 Atul N. Kanetkar |
Resolution of Digital Camera! Digital cameras are classified on their Mega Pixel basis but nowhere their Resolution in terms of Pixels / Inch is mentioned. Do all Digital cameras shoot at same resolution of Pixels /Inch? Pictures taken with Canon Powershot A95 have resolution of 180 Pixels / Inch. But I have heard that for printing Resolution of 300 Pixels or dots per inch is preferred. So a good camera should have higher resolution, isn’t it? Can you throw light on this issue? Also in the camera, there are various settings for compression like Superfine, Fine and Normal for a given Image size ( say 1600 x 1200 ). But images taken with these three settings all show their resolution at 180 pixels / inch. But still their memory size is noticebly different! So what exactly happens with these settings? When we increase the resolution value in Photoshop, what are the implications? Does it really enhance the picture quality? As far as enlargement possibilities with a particular MP camera are concerned, this Resolution factor should be of vital importance. But nowhere reviews of cameras emphasize this aspect? So is this really an important aspect of digital photography?
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John Rhodes |
Atul, DPI or PPI is a print measurement, not a measurement of your camera's sensor. John
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Christopher A. Vedros |
That's right. Your camera doesn't know what an inch is. Shoot in SuperFine and the lowest compression and don't worry how many pixels/inch the image says it is. This will be the best image your camera can shoot.
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robert G. Fately |
Actually, Atul, there are two concepts regarding resolution in digital imaging. The one most folks think about has to do with dpi for printing purposes, and yes, for printing usually about 300 dpi is preferred (but there is a wide latitude in that arena). The other issue is the true resolution of the chip itself. WHile it is certainly true that a camera doesn't "know" what an inch is, and that it's best to use the highest possible pixel count offered by the equipment at hand, there is a true resolution, if you will, for the chip. Think of this - imagine 2 CCDs, both 1 inch square. CCD #1 is a 5 megapixel chip, and CCD #2 is a 20 MP chip. Obviously, #2 has a higher native resolution - it fits twice as many pixels in the same inch as #1. So, if your question pertains to the second point, then you are correct, manufacturers do not print out the resolution of their chips on spec sheets. However, often on sites like dpreview.com the reviewers point out the physical sie of the taking chip and the matrix dimensions (pixels high by wide) so you can do a rough calculation on your own. And, all else being equal, the #2 chip will produce more data for the scene at hand, and most likely a better ability to produce a larger print. The potential downside to cramming more pixels into that 1" square is that as the individual "light wells" become smaller, they are more susceptable to "noise", random electronic blips created from heat (and the more cramped chip space is inevitably hotter). SO, like much in life, there's a compromise to be made. As for the way the camera records the image, this is altogether a different issue. Basically, that 1600x1200 image is what it is. The 180 dpi is merely a convenience set by the manufacturer - digital image formats like jpeg include data such as image size and "final"resoution. But regardless of what those settings are, you can always change them using editing software (like photoshop). So, that 1600x1200 image calculates out to a 5.3 x 4 inch print at 300 dpi, right (just divide each side by 300). But if you change the recolution to 200 dpi and maintain the exact same number of pixels, then the print suddenly grows to 8x6". And 200 dpi isn't all that terrible for printing purposes. The other thing to know is that digital images upsize very well - that is, software can "enlarge" a digital image without introducing artifacts. SO I hope that helps clear up what can be a quite confusing set of issues...
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Atul N. Kanetkar |
Thanks to all of you for your feedback. Bob has explained it very well. I hope this will help me to understand and raise further questions!
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