Using 25 fps clips in 30 fps project

I'm basically a stills photographer, video is a bit of a mystery to me.

From background reading, I have learned that 30 fps is usually the best frame rate to use when setting up a project for consumption online or on modern televisions. This includes here in the UK, where the 25 fps PAL standard is no longer relevant. (Hope I've got all that correct - if not please let me know!)

But one issue remains, which is that if I'm shooting indoors anywhere where there is the likelihood of flicker, I'll need to shoot at 25/50 fps. If I want to insert such a clip into a 30 fps project, what are the problems and solutions?

Thanks for your help!

NickZ2016 wrote:

If you want / need to shoot 25 shoot 25. Outside of North American TV I can't think of any reason you need to shoot 30.

Don't make your life harder than it needs to be just because

As I understand it, it's because the frame rate which works best for phones, tablets and computer monitors is 30 fps. This is worldwide, not just north America. And the old NTSC vs PAL thing no longer applies as we don't use CRT televisions and monitors and never will ever again. The one problem which remains is shooting indoors using an anti-flicker setting, but because of my limited video experience I don't know how big an issue this actually is.

Markr041 wrote:

Steve Balcombe wrote:

NickZ2016 wrote:

If you want / need to shoot 25 shoot 25. Outside of North American TV I can't think of any reason you need to shoot 30.

Don't make your life harder than it needs to be just because

As I understand it, it's because the frame rate which works best for phones, tablets and computer monitors is 30 fps. This is worldwide, not just north America. And the old NTSC vs PAL thing no longer applies as we don't use CRT televisions and monitors and never will ever again. The one problem which remains is shooting indoors using an anti-flicker setting, but because of my limited video experience I don't know how big an issue this actually is.

You are correct.

As I understand it flicker results from an incompatibility of the AC frequency (50Hz) and the shutter speed, not the frame rate. So, normally you would shoot 30 fps at 1/60th. That can produce flicker from 50Hz lights. In those situations, just shoot at 1/50th. My experience shooting in 50Hz places around the world at 30 and 60 fps is that flicker is not always a problem, and when it is I can see it in the viewfinder (LCD) and then I adjust the shutter speed.

Thank you! I'll have no reason to use high shutter speeds for my potential subjects, so I should be fine.

Steve Balcombe wrote:

NickZ2016 wrote:

If you want / need to shoot 25 shoot 25. Outside of North American TV I can't think of any reason you need to shoot 30.

Don't make your life harder than it needs to be just because

As I understand it, it's because the frame rate which works best for phones, tablets and computer monitors is 30 fps. This is worldwide, not just north America. And the old NTSC vs PAL thing no longer applies as we don't use CRT televisions and monitors and never will ever again.

Absolutely.

29.97P, and a shutter speed equal to your local mains frequency will give most people the least trouble. Then some folk will have good reasons for doing something else.  These days, I think the main reason for shooting 25P is that your client tells you to (probably because it's for broadcast on a 50Hz PAL network).

25P or 50P won't help with flicker/banding in places with 50Hz mains.

The one problem which remains is shooting indoors using an anti-flicker setting,

For moving pictures, shot on film or silicon, "an anti-flicker setting" for mains-related lighting flicker is a shutter speed that:

1. Accurately divides the local mains frequency.
2. If (1) is not practical, a shutter speed that accurately divides twice the local mains frequency.

It's possible to quantify "accurately". The more the light flickers (we can quantify that too), the nearer the exposure time needs to be to a cycle-time (period) of the flicker.

"Within 1%" is good enough for most kinds of poor mains lighting that we're likely to run in to.

If the peak-peak light output, as a fraction of the average light output, is below about 1%, then any shutter speed will do.

That "1%" I refer to might be different if you're more picky or less picky than me.

but because of my limited video experience I don't know how big an issue this actually is.

It's becoming less of a problem, because of technological and regulatory changes in lighting, but it can still bite.

If you only shoot in an environment that you control - where you control all the lighting, and it doesn't flicker, or you always shoot off-grid, far away from artificial light sources, you won't have a problem.

Say you're shooting in daylight on a city street. It would not be surprising to have parts of building interiors, such as shops, offices, appartment windows, or signage lit by lighting flickering at 2x and/or 1x mains frequency in shot. Which could be quite distracting on playback, even if they're on the edges of the shot.

This is why, for decades, many US cinematographers have habitually shot movies (24.000P) at 144° shutter angle (1/60.00 s shutter speed). It just avoids an unnecessary risk, and it makes the sense of motion consistent throughout the production.

What mains-powered lights are problematic?

• Gas discharge lamps (Mercury, Low and High Presure Sodium, Fluorescent, HID) running off magnetic ballasts.
• Some incandescent-replacement LED bulbs, particularly dimmable bulbs, and dimmable bulbs which are dimmed. Some incandescent-replacement LED bulbs have essentially no flicker at all.
• Incandescent lamps. Not as bad as fluorescent, but the higher the colour temperature, the more flicker. Also changes colour as the filament changes temperature over a mains half-cycle.

These lights - if they are in good working order - will flicker at 2x mains frequency.   But wear, and minor fault conditions, can cause the output to be different in the two phases of the mains cycle, which makes exposure times that are multiples of a whole mains cycle safer than exposure times which are only multiples of a half mains cycle.

If you see a fluorescent tube, and it's 1" or 1.5" in diameter, it probably flickers (and you may even be able to see the flicker, particularly out of the corner of your eye).

If you see a fluorescent tube, and its less than 3/4" in diameter, it probably has an electronic ballast that runs at 30kHz+, and doesn't flicker.

All this still leaves various light sources that - by design - flicker at frequencies unrelated to mains frequency.   Philips "Hue" variable colour LED lighting gets a few complaints.   Electric welding equipment would be another one.

And another thing.

Ignore RED's "flicker free" calculator.   RED may make good cameras, but that webpage is nonsense.

That's superb information, thank you John!

John Vickers wrote:

Ignore RED's "flicker free" calculator. RED may make good cameras, but that webpage is nonsense.

Haha I'd never heard of it, now you've made me want to read it

Steve Balcombe wrote:

John Vickers wrote:

Ignore RED's "flicker free" calculator. RED may make good cameras, but that webpage is nonsense.

Haha I'd never heard of it, now you've made me want to read it

That is the path to Perdition.