Printing

Print File Resolution

What is the Optimum Image File Resolution?

Just to be clear, I’m referring to the image file’s pixels-per-inch resolution (ppi), not the inkjet printer’s dots-per-inch (dpi) resolution. The latter is the printer’s droplet resolution where a collection of scattered droplets forms a pixel.

300 ppi has been a long-time traditional print resolution. But is your printer really capable of 300 ppi, or is it something else? You would think the printer manual would tell you this, but that answer is nowhere to be found in my Epson manual. According to Epson’s technical support, their maximum resolution is 360 ppi and, based on best available information, 300 ppi for Canon printers. The difference is likely due to Epson’s piezoelectric head technology versus Canon’s thermal head technology (the latter being less prone to clogging). Regardless the technology, neither has ever been purported to have any significant edge over the other in terms of sharpness. Given that, I suggest you use 300 to 360 dpi for Epson printers and 300 dpi for Canon printers as your maximum working resolution for best print results.

Setting the Print Resolution in Photoshop

A 21-megapixel camera can produce a 16x20 print at 234 ppi, an 11x14 at 340 ppi, and an 8x10 at 468 ppi. The question is, say for an Epson printer, should the resolution for the 16x20 print be upsampled to 300 or 360 ppi? The short answer is to leave it at the native resolution.

While that may seem counterintuitive, the reason is any bicubic interpolation inherently reduces sharpness, albeit by a very subtle amount. You may question how a low-resolution image with potentially visible “jaggies” looks better than the same image upsampled to smooth out the jaggies. The reason is if the jaggies are visible, you are viewing the image too close for that resolution. When viewed at a farther distance where the jaggies aren’t visible, the image may appear ever-so slightly sharper than the upsampled image. To be clear, in practice the differences are meaningless, but the point is there isn’t much to be gained with up-sampling.

As for the 8x10 print, we have an excess of resolution. In this case you may want to down-sample to 300 ppi for Canon printers or 360 ppi for Epson printers. The reason is you may not accurately set the output sharpening if the file resolution is higher than the printer’s maximum resolution. If instead of manual sharpening, you are using a sharpening app (to be covered later), all that should be accounted for without you having to down sample. Still, as a practice, I always down-sample to 360dpi (for my Epson printer) before running the sharpening app. Plus, if you are saving the print file, there’s no point in making the file larger than necessary.

What is the Lowest Usable Resolution?

I performed a series of print tests at different resolutions of an outdoor scene and a resolution chart. The test results were enough to convince me that I could print at 240 ppi (and maybe squeak down to 220 ppi) for display-quality prints. The slight loss in sharpness and detail could only be detected with a loupe or, maybe, exceptional eyesight up close. I have yet to observe a photo exhibit where people are walking around with magnifiers in hand or their noses pressed up against the pictures.

If You Must Upsample

Under most normal conditions you shouldn’t need to upsample given that most cameras are at least 20-megapixels and most desktop inkjet printers are limited to 13-inch or 17-inch wide prints. If you want a larger print, you’ll need a 36-inch or 44-inch wide printer (not your typical amateur fare) or, more commonly, you use a lab. Likely, the lab will resample the image for you if you want up-close scrutiny. If instead you want complete control, then here are your options.

Routine bi-cubic interpolation

I’ve already explained where this essentially buys you very little. The exception is Photoshop’s ‘Preserve Detail 2.0.’ This algorithm performs a multi-step scaling process that analyzes the high-frequency detail of the original image to preserve sharpness. The process may accentuate noise, so there is a ‘Reduce Noise’ slider to tone it down. The result is a bit better than standard bi-cubic interpolation, but it’s subtle.

AI scaling

The best option is specialized scaling apps such as Gigapixel AI that intelligently fill in detail between the gaps. Even better is that Adobe Camera Raw and Lightroom now include a similar capability called Super Resolution, though you’re limited to only doubling the image size. This means a 20-megapixel camera can create a 25x37-inch print at 300 ppi and a 45-megapixel camera can generate a 36x54-inch print, also at 300 ppi. To access this feature, right-click the thumbnail image and select ‘Enhance’ and then check ‘Super Resolution.’ Be aware that the file size will dramatically increase.

