Graphic DPI and Professional Printing

[traceyp]

Hi everyone

I want to raise a topic which obviously still has me confused, i.e. DPI and PPI and which is more important when sending something to print. Since I find it confusing this may well turn into a long message in order to express myself adequately - if so then I apologise.

Currently I design a magazine which includes many graphics, both B/W and colour. So far I've had no problems with them and they've all come out nice and sharp with no "jaggies". When I create a graphic, I always save it at 300dpi and size it to the size required on the page. As I say I've never had any problems. I should add that such graphics often include text as well. In this way all my graphics just drop into place with little or no adjustment or stretching necessary.

My problem is the way my partner approaches a similar but smaller task. Back in April he took over as editor of a monthly B/W Gazette for the off-road motorcycle community in the east of England. However, today we received PagePlus10 and I tried creating a PDF from the source file for the November issue. Before completing the task, PP10 displayed information on the source file that previous versions did not display, i.e. errors in the source file.

I was therefore very concerned to find that there were five graphics of below 175dpi so I brought them onto my PC and loaded them into PhotoPaint8. I was horrified to find that all five graphics had a resolution of below 100dpi, ranging from 29dpi to 96 dpi. The only thing in the graphics' favour is that, with one exception, they are very small so its unlikely that anyone other than myself is going to notice the resolution. What he has done is to leave them at their original size, which is quite large, and then size them on the page. Although this brings up the resolution it is still very low compared with what I believe they should be and certainly below 175dpi.

Essentially he has taken a great deal of notice of what David Huss said during a seminar many years ago when David said that you don't need to take much notice of DPI, only PPI. However, I disagree when it comes to professionally printed material. I do agree that PPI is the measure to use for web graphics, but I have always worked on the premise that DPI is essential for graphics in professionally printed publications.

Having created the above PDF and looked at it fairly closely, the offending graphics are pretty "jaggy" and I'm worried that he may well drop a clanger one month and do this with a somewhat larger graphic with all the attendent "jaggies". Fortunately, I've done all the adverts and of course exported them at the size required at 300dpi and they are so much better than the offending graphics.

We've had several arguments on this but neither of us will budge. I would therefore appreciate forum members voicing comments and understandings on the subject. I have again found the thread that took place back in 2001 (search for DPI: TRUTH OR LIE and also DPI: TRUTH OR LIE 2) which was mainly with regard to graphics for the web - but what about printing, what is the important consideration regarding DPI for having graphics professionally printed?

Any assistance will be very much appreciated. If I have to eat humble pie then so be it, otherwise I shall have to pick the right time to say something to my partner! Oh, and I'm sorry for the length of this post.

Tracey

[traceyp]

Hi everyone

I want to raise a topic which obviously still has me confused, i.e. DPI and PPI and which is more important when sending something to print. Since I find it confusing this may well turn into a long message in order to express myself adequately - if so then I apologise.

Currently I design a magazine which includes many graphics, both B/W and colour. So far I've had no problems with them and they've all come out nice and sharp with no "jaggies". When I create a graphic, I always save it at 300dpi and size it to the size required on the page. As I say I've never had any problems. I should add that such graphics often include text as well. In this way all my graphics just drop into place with little or no adjustment or stretching necessary.

My problem is the way my partner approaches a similar but smaller task. Back in April he took over as editor of a monthly B/W Gazette for the off-road motorcycle community in the east of England. However, today we received PagePlus10 and I tried creating a PDF from the source file for the November issue. Before completing the task, PP10 displayed information on the source file that previous versions did not display, i.e. errors in the source file.

I was therefore very concerned to find that there were five graphics of below 175dpi so I brought them onto my PC and loaded them into PhotoPaint8. I was horrified to find that all five graphics had a resolution of below 100dpi, ranging from 29dpi to 96 dpi. The only thing in the graphics' favour is that, with one exception, they are very small so its unlikely that anyone other than myself is going to notice the resolution. What he has done is to leave them at their original size, which is quite large, and then size them on the page. Although this brings up the resolution it is still very low compared with what I believe they should be and certainly below 175dpi.

Essentially he has taken a great deal of notice of what David Huss said during a seminar many years ago when David said that you don't need to take much notice of DPI, only PPI. However, I disagree when it comes to professionally printed material. I do agree that PPI is the measure to use for web graphics, but I have always worked on the premise that DPI is essential for graphics in professionally printed publications.

Having created the above PDF and looked at it fairly closely, the offending graphics are pretty "jaggy" and I'm worried that he may well drop a clanger one month and do this with a somewhat larger graphic with all the attendent "jaggies". Fortunately, I've done all the adverts and of course exported them at the size required at 300dpi and they are so much better than the offending graphics.

We've had several arguments on this but neither of us will budge. I would therefore appreciate forum members voicing comments and understandings on the subject. I have again found the thread that took place back in 2001 (search for DPI: TRUTH OR LIE and also DPI: TRUTH OR LIE 2) which was mainly with regard to graphics for the web - but what about printing, what is the important consideration regarding DPI for having graphics professionally printed?

Any assistance will be very much appreciated. If I have to eat humble pie then so be it, otherwise I shall have to pick the right time to say something to my partner! Oh, and I'm sorry for the length of this post.

Tracey

[John Rayner]

Hello Tracey,

Personally, I give the printer the highest DPI I can get them to take without gagging. The smaller the dot then; the crisper the line, the sharper the detail, smaller the bleed, the better the graphic.

[gwpriester]

Tracey

DPI and PPI are one in the same. Dots Per Inch and Pixels Per Inch.

I think your mistake is when you say you create a 300dpi image and then resize it as needed.

If you resize a 3" bitmap with 300dpi resolution to 6" the dpi will be 150dpi. The resolution of the image changes as you modify the size. Making an image smaller is OK but increasing the size of an image more than a small amount is not good.

The best bet is to make your image the correct size and at the correct resolution. Exporting a 150dpi image at 300dpi is not going to increase the sharpness of the image. It is still going to have the resolution of 150dpi. (That make sense?)

Ask your printer what the best resolution is for the job and then provide your images to that resolution. I'm not sure if the USA resolution is the same in the UK but for magazine ads, most publications print at 133LPI (lines per inch) all the way up to 300LPI for very high quality printing. Double the LPI for the bitmap resolution. Hence, if the magazine is printed at 150LPI, export your images at 300dpi.

Gary

[traceyp]

Gary

With all due respect I am very much aware that you do not make a bitmap larger without reducing resolution. What my partner appears to depend on is to create a large bitmap of low resolution (perhaps 96 or 72 or even lower - one of his graphics is as low as 29dpi!) and then he seems to depend on the reduction in size on the page to increase the resolution nearer to that required but that its just guess work and not very professional at all.

If you re-read my message, I personally already do what you have suggested. I just wish that my partner would the same but he is adamant that DPI doesn't matter "because this is what David Huss told us"! I remain to be convinced that this is really what he meant!

I have always had good results doing things the way I do. I just wish that he would not take chances. I wish he would do things in the same way but he just will not listen. Perhaps he will when it really stands out in a printed Gazette. I can live in hope.

Tracey

[Egg Bramhill]

Hi Tracey,
I always work on the assimption that PPI is a non exsistant unit of measurement.
See This Article
The problem is that almost ALL programs mix PPI and DPI as if they are the same units of measurement. It would appear that in the very early days of computers there was an attempt to tie these units together, which, perhaps, worked loosely early on, but has now become a millstone. This is made worse by software vendors cross mixing the two terms.

I would totaly disregard PPI for printing purposes, and go with your method of DPI. But as almost all programs mix the two this is difficult.

Egg