As I have these two camera and lens combinations I have been curious to see if I could crop the GFX image to match the X-T3 framing and upscale back to 6240x4160px (native X-T3 sensor frame).

Why would you want to do this?

The GFX sensor is 8256x6192px and hold incredible amounts of detail.
The quality of the images are superb.

This is in part down to the sensor, but also thanks to the GF lenses.
The GF250/f4 is staggeringly sharp and I have often wondered if it could match the image quality of the XF100-400/f4.5-5.6 @ 400mm.

I shoot most of my wildlife at this focal length as I need the reach.
However, the XF100-400mm isn’t as sharp at 400mm as it is at 100-300mm.

This got me wondering if the GFX could match or better the results when paired with the GF1.4TC.

The settings:

  • f5.6
  • 1/8s
  • iso 200
  • Electronic front curtain shutter on both cameras
  • Image stabelization off
  • WB 5000K
  • Same focus point on subject

Unless clearly stated no image sharpening has been applied and no processing applied with regards to exposure, WB, contrast etc.
Sharpening has been set to zero in Capture One Pro – not the default setting.

The resulting frame taken by the two camera systems differ a lot.
The 400mm is clearly getting much closer.

XF100-400 @ 400mm

xf full frame - no sharpen


gfx full frame - no sharpen


When viewing thsese two images at 100% we get the following:

XF100-400 @ 400mm

xf 100% - center - no sharpen


gfx 100% - center - no sharpen

As we can see the the X-T3 image is still more zoomed in.

What is interesting, however, is the sharpness of the GFX image compared to the X-T3 image.
The GFX is much sharper.

Here are the full size screenshots:


So, could we upscale the GFX frame to match the X-T3 frame?
And would we retain any sharpness and detail advantage when doing so?

Lets find out…

I did the following:

  • Crop the GFX image to match the X-T3 image
  • Export the GFX image to a TIFF file with the X-T3 file dimension of 6240x4160px
  • Import the TIFF file into Capture One Pro

We now have the two following images:

xf full frame - no sharpengfx tiff imported

Click on the gallery bellow and open each image at full size.
You should clearly see the advantage the GFX file has – even when cropped and upscaled.
X-T3 left – GFX right:


For the record, adding sharpening only benefited the GFX further.


The conclusion is clear – the GFX combination can easily outresolve the X-T3 combination even when cropped and upscaled.

When the GFX is used at its native resolution it is far ahead of the AP-C sensors capability.

So where does this leave the X-T3?

The big benefit of the X-T3 is speed and AF ability.
The GFX cannot hold a candle to the X-T3 on these two points.

There is of course the size, weigth and cost difference.
The X-T3 wins here too.

For me this posts a dilemma.
I shoot a lot of wildlife and the detail and overall quality of the GFX is very compelling.
But the AF is not good enough for any fast action.
Slower moving subjects are normally fine, but flying birds and eratic movement is a problem.
Do I play it safe and use the better AF system or reach for the better quality?

For more deliberate shoots with people or static subjects the GFX is king.





So I have taken a real life shot outdoors of a heron – 90 meters away sitting in a tree.
This should give us a good idea if this can be applied in pracsis.

Settings are iso 1000 – 1/1000s – f5.6 for both systems.
Tripod mounted.

Here are the two shots from the GFX and X-T3 with the same lens combination as above.

heron gfx full frame

heron x-t3 full frame

Here is the crop we have to apply to match the GFX and X-T3 frames:
heron gfx crop outline

Here is the GFX image upscaled to 6240×4160:
heron gfx cropped

Now lets look at the side-by-side images zoomed in to 300%.
It should be noted that I have not applied any editing or sharpening – same as above.
The white balance was set to 5000K, but the conditions changed slightly between swapping the cameras so there is a colour difference.


There are clear differences with the GFX showing better tonal gradations, but to be honest they are very similar.
Considering the GFX has been cropped to almost 25% of its original size and then upscaled 168% this is very impressive.

What it clearly demontrates to me is that the GFX+GF250+GF1.4TC  can, if nescessary, be used in place of the X-T3 + XF100-400mm for static subjects.

What I also discovered is that the GFX can NOT be used to track moving subjects with any repeatable success.
The contrast based AF and total lack of AF-C controls makes it a very frustrating experience for faster action.

I didn’t succeed in getting a single frame in focus on any moving subject by the lake today with the GFX.

The X-T3 on the other hand was great for birds in flight and fast action.
Over 80% of around 350 frames where in sharp focus.




3 thoughts on “X-T3+XF100-400 vs GFX+GF250+GF1.4TC

    1. I do prefer the D500 for wildlife. It is partly the better AF and the way you can assign AF modes to different buttons, but also the optical viewfinder. I don’t like the electronic viewfinders for fast moving subjects.
      I am also lucky to have the Nikon AF-S 400mm f/2.8 lens. This lens is perfect for BIF and wildlife in general.


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