Just crop in Lightroom. Don't enlarge/resample unless you really need to avoid visible pixels in a very large print. Other than that there's nothing gained by resampling.
I do need to resample to fill the required print size.
Is it better to resample in Photoshop from a quality perspective or is Lightroom just as good?
Photoshop gives you more options. Other than that I don't think there are any significant differences.
If you must resample, the trick is to carefully re-sharpen after enlarging. For this reason I would use "Bicubic smoother" in Photoshop (which does very little sharpening), and then use the Camera Raw filter for the sharpening.
The Lightroom/ACR sharpening algorithms are vastly superior to the native sharpening tools in Photoshop. The trouble is you can't use that when exporting from Lightroom - all you get are the three fixed settings in the Export dialog which are not really suitable or intended for this. They are output-specific.
All that said, my point in the previous post was that many people think you "must" have 300ppi for everything going to print. That's a myth and there's no special significance to the 300 number. It's just a theoretical upper limit, beyond which no improvements are possible, and in practice you can go a lot lower before you start seeing any problems. And large prints tend to be seen from further away, which in itself reduces the ppi requirement.
Thanks for your feedback which was helpful. I would still like to know possibly from someone at Adobe whether Photoshop is a better tool quality wise than Lightroom for resizing an image.
I would guess that resampling a raw file would give slightly better results than resampling a rendered RGB file, irrespective of what application does it.
I had to upsample an image for printing several years ago, and did some testing using Photoshop, Lightroom, and some third party software, possibly Perfect Resize.
It turned out that Lightroom produced the best quality image, closely followed by Photoshop.
The image produced by the third party software was maybe a little sharper than the others, but looked unnatural.
You can easily test this yourself - create images at the same pixel dimensions from Lightroom and Photoshop, then compare them at 100% view. Photoshop gives you several options for resampling that produce slightly different results, try Bicubic and Bicubic Smoother.
Excellent suggestion - thanks
I came across this poll When enlarging an image, what approach do you take most often? in the Photoshop forum, and thought I'd repeat the test I did seven or eight years ago.
Turns out that Lightroom still does a better job, and I'd say that the difference is significant.
This is from a 36 MP DNG that I enlarged from 7360 to 10000 pixels.
After exporting the file from LR, I saved the metadata to file, then opened the DNG in Camera Raw, and used Preserve details (enlargement) for resampling. Bicubic sharper produced roughly the same result, and other options were softer - including setting the workflow options in ACR to enlarge the image.
No sharpening has been applied other than capture sharpening in LR/Camera Raw.
Make sure to view the image full size (1417 x 1009 pixels).
Wow. That's a big difference...
Yes it is! And the PS image is not only softer but also has more noise in the sky.
It would be interesting if thedigitaldog could comment on this - he knows a thing or two about LR's resizing algorithms.
LR's Interpolation is a tad better than Photoshop's as it's an adaptive sharpening and conducted in a linear "gamma". I didn't see large visual differences in my testing but yes, LR's was better. Also be sure you have no additional sharpening or other processing going on in LR or it's not an apples to apples comparison.
Great feedback from all contributors. Many thanks.
Having done some further testing, it turns out that PS CS6 produces an image almost identical to the one from Lightroom (slightly less sharp), so this is a bug in PS CC 2015.
The bug report is here: Resize bug in Photoshop CC 2015.5.1 | Photoshop Family Customer Community
Sorry for misleading you all - this was caused by an error on my part.
I had overlooked a setting in the Camera Raw preferences - Sharpening was set to Previews only, which caused the image to open in Photoshop without the capture sharpening I had applied in LR (and saved to the file).
So no wonder the image was much less sharp.
With Sharpening set to All images, the result was almost as good as the image exported from LR.
So LR is still slightly better, like it was eight years ago.