Contest requirements confusion: pixels vs. DPI

Started 2 months ago | Questions thread
edispics Veteran Member • Posts: 3,894
Re: Contest requirements confusion: pixels vs. DPI

Philip Eihuyar wrote:

SunfyreArt wrote:

Hi everyone!

I'd soon like to enter my first photo contest, but their requirements confuse me a bit:

They want a JPEG image, one side of which needs to be at least 4500 pixels, and its DPI needs to be 300. The winners' photos will be displayed either on a screen or printed at 50 cm x 75 cm or 100 cm x 150 cm.

I know it's possible to change a photo's DPI value without changing its size in pixels.

So, is that really all they want? A garden-variety 72 DPI, (for example) 6240x4160 pixel photo whose DPI has been changed to 300? Ô_o

Thank you!

I hope I can answer this actually not too complex question. The requirements of your image must be 4500 pixels of width per image and 300 dots per inch when printed. The dots per inch are refering to the printer's laying down of microscopic dots of ink of the printed image. The pixels width is for the width of the printed image for instance 13 inches wide or 17 inches wide.

If your image is of a smaller pixel count than required, you will just go into an image editing program and upsample the image to the required 4500 pixels width. Downsample if you have too many pixels.

Downscale? OP says AT LEAST 4500 which usually means 4500 or more, no downsampling required.

The image length will automatically be scaled to fit. Then, when you or they print the image in your or their printer to whatever size paper you choose, the requirements will be met.

What requirements. The only stated requirements are at least 4500 pixel width and an internal EXIF data element of 300 dpi in the submitted jpeg file.

OP clearly states he is asked to submit a file, not a print. OP clearly states that the contest organizers will print the winning photo in one of two sizes.

Canon printers natively print at 300 dpi (Dots Per Inch) Since they specify 300 DPI, they probably have a Canon printer (Epsons printer natively print at slightly higher dots per inch -325 dpi I think)

The target sizes specified by OP are 20 by 30 and 40 by 60 cm and there is no requirement for the submitter to upsample to the native print resolution at that target size. The requirement is simply to submit a file with a minimum width specified in pixels.

Native print resolution for Canon is 300/600 and 360/720 for Epson.

BTW, Pixels Per Inch is abbreviated as PPI. If you are printing from an Epson printer, just check with the the hosts of the contest.

OP clearly states that contest will print winners, contest is not requesting prints.

You should have no problem with these simple rules. Just remember DPI= dots per inch (printer) and PPI= Pixels per inch. Choose how large you want to print out your image and you are set.

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