1. Select the background
Start by isolating your image's background – I find that the Quick Selection Tool is often best for this. Select the tool and use the [ and ] keys to make the brush bigger or smaller. Paint over the background until it’s entirely selected. If the tool selects parts of your subject too, then hold down the alt key and paint back over these areas – it might take a little bit of back and forth to get it just right.
2. Refine selection
To tidy your selection, go to Select>Select and Mask (Refine Selection in earlier versions). Under Edge Detection, check Smart Radius and increase the radius to tidy the edges – around 50px works well here. If you’ve got stray hairs to deal with, as I have, then select the Refine Edge Brush Tool from the left and paint over these areas. Again, holding down the alt key removes that area from the mask.
3 Apply Blur
Once happy, press OK and, back in the main window, press cmd + J (Mac) or ctrl + J (Windows) to create a new layer from your selection. Then right-click on your new layer and select Convert to Smart Object – this allows you to go back in and adjust the filters we’re about to apply as many times as you like. Next, go to Filter>Blur>Radial Blur. Set the amount to around 5, Blur Method to Spin and Quality to Best and press OK.
4 Use Mask to tidy
You can lower the opacity of the layer to tweak the blur. My image needs work around the model’s feet, as the effect is unrealistic. Add a Layer Mask (Layer>Layer Mask>Reveal All) and then, using a large, soft Brush set to Black at around 50% opacity, paint over areas to remove blur. I’ve focused on removing it from the same focal plane as the subject. I’ve also masked a large area in the centre of the image.
5 Tweak the colour
Happy? Go to Layer>Flatten Image. Another characteristic of the Petzval lens is saturated colour. This is easily applied by adding a Vibrance adjustment layer (Layer>New Adjustment Layer) and then increasing the Vibrance and/or Saturation. Vibrance is a more subtle form of increasing colour saturation, although I’ve also carefully masked the effect from my subject’s skin here using the Layer Mask and Brush Tool.
A final touch is adding a vignette to the edges, something often seem on images shot with a Petzval. To do this, go to Layer>New Fill Layer>Gradient. Choose a black-to-transparent gradient, change the Style to Radial and make sure Reverse is checked so the image darkens at the edges rather than in the centre. Press OK and, back in the Layers palette, lower the opacity of this gradient to suit – around 20% works here.