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Photography Question 
Karen Slagle
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member since: 4/1/2005
 

D-SLR vs. Compact Digital: Image Quality


I have a Nikon D200 and a Canon Powershot S5 IS. The D200 image size is 12.907 inches by 8.64 inches at 300 ppi. The Canon's image size is 18.133 inches by 13.6 inches at 180 ppi. When I downsize the images from the Canon to 12 inches by 9 inches at 272 ppi, the quality is not as good as the D200. Why is there a difference in quality?

P.S.: I also have a Nikon D70 and it also has better image quality than the Canon. The D70 is 6.1 megapix and the Canon is 8 megapixels. Thanks in advance.

10/16/2007 8:19:35 AM

 
Jon Close
BetterPhoto Member

member since: 5/18/2000
  The D-SLRs have better image quality because they have much larger digital sensors. The sensors in the D200 and D70 are 23.7mm x 15.6mm, while the sensor in the S5 IS is a tiny 5.93mm x 4.46mm. Even at the same or fewer total megapixels, the larger sensors will capture greater dynamic range with far less digital "noise".

10/16/2007 8:29:23 AM

 
Karen Slagle
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member since: 4/1/2005
  Oh I see now. Thank you so much for the answer, Jon.

10/16/2007 8:32:47 AM

 
John G. Clifford Jr
BetterPhoto Member

member since: 8/18/2005
  The larger sensor is part of it, but also the image quality is not directly correlatable with pixel (photosite) count.
First, if you're making a print, always set your print to the printer's native resolution, or an evenly divisible portion thereof. For instance, I have an Epson R300 that has a native resolution of 720 dots per inch (dpi). I generally print at 360 dpi and will down- or up-rez my image to get the pixel count I need. I use bicubic sharper for down-rezzing, and (preferably) Lanczos or bicubic smoother for up-rezzing. (You don't want to use bicubic sharper for uprezzing because it adds sharpening artifacts that get very visible as you resize.)
Another factor with the small-sensor digicam is that the lens is diffraction-limited at a much lower aperture than on a D-SLR. Your D200 is diffraction-limited between f/11 and f/16, while your Canon digicam is diffraction-limited by f/5.6!
The third factor is the quality of the lens. A good D-SLR lens (not the "kit" lenses that many D-SLRs ship with) provides a very high-quality image that is noticeable on larger prints.
When printing at 4x6, I can't tell a difference between my 6 MP Fuji F30 and my D-SLR. Once I get to 5x7 the difference is there... and it is really apparent on an 8x10.

10/16/2007 12:40:20 PM

 
Karen Slagle
BetterPhoto Member
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member since: 4/1/2005
  Thank you John for your enlightening answer. So much to learn and so little time. I appreciate your taking the time to respond to my question, learned something new. Karen

10/16/2007 2:00:35 PM

 
Amanda D. Austwick
BetterPhoto Member
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member since: 8/2/2003
  Hi John C., I use a Nikon D2x and Ps CS2. What does a bicubic sharpner for down loading mean, and a what is a Lanczos smoother?
Thanks,
Amanda A.

12/5/2007 4:16:15 PM

 

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