Digital printing specs

Hi!

My first post as a new member. Looking forward to helping and contributing to the community.

I have a question about digital printing. Seems like there is conflicting information out there and would like to get this straight.

What resolution is acceptable and should you use RGB or CMYK? What file formats do you use? I see more and more people use high quality JPG for print now because its keeps the file size of the PDF smaller.

I’ve been setting up my files the same way for offset and digital: 300ppi and CMYK but some believe it is not necessary when printing digital.

What are your thoughts?

What resolution is acceptable

I still shoot for 300 ppi at finished size mostly because it’s a standard, but I think that’s more of a holdover from traditional printing where you wanted your resolution to be twice the line screen. From my experience, you can get by with less resolution on digital presses and not have any loss in quality.

should you use RGB or CMYK?

Safest thing to do is check with the printer. Some printers these days – especially wide format printers with printers that run more than four inks – will tell you to leave the images in RGB. If it’s bound for print, I work in CMYK.

What file formats do you use? I see more and more people use high quality JPG for print now because its keeps the file size of the PDF smaller.

This makes no sense to me. Why would you want to convert vector art to bitmap art? The printer won’t be able to trap the art. What about multi-page documents? Are you going to convert a 100 page document into 100 separate JPEGs?

All of that said, there is one scenario I run into where I’ll convert vector to bitmap. I work on packaging projects for a client, and the packaging has some layered / drop shadowed / transparent elements. If I send it to the printer, it works fine. However, there are time I have to send this art to FedEx Office to have some mockups printed. The RIP at FedEx Office does not handle the transparency very well. In this case, I’ll make a bitmap version, but the only bitmap is just what FedEx Office’s printer struggles with. Everything else (text, b/w vector illustrations, logos) are kept in vector art.

What are your thoughts?

When in doubt, check with your printer. But I think it’s tough to go wrong with a press quality PDF at 300 ppi and CMYK color.

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“digital print” means way too many different things and all have different file requirements.
Assume there is no set rule when discussing digital printing and call your printer to confirm before designing.

Steve, I think the OP is referring to placed imagery, not the handoff format.
jpg is not a print format. You can use them, but saving as .jpg introduces compression artifacts. Depends on what size you are using them. Ask yourself why a jpg makes a pdf smaller. Then consider the quality of the image that is being embedded and possibly further compressed.

For conventional print (stuff that you could do offset litho or web press) the general rule is CMYK @ 300ppi.

I do exclusively wide format printing, which is also a form of digital print. I’ll take jpgs if you send them, but I’m also more likely to ask for a native file rather than a pdf anyway (it’s an industry standard not to use pdfs in wide format. It’s not because we are backward and dumb.)

Steve is right on the RGB or CMYK thing. Ask. We take native files because we want to apply our own machine profiles to them. That means the images as well. RGB images have more color available for conversion, assuming they have never been converted to CMYK. If you convert an RGB original to CMYK and save it, a LOT of color information is dumped. You do NOT get that back if you convert CMYK back to RGB. Best to just leave it CMYK,

For resolution, I would ask your viewing distance. Max would be 200ppi regardless (unless doing a museum quality photo exhibit, which is a very rare occurance.)

But the minimum might be as low as 25ppi depending on what you are doing. A 40ft x 16ft backdrop sure doesn’t need to be 300ppi. Most billboards are 30ppi. I can’t tell you how many people don’t believe me when I tell them that. I still get large prints sent as .psb (bloated) 300ppi monsters weighing in gigs. If you have to save as a .psb, you are doing something wrong (with very few exceptions.)

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Thank you for the information.

PrintDriver is correct, I was referring to placed imagery for JPGs. Sorry, I should have been more specific.

I’ve always kept my habits of doing 300ppi/CMYK but started to believe that might be old school with newer technology.

In regards to JPG for imagery, some printers prefer I use medium/high quality CMYK JPGs. they claim there isn’t much visual difference and prefer keeping the files relatively small.

Again, was wondering if this is the new standard.

Thanks!

Personally, I would never use or recommend JPEG when designing for print, regardless of the output method.

While that may often be the case, it’s also often not. Depending on the image content (try it with a photo of a bright red car), compression artifacts can be introduced on the very first save as JPEG, even at so-called “maximum quality.” Subsequent saves amount to exponential destruction.

This sticks in my craw. It’s beyond me how that term has been so widely adopted. It almost always means some form of laser or inkjet output, so why can’t we just call it what it is instead of generalizing it and then inevitably trying to generalize an input specification?

