Doug Kerr
Well-known member
With any camera, we have available a lot of choices that affect the character of the image - ISO sensitivity, delivered image pixel dimensions, JPEG compression "quantity", and so forth. These interact in a way that is very dependent on the nature of the scene and the use we will make of the image.
Today I took a number of shots of the same subject with my new Canon Powershot SX20 IS camera, with different combinations of such "settings". I then isolated a small area of each frame for comparison.
Here we see the entire frame taken in one set of settings, in reduced resolution:
The test scene: shot at ISO 200, 4000 x 3000 px (12 Mpx), "high" JPEG compression quality
The white rectangle shows the location of the small areas that will be compared.
Twelve images were taken with every combination of the following "settings":
In the composite mosaic below, the tiles taken at an overall frame pixel size of 12 Mpx are at original camera resolution; the tiles taken at an overall frame pixel size of 8 Mpx have been upsized (a factor of 1.22) to a consistent pixel size for presentation. There is no doubt some loss of comparability by so doing.
There are not really any surprises here.
Note that with regard to the matter of the JPEG compression "quality", this scene excerpt is not best for showing the impact of compression artifacts.
Best regards,
Doug
Today I took a number of shots of the same subject with my new Canon Powershot SX20 IS camera, with different combinations of such "settings". I then isolated a small area of each frame for comparison.
Here we see the entire frame taken in one set of settings, in reduced resolution:
The test scene: shot at ISO 200, 4000 x 3000 px (12 Mpx), "high" JPEG compression quality
The white rectangle shows the location of the small areas that will be compared.
Twelve images were taken with every combination of the following "settings":
Sensitivity: ISO REI 200, 400, 800
Delivered image pixel dimensions: 4000 x 3000 px (12 Mpx), 3264 x 2448 px (8 Mpx)
JPEG compression "quality": "high", "low"
Delivered image pixel dimensions: 4000 x 3000 px (12 Mpx), 3264 x 2448 px (8 Mpx)
JPEG compression "quality": "high", "low"
In the composite mosaic below, the tiles taken at an overall frame pixel size of 12 Mpx are at original camera resolution; the tiles taken at an overall frame pixel size of 8 Mpx have been upsized (a factor of 1.22) to a consistent pixel size for presentation. There is no doubt some loss of comparability by so doing.
There are not really any surprises here.
Note that with regard to the matter of the JPEG compression "quality", this scene excerpt is not best for showing the impact of compression artifacts.
Best regards,
Doug
