Do I have to change number of pixels per inch while downsizing?

[bnnrcn]

My camera shoots with 300 ppi.When I downsize an image I change the dimensions but I don't touch number of pixels.1-Do I have to change it? 2-When or why do I have to change number of pixels per inch?3- If I think mahtematically lowering ppi gives larger images but decreases the image quality.Is this correct?4-Is it possible down size an image by increasing ppi and not changing the dimensions?

[davidedric]

Hi Binnur,

You don't need to change the ppi. Your camera doesn't really shoot in ppi, that is something that your pp software adds in. It means pixels per inch, and is only relevant when you display the image on a display device. Similarly, dpi, or dots per inch, is only relevant when you are outputting to a printer.

[bnnrcn]

Thank you Dave,our computer screens or websites are devices for displaying too,so don't we have to do anything with ppi while e-mailing an image or uploading an image to a website?

Hi Binnur,

You don't need to change the ppi. Your camera doesn't really shoot in ppi, that is something that your pp software adds in. It means pixels per inch, and is only relevant when you display the image on a display device. Similarly, dpi, or dots per inch, is only relevant when you are outputting to a printer.

[Manfred M]

I agree with Dave; the ppi really has no impact when displaying on a computer screen. I can't think of any screens that display at anywhere near this level of resolution. All the ppi really does is apply a scaling factor

If you are printing; the native resolution of Canon and HP photo printes is 300 ppi, while Epson printers run at 360 ppi; so in theory, you might have some level of interest when scaling to print. That being said; modern photo printers have sophisticated processing algorithms, and I have never found a need to scale my shots to a specifc ppi to get good results.

[Geoff F]

Some commercial printing companies will stipulate that you need a specific ppi (usually 300) when submitting files for printing. But in reality it is only the total number of pixels which is important, as previously mentioned.

Also bear this in mind if doing your own printing; but most printers will operate with images at 200 ppi with no problems. Your home printer should resize anyway, but for best quality results it can be useful to get somewhere close to the preferred figure.

Increasing the ppi will indeed produce a smaller image but there will be no improvement in quality over 300 ppi, or thereabouts.

In fact, I have a desktop publishing programme which automatically does this and it can be irritating when they end up with something like 500 ppi instead of reducing the image dimensions and still keeping to 300 ppi.

It also reduces the ppi for no apparent reason after I have correctly resized with my photo editor. So when I try to import an image into a text document, and the image is exactly what I want, the software auto resizes it to much bigger and often with an excessively reduced ppi which isn't what I wanted. So I then have to go into that programmes size/resolution menu and resize it back to my original dimensions.

I suppose that is modern technology for you!

[bnnrcn]

Thank you Geoff.Fortunately I'm not at the stage of printing my photos yet,I have started learning photoshop recently.So, modern technology can stay away from me for the time being

Some commercial printing companies will stipulate that you need a specific ppi (usually 300) when submitting files for printing. But in reality it is only the total number of pixels which is important, as previously mentioned.

Also bear this in mind if doing your own printing; but most printers will operate with images at 200 ppi with no problems. Your home printer should resize anyway, but for best quality results it can be useful to get somewhere close to the preferred figure.

Increasing the ppi will indeed produce a smaller image but there will be no improvement in quality over 300 ppi, or thereabouts.

In fact, I have a desktop publishing programme which automatically does this and it can be irritating when they end up with something like 500 ppi instead of reducing the image dimensions and still keeping to 300 ppi.

It also reduces the ppi for no apparent reason after I have correctly resized with my photo editor. So when I try to import an image into a text document, and the image is exactly what I want, the software auto resizes it to much bigger and often with an excessively reduced ppi which isn't what I wanted. So I then have to go into that programmes size/resolution menu and resize it back to my original dimensions.

I suppose that is modern technology for you!

[bnnrcn]

Thank you Manfred,what you say is releaving,I don't have to do anything with ppi when I have to do a lot of things in PP

I agree with Dave; the ppi really has no impact when displaying on a computer screen. I can't
think of any screens that display at anywhere near this level of resolution. All the ppi really does is apply a scaling factor

If you are printing; the native resolution of Canon and HP photo printes is 300 ppi, while Epson printers run at 360 ppi; so in theory, you might have some level of interest when scaling to print. That being said; modern photo printers have sophisticated processing algorithms, and I have never found a need to scale my shots to a specifc ppi to get good results.

[Mike Buckley]

Everyone,

PPI = pixels per inch and applies only to electronic display
DPI = dots per inch and applies only to printing

As you read the above posts pertaining to printing and see that those posts refer (inaccurately) to PPI, simply correct it in your mind by replacing PPI with DPI.

[Manfred M]

Everyone,

PPI = pixels per inch and applies only to electronic display
DPI = dots per inch and applies only to printing

As you read the above posts pertaining to printing and see that those posts refer (inaccurately) to PPI, simply correct it in your mind by replacing PPI with DPI.

Quite correct, technically Mike; dpi and ppi are device specific. My bad.

[bnnrcn]

So,does this make any difference to the answer for my thread?Do I have to change ppi in electronic display?

Quite correct, technically Mike; dpi and ppi are device specific. My bad.

[Manfred M]

So,does this make any difference to the answer for my thread?Do I have to change ppi in electronic display?

No. Any time I referred to a printer, I should have written DPI, not PPI. Other than that, the answer is correct.

Your computer will downsample any image to display correctly on your screen. In large prints, the printer software will have to upsample to create the print, while on smaller ones, the image will have to be downsampled.

[Mike Buckley]

Think of it this way, Binnur: If you are dealing with an electronic display, ignore the DPI and PPI values. Once you get around to dealing with printing, ignore the PPI value.

That might make you wonder why a PPI value is displayed in software. Actually, my primary post-processing software doesn't display it presumably because there is no fundamental need to change it. I have no idea if my other post-processing software displays it and I would ignore it if it does.

[bnnrcn]

Thank you Manfred,no need to worry then

No. Any time I referred to a printer, I should have written DPI, not PPI. Other than that, the answer is correct.

Your computer will downsample any image to display correctly on your screen. In large prints, the printer software will have to upsample to create the print, while on smaller ones, the image will have to be downsampled.

[bnnrcn]

Thank you Mike I really wondered why ppi was displayed in the software,if there was no need to change the value...If that's the way it is, I might as well ignore it

Think of it this way, Binnur: If you are dealing with an electronic display, ignore the DPI and PPI values. Once you get around to dealing with printing, ignore the PPI value.

That might make you wonder why a PPI value is displayed in software. Actually, my primary post-processing software doesn't display it presumably because there is no fundamental need to change it. I have no idea if my other post-processing software displays it and I would ignore it if it does.