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Blend Calc


romeozanelato

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I think it's C8H10N4O2

 

I suspect something has gone a little wrong with the translation here = what blend do you mean?

 

hi,

 

its a video projection blending..

 

I have a screen with 15,40mt x 8,70mt

1920 x 1080

 

 

with 3 projectors.

 

thanks

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There is no magic formula. You figure out your screens aspect ratio - divide width by height. Generally your "limiting" factor will be height - ie you will be doing a 1 x "n" projector blend. So multiply your projectors native vertical resolution by your aspect ratio - that gives you your horizontal pixel count (Hf). Multiply your projectors native horizontal resolution by the number of projectors - that gives your total horizontal pixels available (Ht). (Ht-Hf)/(N-1) will be your overlap.

 

So with what you have given...

 

Aspect is 1.7701.

 

16:9 aspect is 1.7778, meaning your horizontal pixel count (Hf) would be 1912 pixels - your overlap is 100% (ie a projector stack)... You could do a 2x2 blend or a 2x3 blend - but 3 projectors will not blend.

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hi,

 

can you explain better???

 

if the screen have 15,40mt x 8,70mt and I have used 2 projectors full hd (1920 x 1080),

my horizontal resolution is 3.840 pixels

please explain to me that formula: (Ht). (Ht-Hf)/(N-1)

thanks a lot

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The formula is just (Ht-Hf)/(N-1) - so basically the total number of pixels available (3840) minus the total number of pixels you require gives you how many "spare" pixels you have. spare pixels divided by the number of blend regions (1 less than the number of projectors) gives you your overlap. You want your overlap between 10 and 25%. of your projectors resolution

 

Your problem is that your screen ratio (length to height) is 1.7701:1 - your projectors, at 1920x1080 are 1.7778:1 - so a blend will not help. You want an image height of 8.7m - if you are doing a 1x"N" blend, your vertical resolution (maximum) will be 1080 - with me so far? now 1080*1.7701 is 1912 pixels (that is, the number of pixels you need to fill the screen) - ie LESS than the horizontal resolution of your projector.. You have no need to blend, because you do not need more horizontal pixels. If you were to do a "N"x1 projector blend 1920 is your limiting resolution, so 1920/1.7701 - 1085 pixels. That means doing a 2 projector blend, your overlap would be ((2*1080)-1085)/1 or 1075 pixels of overlap... so you would be throwing 2 projectors and trying to offset them by 5px each and then throwing a blend curve over them that will basically throw away all of your brightness.

 

That sort of screen you want to be doing something like a 2x2 projector blend - and in that case you can set whatever overlaps you want really (based on lens availability). If you only have 2 or 3 projectors available, I would be stacking them to get brightness. 2 projectors blended gives the same overall output per square meter as 1 projector covering just half the area - but you get more pixels to play with. Pixels are not what is limiting you, what is limiting you is brightness - so you want to stack, not blend.

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