DPI vs. PPI - What's the difference?

[Gamerprinter]

A digital image is measured in pixels. When a pixel is printed, it is represented by a dot. Therefore dpi and ppi is the same thing - one in its digital format only (pixels), the other in print (dots).

All graphics are measured interchangeably as dpi or ppi - I've got software that refers to both.

A 200 dpi or ppi image is measured as 200 x 200 dots or pixels. Most software I use only refer to dpi, even when an image is never intended to be printed.

So the issue is semantics. Unless you've got some other specific way to describe 200 pixels = 5 feet, there's only one way for me to make it.

So I do believe I am correct. I am not making it more complicated. The software I refer to mentioning ppi was Micrografx Picture Publisher and it nolonger exists. All other graphics software refer to dpi interchangeably with pixels.

Its a simple question.

[Robbie]

Nice work GP...I'm also quite thoroughly impressed with the exterior map...The interior map shows a LOT of work done, but for my own tastes it may be a wee bit too texture heavy...I'm not saying thats a bad thing, as I'm more of a minimalist in my approach to mapping...I definitely agree that these would go really well with VTT.

As for the dpi/ppi/200 argument...there is no argument really...200 pixels per 5 square feet = 200 dpi scaled print for D&D size miniatures = good for everyone

[RPMiller]

A digital image is measured in pixels. When a pixel is printed, it is represented by a dot. Therefore dpi and ppi is the same thing - one in its digital format only (pixels), the other in print (dots).

All graphics are measured interchangeably as dpi or ppi - I've got software that refers to both.

A 200 dpi or ppi image is measured as 200 x 200 dots or pixels. Most software I use only refer to dpi, even when an image is never intended to be printed.

So the issue is semantics. Unless you've got some other specific way to describe 200 pixels = 5 feet, there's only one way for me to make it.

So I do believe I am correct. I am not making it more complicated. The software I refer to mentioning ppi was Micrografx Picture Publisher and it nolonger exists. All other graphics software refer to dpi interchangeably with pixels.

Its a simple question.

Nice work GP...I'm also quite thoroughly impressed with the exterior map...The interior map shows a LOT of work done, but for my own tastes it may be a wee bit too texture heavy...I'm not saying thats a bad thing, as I'm more of a minimalist in my approach to mapping...I definitely agree that these would go really well with VTT.

As for the dpi/ppi/200 argument...there is no argument really...200 pixels per 5 square feet = 200 dpi scaled print for D&D size miniatures = good for everyone

While I understand and appreciate and agree to some extent with your assessment of dpi, it is not entirely accurate. As I've mentioned I have a background in reprographics from 15 odd years ago as well as some formal training in the area of computer graphics. This dpi/ppi argument has been around a long time and unfortunately those that don't fully understand it are in the majority and even the application designers get it wrong sometimes because of the way the older software worked and used the terms.

Here is just one of many links that you can find on the subject, but I picked this one specifically because it has print shop links as well. Please understand that I'm not trying to be a jerk about this, and I agree that we are essentially saying the same thing, and in this instance it isn't important as the software obviously is doing it correctly, but we really should be using the correct terms and it is always good to learn something new. I've talked to many reprographics folks over the years and many of them get this wrong because they are usually self taught or don't have the diverse background that would have introduced them to the differences in the terms. Not to mention, as I stated, the software itself is misleading.

http://www.rideau-info.com/photos/mythdpi.html

I would encourage everyone to investigate this further, and if we want to discuss it some more, since it definitely falls into the realm of this site, I think starting a new thread would be a great idea.

[ravells]

Might be worth moving the relevant posts from here to a new thread too for when people come to look at the threads come judgement day

Ravs

[RPMiller]

Excellent point! Done.

[Gamerprinter]

I just tried to export my exterior map to 1" = 5 feet at 200 dpi, and the file was over 1.8 GB in size! Note the map is currently scaled at 1" = 20 feet and its set dimensions are 54 inches by 43 inches, which means I have to rescale the map to 216 inches x 132 inches at 200 dpi to achieve proper scale.

This makes for a huge file.

The problem of course is that I need to include the idea that I'm going export at that specific scale when I create the map in the first place, so I can create manageable chunks that export easily at proper scale.

