# Converting image to 300dpi



## ir0n_ma1den

So I just got an email saying that I am a finalist in the Fotoweek DC youth contest!

They are requesting a 300dpi file, so how can I find out if an image is 300dpi, and if not, how can i convert it to the format?

this is urgent,

thanks!


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## Rekd

300dpi is not really a format. It's a measure of pixel density. Depending on the software, image/resize/300 in the DPI box without resampling where you usually find 72 then resize it to the size the paper wants.


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## ir0n_ma1den

According to Bridge:

3812 x 2493

3.46MB

72ppi


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## creisinger

In Photoshop goto:

"IMAGE"

"IMAGE SIZE"

UNCHECK "RESAMPLE IMAGE"

Type in 300 in the "RESOLUTION" field

Click "OK"

Now you got yourself a nifty 300dpi image. Same pixel dimensions though - so technically completely useless...


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## battletone

They probably just put that so they don't end up with a 600x800 image.


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## KmH

For photography there actual is no such thing as DPI (Dots Per Inch, _Dots are round_), it's PPI (Pixels Per Inch, _Pixels are square or rectangular_). This is *the* biggest faux pas in photography today.

Today, DPI only applies in the pre-press industry and ancient dot-matrix printers. 

Plus, ppi/dpi is meaningless unless an image is going to be PRINTED. :thumbup:

For web use or display on a monitor the only numbers that matter are the pixel dimensions. 

From Wikipedia:

"
*[edit] DPI or PPI in digital image files*

*DPI* refers to the physical dot density of an image when it is reproduced as a real physical entity, for example printed onto paper, or displayed on a monitor. *A digitally stored image has no inherent physical dimensions*, measured in inches or centimetres. Some digital file formats record a DPI value, or more commonly *a PPI (**pixels per inch**) value, which is to be used when printing the image*. This number lets the printer know the intended size of the image, or in the case of scanned images, the size of the original scanned object. *For example, a **bitmap** image may measure 1000×1000 pixels, a resolution of one **megapixel**. If it is labeled as 250 PPI, that is an instruction to the printer to print it at a size of 4×4 inches*. Changing the PPI to 100 in an image editing program would tell the printer to print it at a size of 10×10 inches. *However, changing the PPI value would not change the size of the image in pixels which would still be 1000×1000*. An image may also be resampled to change the number of pixels and therefore the size or resolution of the image, but this is quite different from simply setting a new PPI for the file."


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## creisinger

battletone said:


> They probably just put that so they don't end up with a 600x800 image.



... but at least it's 300 dpi...


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## Dwig

creisinger said:


> ...
> Now you got yourself a nifty 300dpi image. Same pixel dimensions though - so technically completely useless...



Actually it can be very useful.

If the image is to be imported into a page layout or illustration application (e.g. Abobe's PageMaker, Indesign, or Illustrator or Quark Xpress, or the old Macromedia FreeHand) having the image tagged at 300ppi will result in the application placing the image on the application's virtual page scaled at 300ppi by default. This saves resizing later in many situations. 

Its most useful, though, when the image is also resized to a particular linear size at the same time. If you resample to, say, 4x5" and 300ppi these applications will place the image on the page at 4x5" by default and the resulting image will reproduce in the final piece at the desired 300ppi if no further scaling is done.


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## Plato

ir0n_ma1den said:


> So I just got an email saying that I am a finalist in the Fotoweek DC youth contest!
> 
> They are requesting a 300dpi file, so how can I find out if an image is 300dpi, and if not, how can i convert it to the format?
> 
> this is urgent,
> 
> thanks!



Dots _per inch_ (dpi) or pixels _per inch_ (ppi) are completely and totally meaningless values unless you know the inches of the printed photo.  Whatever dot sized photo you have can be alleged to be 300 dpi IF you define the inches accordingly.


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