Can someone kindly correct or confirm what I've written below....... I 'm pretty sure I understand the concept but maybe I still don't o.0 Please don't give me more web links.... I've looked at loads and now I'm just trying to put it all in my own words to understand it. 1) ppi/dpi doesn't really matter until an image is actually going to be printed out. Simple definitions : 'ppi' refers to on-screen resolution and 'dpi is the term used by printers regarding printing resolution. 2) the fact that Poser7 only renders at 72dpi DOESN'T MATTER because if you render big enough at that resolution, say 33x34 inches@72ppi you are able to PRINT that image at roughly 8x8 inches 300ppi....... the fact being that you have the same number of pixels in both images but for the 300ppi one they are concentrated in an area about a 5th the size, hence the higher resolution. 3) -If I multiply 2400x2448 thats the total number if pixels in the image ? -If I divide 2400X2448 by my desired res of 300, I get 8x8.16......... so if I send that original 33inchx34inch @72 ppi image to a printer it will be printed at 8x8 inches @300dpi ? Or 10x10"@240 dpi ? 4) The formula is : each desired size of final image (8"x10") x desired dpi(300) = the pixel dimensions I need to tell Poser to render at (=2400x3000 @72 dpi) A biggie for a sunday morning, I know. A common complaint about P7 is it only renders at 72dpi (considered a bug ) so some folk claim it can't be used it you are working in it with the intent to actually print . I personally render along the sizes I mentioned above and get excellent prints. Poser actually does the math for me... I input 8"x8" at 300dpi in the render dimension boxes, it renders out an image at 33"x34" @72 ppi. Same thing. I've tried a couple of times to explain it to counter the gripes about "it's a major bug, can't use 7 because my publisher is unhappy with the low res output, my renders have jaggies , jumping through hoops to make Poser do the resolution I want, too much math," etc. But I give up explaining. Now I just want to make sure I am understanding it for Myself. ( It's also an ongoing conversation where I work..... try getting fashion designers printing out illustrations/photos to understand this !! Lol If I can go into the design studio tomorrow and spit this out in simple english I might see some sharp prints bigger than a postage stamp. )

I'm not going to start a debate, but I can only say from my experience, that theory is totally wrong.   For reference I run my own print house out of my home, and DPI is excruciatingly important.

The Major reason for this, is something rendered and worked in 300 DPI remains, 300 DPI, no matter what size the image actually is.

72 (standard) dpi is perfectly fine, if you render out and create your image in the precise size you want it.   However imagine if you will, rendering out something 24x36.   Considering time constraints,   that is totally not a feesable prospect.   The DPI becomes increasingly important depending on the "stretchability" you want your image to have.

If you render out  a 2x4 image in 72 dpi with amazing details, then place it in photoshop, try this experiment.  Change either the dpi, OR the size to poster size, say, around 18x24, or set it to a base of 300 dpi.  Now look at your image.

What you will see is horrific pixilization, just tiny little squares.  This is precisely why artists who sell their art put up thumbnails and samples in extremely poor quality save for web low dpi...... so that it cannot be stretched or printed out with any kind of copyable quality.  The more pixels you cram into a square inch, the less quality is lost in reproduction and printing.

Usually, no print house or print graphics company will accept anything LESS than a minimum of 150 dpi, 300 is preferred, and over that is exceptional.

Lastly, a poser user who uses post work, such as I do, requires a higher DPI, not just for printing.   To detail and hand paint and do most post work, its impossible at a low dpi, as if you zoom in to say, an eyelash, its indiscernable and just a blob of hazed out pixels, not an eyelash.

Edited P.S.:  I realize you are saying that if you arent printing it you don't need it.  However, as I stated above, truly, you do.   I'm not sure if you have poser and work with it, but rendering takes a lot of time, and to render something out say, in an actual 8x10........ or heaven forbid poster size, would take hours upon hours.   Even so, if you went through all that, if you tried to zoom in in photoshop to detail an eye, the dpi is just way too low to get that kind of clarity you require.

