Which f-stop is the sharpest? GFX 50S Diffraction Test
How do you determine the sharpest f-stop for your camera and lens? Is diffraction more impactful in infrared light than visible light? In this video, I will test the sharpest f-stop on a Fujifilm GFX 50S full spectrum conversion at each aperture with multiple infrared filters, 550 nanometers, 590 nm, 720 nm, 830 nm, 850 nm, IR Chrome, and a hot mirror filter. I’ll share the results and my observations.
Results
Fujifilm GFX 50S full spectrum conversion, GF 45 mm f/2.8 lens
| Filter | Wavelength | Sharpest f-stop |
|---|---|---|
| STC Optics UV/IR (hot mirror) | visible light | f/11 |
| Kolari Vision IR Chrome | dual-bandpass | f/11 |
| Full spectrum | n/a | f/8 |
| Kolari Vision 550 | 550 nm | f/8 |
| STC Optics IRP 590 | 590 nm | f/8 |
| STC Optics IRP 720 | 720 nm | f/8 |
| Hoya R72 | 720 nm | f/5.6 & f/8 |
| B+W 093 | 830 nm | f/5.6 |
| STC Optics IRP 850 | 850 nm | f/5.6 |
Recommendations
| Filter | Adjustment from sharpest visible light f-stop |
|---|---|
| Hot mirror, IR/UV cut, IR Chrome | Use sharpest visible light f-stop |
| 550 to 720 nm | 1-stop lower |
| 800 nm and higher | 2-stops lower |
- Lower f-stops: Sharpness is reduced with f-stops lower than the sharpest f-stop due to less depth of field. The loss of sharpness is minimal. Lower f-stops will not substantially impact sharpness. Use lower f-stops to reduce the depth of field.
- Higher f-stops: Sharpness is reduced with f-stops higher than the sharpest f-stop due to increased visible diffraction. The loss of sharpness is dramatic. Avoid these higher f-stops unless you are explicitly looking for a soft effect, want to create a starburst effect, or are willing to trade reduced sharpness for greater depth of field.
Previous Diffraction Article/Video on Fujifilm X-T20 (APS-C)
Comments
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