ISO / Sensitivity accuracyIn a new addition to our reviews we are now measuring the actual sensitivity of each indicated ISO sensitivity. This is achieved using the same shots as are used to measure ISO noise levels, we simply compare the exposure for each shot to the metered light level (using Sekonic L-358), middle gray matched. We estimate the accuracy of these results to be +/- 1/6 EV. The E-410 proved to have inconsistently indicated ISO sensitivities. In reality ISO 100 proved to be slightly more sensitive than indicated (more like ISO 125) and ISO 1600 slightly less than indicated (closer to ISO 1250).
ISO Sensitivity / Noise levelsISO equivalence on a digital camera is the ability to increase the sensitivity of the sensor. The works by turning up the "volume" (gain) on the sensor's signal amplifiers (remember the sensor is an analogue device). By amplifying the signal you also amplify the noise which becomes more visible at higher ISO's. Many modern cameras also employ noise reduction and / or sharpness reduction at higher sensitivities.To measure noise levels we take a sequence of images of a GretagMacBeth ColorChecker chart (controlled artificial daylight lighting). The exposure is matched to the ISO (ie. ISO 200, 1/200 sec for consistency of exposure between cameras). The image sequence is run through our own proprietary noise measurement tool (version 1.4 in this review). Click here for more information. (Note that noise values indicated on the graphs here can not be compared to those in other reviews). Room temperature is approximately 22°C (~72°F), simulated daylight lighting. Olympus E-410 vs. Canon EOS 400D (Digital Rebel XTi) vs. Nikon D40X
From a noise point of view there's little difference between these three ten megapixel digital SLRs up to ISO 400. At ISO 800 and 1600 the E-410 has the cleanest looking gray and black patches although this is clearly at the expense of detail lost to noise reduction, especially at ISO 1600. The noisiest 'flat area' patches come from the Nikon D40X although it doesnt 'smear' as much detail at ISO 1600. From an overall performance point of view the Canon EOS 400D (Rebel XTi) with its CMOS sensor once more delivers the best compromise between noise and detail. Luminance noise graphHere you can see the clear effect of the noise reduction system (noise filter) on the E-410, it keeps measurable noise virtually flat from ISO 100 (125) to 800, rising only slightly at ISO 1600 (1250).
Indicated ISO sensitivity is on the horizontal axis of this graph, standard deviation of luminosity on the vertical axis. Chroma (color) noise graphThe noise reduction system also works on chroma noise, we even see a slight dip at ISO 1600 (1250).
Indicated ISO sensitivity is on the horizontal axis of this graph, standard deviation of color on the vertical axis. |
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