Dots per inch

[4Lmike]

It seems as though jpeg images come off my camera (D5000) with 300dpi but the RAW images only seem to have 240dpi. Can anyone explain this?

[flat-planedCrank]

I would imagine that the raw dpi is being assigned by whatever you are using to process them?

It doesn't matter at all of course, dpi is basically just 'metadata' unless you actually print it. You can create a 10 pixel by 10 pixel box and set it to 300 dpi or 3 dpi - it's the the 10x10 resolution that matters.

Applications like Photoshop can change the dpi in your image in a fraction of a second, no real processing to be done

[4Lmike]

My CameraRaw isn't working at the moment so I'm using Adobes DNG converter, but I think it was still 240dpi when I used CameraRaw.

Doesn't increasing the dpi in photoshop to a dpi above what it originally had have a negative effect on the quality of the image? I'm sure I heard that somewhere.

flat-planedCrank said:

It doesn't matter at all of course, dpi is basically just 'metadata' unless you actually print it. You can create a 10 pixel by 10 pixel box and set it to 300 dpi or 3 dpi - it's the the 10x10 resolution that matters.

I am thinking in terms of printing. I realise 240dpi is still good enough for printing but a lot of places are picky and say it must be 300dpi.

Edited by 4Lmike on Friday 11th March 18:54

[GetCarter]

What FPC said. It only matters when you print it, and then it only matters how far away you stand when you view it.

It's just a question of information. The more, the merrier.

[Simpo Two]

You can make an image any DPI you like - the canvas size just changes. Double the DPI, halve the image size. No difference.

[flat-planedCrank]

4Lmike said:

My CameraRaw isn't working at the moment so I'm using Adobes DNG converter, but I think it was still 240dpi when I used CameraRaw.

Doesn't increasing the dpi in photoshop to a dpi above what it originally had have a negative effect on the quality of the image? I'm sure I heard that somewhere.

flat-planedCrank said:

It doesn't matter at all of course, dpi is basically just 'metadata' unless you actually print it. You can create a 10 pixel by 10 pixel box and set it to 300 dpi or 3 dpi - it's the the 10x10 resolution that matters.

I am thinking in terms of printing. I realise 240dpi is still good enough for printing but a lot of places are picky and say it must be 300dpi.

Increasing the DPI in photoshop doesn't effect the quality in any way

Quick example:



One of these images is 300dpi, the other is 3dpi - they are the same image.

The image is essentially a series of values for the colour of each pixel (or dot) - DPI is basically just a number stored with that image to tell printers how many of those dots to cram into an inch. So changing that value doesn't actually effect the quality of the image.

If you want to change the DPI of an image in photoshop: Image Menu - Image Size - Untick 'Resample Image' - Change the DPI value to whatever you want - Press OK.


Hope this helps

[4Lmike]

Thanks FPC