Evaluation of Adobe’s Super Resolution

The image below was taken with a 45-megapixel Canon R5 and scaled up to 36x54 inches using Bicubic, Preserve Detail, and Super Resolution. Evaluation was based on a 27-inch, 218 dpi monitor viewed at actual size and a sample of an actual-sized inkjet printout. Viewing distance was up close, which means differences become less meaningful when viewed at a more appropriate viewing distance.



Evaluation Image: Taken with a 45 megapixel Canon R5.

When I compared the native resolution file set to the same size, it was difficult to tell the difference between it and the upsampled Bicubic and Preserve Detail images. Super Resolution, however, was noticeably better with more crisp detail that also created a pronounced sharpening effect.

When all the files were sharpened (with Super Resolution requiring very little), differences evened up somewhat. There were no dramatic differences, but Super Resolution still had the edge lest one caveat. While totally subjective, the question of “realism” needs to be addressed. While results can vary as a function of content and varying spatial frequencies throughout the image, I felt some of the Super Resolution renderings for this image were a little unrealistic.

As an additional exercise, I repeated the evaluation with a giant 12x18-foot image size that equated to 75 ppi without upsampling. Here, Super Resolution shinned with better detail rendering and, surprisingly, much less grain. Again, remember that when stepping back towards a proper viewing distance (which in this case would be over 20-feet) many are not likely to tell the difference. Still, the bottom line is that to produce a super-large print that will be viewed up close, you’ll need to use Super Resolution or an application such as Gigapixel AI (or let a lab do it).

Output Sharpening

My last step before printing is sharpening for output. I do not use Photoshop’s Smart Sharpen or Unsharp Mask filters (or output sharpen in the raw converter). Instead, I use Nik’s Sharpener Pro plug-in that I’ll cover in Chapter-16. If you elect not to use a third-party plug-in, I recommend you read Bruce Fraser’s Real World Image Sharpening with Adobe Photoshop, Camera Raw and Lightroom (2nd Edition), coauthored by Jeff Schewe. In brief, Fraser describes a three-step sharpening process that can usually be simplified into two steps. To be fully versed in his technique, you need to read his book or read a distilled version in Martin Evening’s Adobe Photoshop for Photographers.

Fraser’s process advocates you customize the sharpening based first on the capture media (digital or film type) by accounting for their specific characteristics, such as film grain or digital resolution. The next sharpening phase is assessing the image’s dominance of fine detail (high-frequency) or continuous tones (low-frequency). The last phase, output sharpening, is based on the target media, which is an inkjet printer for many of us. Because I use one camera and most of my landscape images are mid-frequency on average, I combine the first two sharpening steps in Camera Raw using the settings described in Chapter-13. The steps for output sharpening are a little involved and best automated as an Action in Photoshop. Determining the process’s optimum values can be arduous and, thankfully, Fraser’s book has some helpful examples.

Lightroom Output Sharpening

As I have previously stated, I use the sharpening tools in either Camera Raw or Develop to apply only a level of pre-sharpening. If you are flying solo with Lightroom sans third-party plug-ins or access to Photoshop, then you output sharpen in the Print module. By selecting a few self-explanatory parameters under the Print Job tab, Lightroom automatically calculates the correct parameters (similar to Nik’s Sharpener Pro). The sharpening process is based on PixelGenius PhotoKit SHARPENER, which in turn is based on the Bruce Fraser process. You can’t preview the results, but as I’ll discuss in Chapter-16, I don’t think it matters if you could.

The recommended Print Sharpening setting is ‘Standard,' which is the level tuned to the Bruce Fraser process. I ran a one-print test using the Standard setting and compared it to Nik’s Sharpener Pro. The Lightroom version was slightly less sharp, but in practice the difference was meaningless.

