Is upsizing/zooming more effective when using "simple" ratios?

Started 7 months ago | Questions thread
CAcreeks
CAcreeks Forum Pro • Posts: 11,044
Re: Is upsizing/zooming more effective when using "simple" ratios?

TomMartinWC wrote:

Over at answers.microsoft.com people are wondering why certain zooms are more blurry than others, even though the clearer ones are often more heavily zoomed. For instance, a 70% zoom can be more blurred than a 90% zoom of the same picture.

Depends on the algorithm. ImageMagick defaults to Lanczos3 for downsampling, and a different one (forgot the name) for upsampling.

My theory is that zooming/resampling is best done in fixed increments. So a 50% zoom will always look better than a 49% zoom.

This would be true of Bilinear downsampling, but hardly at all with Lanczos. However 50% and 49% are not upsizing as in your subject line.

But many hours of research has yielded nothing concrete. Before I suggest to Microsoft that they abandon their 10% zoom increments I want to know if I'm right that they're not optimal.

That was common about a decade ago, before Photoshop came up with Bicubic Smoother.

To clarify, the product is Microsoft's Photos and I imagine that will draw a few giggles. We're working to make it a respectable photo app, yet aimed at the masses.

Anyone? I don't use this product and have no interest in it.

The problem is that some of the user community is trying to understand the inconsistencies of zooming. Apparently this isn't a problem with most editors but I'd assumed that Microsoft was using fairly standard techniques (although naturally the most basic of them).

If the 50% vs 49% is obvious to you, I'd bet they are using Bilinear resampling.

I'm sure a 50% zoom must be better than a 49% zoom but to what degree? You'd probably need a magnifying glass.

Oh, you can't see it?

So are techniques now so sophisticated that there's no need to worry about simplifying things for the software? If so, was this a problem in the past? I know MS won't change its zooming algorithms but it might zoom in "basic" intervals if we can make a good case for it.

Yes - there is better software out there. If you are interested, much more info here:

http://www.imagemagick.org/Usage/filter/

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