Seating Distance from 100'' Screen

Discussion in 'Home Theater Projects' started by Hubbard Graham, Aug 30, 2004.

  1. Hubbard Graham

    Hubbard Graham Auditioning

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    Hi all,

    I would like to maximize the number of seats I can put in my home theater. I'm buying an 100" diag. screen. My question is where should my 1st row of seating begin. Specifically, How close should viewers sit to have a comfortable movie view. This distance will reflect my choice of seating. I would like to get the most out of my 27' x 13 room.

    thanx for any direction
     
  2. Nick.H

    Nick.H Stunt Coordinator

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    Howdy,

    I have found some information for you regarding seating.

    Seating Guide
     
  3. David Cotton

    David Cotton Auditioning

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    Hubbard, I've been reading that a good standard is to have your seating at a distance of 1.5~1.8 times the diagonal size of your screen, or another commonly used measurement is 2.5 time the width.

    Looks like the article that Nick posted is much much much more technical, detailed and precise though.
     
  4. Jay Mitchosky

    Jay Mitchosky Producer

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    There's a site out there (was sure I had the link but can't find it) that will do the math for you. If I recall from the document referenced above it uses the basic reference point of 1.5 times screen width. It's a simplified means of defining a recommended field of vision. SMPTE indicates the screen should occupy no less than 30 degrees of your field of view, whereas THX endorses 36 degrees. There is another specification for vertical location to define a vertical field of vision (I believe this is optimally around 15%). It all comes down to balancing between sitting close enough to achieve the proper scale so an image looks sufficiently big and involving, yet not so close that it's overwhelming, causes eye fatigue, or results in the image structure being visible (ie. scan lines, individual pixels).

    Remember back in junior high and high school when you scoffed at algebra and geometry, but were warned by your teachers it would come in handy some day. Well this is it! [​IMG] Time to pull out trigometry and Pythagorean theorem.

    If you are basing your screen size on diagonal measurement you will need to use Pythagorean theorem to solve for the height and width. You know the hypoteneuse (diagonal) and you know the aspect ratio (16x9) so can go from there.

    You now have an expected width of screen. Cut that in half to form the opposite side of a 90 degree triangle. You are solving for the distance from your eyes to the screen - this is the adjacent side. You plug in your desired angle (theta) and use tangent to solve for the adjacent side (ie. your seating distance). The angle is based on your field of vision. If you're shooting for 35 degrees horizontal field of vision then half of that is 17.5 degrees (remember that we cut the width of the screen in half to create the right triangle). You can play with these numbers until you're blue in the face. I tried to achieve a 35/36 degree angle from my first row while maintaining the minimum 30 degree angle in the second row. Couldn't quite make 30 back there but it's close.

    If you start running into problems with seating location then wipe the slate clean and don't presuppose a screen size. Locate the seats where you want them or, better yet, where the room's acoustics suggest the best location. That will define your viewing distance (adjacent side). You will plug in your desired viewing angle (theta) then solve for the opposite side using tangent. Double that value and you now have your screen width (which is good as projection screens are usually referenced by screen width and aspect ratio) and convert to diagonal measurement if you choose using Pythagorean theorem. In other words you can work either way: let the screen dictate seating or the seating dictate screen (for acoustic layout the latter is better).

    Wanted to point something out here. You are basing these measurements on the location of the viewer's eyes, not the seat itself. If you have chosen your seat (or already own them) you will need to measure where the eyes end up when in the reclined "movie watching position". Place the eyes first then the seat is located to accommodate that. This becomes much easier if you sketch out a room to scale, including furniture cutouts (with the dimensions in the reclined position and eye position noted). Then you can play around and make sure you have adequate clearance and such for different positions. Everything is interelated.
     
  5. Conrad Ebel

    Conrad Ebel Agent

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    Also, it is dependent on your projector. Usually you can sit closer to an LCD projector (1.5x), than you can a DLP projector (usually around 2x, although some say a little less is fine), without losing picture quality.

    Do your research on the projector you want and there will be good information on the viewing distances.

    Good luck with your project.
     
  6. Jay Mitchosky

    Jay Mitchosky Producer

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    I don't know if I agree with that. I believe DLP has a greater fill factor (ie. amount of space covered by the pixel vs. gaps between adjacent pixels) than LCD, which is more prone to the screen door effect. D-ILA is the best with the highest fill factor. But you are correct in that the type of projector and resulting image structure will have an impact on how close you can sit.
     
  7. Chip_Slattery

    Chip_Slattery Stunt Coordinator

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  8. Jay Mitchosky

    Jay Mitchosky Producer

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    Thanks Chip. That's exactly what I was talking about. Takes care of the math for you.
     

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