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Discussion Starter #1
I 'm a little confused about the 2:35 format. I have a epson 8500ub witch i would like to manually zoom it out to fill up the back bars. If i manually zoom out to fill a 120" 2:35 screen, i was told that it would be the eqivalent of doing 150". Why?

Is there a difference in picture quality between using an anamorphic lense or just doing it manually. I know that i loose the constant height, but i don't understand the difference between the stretch and the manual zoom out?

thanks
 

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I'll try to help if I may:

When you zoom a 2.35:1 image the black bars are still part of the projected image although you may zoom them off the top and bottom of a 2.35:1 screen (zooming AKA poor man's CIH). Therefore the brightness of the image and the pixel size/density is as if you are projecting a 16:9 image of the same width, but taller. If your 2.35:1 screen is 120" diagonal then it's as if you are projecting a bigger 16:9 diagonal (might not be quite 150", but certainly bigger than 120"). You 'waste' 1920x 200 or so pixels as these are the black bars being projected off the screen, so the image viewed on screen is approx 1920 x 810 pixels (this is the same as is natively on the disc).

When using an anamorphic lens (as I do with an Isco II) you use scaling to stretch the image before it goes to the projector's panels so that the whole 1080 'lines' are filled. This is similar to upscaling a DVD but by a smaller amount (it's only the height rather than the width). With a good projector or an external scaler like my Lumagen then this process can be done to a very good standard despite the extra pixels being 'created'. This makes the content of the image look tall and thin, so the A lens then optically stretches the width of the image to the correct proportions so your 2.35:1 screen is filled, but this time will all 1920 x 1080 pixels.

Therefore for a given screen size you have a higher pixel density with a lens compared to zooming. In theory the image should be brighter as you are using the whole panel, but in my case the projector's brightness changes as it is zoomed, so this compensates to some degree. I measured my old JVC HD350 only last week and got 74 Lux when zooming and 78 Lux with the lens, so this wouldn't be noticable. I do prefer the lens version as there is more contrast (due to using less zoom in the projector), higher pixel density seems to add to the image even though I can't see the pixels when zooming and there are no black bars to overspill. Other set ups can find an increase in brightness of towards 20-25% but I have to use minimum zoom when using the lens so there is perhaps a non linear change in my projector's lens aperture over this range when zooming which causes a bigger change in brightness (and a similar change in contrast also due to the aperture).

However, it doesn't suit everyone: I have a very long throw set up which means I get minimal pincushion so I don't need a curved screen (mine is electric so I couldn't curve anyway). If I watch 16:9 content I lift my lens out of the way and my lens has a slight 5% magnification to the image height, so I have to slightly zoom to fill my screen height. I've just yesterday received my new JVC X35 which has lens memory, so that saves me making that small adjustment now. Unless you find a used bargain as I did, then a good lens (a cheap one really is a waste of time on a 1080p projector) is expensive, maybe more than the projector in this case. I have to confess I did consider selling my lens recently and buying the '4K' (Eshift) JVC X55 and going back to zooming myself, so I can understand either option.

I hope I've been helpful and not too biased towards getting a lens, just because it suits my setup. :T
 

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I use the zoom on my 2.35:1 screen. Works awesome... It's beautiful.

On a 16:9 screen, there would be spill over. Some projectors have masking features that will eliminate that. Don't forget, your screen can have a light absorbing black border... Also, properly painted walls (flat and dark) make the spill over unnoticeable.

All this being said... Just get a 2.35:1 screen and it's a non issue. The zoom feature will work flawlessly... No spill concern. The only downside is that 16:9 material will be slightly smaller than if you had a 16:9 screen. A small trade off in my opinion.
 

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Keep in mind also that the image on the BluRay is 16x9 with the black boarders top and bottom so weather you watch it on a 1,85:1 screen or zoom it out to ill a 2,35:1 screen the "actual image" without black bars is still the same visible resolution. So there is no real disadvantage to using the 2,35:1 screen.
 

