Stair Interpolation question

[C***@adobeforums.com]

I am looking for something that will allow me to add resolution to an JPG image I have. I have hear about stair interpolation but don't know what it really does. Can someone explain this too me and outline how it is done in Photoshop?

[Y***@adobeforums.com]

Essentially it means increasing or decreasing resolution by increments or steps, until the desired resolution is achieved. There have been wild postulations that involving using even step increments if you want to get to an even numbered final resolution, etc.

This method of increasing resolution may have some basis in fact with other programs, but not with photoshop.

In principle, increasing the resolution of an image is "fudging" by putting in artificial pixels, based on the surrounding pixels. Using a stair interpolation method you only increase the error of those pixels, by magnifying the error in the first round of upsizing.

Some have claimed visual improvements using stair interpolation, but I've never seen it, and I know of no one whom I respect in this forum that has reported success with this method. In other words, by most accounts, it's hogwash.

Peace,
Tony

[G***@adobeforums.com]

Go under the Image Size dialog and select percent in the Document Size area, then enter 110% in the width and height box. Check Constrain Proportions and Resample Image. Hit OK and the image gets 10% bigger. Repeat until desired size is obtained.

If you like the results, you can set this up as an action. There are a lot of people who say this is the best way to upsize, but my limited experience on my own photos is that the advantage, if any, is very subtle. If you are working with JPEGs that have a lot of artifacts, the artifacts will still be there, just bigger.

Gary

[I***@adobeforums.com]

Do a search of this forum, an action for this was created by Fred Miranda at www.fredmiranda.com.

[T***@adobeforums.com]

Buy Photoshop CS. Reportedly, the new interpolation options (Bicubic Smoother and Bicubic Sharper) produce better result than step interpolation - and they're much faster as well.

[K***@adobeforums.com]

While I haven't done much testing, CS's Smoother (for upsampling) and Sharper (For downsampling) look pretty good.

Ken Storch