How do I know if my digital camera (7.3 megapixels) tales photos 300 dpi?

Answer 1

It's complicated..

Digital cameras have a megapixel (MP) spec. This defines the highest resolution of the image captured by the CCD. For example a 5 MP camera will capture a 2560 X 1920 pixel (picture element) image. As an aside, digital cameras will usually allow several smaller image sizes to be captured (set via a menu setting) which will provide a lower resolution image so more of them can be stored on the memory card. Suffice to say, for any camera there is a maximum image size (pixels wide x pixels high) that can be captured.

As another aside, to save storage space cameras also usually allows one or more levels of "compression" to be specified for images in JPEG format. This doesn't reduce the number of pixels (resolution) but uses technique to store the image in a compressed format ... which beyond a certain point introduces noticable degredation to the image. This is the "fine" or "normal" setting you will see on a menu. If you plan on printing always use "fine".

Ok .. that's it for capturing and storing the image.

Where the confusion over 300 dpi (dots per inch) comes in is that this spec relates not to capturing, but to displaying or printing the image. A stored image will be displayed/printed at whatever dpi the display/print device is capable of (or set to), but the physical size of the displayed/printed image will be determined by the dpi of the device.

For example a computer monitor may be set at 72 dpi and on such a diplay the 2560 pixel wide image assumed above would be over 35 in wide, but if printed at 300 dpi would be only 8.5" wide.

The bottom line is dpi relate to display / printing, while pixels relate to image capture. The relationship between image resolution (pixels) and physical size (display or print) must be calculated using the formula: size (inches) = # pixels / dpi

Clear as mud, huh?

For another explanation see the article at the link below.

Bottom line: any camera can yield images printable at 300 dpi, but the physical size of the image printed will be directly proportional to the MP rating of the camera which took the picture.

Hope that helps.

Answer 2

The easiest way to find out is to take a picture.
Open the picture in Photoshop or Photoshop Elements.
Click on "Image" then "Resize" then "Image Size"
(Or use [CTRL]+[ALT]+[I] < Look at "Resolution" on the window that opens and it will show you what the resolution of the image is.

You can not control the pixels per inch in your camera, as this is a function of the sensor. I have found the following ppi for SOME cameras by the following manufacturers. I wonder if this specification is available anywhere. I have four camera manuals in front of me and I can't find it in any of them.

NIKON - 300 ppi
CANON - 180 ppi
PENTAX - 72 ppi

We "discussed" this by way of question and answers a while back and decided that the ppi file produced by the camera really did not have any effect on the capability to produce a good print. If I take a photo with my wife's 6 MP Nikon and view the image on the screen, it will start out as 300 ppi. If it's a full frame image of 3008 pixels x 2000 pixels, the SCREEN image would be pretty big if I viewed it full sized, but it would print 10.0" x 6.6". If you crop a 5x7 out of this, keeping it as full-frame as possible, it becomes 400 dpi.

With my brother's 6 MP Pentax, the image is 2816 px x 2112 px, but it's at 72 ppi. If you print this without cropping, it would be 39" x 29"!!! If you crop a 5x7 out of this, though, it becomes 402 dpi resolution, which is virtually identical for the Nikon 6 MP camera.

With my son's 6 MP Canon Powershot A620, the image is 3072 px x 2304 px, but it's at 180 ppi. If you could possibly print this without cropping, it would be 17.1" x 12.8". If you crop a 5x7 out of this, though, it becomes 439 dpi resolution, which is a bit better than either of the other 6 MP cameras.

In other words, regardless of the sensor's pixel-per-inch output, 6 MP cameras produced the same resolution when it came time to print comparable images. How about a camera with more pixels?

If I take a photo with my 10 MP Nikon D200 and view the image on the screen, it will start out as 300 ppi. If it's a full frame image of 3872 pixels x 2592 pixels, the SCREEN image would be pretty big if I viewed it full sized, but it would print 12.9" x 8.6", if I had the right paper. If you crop a 5x7 out of this, keeping it as full-frame as possible, it becomes 516 dpi, or higher resolution than the 6 MP cameras. We knew that is would work out like this, though, didn't we?

The REAL question is, what difference does this make in the real world? If we agree that 300 dpi is an excellent resolution for prints, as long as you end up with at least 300 ppi after you are done cropping on the screen, you will get an excellent print as far as resolution goes. All four cameras exceed that amount. I usually resize "down" to 300 dpi before printing, because you can't tell the difference above that resolution anyway. Most people would be quite happy with a 200 dpi print, so go ahead and crop a bit. If you get a print resolution too much below 200 dpi, you will start to see digital artifact in the print and it will be objectionable.

Answer 3

When you take a photo using a 7 megapixel camera at full resolution mode, the number of pixels in generated photograph will have approximately 7 million pixels. If your camera had capabilities of generating a 12 megapixel photo, you can get a photo generated which will have 12 million pixels. Now you tell me can you use a software to increase a photo which has 7 million pixels ( dots ) to 12 million pixels?? Yes, it is possible but it will not add any value , unless you want a wall poster out of the photo. There will be no increase in resolution of the photo. Gotcha?

Answer 4

At highest quality setting, this camera should take photos at 3072 x 2304 pixels. You are probably asking about 300 ppi (pixels per inch), which is the professional print resolution. At 300 ppi, this image (7.3 megapixel) can print to size of 10.2 x 7.7 inches (little smaller than A4.) If you want to print a poster for yourselves, you may safely print at 190 ppi to get poster size of 16 X 12 inches.