shot which was 1024 x 1536, and upsampled 4x times on either side. I created 4096 x 6144.
I really don't know if you call that 400% or as Qimage notes it as 1600%.

Nevertheless, just for fun, I created similar upsamples using two other programs.

In order to maintain a quality level, I saved these snaps with a high JPG setting so I can only get two per post.
So I'll put two here, and make an additional "part II" following.

I also made 4 prints 10 x 5.63 to see on paper.

To Be continued..............

For easier viewing for those with smaller screens....

Maybe this will be easier.

Fred

Well, if you look closely, you will see the filenames of the pairs, the ones that say 4x in the filename were done in FastStone.
The partner in the pair is Qimage Ultimate.

If you look closely at the filernames again, and you se a PS in the name, they were PhotoShop.
The partner was of course done in Qimage Ultimate

In case you want the steps I used, (there are a few more ways to do it),
Place the image in the queue.
Right click on the upper right image in the preview panel, and select CONVERT IMAGE.

The Convert Image dialogue box opens, and you need only place a dot in ADD TO/REPLACE FILTER.  See screen snap. I circled it.

The second dialogue box opens; see next snap.
In the lower left of that box, you see the current resolution of that image. It is currently 506 x 768.
Simply double or quadruple etc. to the size you want. In this case, I doubled to 1012. The 768 automatically doubled to 1536.
Click DONE. Then OK

Have fun!


Fred