Photo filesize

  Birder 1 21:29 29 Oct 2005

How in Photoshop CS do i change the above to 300 DPI

  cycoze 23:12 29 Oct 2005

click on the "image" tab at the top of the screen, click on "image size" in the new box look for resolution, default is probably 72, change it there.

Be warned a 2.5mb file will jump to approx 46mb doing this.

I dont really understand why you want to do this ? i assume maybe you think it will give better printing results, it wont affect the digital resolution.

Have a look click here for an explanation and screenshot of how to do it.

  DieSse 23:46 29 Oct 2005

When in the computer, in the real sense a photo does not have dpi - it just has d. By which I mean it just has a number of dots wide x a number of dots high.

For instance, if a photo has 300dotsx150dots and you zoom it on the screen or to print as 1"x0.5" then it's 300dpi - but if you zoom it to 2"x1" then it's 150dpi - but it's still the same photo with the same actual number of dots!

You start of by mentioning file size - then go on to talk about dots. They are different things - you can make a smaller file size via compression of the data - this doesn't affect the number of dots. On the other hand, if you reduce the number of dots, you will also reduce the file size!

So it all boils down to what you are trying to achieve - and why.

Can you be more specific please.

  Birder 1 07:52 30 Oct 2005



I am trying to send a photo to a photographic library, it states the filesize as being 300dpi.

  DieSse 10:25 30 Oct 2005

"filesize as 300 dpi" has no meaning - it's a bit like saying "collar size 4 grammes" :-))

Ask them what actual size they want, in terms of dots x dots - or if you can post a link to the site we'll have a look for you and/or ask the question of them.

  cycoze 12:41 30 Oct 2005

"dpi" stands for "dots per inch", where the dots are the building blocks for a printed colour photo. Usually one pixel equals one dot. so a 300 pixel wide photo will only be one inch wide when printed at 300 dpi (standard publishing format).

"dpi" is a standard and non-metric term in photo printing. To convert it to centimetres remember that 1 inch equals 2.54 cm. So, 300 dpi equals 300/2.54 dots per cm, or 118 dots per cm.

  David4637 13:32 30 Oct 2005

You should really refer to picture size as say 6x4 inches and with a resolution of say 300 pixels per inch. This equates to 1800 pixles wide by 1200 pixles high. Usually printers are referred to as printing so many dots per inch. You need to understand what is in the first instant quite a complex subject. David

  Birder 1 13:56 30 Oct 2005

Thanks to you all

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