DPI? PPI? and Image sizes? need help with a current print project

[benpek]

I am mainly a digital designer. Meaning do work for screen viewing, such as web and video. I have not done much print work. A few months back I did some magazine ads for a company. I informed them that I have zero experience doing print work, but they said I was selling myself short and was confident I could get it done. The ads turned out absolutely perfect. However, I still had suspicions that certain challenges had not arisen yet to exploit my inexperience.

Well, fast forward to now...

I am working on another print project (against my better judgment), however these images are rather large. Much different than the half page magazine ads I did before.

I am working in Adobe Photoshop for the raster images, and then will be moving to Adobe Illustrator to add the vector layovers for text and logo work.

- The printer stated they needed graphics that were 150 DPI.

- In photoshop there is no option for DPI, only PPI aka "pixels/inch".

- The raw images I have available to me are 11.714" w x 14.763" h (or 4100px w x 5167px h). These images also reflect 350dpi when you view their properties via right click. In Photoshop, when I select the image, copy, then create a new file, the "pixels/inch" field has the number 350 automatically generated.

- The final image I need to make is 40 pixels wide by 55 inches high . It also needs to be 150 DPI.

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Here is my dilemma:

I create a new document in Photoshop at 40 pixels wide by 55 inches high, with a "pixels/inch" setting of 150. I then copy the 350 dpi source image, and past it into the document. Now the image is much smaller than the desired size I need. Because it is 350 dpi, can I scale the image up to fit the document size?

Am I doing something wrong? I need to get to a point where I can get the document layed out correctly, or ask the client for larger images.

Sidenote: I have read in a few places that in Photoshop the "pixels/inch" field really translates as DPI, is this true?

If anyone could clear this up for me, and let me know what steps I need to take to get the image to look nice when printed, please drop a reply. I could really use it.

Thanks,
-Ben

[tZ]

I know what you need to do and do it so often but, don't have photoshop on this computer,lol and don't really know what the menu is called. I think its the third menu from the left. In there is something called image size… I think. You use that to adjust the dpi and size. Sorry that my ps vocab is a little off but, I memorize these things without really knowing were they are,lol.

However, I don't think you will be able to make a 11 x 14 40 x 55 and still have it be 150 dpi. Whenever you increase the dpi the image will get smaller. On the otherhand, whenever you decrease the dpi the image will get larger. So its a very good thing you have 350 dpi source but, I don't think you will be able to scale it to 40 x 55 and still have it be 150 dpi or higher. if you look up scaling factor that is what detrmines this mathmatically. However, I'm quite possitve its not possible to even get the image to be double the current size at the resolution and size you have provided.

If you definatly need this image to scale what you could do is have it printed high quality(150-300dpi) on a 11 x 14 or 8 x 11 piece of paper. Then scan it in at a size determined by the scaling factor to be able to size the image to 40 x 55. So you would prombably need to scan it in(if possible) at like 900 dpi or so(just a quess) in order to size it up to 40 x 55 and still have it be at least 150 dpi… if that makes any sense.

[tZ]

here's the scaling factor thing:

http://www.graphicdesignforum.com/forum/showthread.php?t=15058&highlight=increase+image+size

Its not really a recommended way of approaching this promblem but, it depends on how badly you need the image.

[benpek]

Excellent thanks for the information. You have atleast helped me confirm that the images I currently have are too small in size, and I definatly need them larger.

I am going to read over the scaling factors here as I am eating. :)

Also, I saved the .PSD file for the 55 x 40 inch image, and it took up about 350MB of space. Is this normal? If so I am definatly going to have to find an empty HD to get this client project completed.

[tZ]

yeah… the file will be gigantic in an uncompressed format.

[PrintDriver]

Large format is not for the faint of heart. My work is constantly in the 100's of megabytes. :D

I only get 190mb at 55" x 40" at 150dpi in CMYK 8-bit with only one layer (layers will make a big difference in file size).

You need to watch what you are doing with the 'Resample Image' button. It should be unchecked if you are making a picture larger.

Did your printer tell you what file format he wanted? .tif or .eps are the usuals but an .eps file will be larger.

[urstwile]

The final image I need to make is 40 pixels wide by 55 inches high . It also needs to be 150 DPI.


I presume you meant 40 inches, not 40 pixels wide.

Yes, your image will not hit the target resolution of 150 DPI, it will end up at 94 DPI. You are also correct that DPI and PPI are the same thing, in this scenario.

Depending on the viewing distance of the project you're working on, and the type of image it is (i.e., not strong on super crisp detail to begin with) you might be able to get away with 94 DPI as the final resolution. However, if it's possible for you to get the image at a larger resolution, do so.

If it's not possible, make sure that when you upsample the image that you have Photoshop using Bicubic Smoother as the interpolation method. It does a really good job with this kind of thing. Don't allow whatever layout program you're using to do the interpolation for you, they won't do as good a job as upsampling it natively in Photoshop and importing that upsampled image afterwards.

I'm not saying it's okay to upsample images routinely, but sometimes, when you have no choice, this is the route you should go.

[benpek]

Yea I meant inches there, I was tired hehe.

I usually do all raster graphics work in Photoshop first before bringing it into a Vector based program.

If I scale the image, so it would be 94 DPI, would using the "sharpen" filter a bit help? How does that look when printed? I use it lightly with web work all the time to crispen up images, but have no idea how this would come out when printed.

Also, thanks again for all of your help here. I am up against a deadline on this project and these problems have set me back, so your speedy response is helping me more than you know.

-Ben