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As Klaus always mentions, Olympus DSLRs are rather complicated beings with respect to their effective sensor resolution due to the implementation of a very strong AA filter ("Anti-Aliasing" or low-pass filter). The other manufacturers are also using AA filters (except Leica and Sigma) but the current trend is to use rather weak ones because a strong AA filter works out fine for eliminating moiree effects, however this has a negative impact on the resolution characteristic. Let’s check if the resolution of the PEN meets Klaus’s demands.
The following chart compares the RAW and JPEG output of the Olympus E-P1 to the last Photozone camera tests of the Canon 500D, Nikon D90 and D5000, Panasonic DMC-G1 as well as Olympus E-620. The results are based on RAW files, transformed to DNG and converted to JPEG, using the same Adobe Camera RAW version.
The maximum resolution of the PEN's raw files is about average and on a par with the Nikon D5000. However the JPEG output is a good deal worse and no appropriate option if maximum resolution is needed. Nevertheless, Klaus will be very glad about the effective resolution compared to the Olympus E-620 which indicates a rather weak AA filter on the Olympus E-P1. This fact is reconfirmed by the following chart which shows the higher effective resolution of the PEN despite the obvious lower sharpening level.
As already mentioned in our Review of the Olympus E-620, Olympus applies a heavy amount of sharpening during the post-processing of the straight JPEG output. Fortunately this is not the case with the PEN and due to the weaker AA filter the effective resolution increased dramatically while lowering the sharpening level. Additionally, comparing to the JPEG- the “undersharpened“ RAW-output of ACR contains even more scene information at a lower sharpening level. However, it's quite interesting to see that the small 2,25cm² sensor of the PEN provides almost the same effective resolution compared to the comparatively big 3,73cm² sensor of the Nikon D5000. Let's check the impact of the pixel density of around 5.1 MP/cm² on the dynamic range...
"Dynamic range or light sensitivity range of a sensor indicates the ratio of light exposure between the highest brightness a camera can capture (saturation) and the lowest brightness it can effectively capture (typically when noise becomes more important than signal, i.e., SNR < 0 dB). This range indicates the maximum contrast that can be effectively captured by the sensor. The larger the dynamic range, the better, as the sensor is able to capture higher-contrast scenes.
Note that dynamic range is expressed on a logarithmic scale in EV (same as f-stop), thus an increase of 1EV corresponds to a doubling of dynamic range." (DxO Labs)
Here's an analysis by our partner, the (DxO Lab):
The first "tab shows the measurement values and graph derived directly from a RAW image when displayed on a computer screen at 100% magnification." The second tab display the print performance measurements and graph derived directly from a RAW image after a normalization step that transforms all images, regardless of original resolution, to an 8 Mpix image. The print size we have chosen is a standard 300dpi 8"x12" format, which corresponds to about the physical size of an 8Mpix image printed at 100% magnification." (DxO Labs)
While the dynamic range of 10 f-stops at low ISO is already below average at low ISO, it decreases recognizably by 2 f-stops in mid ISO range and drops below 6 f-stops at high ISO. The overall dynamic range of the Olympus is comparable to the Panasonic G1 and therefore quite bad. Compared to an entry level DSLR like the Nikon D5000 the dynamic range of the PEN is about two f-stops smaller but this is no surprise due the smaller sensor and the higher pixel density of the Olympus E-P1 as generally dynamic range is higher for digital cameras with lower pixel density due to larger pixel size.