24PA loses a stop?

[pootify]

I was talking to a DP at a party recently and the topic of 24P vs 24PA came up (I'm a party animal, I know, I know). He told me that the reason he shoots on 24P setting is because 24PA loses a stop because of how it records. Is this true?

 

[GenJerDan]

Don't see why it would. It's just the method used to fit 24 full frames in a 60 half-frame sequence. The original frames are still being shot the same.

Now, the default settings in F6 may make a difference, compared to F5... Don't know.

Dan

 

[scharky]

Progressive scan CCD's do indeed need more light when recording. So when recording 24p, you do indeed lose light (i'm not sure how many stops to be exact).

 

[GenJerDan]

Well, yes, progressive needs more light, itself But there shouldn't be a difference between 24P and 24PA.

Dan

 

[XCheck]

Well, yes, progressive needs more light, itself But there shouldn't be a difference between 24P and 24PA.

Dan

Right. I don't think there it. In any case, do a simple test - aim the camera on a white wall, turn the marker on, set the iris so that it shows 50% (so the wall would be recorded close to medium gray, not white), and switch between 24P and 24PA to see if there is any difference.

I won't have access to my camera until Friday, so I can't test it for you :grin:

J.

 

[Barry_Green]

24P and 24PA are absolutely identical in regards to light sensitivity. Both lose one stop when compared to 60i.

 

[XCheck]

24P and 24PA are absolutely identical in regards to light sensitivity. Both lose one stop when compared to 60i.

That's what I thought...

 

[thisiswells]

I thought 30p lost a full stop from 60i. And that 24p was a 1/6 stop gain over 30p....
Hardly a visual difference, but maybe useful for light metering among the retentive.......

 

[Barry_Green]

Depends on your shutter speed. At identical shutter speed, 24p, 24pa, and 30p will all be 1 stop slower than 60i (assuming a 1/60 shutter speed).

If you use 1/48 instead of 1/60 you can get a little more light sensitivity out of 24p, but that doesn't change the underlying sensitivity, it just changes the shutter speed.

 

[thisiswells]

Right. I'm thinking in film speak today..
180 degree shutter @ 30Fps is 1/60 or 24Fps is 1/48, etc..

I'll be back in video think probably later today or tomorrow.. What you're saying makes sense.

 

[thisiswells]

So, then from 1/60 to 1/48 would be somewhere between a 1/3 and 1/2 stop difference..
That's good to know.

 

[kmcgrath]

WHY is there is difference in sensitivity between 24P and 60i?

 

[thisiswells]

As Barry said, 'cause your default shutter speed changes. Exposure time affects sensitivity.

 

[Barry_Green]

No, it's more than that. That would account for the difference between 24p and 30p, but not for the difference between 24p and 60i.

The reason there's a difference between progressive and interlaced, for sensitivity, is called row-pair summation, and is described in Steve Mullen's whitepaper "Progressive: What You Need To Know", available at http://www.findarticles.com/p/articles/mi_m0HFE/is_2002_August_1/ai_90473426

 

[kmcgrath]

OK, that makes sense. Using data that would otherwise be discarded improves sensitivity!