Workflow for a printed image?

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Hi,

This is my first topic post - so be gentle! I’ve pretty much got the digital file to look the way I want it to look but I was wondering if anyone has a generally accepted process for making the files ‘print-ready’?

I have a local print shop (in the UK) that I plan to use so I wouldn’t have much use for DIY printer settings.

I’m using Darktable and GIMP for my post-processing so if you could explain your process using those tools I’d be obliged.

I’m interested in things like:

  • How you know your screen colours will look something like the same when printed (by someone else).
  • When you’d use a Matt finish rather than Gloss.
  • When you know a photo (that has been cropped) will be of sufficient quality to be printed at a large size.

Cheers.

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  • You’ll need to profile your monitor if you want the colors to be similar and/or the same. If you’re using a consumer grade print shop, they’ll probably apply their own corrections to your image. Ask them if they have an ICC profile and if they do any additional correction to your image.
  • for color I almost never use full matte, but its personal preference. I use mostly lustre. Glossy if the blacks are deep and the colors bold.
  • print resolution is generally around 300 DPI. Ask your printer what the optimal DPI is, as it varies from printer to printer. Higher end Epson printers use 380 DPI.
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Ok, I’m not sure of things, so take this with a grain of salt. I also bugged pmjdebruijn to help me understand a couple of things clearer, and he was busy so told me to take what he said with a healthy dose of salt as well. So you’re getting multiple doses of salt.

On the good side, any errors will likely bug the smarter folks enough to get them to correct me. :slight_smile:

This is the reason for calibration and profiling of your monitor and the use of soft-proofing print profiles provided by your printer. Calibration and profiling is a bit out of scope for a quick answer, but you should start there.

Assuming you have calibrated and profiled your monitor…

You will want to contact the print shop to obtain a soft-proofing profile from them for their printers. This is usually a function of the type of paper being used as well. For instance, I may want to print something with my print shop, who provides soft proofing printer profiles here: WHCC Soft Proofing Profiles. They provide various profiles for their different paper types (Kodak Professional Supra Endura VC):

You would download the appropriate ICC profile for your intended paper target. This is what you would use to “soft proof” in something like GIMP. I’m not sure which GIMP version you’re using - so I’m going to use 2.8.18 as my example. With your image loaded in GIMP, you’ll now want to see what it will look like using the ICC profile you downloaded previously.

In GIMP, go to Edit → Preferences → Color Management

You’ll want to set your “Print Simulation Profile” to the printer profile you previously downloaded (and set the Softproof rendering intent to “Perceptual” usually). Hit “OK”.

Back on your image, you’ll need to turn on the color proofing display filter to see the proofed result. Open the display filters dialog using View → Display Filters…:

On the left, choose Color Proof and click the right arrow to add it to the active filters. Then click on it in the active filters window to see the options:

Set the Profile to your printer soft-proofing profile (you can leave Intent on Perceptual).

You should now be seeing what your print should look like coming from the printer.

Caveat: someone smarter than me may come along and correct this, but it’s a good rough idea of what the steps would be.

Matte vs Gloss

This is a highly personal choice and will usually depend on the type of print you’re making and what you want the final effect to be. Personally I like the little extra impact a gloss (or sometimes metallic) paper can give to a color print. Colorful images just feel more vibrant on gloss. For B&W images I’ve been happy with matte. This is all personal preference and is an area ripe for experimentation on your part to see what you like. :slight_smile:

Print Resolution

There’s an old rule of thumb that the image viewing distance is usually approximately 1.5 or 2 times the diagonal of the image. With some simple arithmetic + approximations a formula can be worked out where:

PPI ≈ 3438⁄Viewing Distance

PPI ≠ DPI, but I’m making this simplification here anyway.

So what does this all mean? Well, assuming you print A4 (210mm x 297mm), you’d get a diagonal of 14.3 inches (sorry everyone, it’s just the way my brain is wired). So…

1.5 × 14.3 ≈ 21.5 inches.

And,

PPI ≈ 3438⁄21.5 ≈ 160 PPI (at least).

Of course, feel free to go higher than this - at worst you’ll just need to move around a bigger file (but folks can nose up closer to your image and you’ll still retain sharpness).

Quick summary:

Size (view dist.)  
5x7   (13in)  =  266ppi
8x10  (19in)  =  179ppi
11x14 (27in)  =  128ppi
16x24 (43in)  =   80ppi

Where PPI = image size (in pixels) / intended print size.
So an image that is 4096 pixels wide, printed to 10inches wide = 4096px⁄10 inches = 409.6 PPI

Hope this helps, and welcome to the community! :smiley:

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Thank you for making the process much clearer for me. :slight_smile:

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[quote=“jacklarge, post:1, topic:2303”]

* How you know your screen colours will look something like the same when printed (by someone else).

Easiest way: send a photo that looks good on your screen to your lab and say that they must not touch your file (= do not adjust). Based on that, adjust your monitor accordingly before sending the next series. That means when the print was too dark, set your monitor darker so the final print will be lighter (= poor man’s calibration, but quite effective).

* When you’d use a Matt finish rather than Gloss.

You’ll have to find out that yourself again, glossy or matt or lustre give all other results, just try. In general glossy is capable of a higher dynamic range / more contrast / more punch than matte, but it depends on the photo what is “best”. I recently asked a small Epson lab what paper I should use and the lady said send me the photo and I’ll give you advice. She proposed two mattes and one glossy, I tried the first one she proposed, a Hahnemuller matte 310g, and that looks fine. Next one I try is a glossy. In general I can advise to try at least one time those small one-person-one-printer labs, as their results are just quite (really, etc.) good.

* When you know a photo (that has been cropped) will be of sufficient quality to be printed at a large size.

This is plain and simple math. As said, in general 300 pixels per inch (ppi - not to be confused with dots per inch, dpi, which is a printer variable) will do for small prints up to 4x5 inch or thereabout. For larger prints less pixels per inch will do. How much less depends again on the type of photo (grass versus clear sky for example). So if you want to print a photo at high quality at 4x5 inch, you must prepare a file of 4x300 by 5x300 is 1200 by 1500 pixels per inch, so 4800x6000 pixels in total will do. Largely that is.

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I don’t understand the calculation. 1200 by 1500 pixels per inch sounds really wrong (no square).

Ingo

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I think he means 4 inches at 300 ppi should be 1200px? Not sure about the rest… :slight_smile:

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Hello Ingo,

You are right, my mistake. The general rule is that one needs 300 pixels
per inch for a high-quality print in a photolab or with your own
printer. That means that for a 4x5 inch print, you need 4x300 by 5x300 =
1200x1500 px.

In general, take the long side of the print you want to make in inches
and multiply that by 300 to calculate the number of pixels needed.

A 8x10 inch print needs 3000px on the long side, etc… Another general
rule is that the larger the print is, the less pixels you need because
the spectator will watch the print at a greater distance.

Paul.

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Hi Paul,

thanks for clarifying this :slight_smile: Now it’s clearly understandable

Ingo