AVS Forum banner
1 - 11 of 11 Posts

·
Registered
Joined
·
47 Posts
Discussion Starter · #1 ·
Thanks for the help.

As I continue to look into designing a method of masking my 1.78:1 screen for 2.35:1 images, I noticed something odd:

I have a fixed Stewart Firehawk. The viewing area of the screen is 72" x 40.5". The aluminum black border is 3.25".

If I am calculating correctly - a 2.35:1 projected image would be sized at 72" x 30.6". This would require two 5" masks, positioned at the screen's viewing area's upper/lower edge(s).

If I decided to extend the height of the masks to cover the upper and lower Stewart frame edges, each mask would need to be extended in height by 3.25". The final result would be two masks, 8.25".

I'm pretty sure this all checks out, yes?

I just measured the projected image for a 2.35:1 Blu-ray (How To Train Your Dragon). I was surprised to find the distance from the top of the projected image to the upper screen edge and the distance form the bottom of the projected image to the lower screen edge was not symmetrical. in fact the top distance was 5.25" and the bottom distance was 4.75".

And considering these measured distances - upper and lower masks extended to the outer edges of the screen frame would need to be 8.5" (top) and 8" (bottom).

When I display my projector's Test Pattern for image alignment based on throw and zoom - it's pin point accurate top/bottom & left/right for full frame 16x9.

And so is my math correct? And is the projected image position relative to the edges of the viewing area of the screen typically different at the top and bottom?

Thanks again.

-paul.

 

·
Registered
Joined
·
6,752 Posts
There isn't a dead-set scope aspect anyway so you'll likely want somewhat flexible masking points OR will have to mask 2.4 instead of 2.39 or 2.35 and your masking will just soak up a couple lines of pixels (just like most borders do for all four sides).

For the asymmetric bars, I'd doublecheck both your 16:9 content (make sure your PJ isn't half an inch low there as well) and then try to test if other scope movies do the same thing.
Depending on how consistent the asymmetry is, you'll either need to design asymmetric masks (if it's constant), or will have to either use something adjustable or have both top+bottom wider (if it's inconsistent).

If your projector has lens-shift memory settings or the ability to raise/lower the picture via pixel adjustment (like centering your old computer screen), make sure that setting is put to neutral AND make sure you're checking it WHILE using that same input because many displays can memorize different settings for each input. It might be fine for hdmi1 but maybe got bumped a while back for hdmi2..for example.
 

·
Registered
Joined
·
47 Posts
Discussion Starter · #3 ·
There isn't a dead-set scope aspect anyway so you'll likely want somewhat flexible masking points OR will have to mask 2.4 instead of 2.39 or 2.35 and your masking will just soak up a couple lines of pixels (just like most borders do for all four sides).
Yes, and understood. I need to decide on how elaborate I want this to be in terms of flexibility. I may just design a specific size set of masks and live with a small amount of overscan when dealing with various scope aspect ratios.

For the asymmetric bars, I'd doublecheck both your 16:9 content (make sure your PJ isn't half an inch low there as well) and then try to test if other scope movies do the same thing.
Depending on how consistent the asymmetry is, you'll either need to design asymmetric masks (if it's constant), or will have to either use something adjustable or have both top+bottom wider (if it's inconsistent).
When using the projectors's alignment pattern the 16x9 projected image is 100% accurate top to bottom and side to side.

If your projector has lens-shift memory settings or the ability to raise/lower the picture via pixel adjustment (like centering your old computer screen), make sure that setting is put to neutral AND make sure you're checking it WHILE using that same input because many displays can memorize different settings for each input. It might be fine for hdmi1 but maybe got bumped a while back for hdmi2..for example.
The projector has manual lens shift. The proper position of the (16x9) image was set using the projector's alignment pattern. And I believe the projector has a pixel adjustment setting. I'll check it out.

Thanks again.

-paul.
 

·
Registered
Joined
·
6,752 Posts
While you're already having to check everything, make sure actual 16:9 content (movie, not the test pattern) is aligned and not 1/2" low.
 

·
DIY Granddad (w/help)
Joined
·
24,837 Posts
pnMedia,

You best method to create a Masking solution that is fully adaptable to your variances in Format size would be to use a custom sized Chain Pull Roller Blind covered in Black Velvet, one that simply can pull down to mask the area left over after you shift a 2.35 / 2.39:1 image down to set on the lower Screen trim edge.
 

·
Registered
Joined
·
47 Posts
Discussion Starter · #7 ·
pnMedia,

You best method to create a Masking solution that is fully adaptable to your variances in Format size would be to use a custom sized Chain Pull Roller Blind covered in Black Velvet, one that simply can pull down to mask the area left over after you shift a 2.35 / 2.39:1 image down to set on the lower Screen trim edge.
I agree. In fact I spent a few hours in Home Depot, looking around for parts and design inspiration. They have this aluminum molding and square rod material that I've worked with in the past. I came up with an effective way to build a sliding track system that would allow for adjustable masking. However the masks would need to be fixed on frames and extended/positioned above and below the screen when not in use. It's a sloppy implementation and it ruins the clean look of the Stewart that I paid for.

