I recently got a question about the DPI or PPI on which there seems to be a lot of misunderstanding, I have found on the internet this article which clearly explains what it entails, I hope it helps

 

Kind regards

Jan

 

http://www.dpiphoto.eu/dpi.htm

Yep! Pretty much right! I've been saying this for years here in these forums, but this certainly is full of a lot of details.

Thank you very much Jan for bringing back so many informations

(some we know/knew and forget .. some we do not know -in my case though-)

best regards

Thank you very much, this is a very good article :)

Isn't it curious how so many people who would print your work, or even display it online, insist on a dpi value. No wonder so many people think it has meaning. Why is it there in photoshop? I've never come across anything that uses it, including printers. I

 

It gives you a way to see the dimensions of the image. Pixel count is converted to inches based on dots/pixels per inch. I can assign a pixel density to my image for printing and then re-size the image to the correct dimensions. I use it all the time when printing.

Did you read the article, Clyde? My printer asks you the dimensions of the print. The dpi is always the same.

But your printer of PS or whatever software is controlling your printing has to know the dpi or pixels per inch in order to know how to map the pixels inside the dimensions you set. And I've never seen a printer that would only accept one DPI setting, but possible I suppose.

 

Do you let the printer resize the image to fit your dimensions? I always do that in PS or more lately, LR first. I don't trust printer software to resize my images, I always set PS to control the printing and color space not the printer.

 

I read the article 4 months ago, but agreed with everything it said back then.

You are right that it does use different DPI settings, eg for draft prints it will use a low setting and and high quality it will use the maximum possible setting. But I don't need to know that and it is always the same for high quality.

 

I agree that if you want to print much larger than would be ideal for that photo, eg at 25 pixels/inch, then you should use special software to resize the image. PS is not ideal for that, but I can't remember the software that is used.

 

The colour space will depend on the printer capability. Some will only do sRGB, so you need to use sRGB. Others will use ICM, so then you may be able to use Adobe RGB.

 

I worked with printers at times through my life and I always found them to be very difficult. I think its the interface between computers and mechanical devices that creates problems. Whatever it is, once I get them working I tend to leave them alone. Suffice to say that I don't try to make huge prints (the printer isn't big enough anyway) and I always send maximum resolution output to the printer. Resizing down never seems to be a problem. Perhaps it is a "feature" of my printer.

Thanks Lars. Perfect Resize was the product I'd forgotten.. Since I've never had the need to print billboards, I've never used it.