Canon XH A1 Resolution Imatest MTF50

[Jack Jenkins]

Hey Tom thanks for doing the complicated tests, I know this is off-topic but it would be interesting to run your res test on the RED footage that is available -- just for some sort of wow factor perspective. I for one would like to know what sort of resolution divide we are dealing with between these cams.

[Tom Roper]

Originally Posted by Jack Jenkins

Hey Tom thanks for doing the complicated tests, I know this is off-topic but it would be interesting to run your res test on the RED footage that is available -- just for some sort of wow factor perspective. I for one would like to know what sort of resolution divide we are dealing with between these cams.

You and me both. Point me to a clip of an ISO12233 test chart.

[Philip Williams]

Super job Tom, thanks a lot.

[A. J. deLange]

Originally Posted by Tom Roper

Thank you! I was definitely hoping someone could/would answer that.

You are quite welcome but it occured to me that the explanation I gave, while factual and a factor, is not the whole story. What is mainly responsible for the high effective sampling rate is that the edge is modeled by some function (I use a sum of Chebychev polynomials) that best fits it and that the derivative of the edge is then calculated from the fit function - not the actual data. Because the analyst computes the derivatives he may do so at points as closely spaced as he choses and thus the effective sampling frequency can be much higher than the pixel pitch in the camera. The MTF which results is the MTF of the model and is not the same as the MTF which would be measured if sinusoidal targets were photographed. It is a good indicator of average image sharpness though because the average transition from light to dark is accurately modeled.

[Terence Murphy]

Originally Posted by Thomas Smet

One way you could test motion resolution is to use the remote control to zoom in and out. You could do it once as 60i and the second time as 30F and then match up the same exact moment in time and test the resolution.

I'm not sure how the results would turn up because video in motion has lower detail anyways due to motion blur and a lot of other things. Even if resolution of 24F and 30F drops a little bit more during motion does it really matter?

I had suggested panning left-right to avoid having vertical motion blur (assuming a perfectly level camera). Its definitely an academic question. I'm mostly interested in it in wondering how good frame mode is compared to a true progressive frame (the resolution hit is probably greater than 10.6%, but how much greater?).

-Terence

[Tom Roper]

Excellent explanation A.J., thank you.

[Thomas Smet]

Originally Posted by Terence Murphy

I had suggested panning left-right to avoid having vertical motion blur (assuming a perfectly level camera). Its definitely an academic question. I'm mostly interested in it in wondering how good frame mode is compared to a true progressive frame (the resolution hit is probably greater than 10.6%, but how much greater?).

-Terence

The only problem is that you would have to do the pan exactly the same each time for it to be fair. You would have to have some automated tripod head that could repeat a pan. The other thing you could do is shoot something that could be made to move past the camera at a constant speed such as a remote control car or train set. This way you should be able to get two frames of the exact same type of motion and the exact same level of motion blur to find out exactly how much softer the F mode really is in motion of the same type of motion. That was the only reason why I suggested the remote control zoom because it would move at a constant speed and would give the same results every time.

[Terence Murphy]

Originally Posted by Thomas Smet

The only problem is that you would have to do the pan exactly the same each time for it to be fair. You would have to have some automated tripod head that could repeat a pan. The other thing you could do is shoot something that could be made to move past the camera at a constant speed such as a remote control car or train set.

Very true. That's probably why no one has ever answered the question of how much vertical resolution is lost with frame mode. If anyone cares to donate a Canon A1 and Sony V1 to me (for a progressive control), I'd be glad to spend a day generating the data....

I was at the local trolley museum on Sunday with my nephew (who is very into trains), and now I have visions of Lionel trains carrying resolution charts in my head....

-Terence

[Tom Roper]

XH-A1 60i: (01/01/2007)
824.3 Lines Horizontal (MTF50); 810 Lines Horizontal = Limit@Nyquist
674.8 Lines Vertical (MTF50)

XH-A1 30F: (01/01/2007)
823.6 Lines Horizontal (MTF50); 810 Lines Horizontal = Limit@Nyquist
592.2 Lines Vertical (MTF50)

Previous Reported Result for XH-A1 24F:
810 Lines Horizontal (Limit@Nyquist)
590.4 Lines Vertical (MTF50)

Previous Reported Result for Canon HV10:
784.5 Lines Horizontal (MTF50)
704.8 Lines Vertical (MTF50)

**************************************************

I re-ran the XH-A1 test for 60i and 30F for a baseline. The results are normalized for standard 2-pixel sharpening. Everything is consistent with, in fact nearly identical to the previous run.

The finding that 24F loses a bit of vertical resolution compared to 60i holds true for 30F as well, about 12%, not much and hardly observable if at all.

Limit@Nyquist means the camera has reached the resolution limit of the HDV format in the horizontal direction. 810 x 16/9 aspect = 1440. Remember, horizontal resolution is expressed per picture height.

http://vsdrives.com/graphics/resolut...1_60i_Horz.PNG
http://vsdrives.com/graphics/resolut...1_60i_Vert.PNG
http://vsdrives.com/graphics/resolut...1_30F_Horz.PNG
http://vsdrives.com/graphics/resolut...1_30F_Vert.PNG

[Daymon Hoffman]

Thanks Tom great work. That HV10 still amazes me... what a steller little cam. *still pondering wether to wait for a HV10 mk2 or not*

[Steven Fokkinga]

Is it also possible to run this test with different settings for sharpness? Or isn't the program 'fooled' by this because the actual resolution doesn't change?

[Tom Roper]

Originally Posted by Steven Fokkinga

Is it also possible to run this test with different settings for sharpness? Or isn't the program 'fooled' by this because the actual resolution doesn't change?

You can run the test at any level of sharpening, but it normalizes the result to a standard 2 pixel sharpening, so the short answer is no, the program is not fooled.

That's not to say your own eyes can't be fooled. Since sharpness emphasizes the contrast on edges, higher contrast and sharpening lends more punch and the perception of resolution.

[Mark Fry]

Originally Posted by Terence Murphy

...I have visions of Lionel trains carrying resolution charts in my head...

You'd have to use Hornby or Marklin when testing the PAL version... :-)