Sony HDR-FX1 Resolution Test

by John Beale  Jan. 11 2006

This is a quick test of the resolution of the Sony FX1 HDV camera. I recorded video at f/4, 0 dB in HDV mode at two sharpness settings, +14 and +0, with the camera on a tripod about 1 meter from the test chart. This put the zoom lens in the middle of the range.  I used still frames exported from the HDV .m2t video from Vegas as a 1920x1080 bitmap into Photoshop, then directly saved as a JPEG without any manipulation at all.  For comparison, the same test chart is also photographed with a VX2k and a Canon 20D (DSLR) using 50mm/1.4 lens at f/8.

The test chart was hand-assembled from four 11x14 sheets of paper each with approx. 1/4 of the ISO-12233 pattern printed on a 1200 dpi laser printer.  A commercially printed chart would have been cleaner.

I used manual focus for each video camera, and also compared it with autofocus. Both methods reached the same focal point, not surprising since the test chart is high-contrast and full of edges.  The "sharpness" setting on the FX1 defaults to +12. I normally use it at +14 since that seems to be perceptually similar in sharpness to the VX2k once the HDV is down-sampled to SD resolution.  For comparison I also have a VX2000 frame at 720x540 (using default sharpness) and a Canon 20D frame at 3504x2336.  I framed the VX2k to cover the whole width of the test chart assuming the intent is to acquire 4:3 and then crop to 16:9. You could do this comparison other ways too.

Click on the 1:1 center crop below to see the full frame from each camera.

FX1 at f/4, sharp+14 FX1,f/4,Sh+14  FX1 at f/4, sharp+0 FX1,f/4,Sh+0  VX2000 at f/5.6 VX2k,f5.6

Canon 20D, 50mm/1.4 at f/8 Canon 20D, 50mm/1.4 at f/8

If we define "lines of video resolution" as Line Pairs / Picture Height at MTF50P (= resolution at which the Modulation Transfer Function drops to 50% of its Peak value) and set the FX1 to sharp +14 and VX2k at its default, then we get the following results (calculated by Imatest 1.6.5)

FX1:   624 Hor.  498 Vert.  (native 16:9 frame)
VX2k: 481 Hor.  317 Vert.  (native 4:3 frame)
VX2k: 390 Hor.  242 Vert.  (cropped to 16:9)

One could claim 500+ lines of resolution for the VX2k (as Sony has) if you use a different measure of resolution that what I am using here, for example "limiting resolution" where the MTF drops to zero, but this is difficult to measure accurately due to noise and aliasing effects.

For those interested in numerical details, the charts below are from Imatest based on the full frame images above. Imatest plots comparing FX1 with sharp+14 and VX2k are shown here. The full data output including plots is available here.

Camera PH Ch H/V 10-90U
/PH		 10-90C
/PH		 Over
shoot%		 Over-
sharp %		 MTF50U
LW/PH		 MTF50C
LW/PH		 MTF
Nyq		 Lens f-stop Location Gain Misc.
settings		 Gamma Sharp. radius Chr. Aber
Sony FX1 1080 Y Horizontal 1027 676 48.1 35.8 738 512 0.151 built-in 4 15% above ctr. 0 dB sharp+14 0.5 2 0.07
Sony FX1 1080 Y Vertical 549 650 6.1 -9.4 492 545 0.139 built-in 4 14% below ctr. 0 dB sharp+14 0.5 2 0.35
Sony FX1 1080 Y Horizontal 246 326 0.3 -15.1 247 286 0.005 built-in 4 17% above ctr. 0 dB sharp 0 0.5 5 0.06
Sony FX1 1080 Y Vertical 397 560 1.2 -17.6 414 496 0.028 built-in 4 13% below ctr. 0 dB sharp 0 0.5 3 0.29
Sony VX2k 540 Y Horizontal 531 542 3.6 -1.5 498 499 0.488 built-in 5.6 17% above ctr. 0 dB default 0.5 2 0.02
Sony VX2k 540 Y Vertical 426 355 19.6 10.4 334 310 0.178 built-in 5.6 14% below ctr. 0 dB default 0.5 2 0.09

Camera Ch H/V 10-90U
Pixels		 10-90C
Pixels		 Over-
shoot %		 Over-
sharp %		 MTF50U
Cy/Pxl		 MTF50C
Cy/Pxl		 MTF
Nyq		 Lens f-stop Location Gain Misc.
settings		 Gamma Sh. radius Chr Aber
Sony FX1 Y Horizontal 1.05 1.6 48.1 35.8 0.342 0.237 0.151 built-in 4 15% above ctr. 0 dB sharp+14 0.5 2 0.07
Sony FX1 Y Vertical 1.97 1.66 6.1 -9.4 0.228 0.252 0.139 built-in 4 14% below ctr. 0 dB sharp+14 0.5 2 0.35
Sony FX1 Y Horizontal 4.39 3.31 0.3 -15.1 0.114 0.133 0.005 built-in 4 17% above ctr. 0 dB sharp 0 0.5 5 0.06
Sony FX1 Y Vertical 2.72 1.93 1.2 -17.6 0.192 0.23 0.028 built-in 4 13% below ctr. 0 dB sharp 0 0.5 3 0.29
Sony VX2k Y Horizontal 1.02 1 3.6 -1.5 0.461 0.462 0.488 built-in 5.6 17% above ctr. 0 dB default 0.5 2 0.02
Sony VX2k Y Vertical 1.27 1.52 19.6 10.4 0.309 0.287 0.178 built-in 5.6 14% below ctr. 0 dB default 0.5 2 0.09

I would not claim these results are definitive. They may perhaps be worth no more to you than what you paid for them.
I encourage you to do your own experiments.  
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