# Printing question - DPI and image quality.



## RMThompson

Hey guys. I am trying to print a photo that I took of my daughters for my wife's birthday. The photo in question is in Photoshop right now, at the following resolution:

4288 x 2848 Pixels

14.293 inches by 9.493 inches 

at 300 DPI.

So, when uploading this to Walgreens, they give me an indication that the photo doesn't have the resolution needed to print a 24x36 poster, but their website gives us dimensions (3240x2160 pixels) that are needed. My photo exceeds this.

I am wondering if the problem is that I have the DPI set at 300, which is maybe too high for the needed poster? 

So, when printing, what is the DPI that the printer uses?

Can anyone offer some advice?


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## dots

24x36 inches?  then they want 300 pixels per inch. 7200x10800 image.


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## dots

RMThompson said:


> So, when printing, what is the DPI that the printer uses?



Don't know and i wouldn't worry. In future ask printers how many *pixels per inch* they need to print at best quality. Ignore references to DPI. Clarify by asking what PPI.


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## Big Mike

Reason #73 to use a good lab.


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## KmH

RMThompson said:


> So, when printing, what is the DPI that the printer uses?


Way more than 300 DPI, if the printer actually makes dots. If the print machine makes chromogenic prints, there are no dots.

DPI (dots-per-inch) and PPI (pixels-per-inch) are not the same thing, though many use the 2 terms in the same context. Photographs have pixels (which are square or rectangular), not dots (which are round).
DPI is a measure of printer capabilities, not photograph size or resolution.
Printers have to use several dots to render a single pixel. Consequently to print 300 pixels in an inch a pro printer printer will use 1600+ dots.

Plus there is the math that is involved.

To print your 4288 x 2848 px photo at 24 x 36, just do the math - 2848 divided by 24 inches = *118.67 PPI* and 4288 divided by 36 inches = *119.1 PPI*. Your original 4288 x 2848 photo does not have an exact 3:2 aspect ratio.

Reset the PPI to 100 and try again. Walgreen's print machine's RIP software should then be able to make the 24x36 print you want.


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## RMThompson

Hey it actually turns out Walgreens defaulted to a less-than-full-resolution upload option, so I was able to get the poster... the size I had was more than enough for the poster.


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## Redeyejedi

Design215 Photography Printing Guide - DPI vs PPI


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## KmH

From that link:



> Color photographs are printed           using four inks, Cyan, Magenta, Yellow, and Black (CMYK), and four separate           dot patterns, one for each ink.



Only inkjet or offset printer half-tone prints are made that way. Many prints are continuous tone chromogenic prints made on light sensitive paper that has 3 emulsion layers - Cyan, Magenta, and Yellow that are exposed to red, green, and blue light from the image to be printed. The image on the paper is then developed chemically.



> **At 150ppi, printed images will have visible pixels....


 Total Bull****.


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## RacePhoto

RMThompson said:


> Hey it actually turns out Walgreens defaulted to a less-than-full-resolution upload option, so I was able to get the poster... the size I had was more than enough for the poster.



Yeah, you need to watch that, I noticed some of my uploads were getting kind of "odd" colors and pixelated, then I noticed they have full size or faster uploads. Oops! Now set for full size all the time.

There's also something buried in there about auto color correction. I have it off on one account, I haven't done a test to see how much difference it makes, but why do I do color balance and corrections if their stupid machine is going to 'fix" it for me, and ruin the work? :thumbdown:

Don't let people confuse you, almost all the labs use the same machines, the Fuji Frontier. Yes some are better, but in general what you get at some chain is going to be the same product. What might make a positive difference is finding out if the store you go to has a good trained crew and if they actually do the maintenance that's required. I've got a store near me that prints come out with blotches of black on the back and streaks. I know it's dirty rollers and gunk build-up from lazy people at the store not taking care of things. Walgreens one mile away is far better.

If I'm making 4x6 snaps, Walgreen's is just fine. Quality 8x10 you may want to find someone with die-sub or photo paper printing. See what you like and stay with that.

Read what *KmH says right above this. * :thumbup:

Went and looked, here are the two things you may want to adjust. Login, click on My Account (right under your name in the upper right) and look for 

 change it to full size and turn off the one click automatic color correction. Of course if you want the machine to reset your pictures and lose control, then leave it checked. I'd rather have it be what I selected.


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