Sharpening for Print Using Online Print Labs

This is a topic that has been bugging me. I get prints ranging from 8x12 to 24x36 from SmugMug that I order directly off my website and they can go through either EZ Prints or Bay Photo. (There are no local resources available). When I upload hi-res images to my website, I sharpen it to what looks good on screen. EZ prints uses automated algorithms that apply a minimal amount of added sharpening, while Bay Photo applies no additional sharpening at all. I'm considering switching, but I've been using EZ Prints, and the results are good, yet I don't feel like I'm getting the sharpness that I should have. My prints go to a local gallery, and I am displaying them at arts & crafts shows.

Of course, most of us know that sharpening for screen and sharpening for print are two different things. It is my understanding that, when sharpening for print, it may look oversharpened on screen. Also, sharpening applied for a 24x36 print will be different (more) than an 8x12. Print ordering of an image from SmugMug doesn't adjust for this, unless I were to upload a different file, sharpened for each size. Are there any pros who have run into this issue, and how do you deal with it?

Thanks for the help!
P.S. I've posted this question in SmugMug's forum and didn't get a helpful answer.

I also use Smugmug and have had the same question for a while, unfortunately I don't think there is a good solution. I am reasonably happy with the prints but they will never be as sharp as when I sharpen prints for each individual output size. I will follow this thread to see if anyone has any suggestions but I do the same as you. I apply some sharpening before uploading my large jpeg file and allow EZ Prints to apply a little more sharpening. This seems to produce acceptable results.

I've used MPix (mpix.com) for my prints - up to 16 x 24 & they've come back just as I intended. I've not priced them against Smugmug, so I don't know how that stacks up.

Many online printing companies such as Mpix and Smugmug do all the interpolation for you. It makes a photographers life easier when it comes to printing, especially if you are ordering many different sizes. I can't really recommend how to get sharper prints with those methods, but if you really want to take control of your prints you can do the interpolation and output sharpening yourself. Some of the companies mentioned recommend you don't do this yourself (and if you do you'll get horrid results - trust me). However there are a few companies (West Coast Imaging, Aspen Creek Photo, Calypso Imaging, just to name a few) out there that allow you to do this yourself. If you wish to try I'd recommend contacting the company you wish to do business with and make sure their workflow doesn't conflict with yours, as well as to obtain their optimal printing dpi and color profiles. I will add that it can be a pain doing it yourself, and can take quite a bit of trial and error to get your prints looking the way you want and realize what methods work and what doesn't, but I'd personally rather have that sort of control.