Deminishing returns.....

Started 3 months ago | Discussions thread
Alen K Senior Member • Posts: 1,123
Re: Deminishing returns.....

Astrozoid wrote:

Alen K wrote:

Astrozoid wrote:

When you use LENR you get a double whammy hit because not only have you lost half the signal you could have recorded, you are adding noise in each dark that you shoot in the camera. You would add a lot less noise with a good master dark.

I don't understand this. Please elaborate. If I take N light frames with LENR on (generally a bad idea, I agree), I will be using N dark frames, one for each light. Mathematically, there should be no difference between averaging N frames, each with a dark pre-subtracted, and averaging N frames then subtracting the average of N dark frames (the master dark).

Yea, except for one thing.

I can construct a master dark out of as many subs as I like when I shoot darks in my garage.

I don't have to limit it to the same number as the number of lights.

Of course.

If you shoot 16 lights with 16 darks, you will inject X amount of dark-frame subtraction calibration noise. With 64 darks, I will only inject 1/2 as much.

So, separate darks vs LENR darks will inject less noise to the final stack.

Only true if you shoot fewer lights than you want to use for darks. And not so in this case. The OP shot 193 lights, hence because of LENR 193 darks. That's excessive, IMO, but the result will not be worse with respect to injected random noise than shooting a bunch of darks later unless you go crazy and shoot hundreds of them. I don't know how many darks you usually use, but I see that many people use as few as 20 and usually no more than 50. In that case, the OP's 193 will technically inject less random noise. But the difference will be VERY small, certainly not worth the huge waste of time that could have been spent taking more light frames.

So, I don't see this as a "double whammy hit." But the single whammy hit is bad enough!

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