Video Accessories Misc
- Written by John E. Johnson, Jr.
- Published on 23 October 2008
On the Bench
The falloff test results (photo taken at 1/320th second at f/11) showed that a maximum falloff of 0.6 f-stop.
Shown below are the sharpness (resolution) test results for both a JPEG (first graph) and a RAW photo (second graph). You can see that in RAW, the MTF50 was 1752 LW/PH (the resolution for optimal picture quality), and in JPEG form, was 1557 LW/PH, so conversion to JPEG did lose some sharpness. In fact, both the RAW and JPEG versions were slightly undersharpened compared to the standard sharpening.
Chromatic aberration (CA) was very, very low, for both JPEG (0.05 pixel) and RAW (0.1 pixel) photos. This low CA is partly due to the primary lens (no zoom). Theoretically, there should be no chromatic aberration at the center of the lens, but there is no perfect lens out there, so I measure CA at the center. The CA results here show the DP1 lens to be excellent.
Gray scale analysis for both JPEG and RAW is shown below. In both cases, the highlights are suppressed quite a bit to prevent blowing out the bright regions of photographs.
The noise level analysis (lower section of the graphics) indicates noise is increased in the JPEG photo compared to the RAW photo. Sometimes, noise levels will actually decrease because of image processing, but that does not seem to be the case here. The result will be a sharper picture, because noise reduction also reduces sharpness.
I took a photo of our gray scale chart at ISO 100, 400, and 800. Here is the chart. I then cropped out the vertical gray rectangle indicated by the red marker and put the three gray strips side by side for comparison, as shown in the second photo. As the ISO increases, so does the noise, and this occurs with all digital cameras. Some cameras use a lot of noise reduction in their image processing, but this reduces sharpness. The results shown here are actually very good in terms of noise at ISO 800. Other cameras, with smaller sensors, have a lot more noise. So, even ISO 800 is quite usable with the DP1. In any case, like film, there is noise (grain in film) with increased ISO, but there are times when you really need that extra sensitivity to take the photo, and you either just accept the noise, or you don't get the photograph. I want to emphasize that the noise shown here in the dark gray test strip is not the same thing as not performing well in low light situations that I mentioned earlier. The noise test photos here were taken outside during the day when there was plenty of light.
Here is the Gretag Macbeth Color Checker SG chart analysis. The tints look pretty good, but there is overexposure.
And, the Q60 Color Chart. Again, the tints are fine, but this time, there is a bit underexposure.