resolution and dpi

[Linhof]

By using Leaf Aptus 22, I get image file of 61.1M with resolution of 22M (5336x4000 pixels) as claimed by Leaf. I open it by ACW and then edit in Photoshop CS5, dpi is only 240. A little bit confused by the relationship between resolution and dpi... I attached a screen shot for reference.

[John Rodriguez]

It's pixels per inch, NOT dots per inch. The Pixels Per Inch (PPI) setting is basically an instruction to the printer telling it how many pixels to print in an inch. It doesn't matter except when you print. If the long side of your image is 5336 pixels, and you printed it at 240 pixels per inch, the print would wind up being 22.23 inches long (5336/240).

- If you change resolution to 360 pixels per inch and DON'T TOUCH ANY OF THE CHECKBOXES, the print size will stay the same, but the file will be "uprezzed" to create the additional pixels (IE, the computer is creating pixels for you where it thinks they should go). If you are using an Epson printer (which prints at 360 PPI natively), your best bet is to change this to 360 whenever you uprezz.

- If you change resolution to 360 pixels per inch and UNCHECK RESAMPLE IMAGE, the print size will decrease the corresponding amount (it would now be 5336/360 to calculate the long edge), no uprezzing/interpolation will take place.

[Heroique]

Not sure I understand your question, but “204” is the pixel density in the print.

So, 5336/204 is the print’s length on that side (in inches), 4000/204 is the print’s length on that side.

Many people like to print at 300 dpi.

[Leigh]

Resolution and dpi/ppi are not related in any way.

Resolution defines the amount of information present in the image as captured by the camera.

Dpi/ppi controls how large that image will be when printed on a page.

If you had an image 4000 x 4000 pixels and printed it at 4000 dpi, it would print 1" x 1".
If you printed it at 400 dpi, it would print 10" x 10".
A print done at 40 dpi would be 100" x 100".

The image itself has not changed.

- Leigh

[Leonard Evens]

What the others said explains the matter. There is one other confusing point. Printer specifications will often give dpi ratings such as 1440 or 2880 dpi. That tells you the number of dots of ink deposited per inch in the print. But each dot is one of a few available colors. But, a pixel in the image has three or more color values. When a pixel is sent to a printer, the printer must try to match the color of the pixel by printing a bunch of different dots. So many dots are used for each pixel.

To get a good print there is a minimal number of pixels you need to send to the printer. Usually something like 300 ppi is considered more than adequate.

[John Rodriguez]

Ideally you always want to send a file to the printer that is already set to the printers native PPI. The reason for this is Photoshop/Lightroom's interpolation algorithms are better then the printer driver's. So, first find out what the native resolution of your printer is. For Epson printers it's 360 (there is a setting to use 720, but you'll need a file that's natively over 360 to make use of it). Canon printers use 300. For other brands check the documentation, or if you're using a printing service check with them.

[Lenny Eiger]

Ideally you always want to send a file to the printer that is already set to the printers native PPI.

Unless you use a RIP.... such as QTR, StudiopPrint or ImagePrint.


Lenny

[John Rodriguez]

True, although it doesn't sound like the OP is using one.

[Lenny Eiger]

True, although it doesn't sound like the OP is using one.

Granted. However, there are a lot of people here who have done their time, and research, and can speak with authority about a particular topic. Even tho' I don't know you, I assume you are in that category. Some times people speak with authority when they haven't done the work, they just repeat what others have said - or what they think they know.

A lot of these authoritative remarks become the word on the street about a particular issue. I think its important to speak widely, include the exceptions, when people are going to read this forum to learn about how to do things. I don't know if you are correct about this 360 business, I can't say one way or another as I haven't tested it myself. I have always used a RIP for printing, primarily StudioPrint, and I can print to whatever dpi I want, 1122 or 574, for example. I always thought this was simply false but now it appears that if printing thru the Epson driver (and possible in other situations) that it is a factor, large enough to mention. I remember when Versace was trying to tell everyone the sweet spot was 363 dpi. (Let's just say I'm not a fan.)

There are some of the things that are 'word on the street' that are questionable. The effect of diffraction, for example. I have talked to many people who are terrified to go past f11 or f16, for fear that their images will fall apart. My experiments in this area have shown that diffraction is a minuscule effect, with the caveat "at least with the equipment I use".

I generally don't trust anything until I test it myself. But you can't start that way, there are too many things to test. The beginners have to trust what the people say on this forum, which I think is the best there is.

The rules-base that we set up needs to have a lot of - this is opinion vs this is what my test says, and this works if you are doing this kind of printing vs the other kind, etc.

That's my 2 cents.

Lenny