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Resolved Question

Sony 50p 25p

May 19, 2015 9:35PM PDT

Wondering if anyone can clarify something. I have a Sony CX700 HD PAL camcorder. BUT my question is relevant to the NTSC ones as well.

There is a setting to shoot in 50p or 25p, 60,30 ntsc. The 50 p is obviously 50 frames and the 25p obviously 25 frames..

So if the camera is in Full auto mode, it adjusts aperture, iris shutter etc. Well if shooting in 25p, 25 frames, and the aperture is altered for lighting conditions, how is it still 25 frames?'
Really confused. Anyone able to clarify this for me please??

Tony

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I guess I'll try...
May 25, 2015 1:27PM PDT

The aperture (aka: iris) is a hole that allows light in through the lens to get to the imaging chip.

The frame rate is the number of equivalent film frames that pass by the aperture.

The frame rate needs to remain constant in order to properly deal with either the PAL (25/50) or NTSC (30/60) frame rates for certain television playback. Typically, once the frame rate is set, it says there - and no adjustments (automatic or otherwise) will happen.

The frame rate and shutter speed, aperture, video gain are independent. Remember, frame rate must remain constant. If the lighting changes, you can either
* Make the aperture larger to allow more light;
or
* Slow the shutter speed (the shutter remains open longer which allows more light in);
or
* Increase the video gain (basically, use "light amplifiers associated with the imaging chip and pixels).

When light is really poor and assuming the aperture is already wide open, the shutter will be open a long time (1/30 second or longer) which can result in "ghosting" if there is any movement. The video amplifiers kick in and some folks call "grainy" - actually "video noise" - happens. ("Grainy" is more of a still image capture description.) But the frame rate will remain constant.

Typically, faster frame rate is used for slow motion capture. If the frame rate is increased to 250 frames per second, imagine what happens when playback is 25 frames per second. 5 seconds captured at 250 fps and played back at 25 fps turns into 50 seconds playback duration. Once set to 250 fps, that frame rate for capture will remain constant. Because the frame rate is high, LOTS of light is needed to deal with the shutter, aperture and video amplification...

Hope it helps. I didn't like seeing this orphan question.

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thank you
May 26, 2015 3:11PM PDT

Thank you for taking the time to thoroughly answer this question. I had thought as much but was confusing the shutter speed for the 25/50p.

Thanks again for the clarification.

Kind Regards
Tony