What is optimum setting for capture in night from moving objects, when diaphragm is fixed?

Question

I have a camera and I want to capture real-time photos continuously from moving objects in night. my problem is if i reduce exposure time, image will be all black, but with higher exposure, objects in picture are blurred because of their speed. For example my objects are cars with high speed in night.

I also tried to take photos with lower exposure time and then increasing gain and gamma to maximum level. But in this case final photo is very noisy. So I tried processing image after it's token but processing time is high. I can't wait for long time for this processing ( mostly noise reduction processing takes time).

And my camera aperture is fixed also.

So how can I adjust settings in my camera to get optimum image in night from moving objects?

Answer 1

You cannot beat physics.

You have three variables to play with to adjust exposure: Aperture, time, and ISO (which, i'll assume, you mean with "gain"). Since your aperture is fixed, you can only increase ISO at the cost of noise, or the exposure time at the cost of movement blur, as you discovered.

So, you'll have to live with some compromise of these factors, unless you can aquire a better camera (with lower ISO noise, or wider aperture).
E.g. a camera with a bigger sensor usually has better noise characteristics, the aperture is lens-dependant. Be aware that better equipment probably will cost you.

Answer 2

Actually, there are four things you can modify - in addition to shutter speed, ISO and aperture, as mentioned in the other answers, you can also modify the lighting (assuming your subjects are reasonably close).

Since it's unlikely the passing cars would appreciate bright spotlights or flash, You could always look at infrared illumination. You'd need a camera that didn't have an IR blocking filter, so you'd probably be better off with a security style CCTV camera or maybe a webcam (most have the IR blocking filter on the back of the lens, so you might be able to remove that if the webcam is manual focus with a screw in manual focus lens).

Answer 3

You've pretty much worked this one out I'm afraid. In general, you can modify three things when taking a photo:

• Shutter speed
• ISO (aka gain)
• Aperture

You say you can't modify the aperture, so you're stuck with shutter speed and aperture. All you can do is to set shutter speed and ISO so you get the best balance you can between blur and noise.

Having said that, there are other things you can change, but they require more work:

• Get a new camera with a sensor with better low light performance.
• Get a new lens with a wider aperture.
• Add light to the scene, either natural or artificial.