brook

When I take a picture with my digital camera in a format for example of 2832x2128. Isn?t it true that at this point the picture is just a series of horizontal pixels times the vertical pixels and the concept of dpi comes into play only when you are looking at the picture on a medium such as a monitor (72dpi) or printed photo (300dpi). So until it is observed on a medium there is no such value of dpi assigned to the jpg photo. Is that true??

Bacardi

see my answer in the "new" forum.
A puter can only remember ones and zeros, on and offs. So to remember something like a photograph, it needs to be chopped into little pieces calles "picture elements" or "pixels". Indeed: you get something like a mosaic or a grid, and the puter can remember that the fifth element on the seventh line should have these specific intensities of red, green and blue light to build up the colour needed.
(Vectors are another approach, but that's beyond the scope of your question).

brook

OK this might sound like a real rookie response but I will ask it anyway. When somebody says they took a digital photo at say 100 dpi what are they basing that on? How do you take a 100 dpi or a 200 dpi digital photo? My camera has no settings to choose dpi.

wbiss

brook... go back to your original question http://www.photoshopgurus.info/forum...pic.php?t=2917 and you will find the answer!

Again, 72 ppi (forget the dpi) is the "standard" resolution for digital cameras. Yes, you and your friends can increase the ppi, but you will have to decrease the image size to do so!

brook

Thanks, great explanation. I didn't read your other post yet so thanks for pointing me to it. I looked all over the web but you're the only one who finally said the magic words "72 ppi is the STANDARD resolution for digital cameras", thank you.

My digital camera manual (fugi finepix 6900) doesn't even mention 72 ppi or how to change it to other higher resolutions. It only tells about the width and height from various megapixel settings, i.e. 3M gives you 2048 x 1536.

retired_paddza

Your original supposition is basically correct. If you look at the acronym DPI... dots per inch. Right after you take a picture all you have is the "dots" portion... the pixels. There are no measurments imposed on the image until you need to deal with something that uses inches... most commonly a printer. The "standard dpi" of 72 is simply imposed on the image because when it goes into the computer, it will need that information if you were want to print it or open it in photoshop or something. It doesn't make any difference because you are simply dealing with a finite number of pixels. So if you have 72 pixels wide at 72dpi it would be... one inch. If you had an image 1280 pixels wide at 72dpi it would be about 17 inches. The actual pixels are what determine how much actual data is recorded into that "grid". The DPI is just used for output.

Hope that didn't ramble too much ...$0.02 :B

ladyfinger007

Yes, to echo MB there is no resolution on a digital camera file , the image editing program attribute 72dpi by default (see the other thread for the why)

-in fact the only resolution could be the one of the sensor (divide the number of pixels by the sensor size) but even with that, the camera electronics sometimes makes an interpolation to give a given amount of pixels...

BioScanMan

I believe digital camera images are tagged 72 dpi (ppi) since that is the common monitor resolution. The EXIF header tags it at the time of exposure. Most photographers I know shoot at the highest possible camera setting (5 meg. +) so they have as many pixels as possible to work with.

brook

So when I take a digital picture I basically have a grid (or mosaic as Erik says) of pixels horizontal times vertical. If I view those pixels on a 72 ppi (or dpi) monitor then it would default to 72. What if the resolution of my monitor was 96 ppi? I guess the image resolution would default to 96 ppi. Can somebody tell me how to get those pesky pixels to the printer with the least amount of damage to the pixels? Is it better to size them in the PS Image Size dialog box or should I just go to the printing software properties for my HP printer and select "best" output? This is assuming I'm not making any changes to the size of the photo and I'm printing at a 1:1 ratio.

BioScanMan

The image is still 72 ppi. That is what the camera has tagged the file as.

I would never use printer software to resize an image. Photoshop is very good at resizing images at its default settings.