Problem with printing Photoshop poster project

[calcoutis]

Hey all. I am a new member of these forums and I am happy to be a new part of the community. So I could really use your help with a problem I got. To begin with I should point out that I am not an expert in photoshop. What I tried to do is make a project which would contain a bulletin board surrounded by a wooden frame. On the board there are photos(polaroid-like)(resized so many of them will fit in the board) which
are pinned with some push pins. The project went great and I was satisfied with the result but when I sent it from printing the poster turned out to be really grainy especially where the colours are more vivid. When I zoom in with photoshop (140%) there is nothing noticeable. Is there anything wrong with my photoshop settings (project size: 640x340mm, 300ppi) or the problem is with the printing office? Thanks in advance and sorry for a long first post.

[jerryb]

hi,
first i hope medley see your post... he sharp on printing...

also for subject it should have mentioned it about printing not size... smiling...

i really know only the basics... one of the things i was looking for in your post was what the poster size the printers were outputing to? that make a difference...

of course i assume they gave you what paremeter you needed.... for them....

now something to keep in mind... there a world of difference between the monitor and the printer!! your monitor only display in a range of 72-96 ppi where a printer is printing in dots .. hense your viewer will always look good but the printing a different matter.... depending..

in this thread medley gives some info about printing that maybe part of the answer for you....
printing-vt17893.html

do you know what the max dpi the printers use and what they recommend you give them?

[calcoutis]

Thank you very much for your fast reply. As I told you I am not an expert so I really don't know what the max dpi of the machines used is. I know for sure that the poster I received was the same size as my project hence 640x340mm.

[Medley]

A little basic math should explain the situation. First, some conversions are needed:

640mm equals approximately 25.2 inches;
340mm equals approximately 13.4 inches;

You set the resolution of the print (correctly) at 300 ppi, so;

25.2 inches @ 300ppi = 7560 pixels
13.4 inches @ 300ppi = 4020 pixels

So, the printer is printing an image that is 7560x4020 pixels. If the image you give it is NOT 7560x4020 pixels, then the printer will enlarge the image until it meets those dimensions.

Now, if you open your image, go to Image> Image Size, plug those numbers in, and let PS do it's thing, I think you'll likely see why the printed image looks the way it does.

Which leads to the question.. What ARE the pixel dimensions of the original image?

If you'd care to post the image, or email it to me at tandemduo280@comcast.net, I'll see if I can improve the final image for you. But keep in mind, anything more than about twice the width and height of the image is going to cause SOME degradation. How much depends on how big, so to speak.

- Joe U.

[Nanbas]

When I need to print big life-sized picture I use poster creator. It is much easier then Photoshop and it can make huge posters in few clicks.