Just another image born of playing with off-camera flash.
I decided to use the dusk to experiment with rendering everything except the subject black, even though there is no backdrop and it was not yet dark outside.
Since the hat is sitting on a fencepost, I did have to clone out a horizontal wire and a small portion of the fencepost itself. You can see where I was a bit careless and missed some along the left and bottom edges. The rest of the blackness was done by manipulating the light and was not due to post-processing.
S-M-C Takumar 105/2.8
For those who may be interested in how/why this works, are not familiar with it, and would like to try it, I'll include my poor attempt at an explanation:
The power/intensity of light falls off proportionately to the square of the distance from the flash to whatever it is hitting. That means the closer to the light source, the bigger the drop in brightness. The rule is that a two times increase in distance means a four times decrease in brightness. (Doubling the distance quarters the brightness).
How far the camera is from the subject is entirely irrelevant here. The only thing that matters is distance from the flash (or other light source) to the subject. Keep that in mind as you read further...
Imagine we have a subject with some other objects 2 meters behind it and we set the flash 2 meters away from our subject. That would mean the background junk receives 1/4 as much brightness as the subject. That translates into two stops of difference. The background junk will be two stops underexposed. That's enough to throw it into relative darkness and obscurity, but really not enough to black it out altogether.
Now let's take real advantage of the double-distance-quarter-light (known as the Inverse Square Law) to really throw a larger difference of brightness onto the subject and background clutter. If we move the flash closer so it is only 1 meter from the subject the effect on the background brightness isn't all that great, but we have increased by a factor of four the brightness hitting the subject. That means we have to stop down two more f-stops for the subject to adjust for the new postion of the flash.
It may be easier to understand if I use some values from the scale on the back of the flash I used:
At the original 4 meter distance of the background, my scale showed the background would be properly exposed at f2.8 and the 2 meter subject at f5.6 (two stops difference).
At the new 3 meter distance of the background, we only have to close down half a stop (to between f2.8 and f4) to properly light the background. But the 1 meter subject now requires us to close down to f11 for proper exposure.
That means that with the subject properly exposed at f11 the background will now be about four stops underexposed. And four stops underexposed is spelled B-L-A-C-K.
On the other hand, if we want to make sure we get the background well-lit enough to show up nicely in the photo, we need to back the flash way off. The farther the better, within reason and the limits imposed on us by the power of the flash. For example: moving the flash back to 5 meters from the subject (and 7 from the background) would mean a difference of only about 1/2 or one f-stop underexposure on the background, which is well within the range to make sure both show up nicely.
The problem is that, depending on the power of the flash, it may require an aperture that is larger than your lens can handle. In this case my flash shows f1.4 for the subject and f2 for the background. So if you're shooting with a lens that doesn't open up that much, you'd have to move the flash close enough to work with your lens....and that would increase the difference between the light between subject and background.
Another factor, of course, is the ambient light level. In the case of the hat photo I shot at 1/160 at f11. My camera's meter showed me that with no flash at f11 I would need a shutter speed of about 1/5 second. That would be for both the hat
and the background. With the light source 93 million miles away, another couple of meters doesn't give enough difference in light intensity to make any difference
at all and the Inverse Square Law ceases being our friend.
1/160 = (speed I decided to use for flash at f11)
1/80 = minus one stop
1/40 = minus two stops
1/20 = minus three stops
1/10 =minus four stops
1/5 = minus five stops (speed for natural light at f11)
That meant that anything the flash didn't hit was going to be five stops underexposed at 1/160 @ f11. If there had still been enough natural light outside that the background would only be a stop or two underexposed, then all the mumble-jumble above about moving the flash around wouldn't count for a hill of beans. It's kind of hard to overpower the sun with nothing more than AA batteries on your side.
I hope all that was helpful for some of our many friends here at Pentax Forums. Just keep in mind that an important factor in doing all this stuff is that we're only concerned with the distances from flash to subject and flash to background. It doesn't matter if you're shooting the scene with your camera 1 meter away or 10 meters away. (Something I only learned within the last few days).
Here's the first photo I took during this little experimental exercise:
Like the idiot that I am, I forgot to switch from Av mode to M mode. The shutter opened, the flash fired....and I knelt there in stunned stupification wondering why in hell the shutter didn't close again. I stayed as still as I could until it closed, but it turned out to be a 2 and a half second handheld exposure. In body SR is good, but it ain't
that good. The only reason there is any sharp area at all is due to the flash firing and giving it a proper exposure for f11. This turned out to be a good example of how one
can combine proper exposure for both flash
and ambient light in the same photo. That is, it
would be a good example if I had used a tripod and
intended to do that.
As you can see, there was still plenty of light outside for non-flash photography using a tripod and long shutter speeds. Heck, if the lens had been wide open I could have handheld it and come out fine most likely. Everything is blurred due to camera shake and the short focus distance, but you can tell that there was still sufficient light to accurately capture a range of colors and detail all the way to the horizon.
I decided to have a little fun with the failed shot and here's what it looks like after intense post-processing:
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