
Re: New Intervalometer Development - The math of bulb rampin
miznick wrote:
Hi all,
Why are most intervalometers using f-stops and not "e-stops" for lack of a better word?
Because f-stops are always relative to some previous position or starting point, and if I want to change one of my other settings (ISO or aperture), I need to know my shutter speed is going to behave accordingly.
If you're shooting a 1 second exposure, and then you add another whole second, you've added a whole stop.
If you're shooting a 1.5 second exposure, and then you add a whole second, you've added about two thirds of a stop.
If you're shooting a 3 second exposure, and then you add a whole second, you've added about a third of a stop.
If you're up to 30 second exposures and you add a second, you're not making much difference to your shot at all.
For a smooth transition of exposure, it needs to be relative to the previous exposure, the exposure needs to be increased (or decreased) by a certain percentage (whatever fraction of a stop), rather than a fixed amount of time.
miznick wrote:
What is more important - the absolute value of the exposure, or the repeatability of the exposure?
The two kind of go hand in hand, they're both as important as each other. Knowing what your exposure should be is nothing without the ability to reliably implement it in your shot. If it's not reliably repeatable, it's really not all that accurate.

Have to say though, I've never felt the need to get PC sync socket feedback from the Nikon bodies to the Arduino, other than, initially figuring out the shutter lag, when sending in signals through the 10 pin port, and managed very consistent shutter speeds without flicker in the playback (using M42 lenses to eliminate aperture flicker). I don't do it in general operation.
This one was with the 70-200mm f/2.8VR wide open at 200mm on the D300s, with the shutter speed controlled by the Arduino. Exactly the same exposure on each shot, but no flicker at all, and there's been no kind of deflickering done in post. As I said, Nikon bodies (or at least the D200 and D300s) are very consistent from shot to shot.