Resolution Chart Comparison
Shots here are of the PIMA/ISO 12233 standard resolution
test chart (more of which are available in our comparison
database). This resolution chart allows us to measure the actual performance
of the lens and sensor system. It measures the ability of the camera to
resolve lines at gradually higher resolutions and enables us to provide
a definitive value for comparison purposes. Values on the chart are 1/100th
lines per picture height. So a value of 15 equates to 1500 lines per picture
height.
Studio light, cameras set to auto, all settings factory
default. Aperture selected for optimum sharpness. Exposure compensation
+0.7 EV to +1.3 EV. Sigma SD10 & SD9 image produced with default parameters
in Photo Pro.
 |
 |
| Sigma SD10 |
Canon EOS 10D |
 |
 |
| Nikon D100 |
Sigma SD9 |
 |
 |
| Sigma SD10 |
Canon EOS 10D |
 |
 |
| Nikon D100 |
Sigma SD9 |
 |
 |
| Sigma SD10 |
Canon EOS 10D |
 |
 |
| Nikon D100 |
Sigma SD9 |
 |
 |
| Sigma SD10 |
Canon EOS 10D |
 |
 |
| Nikon D100 |
Sigma SD9 |
 |
 |
| Sigma SD10 |
Canon EOS 10D |
 |
 |
| Nikon D100 |
Sigma SD9 |
Measurable findings (three measurements taken for each camera):
| Camera |
Measurement |
Absolute
Res. |
Extinction
Res. |
| Sigma
SD10 |
Horiz LPH |
1550 |
>2000 |
| Vert LPH |
1550 |
>2000 |
| 5° Diagonal LPH |
1000 |
n/a |
| Canon
EOS 10D |
Horiz LPH |
1600 |
1900 |
| Vert LPH |
1450 |
1850 |
| 5° Diagonal LPH |
+ 1000 |
n/a |
| Nikon
D100 |
Horiz LPH |
1600 |
* 1850 |
| Vert LPH |
1300 |
* 1700 |
| 5° Diagonal LPH |
+ 1000 |
n/a |
| Sigma
SD9 |
Horiz LPH |
1550 |
>2000 |
| Vert LPH |
1550 |
>2000 |
| 5° Diagonal LPH |
1000 |
n/a |
* Moiré is visible, + Chart maximum
Definition of terms:
| LPH |
Lines per Picture
Height (to allow for different aspect ratios the measurement is
the same for horizontal and vertical) |
| 5°
Diagonal |
Lines set at
5° diagonal |
| Absolute
Resolution |
Still defined
detail (below Nyquist frequency*) |
| Extinction
Resolution |
Detail beyond
camera's definition (becomes a solid gray alias) |
| n/a |
Not Available
(above the capability of the test chart) |
| n/v |
Not Visible
(not visible on test results) |
* Nyquist frequency defined as the highest spatial
frequency where the sensor can still
faithfully record image detail. Beyond the Nyquist frequency aliasing
occurs.
As we expected identical results to the SD9, and with
good reason considering the design of the sensor and the fact that the
pixel count hasn't changed. That's to a lack of a color filter the X3
sensor doesn't suffer from color moire at the limits of resolution.
Because the X3 sensor doesn't employ an anti-alias (low
pass / blur) filter it continues to deliver detail past Nyquist. Taking
the vertical resolution bar as an example we can count all nine lines
up to our 'absolute resolution' measurement of around 1550 LPH, after
this point lines begin to merge and by 2000 LPH we can count five obviously
combined lines. In a real image this could be the detail of leaves on
a distant tree or bricks on a distant wall. At the time of my SD9 review
there was much debate over the 'validity' of this extra detail. My opinion
on this matter is that this detail is at least of photographic merit,
it is the correct color and represents detail that the human eye although
not able to distinguish perfectly would also see as a broken texture,
it's certainly better than the blurred area we would get from the anti-alias
filter of a Bayer sensor camera.
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