I THINK i get CIH... - AVS Forum | Home Theater Discussions And Reviews
Forum Jump: 
 
Thread Tools
post #1 of 5 Old 04-12-2019, 02:21 PM - Thread Starter
Senior Member
 
MinHeadroom's Avatar
 
Join Date: Feb 2019
Posts: 212
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 56 Post(s)
Liked: 63
I THINK i get CIH...

Hi and thanks,

I’ve never used a projector and am planning my first purchase. I’m also framing my basement and near to running conduit and electrical.

So if l
a) I use the pj’s zoom to fill 2.39:1 (at 120” diag), and
b) i use no zoom for 16:9 (94.4” diag), both using a 46.3” height screen,
THEN
c) For a projected image to fill a 2.39:1 screen with an image, I am projecting a big 16:9 image (127” diag), where the “black bars” are just above and below the screen.

I got this right?



If so, assuming i have a light controlled room covered in black velvet, how important is it for me to put the pj as close to the screen as possible?
(Assume I’m using a 1 gain screen and an Epson 5050 for now please).

If I can manage 16’ to the screen, I can put the PJ in a hush box going into a crawl space.



Last question: If I am getting this right, how critical is it for the lens of the PJ to be at the top of the screen in order to do CIH? I think it depends on lens shift and lens memory, but I-may be missing something. I understand, at least superficially, the lens must be below the top of the screen.

Last edited by MinHeadroom; 04-12-2019 at 02:28 PM.
MinHeadroom is offline  
Sponsored Links
Advertisement
 
post #2 of 5 Old 04-13-2019, 12:41 AM
AVS Forum Special Member
 
ScottAvery's Avatar
 
Join Date: Mar 2002
Location: Great Falls, VA
Posts: 1,719
Mentioned: 23 Post(s)
Tagged: 0 Thread(s)
Quoted: 674 Post(s)
Liked: 196
Your screen size math looks correct. Use an online projector calculator to get the throw range for your screen size. The one I checked says 78 to 163 inch diagonal 16:9 range for a 16 foot throw, so well in range. You could get a brighter image if you got closer, but that is a tradeoff on noise. I'd go with the longer throw, personally, if there was an option for a hushbox.

As long as you are keeping the projector on the centerline there is plenty of room for vertical offset, up to and above screen. Range is reduced if you have to horizontal shift, also. There is a calculator built by one of the forum users that does precise lens shift calculations, but the link is not in my favorites. Perhaps someone else can provide it if you need it.
ScottAvery is offline  
post #3 of 5 Old 04-13-2019, 12:45 AM
AVS Forum Special Member
 
ScottAvery's Avatar
 
Join Date: Mar 2002
Location: Great Falls, VA
Posts: 1,719
Mentioned: 23 Post(s)
Tagged: 0 Thread(s)
Quoted: 674 Post(s)
Liked: 196
Screen seems a little small for a room with 16 foot depth. Are you width limited? I see the ceiling is low but that is not as much an issue for CIH.
ScottAvery is offline  
Sponsored Links
Advertisement
 
post #4 of 5 Old 04-13-2019, 05:02 AM - Thread Starter
Senior Member
 
MinHeadroom's Avatar
 
Join Date: Feb 2019
Posts: 212
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 56 Post(s)
Liked: 63
I THINK i get CIH...

Quote:
Originally Posted by ScottAvery View Post
Your screen size math looks correct. Use an online projector calculator to get the throw range for your screen size. The one I checked says 78 to 163 inch diagonal 16:9 range for a 16 foot throw, so well in range. You could get a brighter image if you got closer, but that is a tradeoff on noise. I'd go with the longer throw, personally, if there was an option for a hushbox.



As long as you are keeping the projector on the centerline there is plenty of room for vertical offset, up to and above screen. Range is reduced if you have to horizontal shift, also. There is a calculator built by one of the forum users that does precise lens shift calculations, but the link is not in my favorites. Perhaps someone else can provide it if you need it.


Thank you- this jives with what I imagined, your confirmation appreciated!

Last edited by MinHeadroom; 07-21-2019 at 08:10 AM.
MinHeadroom is offline  
post #5 of 5 Old 04-13-2019, 05:04 AM - Thread Starter
Senior Member
 
MinHeadroom's Avatar
 
Join Date: Feb 2019
Posts: 212
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 56 Post(s)
Liked: 63
Quote:
Originally Posted by ScottAvery View Post
Screen seems a little small for a room with 16 foot depth. Are you width limited? I see the ceiling is low but that is not as much an issue for CIH.


That’s good to hear given my fear i was going too big. I’m going for two rows (the second sub-optimal), but the main seat will be ~ 9.5’ from the screen. Room width is 13’:
MinHeadroom is offline  
Sponsored Links
Advertisement
 
Reply 2.35:1 Constant Image Height Chat

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off