For a Romantic Look, Try the Gaussian Blur (and Skip the Petroleum Jelly)
Back in the 1970's when the SLR craze was exploding and photographers were all exploring the creative potential of photography, one of the odd things that you were likely to find in almost every photographer's bag was jar of petroleum jelly. It wasn't for soothing the scrapes and scratches encountered while climbing around in nature, but rather for softening focus to give subjects like landscapes and portraits a more romantic look. Perfectly rational photographers (well, maybe not perfectly rational) would smear an otherwise perfectly good UV or skylight filter with a liberal coating of the jelly to give their photos a soft, or more likely a blurred, look--and art directors were eating it up. Using petroleum jelly was so prevalent back then, in fact, that if you looked at the photo cards on the Hallmark card racks, it must have seemed the entire profession was suffering from some sort of communal glaucoma disease.
Still, the romantic look was popular and I sold a lot of photos thanks to that little jar of petroleum jelly--and I ruined a lot of good filters. You can create the same look, of course, in editing and you'll waste a lot fewer filters and your fingers won't be slimy the whole time you're shooting. In Photoshop (and in most other editing programs) there are a number of blur filters available but the one that I use most often is the Gaussian blur (Filters>Blur>Gaussian Blur) and it's very simple to apply. Once you open the dialog box for the tool all you have to do is adjust the intensity of the blur using a slider.
The real trick to controlling the degree of the Gaussian blur, however, is not to apply it to the background layer itself, but rather to a copy of the background layer. (The keystroke command for creating a dupe of the background layer is Command J for Macs and for Windows it's Alt J.) This creates an exact duplicate of the background layer and any changes you make to the copy layer will not permanently affect the background image layer. Now apply the Gaussian blur to the duplicate layer. I usually apply a much heavier degree of blur than I'm going to use in the final image because once that blur is applied to the copy layer, you can tweak its intensity by adjusting the opacity of the blur layer. (The opacity control is in the upper right-hand corner of the layers palette.)
In other words, you're getting a second chance to apply the blur to the image, but rather than just seeing the effect in the tiny preview window of the blur filter dialog box, you're able to watch as it is applied to the whole image--and you can adjust it with settings from 0-100 which provides far greater control. I used a 33-percent opacity for this image with the actual blur set to 9 in the Gaussian dialog box. The blur is probably somewhat difficult to see (a good thing) because you always want to be light-handed on the filter or you just end up with an out-of-focus image (a lesson we had to learn many times back in the petroleum jelly days when we equated more jelly with more creativity).
Just to recap, the process is very simple: Duplicate the background layer, apply the Gaussian blur (fairly heavily) to that copy layer and then use the opacity control to adjust the blur intensity. It's a much more precise way of adding a bit of romance to your images and you can also apply it selectively by just selecting specific areas of an image (applying it just to window box full of flowers in a photo of a house, perhaps). And just think of all the money you'll save on petroleum jelly (not to mention those expensive little filters).