Miskit
I've been looking at some of the screen size calculators for home projectors that are online and at 18 feet viewing distance I'm getting a suggested screen size of 56" x 100". I'd like to know WHAT determines the optimum screen size. Not HOW to get it, but rather WHAT it is. Why wouldn't 60" x 107" be better at the same distance?
I'm using a Sony BRAVIA VPL-AW15 LCD Projector 16:9
I'd like someone to define what it is. What determines it?
Answer
In your context, optimum screen size relates to the aspect ratio, viewing distance, image resolution, and to a lesser degree secondary factors such as screen gain, projector brightness. and screen door effect. It's actually a balancing act. Read on.
First, recognize there is no absolute standard for determining screen size (after all different people have different preferences), BUT there are guidelines for the viewing angle (angle subtended from the viewing position by width of the screen) such as those defined by THX (1st link. Horizontal viewing angle of 40 degrees or less, 15 degree max angle to top of screen) and SMPTE (minimum horizontal viewing angle of 30 degrees).
An obvious result of this is that the perceived screen size (i.e. viewing angle) will vary with distance, and for a constant viewing angle at differing viewing distances the screen size must vary. So for example, a 100" screen at 12 ft would give the same viewing angle as a 50" screen at 6 ft. This is the fundamental reason that there is an optimum screen size for any viewing distance (or more accurately a size range, since personal preference must be allowed for).
Aspect ratio comes into this since screen size is often defined based on the diagonal size of a screen and aspect ratio impacts on this dimension. See the 2nd link for a calculator that takes this into account.
Finally, of the 3 primary factors, image resolution matters because the human eye can resolve detail atfor 20/20 vision) about 1/60 degree of arc. For any image resolution (e.g. 720 or 1080) there will be a distance range where higher resolution can be perceived. See the article at the 3rd link for the full discussion, but as a projector user the important point is that at THX (or SMPTE) optimum distances / screen size the highest resolution possible is recommended ... and these days that means 1920x1080.
Secondary considerations also bear on this question as follows. Projector brightness impact on how bright the image will be at a certain distance. Since image brightness has a recommended minimum and maximum (12-22 ft-lamberts, see 4th link) you don't want to be too far back (brightness drops off with distance) or project on too big a screen (brightness drops with larger screen size). Projectorcentral.com's projector calculator (5th link) is useful here since it shows (caution: based on manu published specs) brightness level as a function of throw distance, screen gain and screen size ... but don't confuse this with optimum screen size.
Higher screen gain can be used to componsate somewhat for low brightness but at the risk of adversely impacting the image through hot-spotting, limited viewing angle and colour shifts).
Finally, "screen door effect" (SDE) must be taken into account when considering minimum viewing distance for any screen size. SDE is visible at close viewing distances as black or dark grey lines around the individual pixels of the image. Different projectors vary in their tendency to show SDE ... with LCOS being the least and LCD and DLP being the most suceptible. Your projector has a recommended (See last link) minimum viewing distance of 1.8x screen width to avoid seeing SDE.
So, bottom line ... there is no single optimum screen size, but there is a minimum and maximum based on viewing angle, SDE effect, projector brightness, etc. Within this range it comes down to personal preference (and physical limitations such as room size).
Hope this helps clarify the interrelationships.
In your context, optimum screen size relates to the aspect ratio, viewing distance, image resolution, and to a lesser degree secondary factors such as screen gain, projector brightness. and screen door effect. It's actually a balancing act. Read on.
First, recognize there is no absolute standard for determining screen size (after all different people have different preferences), BUT there are guidelines for the viewing angle (angle subtended from the viewing position by width of the screen) such as those defined by THX (1st link. Horizontal viewing angle of 40 degrees or less, 15 degree max angle to top of screen) and SMPTE (minimum horizontal viewing angle of 30 degrees).
An obvious result of this is that the perceived screen size (i.e. viewing angle) will vary with distance, and for a constant viewing angle at differing viewing distances the screen size must vary. So for example, a 100" screen at 12 ft would give the same viewing angle as a 50" screen at 6 ft. This is the fundamental reason that there is an optimum screen size for any viewing distance (or more accurately a size range, since personal preference must be allowed for).
Aspect ratio comes into this since screen size is often defined based on the diagonal size of a screen and aspect ratio impacts on this dimension. See the 2nd link for a calculator that takes this into account.
Finally, of the 3 primary factors, image resolution matters because the human eye can resolve detail atfor 20/20 vision) about 1/60 degree of arc. For any image resolution (e.g. 720 or 1080) there will be a distance range where higher resolution can be perceived. See the article at the 3rd link for the full discussion, but as a projector user the important point is that at THX (or SMPTE) optimum distances / screen size the highest resolution possible is recommended ... and these days that means 1920x1080.
Secondary considerations also bear on this question as follows. Projector brightness impact on how bright the image will be at a certain distance. Since image brightness has a recommended minimum and maximum (12-22 ft-lamberts, see 4th link) you don't want to be too far back (brightness drops off with distance) or project on too big a screen (brightness drops with larger screen size). Projectorcentral.com's projector calculator (5th link) is useful here since it shows (caution: based on manu published specs) brightness level as a function of throw distance, screen gain and screen size ... but don't confuse this with optimum screen size.
Higher screen gain can be used to componsate somewhat for low brightness but at the risk of adversely impacting the image through hot-spotting, limited viewing angle and colour shifts).
Finally, "screen door effect" (SDE) must be taken into account when considering minimum viewing distance for any screen size. SDE is visible at close viewing distances as black or dark grey lines around the individual pixels of the image. Different projectors vary in their tendency to show SDE ... with LCOS being the least and LCD and DLP being the most suceptible. Your projector has a recommended (See last link) minimum viewing distance of 1.8x screen width to avoid seeing SDE.
So, bottom line ... there is no single optimum screen size, but there is a minimum and maximum based on viewing angle, SDE effect, projector brightness, etc. Within this range it comes down to personal preference (and physical limitations such as room size).
Hope this helps clarify the interrelationships.
projector question?
lionsroar2
i want to get a projector but i can only put it 6-7 feet away from the wall. how big would the screen projection be: width*height if possible.
also if i do get it and i get a ceiling mount will i be able to point the picture down so it doesnt have to be in the middle of the room?
Answer
Hi there. Projectors with short throw lenses are available with minimum projection distances from 1.1 up to 2.3. 1-2 : 1 means the projector needs to be one to two meters back from the screen for a one metre image .2-3 : 1 means the projector needs to be 2 to 3 metres back from the screen to view a one metre image.Special lenses are available to attach to your projector lens to increase the image from the same distance. If you have the projector mounted on the ceiling make sure you get one with a "lens shift "feature. Which means you dont have to angle the projector down.The projector should be perpendicular to the screen to avoid a distorted image.The lens shift feature moves the image up or down while the projector is pointing straight ahead.
Hi there. Projectors with short throw lenses are available with minimum projection distances from 1.1 up to 2.3. 1-2 : 1 means the projector needs to be one to two meters back from the screen for a one metre image .2-3 : 1 means the projector needs to be 2 to 3 metres back from the screen to view a one metre image.Special lenses are available to attach to your projector lens to increase the image from the same distance. If you have the projector mounted on the ceiling make sure you get one with a "lens shift "feature. Which means you dont have to angle the projector down.The projector should be perpendicular to the screen to avoid a distorted image.The lens shift feature moves the image up or down while the projector is pointing straight ahead.
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Title Post: WHAT IS meant by optimum screen size for a home projector?
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