109 replies to this topic

[deandob]

OK, this time I got out the tape measure instead of going from memory (bad guess on the distance from the screen....). Screen diagonal is 390cm (153") and I sit 400cm from screen for the 1st row in the home theatre (3 rows, 15 seats total). Width is 338cm, so I sit 1.2 screen widths away from the screen. Maybe the reason why I saw a slight degredation in sharpness & contrast with my old prismasonic a-lens is because of the screen size and sitting so close to the screen? The contrast distortion was only noticeable when I connected up a PC, I could see a slight ghost on another part of the screen with high contrast text, I guess due to internal lens reflections.

I don't consider 1.2 screen widths as that close, and the screen does not completely fill my vision periphery but as you can imagine it creates a very immersive picture. You want the image as large as possible - my idea of a home theatre is to emulate the large screen theatre experience. I originally designed the screen to have the maximum size possible and still be able to use my Dunlavy speakers (mains are over 6 feet tall) and not see screendoor. The intent was to use the room for 2 channel listening (it is full of acoustic insulation & traps) but I pretty much only watch blu-ray concert videos now as the audio on a good concert disk is discernably better than a CD.

I have the motors & electronics to automate the masking but need to find time to put it all together. I definitely recommend using horizontal masking for 2.35:1 on a 16:9 screen, it improves the apparent contrast of the image even though the HD750 is pretty good at keeping the black bars somewhat black, the masking makes the image float in a black void and enhances the picture.

Another benefit of a large screen is that the light at 0 IRE level is barely noticeable as the residual light from the projector is spread over the whole screen, effectively lowering the black level (however no increase in contrast as the max white level is also lowered). This advantage is somewhat offset by the fact that I can't use much of the iris as I need more brightness to light up the screen (on a new bulb the iris is 1/2 closed on max bulb to get acceptable brightness).

Now I'm just waiting to see what JVC has in store for their end of year new models as its time to trade up from my HD750 to a model with more brightness and hopefully 3D without ghosts...

Edited by deandob, 31 May 2012 - 09:46 PM.

[Htpc-online]

Dean post some pictures of your room it sounds very impressive!

[deandob]

Sure, I'll post some photos on the weekend. Spent a while designing and building it but I get my moneys worth as its used a fair bit, and it makes a good hobby to keep me out of trouble! I'll take a photo of both 16:9 and 2.35:1 to show how the masking works.

Edited by deandob, 31 May 2012 - 10:03 PM.

[BladeRnR]

Nice post Dean. I completely agree "size" is everything in a HT as it replicates the experience of a commercial theatre and to me this is the whole point of the hobby in this regard. Personally I would sacrifice a tiny bit of PQ for size every single time.

"Maybe the reason why I saw a slight degradation in sharpness & contrast with my old prismasonic a-lens is because of the screen size and sitting so close to the screen?"

Quite right mate and almost certainly. You would not see such degradation with a cylindrical Lens (I have experienced both and use a cylindrical Lens). It's Night and Day as far as PQ goes when comparing a Prism Lens to a Cylindrical type. Masking is critical for serious viewing as you highlighted.

For my dedicated room the route I'm taking is either CIA (Quad-Masking) or CIW (So only horizontal masking is required). I dare say with a projector upgrade your brightness issue will be somewhat diminished

kudos on the Dunlavy speakers (Classics) - they are absolute beasts and I've experienced them a few times over the years. Imposing to say the least!

regards

Blade

Edited by BladeRnR, 01 June 2012 - 09:03 AM.

[minty]

Ok so 4m back is quite further than 1.6m!
That's about what I'm looking at, between 3.5 to 4m from screen, whether it's scope or 16.9 so thanks for checking your distance. So that would place seating at approx. 2x screen height for 16.9 and roughly 2.3x for scope if using CIW with a 150" 16.9 screen. Certain too now that I will only have 1 row of 3 seats setup perfectly for both picture and more importantly audio. 95% certain that I'll go ahead with this change of direction. L & R speakers behind an AT screen will always be at the outer sides of the image regardless of AR, so that can only be good. 140" scope image will be larger than current scope size so that's awesome. No need for an Anamorphic Lens or zooming, just set and forget. Just need to sort a cost effective masking system for scope sources that looks mint and works with a press of a button (manual not an option). Does anybody know of any horizontal masking system that sells in Aus? I'll search anyway but just wondering out loud. Thanks.

