It's a fine line how much a photo can be post-processed before looking 'unreal', and whether a photo should ever be pushed anywhere near that point. There can be many goals when doing post processing -- one can be attempting to create an emotive piece of artwork, for example, or they may be aiming for photojournalism.
Photojournalism has a few cardinal sins. The clone tool is one of them -- no photo that has been touched by the clone tool can be considered 'photojournalistic'. That doesn't mean that it can't be run in a newspaper or a magazine, only that it will be used as a piece of art (technically known as a 'photo illustration'), not as a representation of reality. Photojournalists are allowed to post-process their images, and almost all do. In the past this meant hours in the darkroom dodging and burning and masking and the like; these days it means a few minutes with photoshop. The AP usually asks for photos as unmolested as possible; they have a very lighthanded photo toning method, assuming that each publication will need to do different things to the photo to get that photo to reproduce in the many different printing presses and mediums.
One of the big secrets of contemporary photography, I am discovering, is that almost everything you see in every medium has been heavily post-processed at some point or another. Seriously. That photo of the football player you see in the newspaper? Some guy like me went in with a computer and made sure that that football player's skin tones adhered to certain 'known' CMYK color number values. Someone went in and made sure the uniform was the correct color, that the grass renders as green, that the sky renders as blue. Someone totally butchered that photo so that, when printed using cheap ink on cheap paper, it looks something like the original. All the magazines use the same process. All professional photos are processed at one point or another. The other day I went down to Forberg's gallery and asked the lady behind the desk what he shoots with. He shoots slides... and then drum scans them. There's only one reason to drum scan something... to digitally post process them. And I can see what he's doing in his post processing, too, and it's well beyond what would be easily achieveable in a darkroom. If you aren't digitally post processing your digitally shot photos at all, then you're skipping at least 50% of the photographic process.
That said, that still doesn't address the 'how much is too much' question, and it's a really good question. The answer is that there is no answer. If what you're doing is suiting your application, then it's not too much. When I tone, my application is usually to attempt to make the photograph appear as it did to my eye at the time that I was there. (Usually -- sometimes I'm just going for pure art, and at those times the photos look much more dramatic than what I actually saw, though it may reflect the emotions I was feeling when I took it!) It's good to not lie to the people you are trying to show your image to. If you're toning artistically, don't be shy -- tell them!
Storm photography is extremely difficult in that the human eye can usually process detail in ALL of the scene, whereas your camera is going to have a very stunted dynamic latitude. You want the cloud detail, you've gotta blow out the ground. You want the sky detail, your gonna lose your cloud and your ground. You want the ground detail, your sky will be white. Traditionally, this kind of thing was tackled by using gradiated filters and the like. In contemporary times, this can be tackled by other methods as well; either by digital post processing or through something like HDR or multi-exposure composting. I tend to use digital post processing and very rarely multi-shot composting to simulate gradiated filters, though I've been experimenting a bit with HDR. (The reason that I rarely use multi-shot is that at that point the photo usually becomes disqaulified for being photojournalistic, as the photograph is not a temporally whole event.)
Someone asked about this photo:
This photograph was actually, surprisingly, not very post-processed. But it was post-processed. It was shot as a Canon RAW in the Adobe RGB colorspace, then converted to 16 bit TIFFs*, given some LAB mode tweaks (levels, slight s-curve to the clouds and ground, slight colorspace compression in the a & b channels (10 points, either side, as an adjustment layer, then backed off a bit on the opacity), reconverted to RGB, moved to the sRGB colorspace, downsampled to 8 bit, sharpened, and saved.
Why's the asterisk there above? Because when I did the RAW conversion, I used the Adobe RAW conversion tool to convert it several different times to simulate several different exposures. All of these 'exposures' are of course just different slices of the RAW pie, most of which gets thrown away in the final product. For example, here is the RAW images as shot in the camera:
Nice overall, but the ground is fairly dark and the sky at right is blown out. What to do? Well, use this as a base, and then use several other RAW samples and compost them as neccesary.
For the clouds, use:
For the blown out sky:
For the ground:
This simulates what the eye and brain sees; I sure as heck wasn't getting a blowout in my eyeball when I looked at this scene, and the ground wasn't black, and the sky wasn't washed out. By tapping into all the data the RAW file had, I was able to better render what I actually saw. The end product, again, was:
In actuality, I think the scene as I saw it looked a lot scarier than this, but then I was trying not to get hit by lightning and snap off this shot on a tall metal tripod before the gust front and the hail arrived, so I'm probably just blending in my own emotional impressions.
Memory is weird like that. Ultimately, I dig the rustic, rural, painterly feel the photo ends up having, so I wouldn't dream of pushing it any closer to what I actually saw.
It's basically a taste thing. Taste and honesty. If your taste runs afoul of what you
know a scene looked like to you, then it's a good idea to mention it if you think that people are going to assume that what they're looking at is what you saw. However, if what they're looking at is what you saw, sometimes you'll have to fight them -- as storm chasers, the stuff that we see is so far removed from the realities that most people experience it's easy to forget that things that look normal to us in a print look like The End Of The World -- i.e., unbelieveable -- to most others.
