Allan Kader

Thanks, Ryan :)

Hi folks,

Hope someone can clarify something for me :)

I'm filming a music video soon with a RED MX and I'll mostly be filming with 120fps in 4k/5k.

Whenever I set it to 120fps it automatically sets the shutter speed to 120.

Is there anyway to change it? And why does it lock the shutter speed at 120?

Allan

Thank you so much, aaop lettinen :D

Thanks :)

Hey folks,

Just a few questions about Correct Frame Rate Conversions in Post, Monitor Playback & 3:2 Pull-Down during post that I hope some of you can help answer.

CORRECT FRAME RATE CONVERSION

• When working with footage with different frame rates (24, 23.976, 30fps etc), what's the best timeline settings? If I have the most 24fps footage, should I set my timeline to 24fps and import the other footage into that timeline?
• What happens to the 23.98fps footage when imported to a 29.97fps/29.976fps timeline? Does, e.g. Premiere Pro/Davinci Resolve make an automatic 3:2 pull-down?
• What happens to the 25fps footage when imported to a 23.98fps timeline?
• When does optical flow, frame blending and motion interpolation come into play when conforming from one fps to another fps?
• I know that in most NLE's you can "interpret" the footage and change the native frame rate to something else but when would I want to do that? Maybe some examples would help me understand a bit better.
• When does reverse 3:2 pull-down come into play in post-prouduction?
• What's the difference between 29.97 and 29.976, and when are they used?
• What's the difference between 23.976 and 23.98?
• When you have 24fps footage that you intend to show on television in NTSC (60Hz), do I need to make a 3:2 pull-down? Which then makes it into a i60 footage (which is interlaced for broadcast), correct?

PLAYBACK

• When playing back 24fps/25fps/23.98/23.976 fps footage on an external grading monitor, should I set my monitor to 50Hz to avoid judder? And for footage with a higher fps, should I set it to 60Hz?

Thanks :D

Thanks :)

There are two principal ways colour images are stored on computers.

 

The first is the familiar RGB. Usually, each pixel has three numbers in it. Set them all to maximum value, and you get white. If you want, say, red, set red to maximum value, and green and blue to zero.

 

The second is the less familiar system of component video, sometimes referred to as YUV or other related terms.

 

Component video separates luminance from colour. In the terminology, Y stands for the luminance data, and U and V the colour data.

 

It does this because the human eye sees colour information less sharply than it sees brightness information.

 

Separating the colour information allows it to be sent at a lower resolution. It is possible to have component pixels with Y, U and V values for every pixel, but it is more usual to send the U and V channels at a lower resolution.

 

This is called colour subsampling and saves data space without making a noticeable difference to image quality.

 

4:2:2 means that for every four Y pixels, two U and V pixels are sent. Effectively, the colour information is sent at half the horizontal resolution, compared to the luminance information.

 

Yes, this means that 4:4:4 is better for green screen, because the colour information is more detailed.

 

Bit depth is unrelated to colour subsampling, but yes, 10 bit images have 1024 possible values per channel, whereas 8 bit images have 256.

 

P

Thanks for clearing that up :)

While I have you here, I also have a few more about SDI and HDMI.

• SDI 3G-Level A can carry a higher frame rate over one cable - correct?
• SDI 3G-Level B can carry a higher bit depth over one cable - correct?
• Dual Link HD-SDI can achieve the same as one 3G SDI - correct?
• Can a Dual Link SDI 3G carry 2K?
• What are the benefits of using SDI over HDMI?

/Allan

Hey guys,

I'm currently trying to learn some basics about various aspects of color grading. As such, I have a few questions/statements I'm hoping some of you can help me with answering/confirming :)

• 1 pixel contains the color channels Red, Green and Blue. - correct?

• Each color channel in 1 pixel carries its own luma value (how bright or dark each color can become). And the luma value for each color channel in 1 pixel is between 0-255. If the luma value for each color channel in 1 pixel is 255 it will reduce white. - correct?

• When talking about the bits of an image, you're talking about the bits per channel in 1 pixel. So this means e.g. 8 bits for the Red, Green & Blue channel. This also means that there are 256 different values/shades of color per channel - correct?

• A 10-bit image will be able to reproduce more shades of color. E.g. in terms of gradient. And working with 10-bit footage means more color information to use for grading. - correct?

• 4:4:4 stands for 4 pixels cross and another 4 pixels across below. - correct?

• 4:4:4 is great for green screen as each pixel carries it's own chroma value. - correct?

I hope you guys can help :)

/Allan