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Thread: Masking a Ground Glass for Cinema Aspect Ratios

  1. #1

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    Masking a Ground Glass for Cinema Aspect Ratios

    I'm interested in masking my 4x5 and 8x10 backs (Arca Swiss F-line) for four aspect ratios that are used in feature films. I have two questions:

    What’s the best way to mask the ground glass so that it’s easy to remove the mask and easy to clean up marks or residue?

    Are there any issues with this approach to defining the image area that I should look out for?

    This is not something that I've done before. Thanks for your advice.


    Context:

    Initially, I want to try this with the 4x5 back and the following Rodenstock lenses:

    APO-Grandagon f/4.5 55mm
    Grandagon N MC f/4.5 75mm
    Grandagon MC f/6.8 90mm

    I plan to try the following aspect ratios in landscape orientation:

    2.39:1 (anamorphic widescreen)
    Mask: 5” wide x 2" tall

    2:1 (Vittorio Storaro and some Netflix films; also 12cm wide x 6cm tall still photos)
    Mask: 5” wide x 2.5" tall

    1.85:1 (standard widescreen)
    Mask: 5” wide x 2.7" tall

    1.78:1 aka 16:9 (high-definition television and on-line video)
    Mask: 5" wide x 2.8" tall
    Last edited by r.e.; 27-Nov-2021 at 14:35.

  2. #2

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    Re: Masking a Ground Glass for Cinema Aspect Ratios

    In the studio, we would draw on mylar overlays for the GG... Most art directors would specify a proportion needed for an ad layout, and that had to be followed exactly through the shooting process...

    Using a proportion rule scale was also constantly used on the GG also, and if you can still find one, a small one was made that is perfect for a camera GG...

    Steve K

  3. #3

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    Re: Masking a Ground Glass for Cinema Aspect Ratios

    Thanks guys for the replies. Looks like this will be straightforward.

  4. #4

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    Re: Masking a Ground Glass for Cinema Aspect Ratios

    I'm attaching a table that might be useful to someone in the future. It applies the aspect ratios for seven cinema formats to 4x5 and 8x10 sheet film. The table assumes landscape orientation and full use of the film's long side. This means that the only new value is the height of the image.

    I have not used the nominal film size (5"x4" and 10"x8") for the calculations. Instead, I've used the actual image area after taking into account film holder rebate. As there is variation in film holders, there will be variation in actual image area. However, subject to comments from others I think that my numbers are close enough. They are based on earlier posts in the forum and measurements of my own negatives. The English values below are a slightly rougher approximation than the metric values:

    5x4 Image Area
    4.75" x 3.75"
    120mm x 94mm

    10x8 Image Area
    9.75" x 7.75"
    247mm x 197mm


    My Arca Swiss 5x4 and 10x8 ground glasses have metric grid lines. The 5x4 ground glass has 12 squares by 10 squares that are each 10mm x 10mm. The 10x8 ground glass has the same pattern except that the squares are each 20mm x 20mm.

    I've used metric for the image heights in the table because that's what my ground glass grids use and because I prefer metric anyway. While the heights in the table are accurate to two decimal places, I will of course round these values in actual use. Accuracy to within a few millimetres strikes me as fine.

    I'm particularly interested in trying a couple of the wider aspect ratios (1 through 4 in the table below) with a Rodenstock APO-Grandagon f/4.5 55mm, which I expect to receive this coming week.


    Cinema Aspect Ratios Applied to 4x5 and 8x10 Sheet Film:

    Click image for larger version. 

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    Last edited by r.e.; 2-Dec-2021 at 08:21.

  5. #5

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    Re: Masking a Ground Glass for Cinema Aspect Ratios

    I've used clear red negative masking tape in the past. Scotch 3M 616 Lithographers Tape. "Pressure sensitive - Red "Paklion" film. We used to use it to mask Kodalith negatives. Very important: it was easy to remove and or replace. PM me and I can send you a roll. Haven't had a use for it in probably 30 years!