I realize there are going to be compromises regarding aesthetics, and I am intrigued by your suggestion. Can you elaborate? The mechanics of the roller blind is one thing. How about covering up the installed hardware above, below, and at the sides of the Stewart?

I would really appreciate any suggestions ... so thanks again.

-paul.
 

·
DIY Granddad (w/help)
Joined
·
24,837 Posts
Well...the last one I did had a inset screen with a forward overhang and recessed side areas, so hiding the Roller Bar and it's End hardware was no issue....nor was the Curtain Falls at each end. My method allowed for 4:3 / 16:9 / 2.35:1 masking via a combo of Curtain and Roller usage. It was kept "all manual" for cost and simplicity.
http://www.avsforum.com/forum/110-d...nd-based-16-9-4-3-2-35-1-masking-example.html

Here are two possible solutions you might consider that both address the "Theater Look" and give a very refined look even with the Lights full up.


  • Use slender but adequate Black Velvet Curtain Falls at each end of the Screen to hide the Hardware at each end, and / or a small Valance across the Top to hide the Roller Bar and the Hardware. The Curtains on the end also hide the Pull Chain, or if you get really ambitious, any Comfy Roller Motor assembly.


  • Use a Manual or Electric Curtain assembly w/ Valance that pulls inward to center and masks the top area only. The Side Curtain Falls would be Longer and stand off the wall just enough to enclose the Pull Curtains when they are retracted.

Both methods assure you of a very polished look, and do not involve altering the Frame, nor risking the application of panels directly against the Screen material.

Of course. the Former is more in keeping with a non-Constant Image Height with preference given to maintaining as large a 16:9 image as possible, and simply masking the unused portion of the 16:9 area when a 2.39:1 image is on screen.

The latter eliminates a LOT of fabrication of Roller Bar and hanging Hardware....you could use something as simple as a modest Valance, and 2 short Travis Rods at each end, and one long one across the Screen itself. I'd venture to say that a nice fall of Black Velvet Curtain w/ smallish Pleats stretching across the screen has more potential to look "Special" while doing so at less cost in time and money.

The Former is the simplest but leaves the sides of the Screen looking less adorned.
 

·
Registered
Joined
·
2,730 Posts
Thanks for the help.

As I continue to look into designing a method of masking my 1.78:1 screen for 2.35:1 images, I noticed something odd:

I have a fixed Stewart Firehawk. The viewing area of the screen is 72" x 40.5". The aluminum black border is 3.25".

If I am calculating correctly - a 2.35:1 projected image would be sized at 72" x 30.6". This would require two 5" masks, positioned at the screen's viewing area's upper/lower edge(s).

If I decided to extend the height of the masks to cover the upper and lower Stewart frame edges, each mask would need to be extended in height by 3.25". The final result would be two masks, 8.25".

I'm pretty sure this all checks out, yes?

I just measured the projected image for a 2.35:1 Blu-ray (How To Train Your Dragon). I was surprised to find the distance from the top of the projected image to the upper screen edge and the distance form the bottom of the projected image to the lower screen edge was not symmetrical. in fact the top distance was 5.25" and the bottom distance was 4.75".

And considering these measured distances - upper and lower masks extended to the outer edges of the screen frame would need to be 8.5" (top) and 8" (bottom).

When I display my projector's Test Pattern for image alignment based on throw and zoom - it's pin point accurate top/bottom & left/right for full frame 16x9.

And so is my math correct? And is the projected image position relative to the edges of the viewing area of the screen typically different at the top and bottom?

Thanks again.

-paul.

http://www.avsforum.com/forum/110-diy-screen-section/1169586-my-latest-masking-trial.html
 

·
DIY Granddad (w/help)
Joined
·
24,837 Posts
Yes...the math is correct, but the placement of a 2.39:1 image can vary dependent upon the material and the DVD, as well as how the PJ interprets such variances and projects them.

For all that matters, it's the same with all content. One time the image is perfectly fitted to the screen...with something else there is a line across the Top or the sides.

That is why for my Masking projects I opted for a single Pull down Mask and shifting the image down to the lower edge of the trim.
 

·
Registered
Joined
·
47 Posts
Discussion Starter · #11 ·
Thanks guys for the info and links. I've figured out a way to implement a manually sliding "rail" system that would provide adjustable placement for upper/lower masks. Conceiling the mecanisms on both sides of the screen is another story.

-paul.
 
1 - 11 of 11 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top