T shirt printing - Printer wants RGB files... confused

[SWBGD]

I am currently supplying files to a client so they can have their logo printed on tshirts. They've opted for an online printer. 

I supplied pdf files in CMYK but when they go to upload the site says they only accept: jpg, jpeg, png, gif, bmp, svg  ... so raster files basically. 

As i understand it all printing ends up going to CMYK (+ spot colours etc if specified) eventually, so why do they only want raster files? 

The logo has cut out sections so needs to have a transparent background. So that leaves me with SVG and PNG. I've only ever used SVG for websites, I don't even know how i'd save out PNG files and have them come out at a good resolution and the correct size... very confused. Any help appreciated bending my head around this one. 

[Brad @ Roaring Mouse]

"As i understand it all printing ends up going to CMYK"

Sort of Yes, but really No.

Their printer may very well use CMYK inks, but these are NOT the same as the inks used on, say, an offest press. In fact. most inkjets use more than those 4 inks (mine has 12 inks, for instance.). So, in order to get a colour match, the printer is expecting RGB input first, and using ICC profiles, it's converted to its own CMYK(+more) values that will match what you're expecting to see.

[SWBGD]

Okay thanks, i understand that. I am only dealing with one colour per design but thats by the by. 

What i don't get is how to save the file, in this case 21 x 23 cm to an RGB format whilst maintaining a sharp resolution and the correct size. If i save a PNG at 300 ppi then the physical size increases. I'm aware of the difference between ppi and dpi but if that png is saved at 72ppi then isnt the design going to end up pixelated? 

Perhaps SVG is the way forward in this case?

There's likey something very basic i'm missing here. 

[Brad @ Roaring Mouse]

If your artwork is the right size (21 x 23), when you export to PNG at 300ppi for sure, your file will be correct. 300 is a bit overkill for a T-Shirt, but at least you are sending something crisp.

If you have your artwork in CMYK mode right now, you don't need to convert it to RGB now (that will haappen on the export based on your color settings anyway), HOWEVER if you are using a Pantone Swatch, you should change your document to RGB first, to get the most accurate swatch match before you export.

Check with your online vendor about what to do about whether a white ink is necessary under your colour logo (on non-white shirts)

 

[SWBGD]

I know the RGB values so that isn't a problem. 

I must be doing something wrong then because i have the artboard in illustrator at the correct size.  If i save it at 300ppi it is massive. 

Changing the ppi changes the dimensions for me, or is that just a diplay issue? 

[Brad @ Roaring Mouse]

If you want to double-check the image, open it in Photoshop and look at Image Size.

If for some reason it doesn't say 300 in resolution, uncheck the Resample box below and change it. This won't change how many pixels are in your file, but it will change the dimensions... If everything is right it should be the size you were expecting (21 x 23)

 

[SWBGD]

Thanks, disregard the above commet, i hadnt read this yet. How the pngs displayed when opening with the preview was confusing the life out of me. They are saving at the correct size, thanks. 

[jdanek]

"one colour per design "... why RGB?  How many designs are there? 

[jdanek]

How many colors are to be printed?  One?  How is the online vendor printing the shirts?  Heat Transfer?  Silkscreen?  Inkjet?

"As i understand it all printing ends up going to CMYK "... not t-shirts, but again, depends on how they are printing the shirts. 

"The logo has cut out sections so needs to have a transparent background"... the design is already transparent unless you specifically apply a White or Black behind it.  So, JPG will work.  You really have not explained what the design consists of or the method the online vendor is using.  I'd like to know that before I make a solid recommendation.

[Dave Creamer of IDEAS]

>>>the design is already transparent ......  So, JPG will work. 

How is the JPEG support transparency on the file supplied to the printer?

[SWBGD]

Don't worry about it, it's sorted out. 

The site doesn't actually tell you how they are going to print it, they just say they'll chose the best method depending on the garment (although you can specify in the notes). 

I thought it was odd that they weren't accepting vector files but apparently you can email them. Also the apparent resizing of pngs when saving at different ppi was confusing me but i've got my head around that now.