The best thing to happen to my long exposure photography was studying and memorizing reciprocals. Doing so led to a better understand of how changing the aperture impacted the shutter speed. Memorizing the stops allowed me to do the extended exposure math on the fly.
Above is a picture that is a result of this effort. It’s a 71 second exposure. Well past the 30 second cap that most camera allow users to access in semi-auto (non bulb) modes. There are versions with exposure times closer to 30 seconds, but the movement of water wasn’t enough to generate the desired effect.
When starting off the shutter speeds were easily understood and so memorizing them didn’t require much effort. The apertures (full stop increments) were more difficult to remember, and are actually something that I still run through my head often to keep them fresh. Below are lists of full stop increments for apertures and shutter speeds. If your camera does 1/3 or 1/2 stop changes as well, which most or all do, then your camera will have options not listed below.
The connection between the two is simple. Say you have a 1/60th second exposure at f/8. For depth of field reasons you want to use f/16. that is an increase of two full stops in aperture. This means you need to adjust the exposure by two stops. This puts the final numbers at 1/15th second at f/16. This is also applied if going in the opposite direction. If you want to use f/4 instead then you would adjust the shutter speed to 1/250th second.
Studying these is something that will absolutely improve your photography and not just your long exposure work. The area where this comes in most handy is when the exposure goes over the 30 second mark. Knowing how changes to one setting impacts the other (assuming ISO stays the same) will allow you to quickly adapt to changing situations with confidence, speed, and ease.
1 (very rare air)
22 (typically the limit on most modern lenses)
Shutter speed intervals:
30 seconds (Place camera into bulb mode, if available, for exposure lengths beyond this point)
1/8000th second (Most cameras can’t do this)