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You are here: Home / Lens screening testing / Examples / Good 120mm MF lens

Good 120mm MF lens

On this page, I’ll walk you through a test of a Fuji 120 mm f/4 macro lens on a Fujifilm GFX 50S body. The lens turns out to be superbly assembled.

We want to test the lens wide open. We consult the minimum distance chart:

35 meters is the required distance. I used 37.

Checking target size:

A 16-inch star will be about 300 pixels on the sensor. I used a 22.5 inch star, which will be even bigger.

The image is underexposed by conventional standards to keep the target well away from clipping.

A center crop, somewhat magnified:

Center

 

Ignore the out-of-focus grass. You can see both moire and false color in great profusion. The image is well focused.

If we consider the images in opposite pairs we can look for differences that aren’t radially symmetric. If sufficiently bad, these departures from symmetry are indicators of improper assembly. 

Upper Left

 

Lower Right

If anything, the upper left image is sharper than the center. Both corners above show sub-pixel resolution on the part of the lens.

Top

 

Bottom

No difference in sharpness. Sorry about the density differences; it was a partly cloudy day with fast winds aloft.

Lower Right

 

Lower Left

Again, virtually no difference.

Far Right

 

Far Left

 

Not only is this lens well put together, it is an incredible performer at the periphery of the frame, offering virtually the same sharpness there as it does in the center. And that’s wide open.

 

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  • Good 35-70 MF lens
  • How to…
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      • 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
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      • 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
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    • 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

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