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 / GFX 50S / Fuji 32-64/4 at 44 mm focus shift and autofocus accuracy

Fuji 32-64/4 at 44 mm focus shift and autofocus accuracy

February 8, 2018 JimK 1 Comment

This is a continuation of a series of posts on the Fuji GFX 50S.   You should be able to find all the posts about that camera in the Category List on the right sidebar, below the Articles widget. There’s a drop-down menu there that you can use to get to all the posts in this series; just look for “GFX 50S”. 

A few days ago, I published a study of the focus shift and autofocus errors of the Fuji GFX 50S using the Fuji 45 mm f/2.8 lens. I repeated the test with the 110 mm f/2, and the 63/2.8. Yesterday, I posted the results of testing the last lens in this series, the 32-64 mm f/4. I performed the tests at 64 mm focal length. Now I’ll do the same at 44 mm.

First, focus shift:

I’ve plotted the three Adobe RGB color channels. The graph presents displacement of the image projected on the sensor from the desired green-channel focal plane, not the error in the object field in front of the lens. The reason for doing this is to allow easier comparison of lenses of different focal lengths at various target distances. Negative numbers indicate front-focusing. The image-plane shift is in micrometers (um). The separation of the focal distances of the three color planes is because of the longitudinal chromatic aberration (LoCA) of the lens. There were ten exposures at each f-stop. I’ve plotted lines indicating the average (aka mean or mu) of the sample set bolder and added thin lines above and below the means that are one standard deviation (sigma) away from them. The focus shift is away from the camera as you stop down. That means this lens, at this focal length and at this distance, is undercorrected for spherical aberration.

Here are the circles of confusion (CoCs) implied by the above amount of focus error.

If we look at luminance, here is what the above graph looks like:

The worst case CoCs are under one-half the pixel pitch. Unlike at 64 mm, there is no reason to stop down when focusing this lens at this distance and focal length.

Now we’ll look at autofocus performance, in Af-S mode with the next-to-smallest focusing area:

 

 

Wow! Even wide open, these are good results, and look at the consistency when the lens is stopped down to f/5.6 and narrower.

For completeness, here are the luminance results:

 

GFX 50S

← Fuji 32-64/4 at 64 mm focus shift and autofocus accuracy Fuji 32-64/4 at 32 mm focus shift and autofocus accuracy →

Trackbacks

  1. Fuji 32-64/4 at 32 mm focus shift and autofocus accuracy says:
    February 8, 2018 at 8:32 pm

    […] the last lens in this series, the 32-64 mm f/4. I performed the tests at 64 mm focal length. Earlier today I did the same at 44 mm. Now I’ll finish with the 32 mm […]

    Reply

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

  • 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?
  • Piotr Chylarecki on Who am I?
  • Stefan on Swebo TC-1 OOBE

Archives

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

Unless otherwise noted, all images copyright Jim Kasson.