In my seminars I generally teach methods that are very flexible, allowing you to change your mind and make adjustments even after the document has been saved. Many people refer to this as a "non-destructive" workflow. Over the last six months or so I've been hearing some discussion as to whether this is really "necessary" or not. In fact, going back to December, my pal Matt Kloskowski churned up the waters on this topic with his guest spot on Scott Kelby's blog. If you didn't read it then, it's worth a look.
Matt makes some great points, including saying things like (me paraphrasing here) "I've never had to go back and make changes to a document". At my most recent seminar, a few people questioned whether they should "always" use non-destructive methods. So here's my take on this topic.
Most of the time I use flexible, editable - non-destructive - methods such as adjustment layers, layer masks and smart objects for two basic reasons:
1. just in case
2. why not
Just in case:
Although I agree with Matt that I don't often have to make changes to an exiting document, sometimes I do. For example, I don't know about you but quite often my images look a little different when I print them, so having the opportunity to make some tweaks - very easily - just makes sense to me. Now and then I do work for clients (these days that means family and friends) and it's not unusual for them to ask me to "just change this one thing". Preserving layers (and pixels) though flexible methods gives me the ability to do this.
Yes, this is one of my reasons too: why not use non-destructive methods? Generally speaking it doesn't take any longer to clone on a separate layer, scale a Smart Object, use adjustment layers versus the Image>Adjustment menu or a layer mask rather than erase. (Okay, in a few cases it might take a second or two longer, but not much). What's the downside of using a non-destructive workflow? You have more layers, your file size is a little bigger? So call me paranoid, but I'll happily live with a few extra layers......just in case.
Maybe this stems from something that happened to me years ago. I designed a magazine cover that was a collage of 20 or so photographs, so lots of layers and masks. Once the project as done, and after repeated promises from the client that they'd never use the cover again, I chose to flatten and save it so I had a copy. Well, six months later they called me to say that they had decided to reprint that issue (for the first time in their magazine's history) and "just" needed me to make a few changes. At the time I remember thinking, I wonder if I can say, "no I can't" but realized that wasn't going to work. So I had to rebuild the whole thing from scratch. (and they certainly weren't going to pay me to rebuild it - they were expecting a bill for an hour's worth of "tweaking")
So perhaps that's where my philosophy of "just in case" comes from. Still, it just makes sense to me.
Do I ever pull out the Eraser and delete some pixels? Sure, now and then. But most of the time it's a Layer Mask.
As an aside, it appears the Adobe is gently nudging us in the direction of non-destructive methods in Photoshop CS4 with the changes to Adjustments layers (must more visible than before), the Masks panel and ongoing tweaks to Smart Filters and Smart Objects.
Needless to say, it comes down to personal choose. But do me one small favor: before you flatten, merge down, erase, etc, consider the words "just in case" .