Monstro & Gemini in Low Light

[Björn Benckert]

Bjorn,
Over the last 11 months with Monstro I have shot many scenes that go from daylight, through twilight to darkness (darkness= ~1 hour past sunset). I have seen no contradiction to the principle that ISO is metadata and has no influence on the raw data - ISO only affects the interpretation/display of the data.
Most of the time I shoot at ISO800. I "chase" the light as it falls off by adjusting ND and aperture while watching the GIO scope and the goal posts. My observation is that it is critical to keep the left goal post free of redness if you want to avoid noise. At some point, even with no ND and fast lens I have no more adjustment and I run out of light. The left goal post fills with red and noise severely increases. Adding light would be the only way to keep going but that isn't practical for big landscape scenes (like mountains and canyons).
I've tried ISO1600, 3200 and 6400 with the result that noise is easy to find in low light as ISO goes up. In my opinion if one needs 6400ISO to see the subject, you'll see noise too.
Do you agree? Am I missing something?

Correct, what iso is actually set to when shooting does not matter what so ever. What I mean is if your image looks good when developed with 400 ISO then it will look more noice free than if you for example shot it with 3stops less light and 3200ISO. So yes iso is nothing but post digital gain of the image signal. It what setting you have in camera does not alter your capture as long as it does not make you alter your other settings on the camera, like exposure time, iris closure or what not.

For mountains and canyons the only resort to get more light when lens is wide open and all ND´s are pulled is to open up shutter angle and then lower your frame rate. Iso will simply not bring more light to the sensor or let it capture more light.

 

[Patrick Tresch]

If there is no movement in the picture you could also use a small Frame summing recording mode

 

[Ronald Washington]

I must say looking over some of the post here are some very interesting reads.

 

[Angela Lifman]

Great tip on the color temps, thanks!

 

[Mark A. Jaeger]

Patrick,
You are correct that frame summing is a way of increasing the illumination of a scene. However, my experience has shown that the noise increases very rapidly as you are summing it too. As such, your idea of "small" frame summing is, in my experience, correct. Four frame sums are about it for astrophotography IMO.