patrick j wrote in post #19332073
You were at 1/320th of a second, he is talking about 1 to 3 minutes.
But did he specifically state or mean that he was going to expose for 3 minutes? It's ambiguous, which is why I asked too. It just stated from sun rising, 1, 2, 3 minutes, which could also mean increments every minute or so as it rises to get the longest reflection across the water. I'm not even sure of the exact photo the OP is trying to create, which is why I asked that too.
If he means long exposure for 3 minutes, then sure, I can agree, not going to be a good idea without appropriate filtration, but its still completely doable and safe with just ND filters even and small tiny apertures.
By the way, if anyone is interested and in the future hits this thread, the energy that is problematic is not from UV. UV makes the least contribution to energy that the camera will see, the bulk of the energy is coming from visible spectrum and infrared. Obviously if you're imaging in visible spectrum you cannot block that and keep a color image. So if you want to block the most energy you can, it's going to be with an IR block filter. You can go as far as getting a UV/IR block filter (these are common) but again the UV contributes very small amount, around ~ 5% or so to the energy we're talking here, versus IR which contributes ~ 52% and visible spectrum is the other ~ 43% of that energy in terms of what you can get to handle wavelength blocking for thermal purposes. So if you want to block heat, get an IR blocking filter. They're inexpensive, but make sure its on optically flat glass (ie, at least 1/4th to 1/6th wave).
ND filters block almost all wavelengths (UV, visible spectrum and IR), so they can be used to long-expose the sun like this on a small aperture lens, the energy load is minimal. It's safe to do too. If you're super paranoid about it, you can add an IR block filter on top of this.
So my previous example was a single shot at short exposure, here's the same location a bit before, but long exposure for the same example:
Single 10 stop, 30 seconds exposure time at sunrise. 1 more ND would put it at 60 seconds. 1 more on top of that and we're at 2 minutes of exposure time for the same exposure. Lots of time on the sensor, but at low, low energy, so its safe, with these small aperture systems.
IMAGE LINK: https://flic.kr/p/GsPhA1
img_a1258
by
Martin Wise
, on Flickr
Very best,