Questions about zoom and cropfactor

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gr8pics

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Questions about zoom and cropfactor

PostSat Dec 14, 2013 10:23 am

I wonder, since the cropfactor on BMCC is x2 and that a 100mm lens will have an effective width of 200mm.
Lets say you use a 70-200mm lens
Will the picture be more stable (or easier to keep stable) on a crop x2 factor than a fullframe on the effective zoom width of 200mm?
I mean, with a x2 factor, you only have to zoom in to 100mm to get a 200mm crop, but on a fullframe you have to zoom all the way in to 200mm to achieve the same cropping, and theoretically harder to keep the frame stable...
Anybody understood what i meant?
Chris D
www.medicall-app.com
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balazer

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Re: Questions about zoom and cropfactor

PostSat Dec 14, 2013 11:07 am

Well the crop factor is not 2; closer to 2.2 relative to full-frame. And to rewrite what you said with proper language:

A 100 mm focal length lens on the BMCC has the same angle of view as a 220 mm focal length lens on a full-frame camera.

But no, there's no difference in stability for the same angle of view. A smaller angle of view makes the camera's instability more apparent.
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gr8pics

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Re: Questions about zoom and cropfactor

PostSat Dec 14, 2013 12:41 pm

Well, you repeated what i just said, but in another factor ;)

So the a digital angle of view is the same as an analogue angle of view, so to speak?
I thought the distance between the parallax point and the tip of the lens would play a role here?
Chris D
www.medicall-app.com
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David Dearing

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Re: Questions about zoom and cropfactor

PostSat Dec 14, 2013 3:10 pm

Some day you all will switch from thinking in film terms and start thinking in digital terms. There is no crop factor. There's only Field of View and Resolution. Nothing else matters at all.

The image plane of any lens is exactly the same phisical size regardless of what sensor you put into it. If you sample a smaller portion of that image plane and have the same resolution as a larger sensor, then obviously any movement would be more easily seen because you have a higher resolution of a smaller area of the image plane. In other words, if you have a HD "full frame" sensor, your pixels might be 15um (I don't know for sure, but you can look it up). The smaller sensor, using the same HD resolution, would have much smaller pixels- say 7um. So any movement of the picture in the larger, less resolved sensor (full frame) might be contained inside that one pixel (not bloodly likely, but you get the picture).

Hope that helps. You all need to stop thinking in terms of frame size compared to some standard, or zoom, or magnification, or whatever. Digital photography is concerned with FOV and resolution- that's it. The other stuff is for the dinosaurs.
David Dearing
DJI Mavic Pro
BMPCC w/12-35mm Lumix HD
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gr8pics

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Re: Questions about zoom and cropfactor

PostSat Dec 14, 2013 3:46 pm

So that means it IS more favorable to use a 100mm on a x2 crop than on a full frame in terms of stability, if we compare the field of view since you have to use more zoom on full frame to achieve the same view?
Chris D
www.medicall-app.com

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