When I sit down with my photography mentor, I always learn something ridiculously simple but indispensable. I pay a lot of attention to his critiques of my work–he’s a master and veteran of film, fashion and print. I’m going to share one of the best tips he’s given me yet: keeping dresses truly white.
The first time I shot a wedding dress on a sunny day, I didn’t realize how much blue the white picks up–just like water. Here is how I started out:

To determine how much (if any) blue is in the dress, I opened Photoshop and created a duplicate layer of the image. On the top menu bar, click Image –> Adjustments –> Hue/Saturation. Change the “Master” channel to “Blues” and bump it up to 100%.

WOW, that’s a lot of blue I can live without. Ick. In the same window, change 100% to -%100.

So much better! Now just erase the elements of that layer that really should be blue (like eyes, sky, etc.) and you have your final shot with a truly white dress.
I created an action for this and used it on almost every shot of the bride during my last wedding. It’s quick and easy, and makes a huge difference in the integrity of the photo.
