DPI for jpeg

[indigenous]

I just got a D200 and i am shooting at the biggest jpeg file, uncompressed, and at optimal quality. When i open the profile in PS the file only has a dpi of 75. Is this correct? am i doing something wrong? I know that RAW is a bigger file and it has a dpi of 300, but is the largest jpeg file really that far behind?
Is there anything i can do to improve the jpeg quality?

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[Mohain]

It doesn't matter what frequency your image is, it matters what the overall pixel width is. e.g. a 3872 px image will print at 13" wide at 300DPI. If you want to print at 200DPI then you will be able to print 19" wide, etc, etc ...

[Big Mike]

DPI (Dots per inch) is a printer setting.

PPI (Pixels per inch) is used to size an image on the screen. As mentioned, what really matters is the actual size of the image...measured in pixels.

A large JPEG and a RAW file should be the same size (in pixels)...but the file size should be different.

[Digital Matt]

DPI is the last step in printing, and it tells the printer how close to print the dots together.

Pixel Dimension / DPI = Size in inches.

A 300 x 300 jpg will print at 1" x 1", at 300 dpi, or 4.16" x 4.16" at 72dpi.

[indigenous]

so what should i print an 8x10 at to get the best possible image? should i even change the dpi or just the size of the image in PS?

[Big Mike]

When I make an 8x10 print...I set the size to 2400x3000 pixels.

Here is a tip...you can use the crop tool in PS. When you activate the crop tool, you can set the aspect ratio and 'resolution'. 4x6, 5x7 & 8x10 (@ 300 PPI) should all be presets that you can select from the drop down.

Then when you crop the image...it is set to the correct aspect ratio and size for printing.

[indigenous]

i guess i was used to scanning film, when it asks you what dpi you want it scanned @.
when you shoot do you use jpeg or raw? i noticed raw images were preset @ 300 dpi when i open them and jpeg @ 72. i guess it just threw me off.

[Big Mike]

I shot either large/fine JPEG or RAW....RAW mostly.

i noticed raw images were preset @ 300 dpi when i open them and jpeg @ 72. i guess it just threw me off.

Don't feel bad...people have been getting confused about this for several years. It's just a number...You can change the PPI setting to 10000 if you want...it won't change the image (unless you resample it).

[markc]

Even resampling doesn't help all that much. There is some argument to that, as some people suggest resampling up in steps to get a better prints, but when it comes right down to it, you can't add data. Use the original size to help determine if the pixel x pixel size is large enough for the inch x inch size you want to print at. You can experiment for yourself to see if resampling up will actually give you a better print on your equipment. A lot of the times it just makes for a larger fille.

[Big Mike]

Good point...and if the image you want to print, is larger than your pixel size/300...you can still get a good image. 300 PPI is just a standard number. Some people print from 240 PPI etc. It's up to you to decide what is acceptable to you.

[Digital Matt]

Check with your printer before you go sending images less than 300 dpi. A lot of photo printers print at 300 dpi.

[indigenous]

The printer is cool, ive been useing it for a while. This is just my first expedition into digital photography. I guess ill just shoot raw images. I liked the fine jpeg, but raw just looks sharper, less images per memory card, but better quality.

[markc]

Check with your printer before you go sending images less than 300 dpi. A lot of photo printers print at 300 dpi.

That's where the DPI vs. PPI confusion comes in. Even though Photoshop and other software say DPI, they mean PPI. It's the number of pixels that are printed per inch. When printers use DPI, they mean actual drops of ink. Most times, unless you print really small, a single pixel will take many drops to print.

If you have a 900 x 900 pixel print, and print at 100 PPI, it will make an image 9" x 9". If you print using 300 DPI on your printer, the image will be 2700 x 2700 ink dots. Each pixel will be printed using 3 dots x 3 dots each (with some overlap depending on how the driver handles dithering, etc.).

DPI setting for the image (really PPI) is really only there to help you figure out if the number of pixels you have is going to be good enough for the number of inches you've chosen. The diver will handle how many DPI the printer actually uses. 300 DPI minimum and 300 PPI minimum are both good general numbers to go by. Better PPI in the image will give you more detail as long as the printer DPI is as high or higher than the PPI. Higher PPI will allow the printer to make better use of the driver's dithering to blend colors and make it so you won't see individual ink dots.

[indigenous]

well when i open the jpeg in PS it says the image size is roughly 32x39 and 75 dpi. if i changed this to lets say 11x14 would the quality be good.

[Digital Matt]

Mark, lots of printers require that the PPI be set in the file to 300, and that is what they refer to when creating the size of the image. We have a dye sub at work that works this way, as does the Noritsu at the lab we use.