Photoshop a low-res image to make it appear higher-res
I want to enlarge an image to a bigger size. This will cause pixelation. So I want to apply some treatment to it in Photoshop that will suppress some of this pixelation. Of course I cannot generate new pixel information, only smoothen it etc. so that the pixelation is not so much apparent in full views and prints. Example, one effect popular with photographers is to copy the image into a second layer, set its blending mode to overlay or soft light etc., then apply a blur to it. This somewhat smoothens the image. But it also changes its appearance into a glowy kind of look (which is the aim, usually). I want a treatment that will fake the appearance of a higher-res smooth image without too many side-effects.
Any tricks of this kind that anyone knows of?
In general, enlarge the image using Bicubic interpolation (sometimes, depending on the image, "Bicubic Smoother" works better, but usually straight Bicubic is more satisfactory), then either use Smart Sharpen to bring back the edge contrast, or copy the layer, set the blend mode of the copy to Overlay, and run
Filter > Other > High Pass.
Sometimes you can get a better result if you increase the size by a smaller amount, apply a sharpen (not too much!), then increase it some more, apply another sharpen, etc., until you reach the size you want. This takes patience and a lot of trial and error to make it work for any give image, so I don't recommend it except in extreme cases, but once in a while it will allow you to push enlargement beyond where you can go without that intermediate sharpen.
My experience is that the best approach varies according to the image, the amount of upsizing and the result you're looking for. There is a limit to how far you can scale any image before the result becomes too fuzzy to be useful, and the definition of what is useful depends entirely on your application. For graphic design work it is almost never worthwhile to upsize an image more than about 10%.
In Photoshop, enlarging should not cause pixelation by default. Go into Edit > Preferences > General... and make sure that "Image Interpolation" is set to one of the Bicubic options (there is even one for enlarging it looks like). Also, if using Image > Image Size... to resize a photo, make sure at the bottom the Image Size dialog you have "Resample Image" checked and one of the Bicubic options selected from the dropdown menu. Other than that... what Alan said.