Let me address the technical reasons for why planning to "fix it" just doesn't cut it. The bottom-line is every time you make an adjustment in Photoshop, your image degrades oh so slightly. By nature of digital manipulation, images degrade whenever you move the slider, change the contrast, rotate, or any other changes. You can see the effects directly if you look at a histogram.
Try this experiment. Open a file in Photoshop that needs fixing. Look at its histogram and see how smooth the slope is. I'm not looking for smoothness per say. I'm really looking for spikes and discontinuities in the histogram. For pure images that haven't been adjusted there won't be any of these abnormalities
Now, apply an adjustment to the image either directly or through an adjustment layer. Try fixing the contrast, brightness, or anything else. Notice the histogram. Right away you'll start seeing it morph. Not only will it show the slight adjustment to the image's tonal qualities, you may begin to see these spikes or discontinuities. Essentially, what you're seeing here is the image being slowly degraded. "Hey, I don't see this on screen" you're saying. No, you may not but damage is being done to your image regardless. Since screen resolutions are so poor, you may not see these affects on screen but on print. Viewing prints is an entirely different matter than viewing on screen. You can get away with things so much more on screen that wouldn't be tolerated on print. Notice, if you apply enough adjustments you'll begin to see the damage directly on screen. Even the screen view won't hide the bad reality that's happening to your image.
The bottom-line message I want you to take away here is making adjustments damages quality of your image. While it may not be much doing enough adjusting can potentially significantly affect how your image appears. Anything you can do to minimize these kinds of adjustments is a sure way to minimize the damage.
What about the non-technical reasons for not planning to "fix it" in Photoshop. There's the whole integrity of the image making process. As I already noted, at the moment the trigger is pulled and the image is captured. Everything you're ever going to make of the image is now frozen. The intangible ingredients you used to make the image are either there or not. The contrast, the composition, the basic elements of the image are either captured for all to see, or they aren't. Similarly to the technical reason for not making adjustments, distrupting the thought process that created the image will degrade the image's quality. While this won't directly affect the image's technical integrity, distrupting the thought process mid-stream by doing things well beyond what was intended at capture will diminish the images quality.
Look at this as an example. Let's say you're shooting a set of birds but can't get close enough. That's okay you're saying to yourself. I'll just crop it in Photoshop and make it look like I'm closer. That's fine for small crops or if you aren't planning on enlarging the image. However, if your looking to make wall-sized enlargements, you need every pixel you can get to keep the final print from degrading. This makes cropping unacceptable.
Let's consider another point of view with cropping. If you haven' seen it yet, smaller digital sensors increase depth of fields. This is related to how much you enlarge the image from it's sensor size and the technical term "circle of confusion". The larger the sensor, the smaller the depth of field. Let's say you planned on having a very blown out and clean background. Everything looked great in the view finder but find after cropping and enlargement the background isn't as clean thus distracting the viewer from the subject. In both these examples "fixing it" did not let what you thought you saw in the view finder become reality.
Adversion to cropping is just one of many perspectives I promote. Similar perspectives can be given to exposure, contrast, sharpness... just about anything.
For my part, unless the image capture is incredibly unique, I delete images requiring aggressive Photoshop manipulation. While I'm editing my images, if it looks like I didn't get the exposure right, the composition correct, blown out a highlight, or didn't get any of another of a million technical details correct, I'll delete the image without prejudice. I do this if for no other reason than simplifying my photographic life.
Even though the digital photography revolution has put a tremendous capability in the hands of normal photographic human beings. One thing it hasn't done is simplify our lives. Image manipulation is a time consuming process requiring clear vision and conscious effort. Fixing things after the fact that could've been gotten right in the field is less efficient. Beside the whole point adjusting an image's brightness in Photoshop degrades the image's quality, getting the exposure right in the field the first time is simply less time consuming. Always fixing things after the fact does nothing to improve a photographer's craft out in the field. Being deligent when editing and going aggressively after the less the ideal captures does wonders for keeping a photographer focused on the right thing--the image--verses being a technically brilliant computer user. While having some skill working with Photoshop is highly useful for any photographer, being focused on being a camera shooter and image maker keeps a photographer's emphasis true.
Remember, this article is about the image verses the tools you use. So, when in the field and you notice that you've accidentally blurted out " I'll just fix it in Photoshop" stop right there, wash your mouth out with soap, and get on with getting it right the first time in the camera.
Cheers
Tom
