I’ve been doing all my printer resampling testing by scanning actual printed output. I think that makes sense when you trying to evaluate the complete system. It allows you to see how the resampling interacts with the printer itself, and also allows you to see what differences in resampling more important for actual printing. However, it’s instructive to look at the resampled images before they are printed, especially if you’re trying to reverse engineer what the resampling program is actually doing or trying to decide if small differences are the results of real differences between the sampling algorithms, or just the way the printer printed the images.
In this post, I will show you what the images look like before they are printed. In order to make differences more obvious, and reduce the amount of extraneous image processing, I started with our 145 pixel per inch image and resampled it to 720 pixels per inch in all cases. The results are posted here as actual size, saved using JPEG compression with the maximum quality setting in all cases. In Lightroom, that quality setting is 100; in Photoshop, the maximum setting is 12. I’m not sure why the two parts of Adobe couldn’t get together on how to specify compression quality, but there it is.
When the resampling is performed in Photoshop, producing these test images is straightforward: perform the resampling, and save the file. In Lightroom, I used the ability of the print module to export files as JPEG images.
First, let’s look at the kind of resampling the Epson printer driver does – nearest neighbor:
Kind of blocky, huh? That’s probably not what you want your printed images to look like, and the reason why resampling for printing is so important: you just can’t leave it to the printer.
Next, Lightroom with no sharpening:
This is the “first do no harm” approach to resampling. There’s nothing wrong with it, but it’s certainly not for very crisp.
Next, Lightroom with standard sharpening:
My take away from this image is that you don’t have to be too worried about turning sharpening on in Lightroom. It’s probably not going to do any harm. This image doesn’t look too bad even without the softening that printing it would cause.
Next up is bicubic smoother, which is what Photoshop recommends for enlargement:
It’s not the same as Lightroom without sharpening, but there are no important differences.
Let’s see what happens with bicubic automatic:
This is essentially identical to bicubic smoother. My guess is that the automatic option for resampling tells the program to look and see whether the images being enlarged or reduced, and picking bicubic smoother if it’s being enlarged, and bicubic sharper if it’s been reduced.
For completeness, here’s bicubic sharper:
It’s not as good as bicubic smoother, but the artifacts are tiny. If you accidentally picked the wrong bicubic interpolation, it’s not going to ruin your print.
And last, here’s what happens when you use Perfect Resize with the defaults:
Pretty spectacular, isn’t it?