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 — Lindbloom’s desk

Comparing Downsampling algorithms — Lindbloom’s desk

September 26, 2014 JimK Leave a Comment

This is the second in a series of posts 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 is what I consider to be the state 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.

The test target I’m using is a ray-traced image of an imaginary version Bruce Lindbloom’s desk, resized to 15% of its original linear dimensions. This image, being synthetic, has no photon noise and is thus a good way to judge the performance of the various algorithms without regard to how they deal with noise.

Here’s the whole image.

DeltaEp2s50

Here are crops from the downsampled images after having been enlarged 400% using nearest neighbor and JPEG’d. My comments are below each image.

 

Nicubic Sharper
Bicubic Sharper

There is haloing visible on the edges of the cubes in the color solid and in some of the patches in the Munsell chart.  There is a striking change in apparent brightness of the parts of the paper clips that are near the black parts of the desktop. In fact, all the downsampled image suffer from this defect to a greater or lesser degree. There are halos around the black figures on the desktop. This is not good performance.

Bilinear Interpolation
Bilinear Interpolation

There are no halos around the Munsell patches or the color solid cubes. The edges of the Munsell patches are soft. There are some brightness anomalies in the paper clips, but they’re nowhere near as bad as with bicubic sharper.

EWA deblur = 50
EWA deblur = 50

The EWA image with moderate deblur has the most realistic depiction of the paper clips. There is no haloing at all. Very good performance.

EWA deblur = 100
EWA deblur = 100

Stepping up the deblurring to 100 surprisingly doesn affect the paper clips much. There is a hint of aliasing in the yellow Munsell patch.

Lightroom Export High Sharpening
Lightroom Export High Sharpening

The paper clips are even worse then bicubic sharper. There is distinct haloing. The haloing on the magenta Munsell patch is associated with a hue shift.

Lightroom Export Low Sharpening
Lightroom Export Low Sharpening

Not too bad performance on the paper clips. A little haloing, but also not bad.

Lightroom Export No Sharpening
Lightroom Export No Sharpening

More modulation of the paper clip brightness by the background that EWA with deblur = 50. Image is less punchy, too, but I think it’s in second place.

Lightroom Export Standard Sharpening
Lightroom Export Standard Sharpening

As you might expect, halfway between Lightroom Low and Lightroom High sharpening. Too much haloing for my tastes, but might be OK if printed to a printer that rolls off the high spactial frequencies.

The Last Word

← Comparing downsampling algorithms — ISO 12233 Comparing downsampling algorithm noise performance →

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 Fujifilm GFX 100S pixel shift, visuals
  • Sarmed Mirza on Fujifilm GFX 100S pixel shift, visuals
  • lancej on Two ways to improve the Q2 handling
  • 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

Archives

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

Unless otherwise noted, all images copyright Jim Kasson.