Maximising pixels for better prints
It’s a common mission which can become a complex topic, but printing fundamentals boil down to some simple solutions.
A whole range of factors can influence a print, some are within our control and others aren’t. This article looks at editing, pixels to prints, and how pixels can be optimised before ink is committed to paper.
First though, lets consider what else influences the final print…
- The paper choice
- The light source (warmth, brightness, spectral distribution)
- The screen (colour temperature, brightness and contrast)
- The profiles and printer used
- File format such as resolution and other technical considerations
- Our visual perception
For about a year, I compiled a list of problems. Not my own personal issues, but things I discovered in images which prevented them from making optimal prints. That’s not to say the images weren’t good, some were in fact stunning and went on to win awards much more valuable than the paper they were printed on. But some just weren’t optimised for a printing.
The images came from a range of people, representing a range of skill levels and different working environments from calibrated workflows to laptops beside windows.
Here I’m sharing the top hitters, niggly technical stuff that influences a print. These principles are technical in nature and should always be applied hand in hand with the creative intent.
The results were something like this
- Tonal values not appropriate 46%
- White point 46%
- Black point 13%
- Too dark 39%
- Too light 0%
- Too warm 33%
- Too Cool 2%
- Spicks and specks 24%
- Under sharpened 22%
- Over sharpened 13%
By far the biggest general issue (at 46%) was related to tonal values, getting lights light, darks dark and everything in between in the appropriate range. This is a broad topic which can be broken down further.
This is an image I would like to print
And the original histogram.
Lets start adjusting tonal values by considering the black point
Notice there is space before and after the histogram curve, meaning the image doesn’t have solid blacks or whites. The contrast range of paper is lower than a screen, so full blacks are usually needed in prints to maximise the contrast range. By adding a true black the image will appear brighter because our sense of tonality is perceived against it.
The histogram after the blacks are shifted. The image now contains a solid black.
The histogram after shifting the white point right, to make more effective use of paper white.
After setting black and white point, can you see the added contrast?
The changes in this image are relatively small, but they make an important difference in the print. I’ve come across images that require much more adjustment than this one.
Not all images need a full black or white point but most do, especially a black point. It’s typically less important to have a pure white point because colours shifted towards white can start looking washed out.
After reviewing many images, is noticed little consideration to white point, 46% needed adjustment, they didn’t necessarily need a true white but the brightest point just needed to be higher. I believe this is because many monitors are too bright to represent a print well, it’s also the reason I haven’t yet come across an image that will print too brightly, they’re always on the dark side…(hmmm, wasn’t there a trilogy about that)
This is a typical example of adjustments on the dark side (left) corrected for print (right)
After making large tonal adjustments, re-assess the saturation levels, they can often be shifted as a result of tonal adjustments.
When assessing the tonal values for a print, it may be helpful to use a white background colour to simulate the image sitting on white paper.
In between tones
With the black and white point set, check if the remaining tones also fall correctly into place, bright snow for example should have a lightness (L) value of around 90%, I’ve come across many images where white snow sits closer to 60% and would print as a grey.
If you’re unsure what the correct values are, refer to this table. To find the (L) values in Lightroom or Photoshop hover over the area you’re interested in, and read the (L) value from the info pallet’s shown below.
In Lightroom use the LAB display under the histogram, if it doesn’t appear or shows RGB values, right click and select LAB.
In Photoshop, turn on the info pallet and read the LAB values.
Surprisingly many images I received were a little on the warm side (33%), but few were too cool (2%). I need to be careful here because the colour temperature also reflects the mood of the image and there are creative reasons to shift an image in either direction, a snow scene for example may be tinted towards blue to represent coldness.
I think the reason for this yellow bias is again caused by monitors, many displays are just too cool (blue), so when I recieve the image, it’s been adjusted towards yellow to compensate. The ‘standard’ white screen is calibrated to 6500K which is already a little cool to match a print, but I have found many monitors are much bluer than that.
To assess colour balance, you can check for colour variation, if the image seems to have an overall tint, or flat or muddy colours, shift the white balance until you see better colour variation, just be mindful how this affects the mood of the image.
A quick point on screen appearance
A fundamental of all this colour (and tone) management is your display. Unless you have calibrated in some way it could be displaying almost anything and how will you ever know what’s ‘correct’. I’ve already mentioned that many displays are simply too bright to represent a print, and that’s just the tip of the iceberg. The best option is to calibrate the monitor using hardware (such as a spyder), or if you don’t intend to spend on hardware there are some options for visual calibration listed at the end of this article. Keep in mind the calibration can be made to different standards and luminance levels, some will better represent prints than others.
Soft proofing in Lightroom or Photoshop can be useful, but it’s of limited use if the display is still an unknown.
Spicks and Specks
Another common issue at 25% was spicks and specks, images that just need a tidy up of little blips like sensor dust spots or weird little photoshop errors. These are missed because screen resolution is much lower than a print, so all these little errors suddenly become noticeable on a large print.
A high definition monitor (1920 x 1080) can display only 2 megapixels of data, if it’s displaying a 24MP image most of the detail is invisible. To remedy this, zoom in and display the image at 100% and check for spicks and specks then.
Sharpening for print
Sharpening works by adding contrast to edges which gives the appearance of a sharper image. An over sharpened image will appear to have a fine grain over the whole image, or halo’s or artifacts around high contrast edges. Under sharpened images appear a touch soft, but it’s easier to correct an under sharpened image than an over sharpened image. The generally accepted practise is in three stages, First input sharpening when the raw file is converted, secondly creative sharpening, third output sharpening prior to printing or saving the image for a specific use.
In Photoshop, you may refer to this quick sharpening formula for print output sharpening.
If printing from Lightroom, make use of ‘Print Sharpening’ in the print module.
Only apply sharpening once, if you sharpen in Photoshop, don’t sharpen again in Lightroom!
The print process slightly softens the image, so after print sharpening it’s normal for the image to look slightly grainy when viewed very close.
These tips aren’t quite the whole picture but can get you 80% of the way towards better looking prints.
Visual calibration aids
Open a black and white image and adjust your monitor colour balance until it looks most neutral, it’s not perfect but can improve results. Even better, use a grey scale image that transitions from full black to full white.
Lower the brightness of your screen until it better matches the paper you’re printing on.
Windows also has a built in procedure you can follow to adjust colour balance and gamma. (Display settings > advanced > color calibration)
Option 3 (getting better)
Norman Koren has some good advice on monitor calibration, he has images prepared to help visually set the monitor straight.
Option 4 (even better)
Quickgamma windows software which can aid visual screen calibration.
Option 5 (best, seriously, just skip straight to this if you can)
Hardware calibration with spyder, color munki, X-rite etc.
When calibrating to match a print, set the screen brightness and colour temperature to better represent paper white, a quick general use formula is 5800K, 80-100cd, 200-1 or 250-1 contrast ratio.