Tiari's right... and there are a couple of other considerations, too.... when Photoshop changes size or resolution, it does a resample, which tends to be why you get "jaggies".... you can use photoshop to increase the resolution up to a point before things start to go wahoonie shaped... I don't know what your output format is, but if you have an option, (Via the printer), to output as a file, you will be able to set the DPI... On the side, not many seem to have noticed, but 72 pixel is the default setting for Photoshop. Lou.

Thanks both of you for your replies. Yes, archdruid I had noticed that about Photoshop and the 72 ppi. In Poser I input sizes to render like I have said above ie 8x8" @300 (2400x2448) and had noticed how photoshop puts the rendered image as 33x34" @72. ( Tiari, actually my 2400x2448 renders don't take forever, maybe 2 hours tops tho I never use reflections ((the one time I did the render took 17 hours, aaaccck, toooo long !! )) and often only have shadows on for one light. One of the things I do in Poser is develop and render out characters and then paint costumes on them for film and theatre designers who don't have drawing skills and for that I have to do 8x10 prints at at least 250 dpi... so I am very aware of the importance of working on large enough images in Photoshop to get good detail in and sharp prints out ! The "Walking With Cavemen" illustration on the E-On website gallery is an example of what I do tho that is kinda old now. However my main query is really that both of those image dimensions contain 2400x2448 total pixels so in terms of pixels they are the same size. I'm not saying above that ppi/dpi doesn't matter at all ever but that it only really comes into play when an image is being actually printed out. For on-screen viewing it is the total number of pixels in an image that makes it clear to view, or if not enough, jaggies instead. This is what I thought I understood from reading various web pages on the subject. On screen res itself has more to do with total number of pixels and dpi is important when actually printing as it relates to the dimensions of the printout and its sharpness. Don't worry, I'm not trying to start a big debate.... I just wanted confirmation that my understanding of dpi in terms of printing and total pixel numbers via the formula I mention above is correct. That is 2400x2448 pixels will do a 33x34 print out at 72dpi, but it also will do a 8x8.16 print at 300dpi. Or not. thanks again.

Correction to above : oops, E-Frontier gallery that is , not E-on

The general idea is, pixels per square inch will remain the same pixels per square inch, no matter what the size.  The DPI determines that.  You can go with 72 DPI and render large, but its when it comes to printing, even print houses don't want that.  Each has their own base minimum, but most are well above that base.   The reason is because, as a printer sees it, no matter how good it looks on your monitor, its only placing ink in 72, instead of 300.

For instance, in a digital camera, you can usually set the DPI yourself.  If you take pictures at 72 or 300, they are the same "size" but look at the quality.

You might be interested in the following even as you know about printing . These are the links I got my info from. The first on has a calculator to determine what sizes you can print . Useful ! http://www.mattspinelli.com/ppicalc.html http://www.ransen.com/Articles/DPI/Default.htm http://www.photoshopninja.com/2005/07/image-resolution-and-dpi-explained/ I guess I understand well enough in interms of my own needs. Thanks again for your input.

Your original post was correct Gini - Tiari is talking about something else, rendering too few pixels and then resampling to make the image larger in its pixel dimensions. As long as you have Resample unchecked in the Image>Image size dialogue in Photoshop then that won't happen, all you're doing is changing the size of the pixels at print time. And the 72 PPI image will take exactly the same time to render as a 300 PPI image with the same pixel dimensions, PPI has no bearing on render time, quality, or file-size as long as the pixel dimension are kept constant - which you are doing.

@ Rhaseltine- Thankyou . Having looked at so many webpages explaining it I was now starting to think my reading-comprehension abilities were being lost along with my youth and beauty ; ) Phew

Can't help it - gotta chime in here - yes, you have it exactly right Gini. Don't get frustrated - everything is in fact theoretical until you go to output - at which point you need to have the appropriate dpi for the desired output size (which is where Tiari is going - but not taking into account that you're talking about rendering a high pixel dimension in the first place).

Yes, you render an image 2400x3000 pixels if you want to eventually print an 8x10 at 300dpi - or a 16x20 at 150dpi - see, it's the same 2400x3000 but you're only changing the real worl output for a print you will hold in your hands. Until then, it's merely pixels in a digital file and can be set to 10dpi for all that matters.

