Best fast shutter speed

[DigitalDrone]

Hi Everyone,

For video, what would be the minimum shutter speed necessary to shoot in, in order to get a crisp image when I freeze a frame (for inspection work)?

Thanks.

 

[InterMurph]

If you need the best still-image quality, you should take still images in DNG format. In all video modes, images are compressed tremendously, even more than standard JPG still-image compression.

At any rate, the answer to your question is, "it depends". It depends on the other two exposure values (aperture and ISO). It depends on the amount of light available. And it depends on how much movement there is between the drone and your subject.

I suspect that your subject is not moving at all, and that the drone is moving slowly. In that case, I would guess that 1/160th of a second will get you as much sharpness as can be had, and that anything faster (1/200th, 1/250th, 1/320th, 1/500th, etc.) will not provide any additional sharpness.

And that is where the other exposure controls kick in. If you insist that 1/1000th is necessary because you want to freeze it as much as possible, then you will have to compensate for that by adjusting aperture and/or ISO. And since you can only open up your aperture so much, that generally means increasing your ISO sensitivity. And doing that will definitely make your image less sharp.

So here is what I would do:

1. Operate in manual mode
2. Start at ISO 100, f/5.6, and 1/160th.
3. If the resulting image is too dark, then you should first open up the aperture (f/5.0, f/4.5, f/4.0, etc.). If that solves your problem before you hit f/2.8, then I think you are done.
4. If that does not solve the problem, then you need to try increasing the ISO. But once you hit ISO 400 on this camera, you will start to become dissatisfied with the noise introduced into the image.
5. If you have a "too bright" problem instead of a "too dark" problem, then you can solve it by shortening your shutter speed (1/200th, 1/250th, 1/320th, 1/400th, 1/500th, etc.) until the problem is solved.

The mistakes you can make here:

1. Keeping the shutter open too long, which will produce blurry images
2. Setting the ISO too high, which will produce noisy images
3. Setting the aperture too high (f/11, f/14, f/18), which will require you to do 1) and 2) on this list.

 

[AMGPilot]

Disregard Intermurph's reply, he's not taking focal length into account, doing inspection work that's what is most important.

M4/3 sensor has a 2X crop so at a minimum you want your shutter speed to be 4x the focal length (the old 2x focal length rule is film based and relies on the size of the film grain). If you are shooting inspection work with a 90mm lens you want a minimum of a 1/400th of second exposure. On a sunny day that will still net you a f/16 stop on the lens, but thats going to introduce diffraction issues so you can either add ND's or if shooting stills raise the shutter speed in order to have a f5.6 or f/8 on the lens. Looking at a MTF chart will tell you what the optimum stop is and that will also help your inspection photos by increasing the DoF

 

[InterMurph]

OK, I agree that effective focal length is important. And if you are using a 45mm lens, then the effective focal length is 90mm.

But I'm not sure I agree that 1/400th is the longest shutter speed that could be used. The 1/2x rule is more of a guideline, and it is a guideline for hand-held cameras and lenses. We have an active gimbal that is helping hold the camera steady.

But I think my method is still correct; minimize ISO, start at f/5.6, and see which shutter speed gives non-blurry results.

 

[DigitalDrone]

Disregard Intermurph's reply, he's not taking focal length into account, doing inspection work that's what is most important.

M4/3 sensor has a 2X crop so at a minimum you want your shutter speed to be 4x the focal length (the old 2x focal length rule is film based and relies on the size of the film grain). If you are shooting inspection work with a 90mm lens you want a minimum of a 1/400th of second exposure. On a sunny day that will still net you a f/16 stop on the lens, but thats going to introduce diffraction issues so you can either add ND's or if shooting stills raise the shutter speed in order to have a f5.6 or f/8 on the lens. Looking at a MTF chart will tell you what the optimum stop is and that will also help your inspection photos by increasing the DoF

Thank you for your reply. Just so I understand a bit better, what is the 2x focal or 4x focal based on, why is this rule of thumb and what does this improve?

Thank you again.