  6. #6

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    Re: Masking a Ground Glass for Cinema Aspect Ratios

    Quote Originally Posted by Greg View Post
    I've used clear red negative masking tape in the past. Scotch 3M 616 Lithographers Tape. "Pressure sensitive - Red "Paklion" film. We used to use it to mask Kodalith negatives. Very important: it was easy to remove and or replace.
    Thanks Greg. I'm looking into the 3M tape and how easy it is to remove the tape and residue from my ground glass.

  7. #7

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    Re: Masking a Ground Glass for Cinema Aspect Ratios

    The attached screen capture from RED Cinema Cameras shows the horizontal differences between certain of these aspect ratios overlayed on a single photograph. While not shown in this photo, RED Cameras are natively set up for the 2:1 ratio championed by Vittorio Storaro (e.g. Apocalypse Now). Netflix is using 2:1 (e.g. House of Cards), and 2:1 was also used for the 2018 Best Picture winner at the Academy Awards, Green Book.

    From the table attached to post #4, note that a 2:1 image from 5" x 4" sheet film is about the same size as an image shot on 120 roll film with a 12x6/6x12 camera or roll film back.



    Click image for larger version. 

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    Last edited by r.e.; 1-Dec-2021 at 17:11.

  8. #8

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    Re: Masking a Ground Glass for Cinema Aspect Ratios

    I have two reasons for doing this. One is simple interest in what large format still images in some of these aspect ratios will look like. My practical reason is that I'm interested in making still images for incorporation into a video without letterboxing or cropping the images.

    My interest in this was revived when I watched Chris Marker's La Jetée recently, a film that I last saw many years ago. La Jetée is a short film (28 minutes) made up almost entirely of still photographs*. In the opening credits, Marker calls the film a "photo-roman" (in English, a "photo-novel"). Terry Gilliam's film 12 Monkeys, as Gilliam acknowledges in the opening credits, is based on Marker's film.

    If anyone is interested, La Jetée is available from Criterion** and there are copies on YouTube and Vimeo. NY Times film critic A.O Scott talks about the film in this video:

    'La Jetée' | Critics' Picks | The New York Times




    There's also a Wikipedia article: https://en.wikipedia.org/wiki/La_Jetée


    * Marker is said to have shot the film with an Asahi Pentax.

    ** Criterion sells more than one version of this film with respect to language. If you want the French original, note that the version that Criterion sells via the Apple Store in the U.S. only offers dubbed English. This copy on Vimeo (720p) has the original French with English subtitles. Under "CC" select English:


    Last edited by r.e.; 28-Nov-2021 at 16:25.

  9. #9

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    Re: Masking a Ground Glass for Cinema Aspect Ratios

    Since writing the above posts, I've come across a 2004 thread that I missed on my initial search but which is useful: How best to mask ground glass to change aspect ratio

    There's also a two page 2019 thread titled Aspect ratio of 10x8 and 5x4? That thread starts by dismissing the original poster's question. New to large format, he wanted to know what the aspect ratio is for 4x5 and 8x10. I think that it was a perfectly good question and I approach the issue differently from most of the posts in that thread. For my purposes, the nominal aspect ratio of 4x5/8x10 is 1:25:1. The aspect ratio for the actual image area is only marginally different at about 1.26:1. See post #4 and the attached table for what I mean by nominal image area and actual image area.
    Last edited by r.e.; 1-Dec-2021 at 17:12.

  10. #10

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    Re: Masking a Ground Glass for Cinema Aspect Ratios

    Quote Originally Posted by r.e. View Post
    Thanks Greg. I'm looking into the 3M tape and how easy it is to remove the tape and residue from my ground glass.
    Tape is very easy to remove, Honestly never left any residue. If it did I would first try some film cleaner, otherwise I'd use what I consider the best residue remover: Seal UNSEAL ADHESIVE RELEASING SOLVENT but only outside in the open. Warning on the side of can reads "IF INHALED: Move to fresh air. GET QUALIFIED MEDICAL ATTENTION"... it can't be good for you would seem to be an understatement.

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