Attached Link: http://www.renderosity.com/news.php?viewStory=13267

From the look of the samples on the Alienskin site, it does produce decent up sizing. I'm sure there can be instances where you can lose some detail, but like Paula mentions too, probably only noticable in print. They (Alienskin) are also offering a bundle of 3 products for 199, which if you have CS or higher, and you choose "Blow-up, Exposure, and Impact", you should be able to handle most any issue that crops up. Check out all the examples in these 3.

Illustrator already handles this issue with vector graphics which is incorporated into their "Smart Objects". You can create a base "?????.AI" (illustrator format) file which can be used within the Adobe Suite products, Re-size in either direction with no change in quality from the original.

My only thought is changing an original render, then trying to match to a Mask(alpha) render, it may not match perfectly even if you resize the Mask with the same plugin.  Yet there are lots of tricks to handling this situation too.

Good quality company, with a great track record. Usable with top notch packages.........Try the Demo, I'm going to.

Attached Link: irfanview.com

Time for DL'ing............

Irfanview is an amazing freeware image viewer. It does many other things than just viewing, but that's another story.

Irfanview, like many other viewers will re-size images, and it does so quite well, with good aliasing. I would suggest trying out various programs of any kind (that will resize), and see what results you get.

Myself, I use Thumbsplus to resize and save my images. It gives a sharper result. But, if I need small, fine lines aliased well, and not oversharpened (pixelated), I will use Irfanview. But, I'm talking about re-sizing downward.

Just to resize an image to be able to print out larger, no program that resizes images is a true match to rendering out to the final size you need, period. Yet, sometimes when you have to, you have to. But, some printing companies will not accept resized images (for client work). I know any art contest will not accept them.

Yet, if ya gotta do it, and there is no way around it, I would try out Alienware. I think all their plugins are fully functioning for 30 days. Plenty of time for experimentation. And, I have never been dissapointed with their plugins.

an alternative for blowing up image sizes is rasterbator which is a freeby. But as AS said you won't beat rendering big, nothing can magically add extra detail!