This is the 61st in a series of posts on the Fujifilm GFX-50S. The series starts here.
In the previous post, I looked at the general rendering of the GFX with the Fuji 23 and the a7RII with the Batis 18. Now I’m going to show you some images designed to get a handle on distortion.
It’s be easier to tell what’s going on if I add some construction lines.
Don’t look at the copper flashing; it’s not perfectly straight. The wooden beams are, though. The batis distortion is minimal unless you’re doing upper-level architectural work. It is of the mustache variety, with the beam appearing to sag as you come in from the sides, and then rising again in the center. The above images have no distortion correction applied; the lens profile correction in Lr is turned off.
Now let’s look at the Fuji 23mm f/4 image with no correction. In order to see it without correction, I converted it to a DNG file with lens corrections set to “Ignore”, and then opened that in Lr.
We don’t need construction lines here. You can see that the Fuji distortion is of the “barrel” type, with the beam appearing to rise slightly in the middle, and there is much less of it.
Turning on Lr’s lens profile correction tames the distortion quite a bit:
If we turn on lens profile correction for the Batis, here’s what we see:
The moustache distortion is gone.
It’s interesting to look at the Fuji corrected and uncorrected images superimposed:
Let’s zero in on that upper right corner:
That’s interesting. The field of view (FOV) is wider in the corrected image than it is in the uncorrected one. That means that there must be extra pixels not normally visible that the camera provides for use in distortion correction.
Left eye, a DPR contributor, provides the following insights on the way the GFX and Lr/ACr work together to do lens distortion correction:
The GFX corrects for distortion live-in-camera, so the view in the EVF and LCD are corrected in real-time. This affects the JPEG preview image and recorded JPEG images, but not the raw data itself. Correction hints to the raw processor are incorporated in the metadata.
ACR / LR ‘honors’ the GFX’s approach and also automatically applies the correction – to match what you saw when framing through the GFX EVF/LCD. This automatic correction cannot be turned off in ACR / LR (and can’t be turned on, as it’s already on, and fixed on).
The necessary correction data is passed within the .raf file to ACR / LR for the correction – it makes no difference if the lens has only just been released. ACR / LR doesn’t need it’s own distortion profile for these lenses, it’s given in the file’s metadata – which in any case is the best approach (not having to wait for an app to support a lens).
This is different from the way that Sony does lens distortion correction; it counts on the lens profile in Lr/ACR to do the work. You can turn that on and off in Lr, and the default is off. Iridient Developer and Iridient XTransformer allow you to defeat the Fuji lens corrections if you wish to do so.