What settings for maximum light sensitivity?

G

galt

Well-known member
I have seen some discussions about various settings to use for those really dark locations, but nowhere have I seen them all in one place. I have seen people mention 60i, gamma, shutter speed, gain, but no one post has suggested actual settings or combined them.

Can someone please help me by giving me as much info as possible about how you would set your DVX for shooting in the darkest situation you could imagine? And since grain is in the eye of the beholder (sometimes any image is better than no image), lets just ignore it and assume I am willing to crank the gain to 18dB as well. And if you want to indicate where you would back off settings to cut grain when you can (is gain the first choice and shutter speed the last?) , that would be helpful too. But the optimum starting settings would be helpful.
 
There are three things that effect the light sensitivity:

1) CCD gain (you can use up to 18 dB in the DVX)
2) Shutter speed (can be set as slow as 1/24 of a second in 24P or PA mode)
3) Wide open aperture (depends upon the focal length)

With all three applied, it can shoot in very low light conditions. I wouldn't try the 18 dB gain setting unless it is really needed, a lower setting is better as you will experience less noise (6 dB won't cause much). Also, setting the shutter to 1/24th of a second (basically off) will cause considerable motion blurring if there is much movement. If there is relatively little motion, this will give you 8 dB more light than 1/60th of a second without any noise penalty.

There isn't an "optimum" it will depend upon the conditions you are shooting under.
 
So you are suggesting that there is no difference between 24p at 1/24 and 60i at 1/60?

And also that gamma settings, white balance, coring, detail, pedestal don't matter?
 
24p at 1/24 of a second is similar to 60i in that neither utilizes the shutter, however, 60i still samples the frame in two passes (fields) while 24p leaves the CCDs active for the entire exposure. 24p at 1/24th will have noticeable greater motion blurring than 60i.

Gamma does not directly effect the sensitivity, rather it modifies the slope of the response in the middle of the curve. White balance effects the red/blue relative gain, but not the overall gain. The master pedestal effects the lower portion of the gain curve and can be used to a slight advantage in very low light situations, however at the expense of the overall dynamic range. Coring and detail settings will not have any noticeable significance in terms of overall gain.

Again, there isn't an optimum configuration for all low light conditions, you need to consider other aspects such as motion and the overall look you want to obtain.

Is there a specific situation that you want to consider?
 
It still won't give you as bright an image though as progressive doesn't have row pair summation like interlaced does.
 
For ultimate sensitivity, you could shoot in 60i, either at 18dB gain or at 1/4 shutter speed (can't have both at the same time). 1/4 would probably give you a brighter picture than 18dB would. Make sure ND filters are off, zoom all the way out and open the iris all the way up. Consider using detail coring +7 to smooth out the noise that will undoubtedly be crawling around your picture.

Then, when all that fails, get a $39 Bescor camera light -- that'll do far more for your image quality than any of the above suggestions.
 
Row summation nets a 6dB increase in sensitivity (2:1) however, 24p (or 24pa) without using the shutter (1/24) gains 8dB (2.5:1) when compared to the same frame rate with a 1/60th of a second shutter, and it has the aesthetic advantage of being a progressive format.

Certainly 18dB of gain will accomplish the greatest difference, but the noise contribution will be considerable. The idea of smoothing out the noise will only partially obscure the considerable quantity that will be present. Since noise is uncorrelated (mostly thermal and shot noise) there isn't any real method of effectively detecting or reducing it. As Barry Green has pointed out, a little bit of light will certainly make more difference than any camera setting. This is likely the best suggestion, assuming that you can use light in your situation.

You still haven't addressed the question if this is a general interest question or is their a specific situation that you want to address?
 
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