the last word

Photography meets digital computer technology. Photography wins -- most of the time.

  • site home
  • blog home
  • galleries
  • contact
  • underwater
  • the bleeding edge
You are here: Home / The Last Word / Comparing downsampling algorithms — ISO 12233

Comparing downsampling algorithms — ISO 12233

September 25, 2014 JimK Leave a Comment

For the next few posts, I’ll be showing images that have been downsampled using several different algorithms

  • Photoshop’s bilinear interpolation
  • Ps bicubic sharper
  • Lightroom export with no sharpening
  • Lr export with Low, Standard, and High sharpening for glossy paper
  • A complicated filter based on Elliptical Weighted Averaging (EWA), performed at two gammas and blended at two sharpening levels

The last algorithm appears to me to be pretty much the stat of the art in downsampling. It’s implemented using a script that Bart van der Wolf wrote for ImageMagick, an image-manipulation program with resampling software written by Nicholas Robidoux and his associates. I’ll be reporting on it later; I’m still working out some of the details with Bart.

The first test chart I’m using is the ISO 12233 chart, resized to 10% of its original linear dimensions. This is useful to see how much aliasing the various algorithms allow, and also to look for edge artifacts. The chart I used is a low-contrast version so that overshoots will be visible.

12233LoCp1s50

I’ll show you crops that have been enlarged 4x using nearest neighbor and JPEG’d. If you want to see the original, uncompressed Photoshop stack, please contact me.

Bilinear interpolation
Bilinear interpolation

A lot of aliasing, extending from the slanted edges marked with 4 clear through 10. The worst of all the algorithms in this regard. No haloing, no crunchiness.

 

Bicubic Sharper
Bicubic Sharper

There is quite a bit of aliasing in the slanted lines marked with 4. Aliasing less than bilinear, but still visible in lines marked 10.Haloing is visible around the slanted edge and the crop marks. Numbers are crunchy.

Lightroom, no sharpening
Lightroom, no sharpening

Almost no haloing. Aliasing low in lines marked with 4, and invisible above that.

Lightroom, low sharpening
Lightroom, low sharpening

Some haloing. The sharpening makes some high frequency aliasing visible, but not bothersome.

Lightroom stnadard sharpening
Lightroom standard sharpening

A little haloing. A little more aliasing visible.

Lightroom, high sharpening
Lightroom, high sharpening

Distinct haloing, if you’re looking for it, but not bad compared to bicubic sharper.

EWA, deblur = 100
EWA, deblur = 100

Areas with high spatial frequency are lighter than with the other methods. Aliasing slightly less that Lr with no sharpening. Very slight haloing.

EWA deblur 50
EWA deblur 50

No haloing. Best control of aliasing of all. Best delineation of slanted lines labeled 2

Stay tuned for more images.

The Last Word

← Lightroom downsizing: export sharpening noise effects Comparing Downsampling algorithms — Lindbloom’s desk →

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

March 2023
S M T W T F S
 1234
567891011
12131415161718
19202122232425
262728293031  
« Jan    

Articles

  • About
    • Patents and papers about color
    • Who am I?
  • Good 35-70 MF lens
  • How to…
    • Backing up photographic images
    • How to change email providers
  • Lens screening testing
    • Equipment and Software
    • Examples
      • Bad and OK 200-600 at 600
      • Excellent 180-400 zoom
      • Fair 14-30mm zoom
      • Good 100-200 mm MF zoom
      • Good 100-400 zoom
      • Good 100mm lens on P1 P45+
      • Good 120mm MF lens
      • Good 18mm FF lens
      • Good 24-105 mm FF lens
      • Good 24-70 FF zoom
      • Good 35 mm FF lens
      • Good 60 mm lens on IQ3-100
      • Good 63 mm MF lens
      • Good 65 mm FF lens
      • Good 85 mm FF lens
      • Good and bad 25mm FF lenses
      • Good zoom at 24 mm
      • Marginal 18mm lens
      • Marginal 35mm FF lens
      • Mildly problematic 55 mm FF lens
      • OK 16-35mm zoom
      • OK 60mm lens on P1 P45+
      • OK Sony 600mm f/4
      • Pretty good 16-35 FF zoom
      • Pretty good 90mm FF lens
      • Problematic 400 mm FF lens
      • Tilted 20 mm f/1.8 FF lens
      • Tilted 30 mm MF lens
      • Tilted 50 mm FF lens
      • Two 15mm FF lenses
    • Found a problem – now what?
    • Goals for this test
    • Minimum target distances
      • MFT
      • APS-C
      • Full frame
      • Small medium format
    • Printable Siemens Star targets
    • Target size on sensor
      • MFT
      • APS-C
      • Full frame
      • Small medium format
    • Test instructions — postproduction
    • Test instructions — reading the images
    • Test instructions – capture
    • Theory of the test
    • What’s wrong with conventional lens screening?
  • Previsualization heresy
  • Privacy Policy
  • Recommended photographic web sites
  • Using in-camera histograms for ETTR
    • Acknowledgments
    • Why ETTR?
    • Normal in-camera histograms
    • Image processing for in-camera histograms
    • Making the in-camera histogram closely represent the raw histogram
    • Shortcuts to UniWB
    • Preparing for monitor-based UniWB
    • A one-step UniWB procedure
    • The math behind the one-step method
    • Iteration using Newton’s Method

Category List

Recent Comments

  • JimK on Sony 135 STF on GFX-50R, sharpness
  • K on Sony 135 STF on GFX-50R, sharpness
  • Mal Paso on Christmas tree light bokeh with the XCD 38V on the X2D
  • Sebastian on More on tilted adapters
  • JimK on On microlens size in the GFX 100 and GFX 50R/S
  • Kyle Krug on On microlens size in the GFX 100 and GFX 50R/S
  • JimK on Hasselblad X2D electronic shutter scan time
  • Jake on Hasselblad X2D electronic shutter scan time
  • Piotr Chylarecki on Who am I?
  • JimK on Who am I?

Archives

Copyright © 2023 · Daily Dish Pro On Genesis Framework · WordPress · Log in

Unless otherwise noted, all images copyright Jim Kasson.