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I use the zoom on my 2.35:1 screen. Works awesome... It's beautiful.

On a 16:9 screen, there would be spill over. Some projectors have masking features that will eliminate that. Don't forget, your screen can have a light absorbing black border... Also, properly painted walls (flat and dark) make the spill over unnoticeable.

All this being said... Just get a 2.35:1 screen and it's a non issue. The zoom feature will work flawlessly... No spill concern. The only downside is that 16:9 material will be slightly smaller than if you had a 16:9 screen. A small trade off in my opinion.
Now I'm confussed. :D If you zoomed 2.35:1 on a 16:9 screen then there would be big sections of overspill each side of the screen (assuming you zoomed to fill the height). If you used the projector to mask this then you'd lose a big chunk of the picture. If you zoom on a 2.35:1 screen then the overspill is usually bigger than most screen borders (for example my screen is about 10" over spill top and bottom if I zoom), so a dark screen wall is a must if zooming, especially with lower contrast projectors. If you don't want smaller 16:9 just buy a 2.35:1 screen that is the same height as your existing 16:9 screen. Of course 16:9 will still look smaller than your 2.35:1, but I just take the view that 2.35:1 is meant to be bigger.
 

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Discussion Starter #6
I'll try to help if I may:

When you zoom a 2.35:1 image the black bars are still part of the projected image although you may zoom them off the top and bottom of a 2.35:1 screen (zooming AKA poor man's CIH). Therefore the brightness of the image and the pixel size/density is as if you are projecting a 16:9 image of the same width, but taller. If your 2.35:1 screen is 120" diagonal then it's as if you are projecting a bigger 16:9 diagonal (might not be quite 150", but certainly bigger than 120"). You 'waste' 1920x 200 or so pixels as these are the black bars being projected off the screen, so the image viewed on screen is approx 1920 x 810 pixels (this is the same as is natively on the disc).

When using an anamorphic lens (as I do with an Isco II) you use scaling to stretch the image before it goes to the projector's panels so that the whole 1080 'lines' are filled. This is similar to upscaling a DVD but by a smaller amount (it's only the height rather than the width). With a good projector or an external scaler like my Lumagen then this process can be done to a very good standard despite the extra pixels being 'created'. This makes the content of the image look tall and thin, so the A lens then optically stretches the width of the image to the correct proportions so your 2.35:1 screen is filled, but this time will all 1920 x 1080 pixels.

Therefore for a given screen size you have a higher pixel density with a lens compared to zooming. In theory the image should be brighter as you are using the whole panel, but in my case the projector's brightness changes as it is zoomed, so this compensates to some degree. I measured my old JVC HD350 only last week and got 74 Lux when zooming and 78 Lux with the lens, so this wouldn't be noticable. I do prefer the lens version as there is more contrast (due to using less zoom in the projector), higher pixel density seems to add to the image even though I can't see the pixels when zooming and there are no black bars to overspill. Other set ups can find an increase in brightness of towards 20-25% but I have to use minimum zoom when using the lens so there is perhaps a non linear change in my projector's lens aperture over this range when zooming which causes a bigger change in brightness (and a similar change in contrast also due to the aperture).

However, it doesn't suit everyone: I have a very long throw set up which means I get minimal pincushion so I don't need a curved screen (mine is electric so I couldn't curve anyway). If I watch 16:9 content I lift my lens out of the way and my lens has a slight 5% magnification to the image height, so I have to slightly zoom to fill my screen height. I've just yesterday received my new JVC X35 which has lens memory, so that saves me making that small adjustment now. Unless you find a used bargain as I did, then a good lens (a cheap one really is a waste of time on a 1080p projector) is expensive, maybe more than the projector in this case. I have to confess I did consider selling my lens recently and buying the '4K' (Eshift) JVC X55 and going back to zooming myself, so I can understand either option.

I hope I've been helpful and not too biased towards getting a lens, just because it suits my setup. :T
Thanks for such a complete explanation, my confusion is something of the past now.
 
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