Here you will find the results of a test in which image noise in homogeneous colour areas is measured at different ISO and internal sharpening settings. The test is performed both with an Olympus C5050Z and an Olympus C2000Z digital camera (the C2000 for comparison).
There are also graphs showing how file size changes at different ISO and internal sharpening settings.
For questions or comments send me an email.
 
 

Conclusions

• Noise at ISO 64 is substantially lower than at ISO 100, 200 and 400.
• Noise increases as the sharpening level is increased.
• In this test, at ISO 400 noise is surprisingly lower than at ISO 100 and 200 for many sharpening levels. Perhaps there is some kind of noise reduction mechanism which gets activated at ISO 400, but not at ISO 100 or 200. However this ISO400 noise reduction filter is only applied in image areas which contain no detail and the noise in the other parts of the image is not reduced. In other words it still makes sense to use ISO 100 and 200 - the ISO400 filter simply helps reducing the noise where it is most visible. See this page for details (CAUTION: large files - the page has a size of 1MByte).
• Compared to an Olympus 2000, a 2MP camera with larger pixels (4x4 micrometer vs. 2.8x2.8 for the 5050):
• at ISO 100 the 5050 has more noise at all sharpening levels
• however at ISO 64 the 5050 has the same noise level as the C2000 at ISO 100, if sharpening level is low
• at ISO 400 the 5050 has less noise than the C2000
• at ISO 200 the 5050 has more noise than the C2000 at all sharpening levels except the lowest ones
• File size increases with increasing ISO and sharpening level; for instance at ISO 400 and sharpening 0 the SHQ JPG file size is almost 50% larger than at ISO 64 and sharpening -3. Therefore you can save a lot of memory space if you shoot at low ISO and sharpening levels.

Test procedure

I prepared two scenes containing objects with smooth, non-reflective surfaces with homogeneous colour and no texture.
 

Scene 1: glass table  (the white sheet of paper is the back side of a photo)

Scene 2: a Ricola sweets box (macro shot without flash)

To measure the noise I chose areas with no texture and homogeneous colour. I didn't measure the noise in image areas containing detail (would be very complicated, if possible at all - you'd have to subtract each image area from the corresponding image area of a noiseless image).
 

Scene 1

Scene 2

In a noiseless image, the standard deviation in an area of homogeneous colour should be zero. Therefore, the higher the standard deviation, the bigger the noise.

I took a total of 44 shots for each scene (ISO 64, 100, 200 and 400; sharpening levels -5 .. +5) with shutter priority, i.e. exposure time was fixed and the camera would choose the aperture to properly expose the image.

I also took three shots (ISO 100, 200 and 400) with an Olympus C2000 digital camera (2MP at 1600x1200) to compare the noise levels (for the C2000 images the size of the noise measurement area was approx. 50x50 pixels). The C2000 has bigger pixels (4x4 micrometer vs. 2.8x2.8 for the C5050), therefore noise should be lower.

With the histogram function I measured the standard deviation in the noise measurement areas of each image. The results are shown in the graphs below.
 
 
 

Scene 1

Comments

• Noise at ISO 64 is substantially lower than at ISO 100, 200 and 400.
• Noise increases as the sharpening level is increased.
• In this test, at ISO 400 noise is surprisingly lower than at ISO 200 for almost all sharpening levels. It is even lower than noise at ISO 100 for sharpening levels greater than 0. Perhaps there is some kind of noise reduction mechanism which gets activated at ISO 400, but not at ISO 100 or 200. However this ISO400 noise reduction filter is only applied in image areas which contain no detail and the noise in the other parts of the image is not reduced. In other words it still makes sense to use ISO 100 and 200 - the ISO400 filter simply helps reducing the noise where it is most visible. See this page for details (CAUTION: large files - the page has a size of 1MByte).
• Compared to an Olympus 2000, a 2MP camera with larger pixels (4x4 micrometer vs. 2.8x2.8 for the 5050):
• at ISO 100 the 5050 has more noise at all sharpening levels
• however at ISO 64 the 5050 has the same noise level as the C2000 at ISO 100, if sharpening level is low (below -1)
• at ISO 400 the 5050 has less noise than the C2000
• at ISO 200 the 5050 has more noise than the C2000 at all sharpening levels except the lowest ones
• Concerning the file size:

• File size increases with increasing ISO and sharpening level; for instance at ISO 64 and sharpening -3 the file size for this particular image is 2120 KByte, while it is 3025 KByte at ISO 400 and sharpening 0.
• Therefore you can save a lot of memory space if you shoot at low ISO and sharpening levels.

Scene 2

Comments

• Noise at ISO 64 is substantially lower than at ISO 100, 200 and 400.
• Noise increases as the sharpening level is increased.
• Here, ISO 100 has almost the same noise as ISO 200.
• In this test, at ISO 400 noise is surprisingly lower than at ISO 100 and 200 for all sharpening levels. Perhaps there is some kind of noise reduction mechanism which gets activated at ISO 400, but not at ISO 100 or 200. However this ISO400 noise reduction filter is only applied in image areas which contain no detail and the noise in the other parts of the image is not reduced. In other words it still makes sense to use ISO 100 and 200 - the ISO400 filter simply helps reducing the noise where it is most visible. See this page for details (CAUTION: large files - the page has a size of 1MByte).
• Compared to an Olympus 2000, a 2MP camera with larger pixels (4x4 micrometer vs. 2.8x2.8 for the 5050):
• at ISO 100 the 5050 has more noise at all sharpening levels
• however at ISO 64 the 5050 has less noise than the C2000 at ISO 100, if sharpening level is lower than +1
• at ISO 400 the 5050 has less noise than the C2000
• at ISO 200 the 5050 has more noise than the C2000 at all sharpening levels except the lowest ones
• Concerning the file size:

• File size increases with increasing ISO and sharpening level; for instance at ISO 64 and sharpening -3 the file size for this particular image is 1725 KByte, while it is 2577 KByte at ISO 400 and sharpening 0.
• Therefore you can save a lot of memory space if you shoot at low ISO and sharpening levels.

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