Printing the Image

My printer is the Epson P800, a 17-inch inkjet printer that uses pigment inks. The longevity of pigment inks is important for reasons other than your masterpieces not fading. You need archival prints if you intend to sell them or even present them as gifts. Also, consider the perilous future of your digital files many years from now. I’ll later address file archiving, but for now you may someday find a print becomes your only surviving record of an image.

Now I don’t mean to dismiss dye-based printers. The current generation of dye-based inks, when used with the appropriate paper, have good archivability. In addition, they have a wider color gamut and better vibrancy. If you are constrained by budget or want the most eye-popping printout, a dye-based printer is a good choice; only mind the paper type to ensure reasonable archivability.

Print Dialog Settings

Before printing, you must have the correct color management settings. The settings I use and recommend are shown in the Print dialog box below. Make sure you disable the printer’s color management and choose for Color Handling: ‘Photoshop Manages Colors.' To disable the printer’s color management, select Print Settings and, for an Epson printer, set Color Mode to ‘Off (No Color Management).' Also, don’t forget to select the proper paper profile. Finally, select Black Point Compensation and enable 16-bit color if your driver supports it.



Photoshop’s Print Dialog Box

Photo Paper

I was a long-time user of Epson’s resin-coated Ultra Premium Photo Paper Luster. I always preferred the Luster paper over non-resin paper because it had better vibrancy and contrast with superior shadow detail and richer blacks. However, after evaluating Epson’s new Legacy fine-art paper, I’ve determined that their Platine and Baryta papers were superior to Luster in almost every aspect (even in spite of their lower color gamut). Since they command a premium price, I use them only for my “wall hangers” while using Luster for less critical prints. (Note: Baryta is no longer listed on Epson’s website.)

Third party paper

Of course, there is a staggering variety of other papers available from Epson and Canon, and third-party suppliers such as Moab, Hahnemühle, Canson, and Ilford. If you’re a black-and-white enthusiast, you may prefer a rag-based paper (often referred to as fine-art paper) for a more classic look. Some manufacturers offer sample packs that are an economical way to experiment with various paper types. Just make sure whatever paper you buy has an available profile and that it works with your setup (I’ve had issues with some third-party profiles). Also, at least on Epson printers, the print driver does not automatically set the proper paper thickness for non-Epson paper. That can be an issue with the thicker fine-art papers. Instead, you have to manually enter it in the Advanced Media Control menu. To do that, click: Print → Print Setting… → change Layer to Printer Settings → select Advanced Media Control → enter paper thickness.

Evaluating a print

When the print emerges from the printer, be mindful of the light you use to evaluate it. My experience is many daylight fluorescent desk lamps still have a slight cold or green cast, and tungsten bulbs have a slight warm cast. You can buy expensive color-corrected light sources for viewing prints, but a cost-effective solution is an Ottlite desk lamp. A bigger problem is once a print is displayed, it is often subjected to varying light conditions. A displayed print can be lit during the day by sunny or overcast window lighting, and at night by tungsten or fluorescent interior lighting. The print can even pick up a slight green tint from the photo frame’s glass depending on its quality and iron content, or a yellow tint from UV glass.

Poor screen-to-print matching

You can only judge screen-to-print results when Proof (View → Proof) is enabled and setup correctly. If the prints come out abnormal, fix the problem rather than using manual adjustments. Make sure the print dialog settings are as previously described. If you did not disable the printer’s color management or enabled ‘Photoshop Manages Colors,’ you will see weird results. If you are attempting to use an uncalibrated monitor, then you must calibrate it. If you see density problems (usually too dark) and your color management settings are correct, then your monitor may be too bright to be calibrated properly. Finally, if all else fails, run a nozzle check on your printer to make sure you don’t have a clog.

If your print seems in all respects the same as the monitor except has a duller look, make sure ‘Simulate Paper Color’ is enabled in the Customize Proof Condition box (click: View → Proof → Custom). ‘Simulate Paper Color’ simulates the dullness of white paper and should bring the screen’s display more in line with the print.