DPI Question

[DMCdigitalmedia]

Hello ,

I have a Sony F828 and even on RAW settings the image says it is 72 DPI,yet my old Nikon shoots at 300 DPI one of my customers said the Marketing department is rejecting the 72 DPI photos. What gives..the 72 DPI look great and are HUGE files...quality appears better than the Nikon ..it is just the DPI number I dont get.

[goose443]

DPI in and of itself isn't going to tell you much about the image. It's DPI in relation to the size of the image that's important (among other things). If you have a huge 72DPI image you can easily resize to a 300DPI image while reducing the size propotionately. This will not affect the quality of the images but it will give you a much higher resolution file (at a much smaller image size). As far as I know most digital cameras shoot at 72 DPI but the number of pixels that make up the file can be quite huge.

[edgework]

Originally Posted by DMCdigitalmedia

Hello ,

I have a Sony F828 and even on RAW settings the image says it is 72 DPI,yet my old Nikon shoots at 300 DPI one of my customers said the Marketing department is rejecting the 72 DPI photos. What gives..the 72 DPI look great and are HUGE files...quality appears better than the Nikon ..it is just the DPI number I dont get.

In the Image Size dialogue, turn Resample Image off. Then set the resolution to 300 dpi. Your image will shrink from poster-sized dimension down to photograph dimensions. Same pixels, just more packed into a given space.

[studioj]

Ok, lets be more graphical on this.

You need a software to resize your images. It really does not matter wich number gives you the digital camera, the finished picture it's the important.

I suggest photoshop to edit the size, and I know two ways, bought really fast.

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The first it's IMAGE SIZE, you will find a dialog box called "RESAMPLE IMAGE", turn it off as I show in the first attachment, next change the 72 DPI value to 300. In my case, an image that was 60.59 cm wide, now it's only 14 cm.

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The second option it's use the crop tool (showed in the right corner of attachment 2), clear the first 2 values, and just put 300 on the DPI, then hold click from a corner to the other to make a square of your picture, this will give you a 300 dpi pic.

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Save and that's all

[Gary Richardson]

The important thing is number of pixels in your image. eg a 3Mpixel picture will be approx 1500x1000 pix in size.

The dpi (should properly be named ppi(pixels per inch)) only indicates the density of the pixels. The higher the number, the denser the pixels, and hence the sharper the picture.

However, as your overall image size is fixed (1500 x1000 in this case), the larger the PPI, the smaller the picture size.

If PPI is 300, then picture size would be 1500/300 x 1000/300 = 5 x 3.33 inches
If PPi is 150, then picture size would be 1500/150 x 1000/150 = 10 x 6.66 inches

So as you can see, the same image file can produce pictures of varying size. As you may imagine, since you have a fixed number of pixels (set by camera settings and CCD size), as the picture size increases, the pixels get further and further appart, and the picture quality gets poorer and poorer.

For most printing, a pixel density of between 250-300 PPI is considered necessary for good results.

Note: PPI = pixels per inch, and is the number of pixels found in each linear inch of your image.
DPI = dots per inch, and is used by printers to indicate the number dots printed per inch by your printer. Printers may print many dots for each pixel of image, so there is no direct correlation between DPI and PPI.