I often photograph objects, makeup, products on a plain white background for my blog photographs. It makes a simple clear image that shows off the product well and keeps things looking fresh. But achieving this pure white (or close enough) backdrop for my photos is something that often happens afterwards in editing software such as Photoshop. I use CS5 but the tips and tricks I'm about to show you as far as I know are available in most versions of Photoshop.
You don't need an expensive studio set up to achieve this look for your blog photographs. I'm going to show you the main steps I apply to all my blog images when I want a white background. I take the majority of my blog photos at home, in my bedroom using very simple and inexpensive equipment. These days I'm much happier with grey toned backdrops but sometimes a product may require a bright white space for that 'studio' look.
Firstly I photograph my objects on a white table top or in the past I've used a large white sheet of card and a white wall. I use as much natural light as possible (big window) and a small continuous softbox to make less work for myself in Photoshop. I make sure my camera settings are set for a light bright photograph but I don't want anything to be over-exposed. This is when you'll start to loose detail and sharpness.
Even with all this light, the white background can still look grey and a little dull. So here's how I fix it...
How to Edit a White Background in Photoshop
Open up your photo in Photoshop. Duplicate the layer so you can always revert back to the original. I always start with Curves. Hit 'CTRL+M' for the shortcut or go to Image > Adjustments > Curves to open up the Curves box. I bring the whites up slightly, and then the blacks down slightly. Forming this subtle curve seen above. You do this by clicking and dragging the line. Don't go overboard! We can always come back and repeat this step again. Click OK.
Next I go to Levels. 'CTRL+L' or Image > Adjustments > Levels. I bring up the white as seen here on the right hand side of the graph, and then bring back down the black a tiny bit for contrast. This will brighten up any areas on your image that are white and enrich any areas that are black. The grey slider is useful too, just move things around to see what happens to your photo. I don't stick by any strict numbers, each image is different.
By now you should your photo is brightening. The background appears whiter and the contrast is stronger. However you may have shadowy grey corners still lurking about, and outer edges of your image may appear duller than the center frame. I grab my Dodge tool (lollipop) which is a lightening tool. I reduce the exposure to around 50-70% seen in the first photo at the top and then go about sweeping the brush along the outer edges of my photo. A little at a time, short but smooth clicks. You can always hit CTRL+ALT+Z to reverse any mistakes. Avoid going over the objects in the photo too much as you will lighten up areas that don't need lightening.
Looking better! If needed I may go into Image>Adjustements>Selective Colour. From here I choose the colour 'Whites' from the drop down list and move the Black slider down to around -25% this will reduce any black colour (or grey tones) found in the white areas of the image.
After all this tweaking and adjusting you may find your image is now looking a bit too bold and overdone. This can usually be sorted by reducing the saturation slightly. 'CTRL+U' brings open the Hue/Saturation box or Image > Adjustments > Hue/Saturation and you can slide down the Saturation bar to your desired look.
Compare to your original to see how much it's been improved! You will never achieve clinical strength pure white product shots using this technique, for that you'd need studio lights and much more expensive equipment. But this is a simple solution for everyday images and for clear and professional looking product shots.