Wednesday, 28 July 2010

Photo Information

I have a Fuji compact digital camera which I have always been happy with. I recently noticed that even when I take images at the highest possible quality setting when I went into Photoshop it indicated that the image was 72 dpi. There are times when I need to take my own high res images for The Crafter's Way so I contacted Fuji to find out what I was doing wrong. The response was unbelievably quick and easy to understand. I thought it might also  be useful to others so ihave posted their response here.

Most digital cameras use pixel resolution as a standard unit of measurement (PPI – Pixels per inch, Hence example:6 Mega Pixel = 6 Million Pixels) rather than DPI (Dots Per Inch, relative to printer values, most Minilab printers will print photographs at 300 DPI).

Although programmes like Photoshop have a preset that usually displays the DPI may at 72, that is only display presentation of the image to allow the software to optimise it’s graphics memory when displaying the image on screen at a faster rate.

The 72 DPI, is not a true indication of the image resolution and you would find that the pixel resolution based on the file size relates to the PPI content of your photos, which would be large enough to print images at a higher DPI (default standard of photographic lab printers is currently set at 300 DPI).
I have included information below regarding further information about pixel resolution and DPI.

To get an idea of the DPI that can be used and what print size will be achieved, simply divide the pixel dimension by the desired DPI. For example, take a photo with a pixel resolution of 1800 x 1200.1800 divided by 300 (DPI) equals 6 inches. 1200 divided by 300 equals 4 inches. Therefore you can obtain a 6x4 inch photo print at 300 DPI quality from a 1800 x 1200 photo.

72 DPIon a 6x4" photo = 432 x 288 pixels.

300 DPI on a 6x4" photo = 1800 x 1200 pixels.

300 DPI on a 8x12" photo = 3600 x 2400 pixels.

300 DPI on a 10x15" photo = 4500 x 3000 pixels.

Please click on the link above to view an Image Resolution Guide, readily used by our department.

'Base' is a unit of measurement that is used with digital film scanning. Here is a guide to how the units work.....

1 Base = JPG 1MB when open, approx 200kb when compressed/ closed ( 72 DPI @ 6x4 inches ) 420 x 280 pixels.

4 Base = JPG 6MB when open, approx 1MB when compressed/ closed ( 300 DPI @ 6 x 4 inches ) 1800 x 1200 pixels.

16 Base = JPG 22MB when open, approx 3MB when compressed/ closed ( 300DPI@ 8x12 inches ) 3600 x 2400 pixels.

32 Base = JPG 39MB when open, approx 5MB when compressed/ closed (300DPI@ 10x15 inches) 4500 x 3000 pixels.

Many labs can scan these as uncompressed files such as Bitmap or Tiff.
Some third party software packages (something like Adobe Photoshop) offer the ability to magnify your photos and crop or trim areas. For best results use the highest resolution available for your camera (2 megapixels).
A camera that is capable taking a 4 megapixel image has the pixel dimensions of approximately 2400 x 1800.
To get an idea of the DPI that can be used and what print size will be achieved simply divide the pixel dimension by the DPI.
For example the maximum DPI for a normal print is 300; 2400 divided by 300 equals 8 inches and 1800 divided by 300 equals 6 inches. Therefore you can obtain a 8" x 6" print from the camera at 300 DPI. An approx guide would be:

1 megapixel (effective megapixel 1.2) = Image resolution 1280 x 960

2 megapixel (effective megapixel 2.0) = Image resolution 1636 x 1236
 As digital files (such as .jpegs) taken by digital cameras do not match the aspect ratio of standard print sizes. Faced with this, our printing labs can choose to enlarge the image to fill the print entirely (but cropping some image area at the same time) or leave a white border on 2 sides and give you the whole image.
The width divided by the height of an image or "aspect ratio" is usually expressed as two integers,
e.g. width/height = 1.5 is expressed as width:height = 3:2.
3:2 aspect ratio of 35mm film, 4:3 aspect ratio of most computer

6"x4" prints, and most digital SLRs monitors and digital compact cameras

 Hope you find this as useful as I did. Now I just have to come up with another reason why I take such lousy shots.

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