Edited by seatonrocks, 01 June 2012 - 03:00 PM.

[bbar]

seatonrocks, on 01 June 2012 - 02:58 PM, said:

Ok so 4m back is quite further than 1.6m!
That's about what I'm looking at, between 3.5 to 4m from screen, whether it's scope or 16.9 so thanks for checking your distance. So that would place seating at approx. 2x screen height for 16.9 and roughly 2.3x for scope if using CIW with a 150" 16.9 screen. Certain too now that I will only have 1 row of 3 seats setup perfectly for both picture and more importantly audio. 95% certain that I'll go ahead with this change of direction. L & R speakers behind an AT screen will always be at the outer sides of the image regardless of AR, so that can only be good. 140" scope image will be larger than current scope size so that's awesome. No need for an Anamorphic Lens or zooming, just set and forget. Just need to sort a cost effective masking system for scope sources that looks mint and works with a press of a button (manual not an option). Does anybody know of any horizontal masking system that sells in Aus? I'll search anyway but just wondering out loud. Thanks.

My calcs are 2.0 for 16:9 is 2.7 approx for scope

[minty]

bbar, on 01 June 2012 - 04:18 PM, said:

My calcs are 2.0 for 16:9 is 2.7 approx for scope

Thanks mate, I didn't calculate, just guessed lol! 2.7 will still be fine, anyhow if I just have one row I can move the seats forward, but doubt I would need or want to.

[deandob]

I haven't been able to find an automatic horizontal masking system in AU but do recall someone on AVSFORUM putting something together for sale a couple of years back. For my automated solution I have 2 low geared motors connected to a PIC microcontroller that is in turn connected to the HTPC, so control is through the PC (I have written a home theatre console application that pops up when the mouse is moved, controls the curtains, lights & projector power through the PIC). All pretty custom but if you are interested in electronics DIY I can share the microcode & the design. Another cool feature for the theatre is that I use Microsoft kinect to control things, like raising both hands to raise the lights, lowering both hands to drop the lights, open the curtains by parting my hands open, close curtains by parting hands closed, the masking will work the same way except parting my hands vertically to shift the mask. The mask has several settings for different aspect ratios.

Just waiting for my 3D printer to arrive to print the mounting & motor pully so I can automate the mask, everything else is built & working.

[bbar]

seatonrocks, on 01 June 2012 - 05:17 PM, said:

Thanks mate, I didn't calculate, just guessed lol! 2.7 will still be fine, anyhow if I just have one row I can move the seats forward, but doubt I would need or want to.

Would agree.

[Highjinx]

deandob, on 01 June 2012 - 06:31 PM, said:

I haven't been able to find an automatic horizontal masking system in AU but do recall someone on AVSFORUM putting something together for sale a couple of years back. For my automated solution I have 2 low geared motors connected to a PIC microcontroller that is in turn connected to the HTPC, so control is through the PC (I have written a home theatre console application that pops up when the mouse is moved, controls the curtains, lights & projector power through the PIC). All pretty custom but if you are interested in electronics DIY I can share the microcode & the design. Another cool feature for the theatre is that I use Microsoft kinect to control things, like raising both hands to raise the lights, lowering both hands to drop the lights, open the curtains by parting my hands open, close curtains by parting hands closed, the masking will work the same way except parting my hands vertically to shift the mask. The mask has several settings for different aspect ratios.

Just waiting for my 3D printer to arrive to print the mounting & motor pully so I can automate the mask, everything else is built & working.

Innovative.......voice commands are another option.


You Tube have some nice DIY  masking options....search Beamax

There is also one for 4way masking.

http://www.youtube.c...r/beamaxscreens