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    Respected Pilot Shrimpfarmer's Avatar
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    Anyone good with maths?

    I can't get my head around this so maybe someone good with maths can solve it.

    If I have a 1080p film size the pixels in a frame measure 1920 x 1080
    In a 720p project the pixels are 1280 x 720

    Now if I choose to edit a film in 720p using 1080p footage, how far can I zoom into that footage without losing any definition?
    I fly Phantom 2 with Gopro 3 Black, Zenmuse, Imersion RC600, Black Pearl Monitor.

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    Just wondering if my math is correct. If you zoom 1080 in 2.25 times you will reach a 720 pixel count. 1920 X 1080=2,073,600
    1280X700= 921,600.
    Divide 2,073,600 by 921,600 and you get 2.25.
    Hope this help and as usual I welcome being correct if someone else wants to have a crack at it.

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    Respected Pilot Shrimpfarmer's Avatar
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    Thanks for that. You can be the site accountant
    I fly Phantom 2 with Gopro 3 Black, Zenmuse, Imersion RC600, Black Pearl Monitor.

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    That is of coarse if I'm right. Try it out on some test footage first so I won't feel bad if I'm wrong

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    Respected Pilot Shrimpfarmer's Avatar
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    I tried to do it by sight but its really hard.



    In Final Cut Pro X my editor, any clip added to the timeline starts out at size =100% That shows the entire clip on screen but obviously its at a reduced resolution because the source is bigger. So its the % increase I can zoom that slider that should give me maximum resolution without quality loss.

    Based on your figures if 1% of the 1080p size is 20,736. Then if I divide 720p total pixels by 20,736 I get 44.4 Does this mean I can slide the scale to 144% ?
    I fly Phantom 2 with Gopro 3 Black, Zenmuse, Imersion RC600, Black Pearl Monitor.

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    I'm afraid this is where my usefulness runs out sorry.

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    Flight Ready Visioneer's Avatar
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    I'm not familiar with your editing program but it's interesting that they call it "zooming".

    If I were doing that with a photograph, I would be cropping it, i.e., selecting just a portion of the full frame for view. To zoom I'd have to be using a camera where I was changing the focal length - in photography that's how zooming is defined. Guess I never thought of my darkroom cropping as zooming*. For example, if I had a camera with a 30mm lens, I'd zoom it 2X by changing the focal length to 60mm. Rather than calling it cropping, they've called it zooming ... which is pretty much an inverse way of looking at cropping - and that's a clue here.

    When you zoom in by 2X you only capture 1/2 the height and 1/2 the width of the 1X image. In your case you want to capture 2/3 of the 1X image (1280/1920=720/1080 = 2/3). So the inverse (zooming) would be 1.5X (or presumably 150% in your case). You may find the first few paragraphs of the following link helpful (just so you don't think I'm making this stuff up) - Optical zoom - Learn - Snapsort

    Of course, regards maintaining the original resolution, the above assumes that your program is, in fact, simply extracting the pixels you select when it "zooms", and not manipulating them in any way. Photo/video editing tools are notoriously full of algorithms that are used to effect their various capabilities. One wouldn't think cropping would need such, but you never know.

    * I digress (I've been known to do that) as to why I don't consider this "zooming". If I have an object in a negative/photo that's 1000 pixels by 1000 pixels, I can crop and enlarge it all I want, but the resolution of that object is never going to be better than 1000 pixels by 1000 pixels ... I'm just going to be making the pixels bigger with an enlargement. So I've cropped and enlarged, but I've not "zoomed". (Yes, I can digitally manipulate the image and create interpolated new pixels in between the optically gathered ones - that's what digital zooming does and why it loses resolution - the new pixels are not "real"). However, if I have an object in my camera's viewfinder that'll use up 1000 by 1000 pixels on the film/sensor, and I switch to a lens with twice the focal length, that object will now imprint 2000 by 2000 optically gathered (real) pixels on the film/sensor. Now I have "zoomed" ... the resolution of this object is 4 times what it was at 1000 by 1000 pixels.

    (BTW - I know film has grains, not pixels. Pixels is just a convenient term here for "smallest point of brightness & hue" recorded by the media in use)
    Last edited by Visioneer; 04-21-14 at 08:19 PM.

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    Respected Pilot Shrimpfarmer's Avatar
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    Comprehensive response Visioneer. Thanks very much for that explanation
    I fly Phantom 2 with Gopro 3 Black, Zenmuse, Imersion RC600, Black Pearl Monitor.

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    Respected Pilot Shrimpfarmer's Avatar
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    Actually in Final Cut Pro X the control is called scale not zoom. It can be changed from 0 to 400%

    What prompted me to play with this is that Vimeo generally like the films to be 720p as it allows most people to replay them. If I shoot 1080p on my Gopro that gives me a lot of leeway to re-frame the image and to add a zoom where none existed. If I shoot in 2.7K its almost like having a zoom lens on a Gopro.
    I fly Phantom 2 with Gopro 3 Black, Zenmuse, Imersion RC600, Black Pearl Monitor.

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    Flight Ready Visioneer's Avatar
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    You're welcome. I thought I knew the answer but I did a little research anyway, just to be sure. Guess it's just my nature that certain puzzlements intrigue me and I "gots to know" (a vague "Dirty Harry" reference).

    And, actually, "scale" as in "scale up" probably makes more sense than either zoom or crop. Crop doesn't really imply "enlarge", but that's what usually happens to an image part that's been cropped. What Final Cut Pro X is really doing is cropping (extracting a portion of the image) and enlarging (filling the 1280/720 pixel frame with the cropped image). I'll be sure to let Final Cut Pro X I'm OK with their terminology.

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    Ooops! Sorry, I posted this twice.
    Last edited by Raromama; 05-06-14 at 12:04 AM.

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    Hello Shrimpfarmer

    You can scale to 150% however you might find the following info from Larry Jordan's website interesting.

    http://www.larryjordan.biz/fcp-x-cha...ject-settings/

    Max Federman says:
    November 27, 2013 at 12:31 pm

    Larry– please please help with this workflow question…

    Often in FCP 7 I use a method of scaling video footage where I set the sequence to 720p and then drag in 1080p clips of the same frame rate. When dragged in, the 1080p clips read 66.7% in the Scale settings. This allows for various re-framing to take place in the sequence. As long as 100% is not exceeded, the quality comes out great.

    Now in FCPx, I am trying to use this same technique and found your helpful post here explaining how to change the project settings. What’s troubling is that when I insert a 1080 clip into the 720 sequence, the 1080 clip reads 100% in the Scale rather than 66.7%. In this case I am trying to reframe a rudimentary 8mm film transfer. I am loving the time saving background tasks and direct to Blu-Ray function but until I get this size issue worked out I will have to work in another program.

    Very appreciative of any help– thanks Larry– great tutorials by the way; your DVDSP tutorial saved me days of my life a handful of years ago!
    Reply

    Larry Jordan says:
    November 27, 2013 at 10:18 pm

    Easy – but different than FCP 7.

    Select the clip you want to correctly scale in the Timeline of FCP X.

    Open the Inspector and scroll down to Spatial Conform. Change it from Fit to None.

    Done.

    Larry

    Hope this helps.

  13. #13 Top |
    Respected Pilot Shrimpfarmer's Avatar
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    Thanks Raromama. I use this function all the time now in my films. I have given up rendering in 1080p just so that I can reframe clips if needed. Works very well with Vimeo.
    I fly Phantom 2 with Gopro 3 Black, Zenmuse, Imersion RC600, Black Pearl Monitor.

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