Okay. That question makes a little more sense, now.

I would not use JPEG for images, though. It is possible take a nice, clean, high res image and save it as a high quality JPEG with little issues. I typically see quality issues if the JPEG is compressed too much or a file is saved as a JPEG multiple times. Each time it is re-saved, you’ll loose something.

If you want to make your PDFs smaller, take a look at the compression controls in the save as dialogue box. You can elect to downsample the res, and you can choose what type of compression, if any, gets applied to images. Use these two in tandem to get your file size down, of that’s an issue, while keeping an eye on quality.

Agreed.
I have always asked for native files and most often 300dpi. File size shouldn’t be an issue with the speed of moving big files today.
Do as much art as you can in Illustrator, adding your raster images to the vector file. Stick with CMYK and unless you’re printing spot colors, PLEASE convert your spot colors before you send the file.
We do both digital and offset depending on the run size. The client may want 30,000 folding cartons now and couple of months down the road need 300 to fill a quick order. I can go to the original file and prepare it for whatever output format I need at the time. Never assume, always ask. No question is a dumb question, it only shows your concern for the best output and a true interest in the end result.

My two cents.

You need to remember that you need a specific color profile to have a specific CMYK output or conversion from any RGB art to a CMYK file. And I have never encountered a provider that gives you any profile at all. So, sending an RGB file with a defined color space, sRGB, or Adobe 1998 for example, allows the printer (machine) to make the decisions on the ink values.

When I am using a new “digital” printer I will be using for a while, I normally print two groups of swatches or test images, one CMYK and one RGB. But normally I stick to the RGB files. Making these tests I always conclude that the CMYK files are converted to RGB and converted again internally, and on this process, they lose some saturation.

Regarding the use of a JPG file, yes, it is common, especially on big size prints. Try to stick to a PDF file with vectors as vectors, and with zip compression. But I will stand on behalf of the JPG format if the main image is a photo.

There are several types of JPG compression. Mainly a 4:4:4 and a 4:2:2. Using the minimal compression (max quality) on a good program will use the 4:4:4, and this will show almost no artifacts even analyzed with the computer itself. (I can show the test files later if you want/need) JPG also will save the color profile and the intended resolution.


But when you are using plates, on an offset commercial print, yeap, you should stick to TIF and CMYK files with the correct color profile for the paper/system you are using.

When I am using a new “digital” printer I will be using for a while, I normally print two groups of swatches or test images

Are you the printer? Or are you sending CMYK and RGB swatch files out to a vendor to print by “pushing the button”? What makes you think the CMYK files are converted to RGB and converted back again. That only happens in toy desktop inkjet printers. A print vendor using a professional workflow rip isn’t doing any back and forth converting like that. They go direct to profile from whatever you send, using the most direct method so that there is very little loss of color info (assuming it is there to begin with.) There is absolutely no benefit in going from CMYK to RGB because the CMYK color gamut is smaller than the RGB gamut and for the most part fits within the RGB gamut. You can never get the color back that you removed when converting an RGB image to a CMYK (once the image is saved and closed. You can always step backwards if the image is still open in Photoshop.)

JPG compression might be fine at the highest quality setting and for a few saves, but each time, you are degrading the image. You are losing info in the deep shadows and top highlights every time. You don’t want to be using jpg compression on “big sized prints” because you are introducing visible artifacts to the image that will enlarge when you print big. They will become more noticeable. For quality’s sake you want to stay in either .psd or .tif format. I’d prefer the .psd as the file weight is somewhat smaller than tif but that’s a personal preference. Applying compression to a tif for output can introduce some unwanted errors when images are placed into output programs. Some older rips hate LZW. Quark used to do horrible things to images if they were rotated and had LZW compression applied. We called them “the white zippers.”

Most conventional printers of any quality offer Job Options that you can download and install so that your PDFs output to their printing workflow standards. If I’m doing conventional digital cmyk stuff (not often) I work with printers who can provide job options, and provide a hard proof. It’s a vetting choice. With large format, as I said, the profiles are more customized and best applied to native files by the print vendor themselves. What profile you submit stuff in is Country dependent. In the US, the customary profiles are Adobe RGB and US web coated (SWOP) v2. They’re different in Europe and different in Asia.

sRGB has a limited color gamut and is more of a web format than print. Ideally a photo would be processed from RAW to the ProPhoto RGB color profile (largest RGB gamut of them all) but that rarely happens.

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