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Discussion Starter · #1 ·
A lot of newbies like me come to these forums to learn from the experts – people who have experience in this endeavor. I want to give a shout out to those gurus who give their time to help us newbies gain an understanding of this topic. Maybe I can give a little back and enlighten other beginners on something I recently figured out.

I have just installed a BenQ HT1075 in my makeshift basement theater and we have been enjoying it immensely. Its intended purpose is movies and recorded concerts (Blu-ray, DVD, and Netflix streaming) and some light gaming (Wii). For now, we are projecting onto a blank white wall so we can try out different screen sizes to determine what size we ultimately want to buy. This has led to a few lessons that the experienced here will understand, but maybe other newbies don’t know when they get started.

Our current viewing distance is about 10 to 11 feet from the screen. When we started, the first movie we watched was a 16:9 presentation of “The Avengers”. I felt that the 135” projected image might be just a bit too big for me, but I left it alone. Since then, we have watched 2.40 presentations and that seems much better to my eyes. Most movies in my collection are done with this aspect ratio. It seems better to me because the height of the projected image is shorter and my eyes aren’t wandering up and down so much. My first discovery is that, left alone, the projected image is Constant Image Width (CIW) regardless of the film’s aspect ratio. When I started this process, I had thought that I wanted to get a 2.35 (Cinemascope) screen and attempt a Constant Image Height (CIH) idea, putting up with black bars on the sides of my few 1.78 movies. Even tho my projector doesn’t have the zoom range to quite pull this idea off, I have since discovered another reason why this is a bad idea – at least for me. It’s all in the maths.

When HD first came out, the specification everyone focused on is vertical resolution (i.e. “full 1080p”). When you watch an HD image at 1.78, you get 1920 x 1080 pixels. I’m pretty sure that’s the full resolution of the HD display chips used in all the projectors in this price segment. What I didn’t understand is that since most movies are done at 2.40, and you can’t exceed the resolution of the display chip in your projector, the wider (shorter?) image is created by masking off the top and bottom pixels to create the correct aspect ratio. So, a Cinemascope movie on our projectors is displayed at something like 1920 x 800 pixels. That all-important vertical resolution isn’t “full HD” anymore.

Using my 135” display size (66h x 118w), I’m getting about 16 pixels per inch, as long as I stick with CIW. Whether the image is 1.78 or 2.40, the pixel pitch is the same, so it looks fine to me. Now, if I had tried to create a CIH situation, I would be blowing up that same 1920 x 800 pixel image to 66” high (135” wide!), reducing brightness and (maybe more importantly) decreasing the pixel pitch to about 12 pixels per inch. A 16:9 DVD displayed on my 135”screen has a pixel pitch of about 8 pixels per inch, so I would consider that Cinemascope CIH image as “Medium-High Definition (MHD)”. It’s still pretty good, better than DVD, but not “full HD” in my opinion. There are Cinemascope display chips in projectors (2560 x 1080 native), where I think you could have a fantastic CIH theater experience, but those projectors are quite expensive. Wouldn’t it be great to see a UHD (4k) Cimenascope (5120 x 2160) display? Wow. :D

So, the bottom line in this long-winded explanation is that it is my opinion, fellow newbies, that in most cases you are better off buying a screen that matches the aspect ratio of the chip inside your projector. For those of us in this forum, that means a 16:9 (1.78:1) screen. Buy a screen big enough that you enjoy the height of a projected Cinemascope movie. For me, I’m pretty sure that’s going to be a 135” screen for my 10 foot viewing distance. That gives me a 49” high display for most of the movies I watch, which is just about perfect.

Thanks for reading.

Steven
 

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For those of us in this forum, that means a 16:9 (1.78:1) screen. Buy a screen big enough that you enjoy the height of a projected Cinemascope movie. For me, I’m pretty sure that’s going to be a 135” screen for my 10 foot viewing distance. That gives me a 49” high display for most of the movies I watch, which is just about perfect.

Thanks for reading.

Steven
Yes, and no. What you say it true for using the "zoom lens" method of 2.39:1 where you are throwing away the light and image capacity of the 16:9 panel so it overflows the top and bottom of a 2.39:1 screen. What you have missed is that an anamorphic lens -- and there are used ones for $500 or so -- retains ALL of the light from the 16:9 panel when used on a 2.39:1 screen. Using the Aspect Mode feature of the 1075HT, the projector will scale the 800 pixels up to 108o and give you your "full HD" picture again. The scaling is not "perfect" but it is actually better than the scaling of DVD's up to 1080P to me eye. So for "people in this forum", meaning I suppose the under $3,000 digital projector crowd, you can have the best of both worlds on a 2.39:1 screen and still be well within budget.

http://www.avsforum.com/forum/68-di...ready-lens-shift-1000-a-348.html#post29351849



 

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Discussion Starter · #4 ·
Yes, and no. What you say it true for using the "zoom lens" method of 2.39:1 where you are throwing away the light and image capacity of the 16:9 panel so it overflows the top and bottom of a 2.39:1 screen. What you have missed is that an anamorphic lens -- and there are used ones for $500 or so -- retains ALL of the light from the 16:9 panel when used on a 2.39:1 screen. Using the Aspect Mode feature of the 1075HT, the projector will scale the 800 pixels up to 108o and give you your "full HD" picture again. The scaling is not "perfect" but it is actually better than the scaling of DVD's up to 1080P to me eye. So for "people in this forum", meaning I suppose the under $3,000 digital projector crowd, you can have the best of both worlds on a 2.39:1 screen and still be well within budget.
Kirk,

I appreciate the response. I'm just trying to understand how that would work. Aren't you basically taking square pixels and making them rectangular by stretching them with the lens? There is only so much resolution in the display chip. A true Cinemascope display chip has a native resolution of 2560 x 1080. If the anamorphic lens fills the same size/shape screen with an image with only 1920 pixels, they must be stretched horizontally. Right?

Have a great weekend.

Steven
 

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The A lens will use the full light output from the projector although there is some light lost due to the optics and the cheaper the lens the more image distortion. As far as resolution the Image from a BR disk will still only be 800 pixels high and you no longer have 1 to 1 pixel mapping. With today's bright projectors light output is not as much of an issue in most cases so an A lens is not as desirable as in the past, is it better than the zoom method, most likely. If you don't have power zoom and shift I would say its a necessity for a 2:40/39/35 screen
 

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Kirk,

I appreciate the response. I'm just trying to understand how that would work. Aren't you basically taking square pixels and making them rectangular by stretching them with the lens? There is only so much resolution in the display chip. A true Cinemascope display chip has a native resolution of 2560 x 1080. If the anamorphic lens fills the same size/shape screen with an image with only 1920 pixels, they must be stretched horizontally. Right?

Have a great weekend.

Steven
Yes, the pixels become rectangular. A zoomed 2.4:1 movie has 1.5M square pixels actually coded on the bluray, while the projector is capable of 2M square pixels. The projector Aspect Ratio "Letterbox" on the 1075HT or W1070 manufactures an extra 0.5M square pixels making the 2.4:1 content look tall and skinny, then the A-lens stretches them into rectangular pixels.

The advantage is multiple: 1) getting all the light possible from the projector, 2) getting a wider image from a shorter throw, 3) not having to zoom or focus when changing between 16:9 content and 2.4:1 content -- you just slide the lens aside, 4) not having the image top/bottom change height between modes, 5) getting more resolution -- even if it is the result of scaling rather than real data, 6) the projector doesn't need to have a zoom lens at all -- much less the 1.35 minimum necessary to do a zoom method 1.78 -> 2.4.
 
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