The fact that Poser renders at 72ppi is a non-issue - RHaseltine is exactly right about simply changing the "setting number" of dpi/ppi by making sure Resample is unchecked - you are never making any size changes to your original 2400x3000 image as it's still the same dimensions - in a computer until it goes out to print.
Hope that helps-
-Lew ;-)

Thanks Lew ;-) It's firm in my head now.

an interesting test to do... when you have rendered the image. lets say as a .tiff. open the .tiff in photoshop imediatly go to the menu " image" and "choose image size" does it say it's 300 dpi. if the answer is no, it will print at the resolution displayed. don't resample the image just change it to the correct dpi in PS and the output size will change. also check your page set up, the user imput here may be effecting the printer's output.

@Karosnikov - I think you have it a little backwards - we're not talking about the dpi/ppi being important - we're talking about the actual pixel dimensions being important. In your example above, your image is 156x302.

Yes, your printer will print the physical dimensions in INCHES or CENTIMETERS based on the SETTING of the dpi - in which case as your example indicates will be 5.5x10.65CM. Change the dpi (while Resample is unchecked) to 300 and your printer will spit out a .52x1.006CM image - the 156x302 has never changed - just the SETTING of the dpi for your printer.

It's your job, as the artist, to make sure you have rendered to a sufficient size to begin with - not jjust some little rendering you hope will fit your target destination.

Before you render, you will make the decision of size - this shouldn't be "Oh, I'll justmake it this" because as a professional you should have some form of use for this once rendered (publication, wall prints, computer wallpaper - whatever). If this is for a specific printout - let's just say an 8x10 inch that at the end you want set to 300dpi - you will render the dimensions specifically for 2400x3000 pixels. It's math - not output resolution.

Pixel dimensions (3000x4000 as opposed to 156x302) - not dpi - is what matters most. You can always go smaller for your ouput aize - but going bigger is problematic as you introduce artifacts.

I must have no idea what I'm talking about... ignore that post.

It's all good - I cross my wires all the time ;-)

I work from the bottom up not from the top down... my resolution my not be in context, but it may help someone.

This is a piece I wrote for our clients, trying to explain the issue to them. While it grossly oversimplifies in some cases, and is geared toward our particular business (wallpaper borders and murals), it may be helpful to some.

---

A Quick Primer on Image Size, Printing, and Resolution

We frequently receive files to be made into borders or murals that are simply too small to be usable. There seems to be a lot of confusion out there about file sizes and printing resolution, so I'm going to attempt to clarify the subject here.

The first thing to understand is that most computer image files are made up of dots called pixels. These dots are very small, and very close together, and when we look at them they seem to make up areas of solid colors and shades.

The best way to describe how big an image is is to state how many pixels high and wide it is. For example, an image on your computer screen may be 900 pixels wide and 600 pixels high.

We can't really say how many inches high or wide an image is without specifying how we're looking at it. A computer monitor may fit 72 pixels onto each inch of the screen; in that case, our 900 x 600 pixel image is 12.5 by 8.33 inches. We would say that the picture is 12.5 inches wide at a resolution of 72 dots per inch.

If we were to print the image instead of looking at it on a monitor, it might be very different. Printers cram a lot more dots into each inch than monitors, so the image will be smaller. If it is printed at a resolution of 300 dpi, it would only be 3 inches wide!

The three properties are related like this:

    **Size in Inches = Pixels divided by resolution

    Pixels = Resolution times Size in Inches

    Resolution = Pixels divided by Size in Inches**

In other words, if we know any two, we can figure out the third.

The number of pixels is always fixed unless we resample the image. The resolution and the size in inches change in relation to each other. Higher resolution equals smaller size, and vice versa.

Printing Resolution

We've already mentioned that a lot of computer monitors display images at 72 dots per inch; a lot of magazines on slick paper are printed at a resolution of 300 dots per inch. We have found that we get the best results printing our borders and murals at a minimum of 150 dpi.

This means that a 9 inch high border, for example, should be 1350 pixels in height.

To figure out how big a file needs to be, just multiply the height you want it to print to by the resolution (in this case, 150 dpi); this will give the necessary vertical dimension in pixels.

One further note: taking an existing file or scan and sizing it up in Photoshop is not a substitute for obtaining a larger file; you are effectively reducing the printing resolution by doing this.

Bravo - well said ;-)