In regards to the DPI vs. PPI discussion, points to keep in mind:

1. Pixel or "picture element" is a basic element of color described on a video screen. Your screen has a set resolution that you can rescale if you have the right size monitor and proper video card. This however is measured both in pixels and dots per inch.

A pixel is square and is created using light shot through a monitor into your eyes.

A printed dot is a circle that is created from nozzles of inkjet paper or colored toner from a laser printer and is viewed by white light bouncing off the paper so your eyes can see the color (simplified explanation)

2. Most graphics software, even web graphics is not interdependant of DPI for measurement scale. Digital graphics and dpi can not be separated - not by definition of most graphics applications. They offer no "PPI" option.

I agree that a pixel and a dot are two different things, however software developers don't know the difference.

Regarding software and to help others understand how to create properly scaled map graphics for VTT use, they are treated as the same. You can't treat them as "apples and oranges" that will only confuse others.

Know then that a pixel and a dot are two different things. But if you want to 200 pixels to equal 5 feet in VTT scale, then you have to create your graphics at 1 inch equals 5 feet scale saved at 200 dpi - to get what you're looking for. That's all I'm saying.

My only question now is what is the dimensions of a standard map used for VTT use, in other words how many "feet" is shown on the monitor and how many feet are allowed off monitor that you can "scroll/move characters" within the same map?

If I knew that I could optimize my map designs for that scale and dimension in mind and create optimal VTT maps.

[RPMiller]

Please read through the article I linked to.

[kalmarjan]

In regards to the DPI vs. PPI discussion, points to keep in mind:

1. Pixel or "picture element" is a basic element of color described on a video screen. Your screen has a set resolution that you can rescale if you have the right size monitor and proper video card. This however is measured both in pixels and dots per inch.

DPI is a measurement for printers ONLY. If you are speaking about screen resolution, it is better to refer to it is PPI.

2. Most graphics software, even web graphics is not interdependant of DPI for measurement scale. Digital graphics and dpi can not be separated - not by definition of most graphics applications. They offer no "PPI" option.

The two major ones, Photoshop, and GIMP measure these by Pixels/Inch, or PPI.

I agree that a pixel and a dot are two different things, however software developers don't know the difference.

Not true. In my experience, it is the user who does not know the difference. You will hardly ever see a setting in creating a new graphic or render that says "X number dots per Inch". The only time you will run into DPI is in print dialog boxes, where it is VERY important. This is usually based off your printer, but sometimes you can set the PPI to closely match the DPI. It is relatively based on the profiles you have set up for your printer within a program like photoshop.

Regarding software and to help others understand how to create properly scaled map graphics for VTT use, they are treated as the same. You can't treat them as "apples and oranges" that will only confuse others.

Know then that a pixel and a dot are two different things. But if you want to 200 pixels to equal 5 feet in VTT scale, then you have to create your graphics at 1 inch equals 5 feet scale saved at 200 dpi - to get what you're looking for. That's all I'm saying.

At that scale, each foot would be equivilent to 40 px. So a map size of 50 feet (or 10 5 foot squares) would be 2000 px X 2000 px.

My only question now is what is the dimensions of a standard map used for VTT use, in other words how many "feet" is shown on the monitor and how many feet are allowed off monitor that you can "scroll/move characters" within the same map?

If I knew that I could optimize my map designs for that scale and dimension in mind and create optimal VTT maps.

This would really depend. Again, I submit that it is up to you, and your players. It really helps to think of VTTs as web applications. Having a map that is 100 feet square equaling 4000 x 4000 px would be okay, if your VTT could handle that. Depending on what is on that map though, you could be looking at a significant filesize. If you are running a map that is like one of my photos (at 8.1 MP) then a 3264 x 2448 map size could run at 944 Kb unoptimized. If you were to save that out at 80%, you could be looking at a filesize of 755 Kb, which is not too bad.

I hope that helped out.

Sandeman

[Kepli]

Many thanks for the explanation and especially the link RPMiller. I knew almost all of this already, but it is tough to explain to others. Now I can just point them to the link and let them read the complete story

[RPMiller]

My pleasure Kepli! It was a real stickler for me for some time as well so I can't really fault those that are going by age old assumptions. Now that the information is out there is no excuse for ignorance any longer. Hopefully folks will look into it more and it will finally start to click for them like it did for me.

P.S. You have a typo at the end of your sig. Fortunately no one reads them, otherwise they would have pointed mine out a long time ago.