D40 dpi Issue

[LemhiRG]

Hi everyone,

I have a Nikon D40, and recently noticed a peculiarity. Without changing any settings (I promise), it will take some sets of pictures with 300dpi quality, and others in 72dpi. I only want it to take in 300dpi. I am not shooting in RAW (too much time to edit the majority of my photos), but instead in JPEG fine. Is this something to do with the camera, or perhaps in the way I import them? I generally copy files from my SD card right into a folder on the computer, and use Fotostation to catalog/key them before editing in Photoshop Elements 5.

Thank you!

Sara

[Codebreaker]

You don't actually take images with any DPI settings. All you capture is a number of pixels. DPI or PPI settings are only relevant when you want to achieve a specific physical size, such as when you go to print. Until that time you are working entirely with Pixel Dimensions.

Now it just so happens that in the EXIF data fields there is an entry for a DPI setting. For Digital Cameras this is purely a recommendation and whatever the manufacturer decides upon. If there is no entry then the default is 72PPI.

It's real use is for electronically scanned documents, for example, which finish up as a number of Pixels. To get it to reproduce at the same physical size as the original the scanning DPI would be included.

The magic formula is :-

Pixle Dimensions / Resolution = Physical Size

Hope this helps

Colin

[Grant]

Sara

Are you sure it is the D40 changing you DPI and not your software? Because unless you are printing directly from the camera DPI is meaningless.

--

[LemhiRG]

Hmm, okay. So I guess that leads to the question, what do I do about it? Are you saying there isn't a quality difference between one that is marked as 300 ppi in Photoshop, compared to one marked as 72 ppi?

I feel like there is a difference in quality, but I could be imagining it. I also can't figure out why some are coming up as 300, and others as 72.

SS

[RobertSchuldenfrei]

Hmm, okay. So I guess that leads to the question, what do I do about it? Are you saying there isn't a quality difference between one that is marked as 300 ppi in Photoshop, compared to one marked as 72 ppi?

I feel like there is a difference in quality, but I could be imagining it. I also can't figure out why some are coming up as 300, and others as 72.

SS
Hi,

As the above comments indicate it is not the D40. I use the Nikon supplied PictureProject program to move the images from my D70s to the computer. It always sets the DPI to 300. If you vary the moving program, like you might use PSE to download the images, your ppi could be set by that program. If you read the memory card directly, that will have an influence on the ppi.

How do you transfer your pictures?

Hope this helps,

Bob

[Codebreaker]

There is no difference in quality of the image you have taken. You have still captured the same number of Pixels.

Let's for example assume you have a 6Mpixels camera which produces images of 3000 x 2000 pixels. Marking these as 72, 300, 1024 or whatever PPI makes no difference to the source image - it's always 3000 x 2000.

Now let's assume you want to print this.

If you want to print a 6 x 4 then the resolution will be 500PPI

3000/500 x 2000/500 = 6 x 4.

If you want to print at 10 x 6.67 then the resolution is 300PPI

3000/300 x 2000/300 = 10 x 6.67

Pixels Per Inch or PPI (often confused with DPI) is a physical dimension - your camera has no concept of the physical size of the resulting image. That's for you to decide when you print or display it.

Colin

[LemhiRG]

Thanks everyone, I have at least figured out the source of my problem.

If I download to my computer, then open in Elements, ppi stays 300. If I download to my computer, open in Fotostation Pro and catalog the photos, it automatically converts them all to 72ppi. So it must be something with Fotostation Pro, and luckily not my own idiot self. :)

Thanks everyone!

Sara

[Codebreaker]

Sara....

Please understand - nothing is converting your images. You still have the same number of pixels you started with and that's the only important thing.


Colin