Shutter speed of 1/25 for PAL video in low light - a good idea or not?

[Dave2ic]

I have a Sony NEX-F3 that I am going to be shooting some video with in fairly low light at 1920x1080 25p

I understand the general guide would be to use a shutter speed 2x my frame rate - i.e. 1/50 second. However, in low light would it be better to use 1/25 second so the ISO of the camera wouldn't need to be so high?

I think if I use 1/50 second the video will have more noise due to the higher ISO, but are there technical reasons why it's a bad idea to use a shutter speed the same as your frame rate? If not 1/25, then what about something in between like 1/30 or 1/40 second?

[poisondeathray]

Best idea is to add more light. Always.

1/25 will allow more light to the sensor, but you will get more motion blur.

Usually not a good idea to use non evenly divisible "inbetween" rates (with respect to the electrical grid frequency - eg. 50Hz in 50Hz areas) with non natural light sources - you risk flicker with most CMOS cameras (global shutter CMOS sensors exempt)

Noise can be improved on significantly by noise removal plugins and techniques e.g. neat video, avisynth

[Dave2ic]

Best idea is to add more light. Always.

1/25 will allow more light to the sensor, but you will get more motion blur.

Usually not a good idea to use non evenly divisible "inbetween" rates with non natural light sources - you risk flicker with most CMOS cameras (global shutter CMOS sensors exempt)

Noise can be improved on significantly by noise removal plugins and techniques e.g. neat video, avisynth

If adding more light is not an option (it's an indoor event), would you recommend I use 1/50 sec shutter speed and reduce noise in the resulting video? I guess you can reduce noise but you can't really do anything if your video has blurry motion.

[poisondeathray]

It would depend on what kind of "indoor event". eg. If it was some conference where people sit stationary at tables giving speeches that's entire different than say indoor track and field where there is a lot of motion. 1/25 would probably be perfectly acceptable in the former, not so good in the latter

You should practice shooting and getting to know the ins/outs of your particular model in simulated situations before the event (just practice handling and knowing what to expect in low light situations).

You almost always have to add some sort of noise removal in low light situations. Even cameras with exceptional low light ability will have noise . Also note - everyone's definition of "low light" might be different

[Dave2ic]

It would depend on what kind of "indoor event".

It's a Xmas concert at my kids school, and I guess there will be some dancing so according to your advice I'd be better off with 1/50 sec.

Actually, regardless of the motion of the subject matter I guess if I am going to be panning the camera around the hall I'd be better off using 1/50 too.

Thanks for you advice.

[budwzr]

It's the f-stop of the lens that determines low light performance. Sony is notorious for making up their own camera lingo, that doesn't translate into reality.

Example: SDOT - Super Dynamic Oscillating Technology assures that handheld shots are smoother.*

*Compared to filming on a roller coaster with a ****-a-roach in the seat.

[Cornucopia]

Whichever way you go, you will increase your footage's value and usability (including noise reduction) if you were to use a tripod.

Scott

[Dave2ic]

Whichever way you go, you will increase your footage's value and usability (including noise reduction) if you were to use a tripod.

I will be using a tripod.

[Dave2ic]

It's the f-stop of the lens that determines low light performance.

Ok, but given that I will be setting the shutter speed and using the widest aperture possible for whatever focal length I'm at, the only variable is ISO.

So if I double the shutter speed (1/25 sec instead of 1/50 sec), the ISO can be 1 stop lower, resulting in cleaner video. But as it's been pointed out, there will be a compromise in that motion will look blurry.

[budwzr]

So you don't know know your lens' aperture range? You can easily test it now. Go to a low light area, set the mode to Aperture Priority, open the iris all the way, and see what ISO the camera selects. Anything over 800 is no good, too noisy. Even 800 will be grainy, but "maybe" usable.

At 800, you would have to do extensive work on it. And don't forget to turn OFF the auto exposure! In fact, you should focus manually too, otherwise the autofocus will probably not get a lock quickly enough in low light, or lock onto the wrong place. And the focus assist lamp will fire.

[Dave2ic]

So you don't know know your lens' aperture range? You can easily test it now. Go to a low light area, set the mode to Aperture Priority, open the iris all the way, and see what ISO the camera selects. Anything over 800 is no good, too noisy. Even 800 will be grainy, but "maybe" usable.

At 800, you would have to do extensive work on it. And don't forget to turn OFF the auto exposure! In fact, you should focus manually too, otherwise the autofocus will probably not get a lock quickly enough in low light, or lock onto the wrong place. And the focus assist lamp will fire.

It's the kit lens which is f/3.5 at 18mm (widest) and f/5.6 at 55mm (full tele).

ISO 800 looks passable, but could benefit with some noise reduction. I'll look into that option with AviSynth.

This was essentially what I was getting at with my original question. Would I be better off at 1/25 sec shutter and ISO 400, or 1/50 sec shutter and ISO 800? I've concluded that I'd be better off with ISO 800 and then apply noise reduction, as you can reduce noise but not blur.

Thanks or the tips about manual focusing too - although that does mean I can't really zoom during video as the focus would need to be changed too.

As it turns out the light wasn't too bad at my kid's concert and I didn't have any problems. It's summer over on this side of the world (New Zealand) so there was plenty of natural light coming through the windows.

[Dave2ic]

Noise can be improved on significantly by noise removal plugins and techniques e.g. neat video, avisynth

I've used Avisynth before so no how it works - but I'd be grateful if you could please advise on a good noise-reduction plugin and basic script syntax to get me started.

Avisynth is a very powerful tool but it's sometimes hard to know where to start!

[poisondeathray]

Noise can be improved on significantly by noise removal plugins and techniques e.g. neat video, avisynth

I've used Avisynth before so no how it works - but I'd be grateful if you could please advise on a good noise-reduction plugin and basic script syntax to get me started.

Avisynth is a very powerful tool but it's sometimes hard to know where to start!

Well you can try MCTemporalDenoise, SMDegrain , etc..

You might start with something like MCTemporalDenoise(settings="medium")

Here is a list of some plugins you might try
http://avisynth.org/mediawiki/External_filters#Spatio-Temporal_Denoisers

But you're better off posting a representative sample , and people will give you various approaches and suggestions as to what you might do

The reason is, a customized approach to a specific problem will give you better results. If you want generic help, you'll get generic suggestions thus "generic" results . There are different types of noise problems and if you don't know the correct terms to describe them you might be using a suboptimal approach

[budwzr]

...Thanks or the tips about manual focusing too - although that does mean I can't really zoom during video as the focus would need to be changed too...

You can "foot zoom", slowly, then stabilize later. There's no zoom in your lens anyway, only wide angle.

[jagabo]

Noise reduction in software should always be your option of last resort. Do everything you can to get clean footage first. Whether you can get better video shooting at ISO 400 with a 1/25 second shutter speed, or ISO 800 at 1/50 second plust post processing NR, will depend on many factors. You should run your own tests.

One other thing to keep in mind, when shooting stuff on stage you typically have a dark background with a few performers brightly lit in the center of the frame. The automatic settings of most cameras will see all that dark area and attempt to lighten it up, resulting in blown out (beyond repair) brights. Exactly the things you want to see will be washed out. So you need to use manual settings or otherwise compensate.

[Cornucopia]

Yeah, if your cam has auto "backlight compensation", this could help in that situation, even for consumer cams.

Scott