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Discussion Starter · #1 ·
Ok, yea, I searched, but didn't see a specific answer to this. This might be a good addition to the FAQ as it's not mentioned in there either. Noobs have such great questions.


Ok, specifically, what I'm trying to understand is how the ALens affects the width of the image. Let's say that right now I have a 106" standard screen (16:9) with a 90" wide image on it and were to buy a AVS1. Will the resultant image be 90" wide or ~128" wide? Will it be somehwere in between, or just exactly what will I end up with? Am I correct in assuming that the projected 16:9 image becomes wider and that that image would no longer fit on the scren I have? Y/N?


TIA.


[Edit]

The reason for my confusion is that I've read here in discussions about brightness increase due to an ALens stating 'realistically' a 25% increase due to the 33% more pixels, bla bla bla, and then some loss in the glass, bla bla bla, but nowhere do I see anyone also mentioning that the screen has increased in size by (2.35/1.78) so you have 32% more square footage to light up, thus actuallty causing the image brightness to decrease (Per sq/ft) in addition to the lens loss. [/edit]
 

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A horizontal expansion lens will stretch the image by 1.33, i.e take your 16x9 (1.78:1) image and make it 2.37:1. That's why we call it "constant height", the height stays the same and the width changes to fit the aspect ratio of the source.


So your 90" wide image would get stretched to 120".
 

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Quote:
Originally Posted by K-Spaz /forum/post/16930154


Ok, specifically, what I'm trying to understand is how the ALens affects the width of the image. Let's say that right now I have a 106" standard screen (16:9) with a 90" wide image on it and were to buy a AVS1. Will the resultant image be 90" wide or ~128" wide? Will it be somehwere in between, or just exactly what will I end up with? Am I correct in assuming that the projected 16:9 image becomes wider and that that image would no longer fit on the scren I have? Y/N?


TIA.


[Edit]

The reason for my confusion is that I've read here in discussions about brightness increase due to an ALens stating 'realistically' a 25% increase due to the 33% more pixels, bla bla bla, and then some loss in the glass, bla bla bla, but nowhere do I see anyone also mentioning that the screen has increased in size by (2.35/1.78) so you have 32% more square footage to light up, thus actuallty causing the image brightness to decrease (Per sq/ft) in addition to the lens loss. [/edit]

To answer your first question - Yes. and the width will be what JDLIVE replied; 120".


2nd, what you listed on the 2nd paragraph is the advantage when you using a-lens instead of using zoom via your PJ.


Last, beside the a-lens, you also need to use your horizontal expanding function in your PJ a.k.a. "H-fit" in order to use the CIH's 2.35 image.
 

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Discussion Starter · #4 ·
Thanks guys, I know it seems a stupid question, but, it's sorta like asking if a HT receiver with HDMI Input will accept audio via HDMI. Well, it would seem that yes, this thing does audio, and basically that's all it does, and this IS the input, so, therefore of course it will play audio via that HDMI/ But alas, that's not the truth unless you specifically ask that question before purchasing. You may just end up with a receiver with a whole bunch of hdmi in's that still requires an additional optical cable for each sources audio.
 

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Quote:
Originally Posted by K-Spaz /forum/post/16930154


[Edit]

The reason for my confusion is that I've read here in discussions about brightness increase due to an ALens stating 'realistically' a 25% increase due to the 33% more pixels, bla bla bla, and then some loss in the glass, bla bla bla, but nowhere do I see anyone also mentioning that the screen has increased in size by (2.35/1.78) so you have 32% more square footage to light up, thus actuallty causing the image brightness to decrease (Per sq/ft) in addition to the lens loss. [/edit]


The brightness increase is sort of confusing no doubt. The actual phrase/idea/marketing comes from the days of 4:3 projectors and Vertical Compression lenses. In that configuration people would take a 4:3 projector, add a VC lens which compresses the image horizontally making at smaller 16:9 image. Because the image is smaller, but the same amount of light is projected, the image is theoretically 33% brighter. Of course there's some loss in the lens so 25% is a more "realistic" figure. You can obviously do this with 16:9 projectors to make a 2.35:1 image (this is what I do, though to be CIH you must leave a VC lens in place all the time).


That's all pretty easy to understand. The "increase" marketing/idea has stuck around with 16:9 projectors and Horizontal Expansion lenses is still true, though not in as clear of a way. Obviously as you noted, an HE lens makes the picture bigger, thus it will be dimmer than without a lens.


What you have to do is realize what is really being compared. What's being compared is the brightness of an particular size image (in this case 2.35:1) with the lens and without. With a VC lens it's very clear as inserting the lens doesn't change the 2.35:1 size, but "brings in" the light that would have been wasted projecting the bars without it, by compressing the light path.


If you've followed so far, hopefully you're beginning to realize the same applies with an HE lens. For a given 2.35:1 image size, and with all else equal (ie projector zoom) whether HE or VC, since you're using all the projector's light, you're not wasting the 1/3 of the light that would go into the bars without the lens, thus your image is about 1/3 brighter with, than without a lens.


Now the tricky bit enters because unlike a VC lens, the HE lens effectively changes the throw ratio of the projector, it decreases the throw by making the image wider. So compared to no lens in place, the 2.35:1 image is 1/3 wider/larger, and thus about 1/3 dimmer than without the lens due to the size change.


And since the throw is changed, if you compare the lens to zooming, many projectors aperture changes (opens) as you zoom, letting more light through. So if you go look at cine4home's article on a zooming vs lens on the AE3000, you'll see the the increased light output basically negates the decrease in brightness due to the larger size so for a fixed projector location, with something like the AE3000 there's no meaningful brightness difference either way.


It should be noted that if the projector has a constant aperture, ie constant light output across it's zoom range, that since the zoomed area for the wider 2.35:1 image would be approximately 80% larger, and thus 80% dimmer, vs only 1/3 or so with the lens. But as noted in the last paragraph, most projectors aren't like this.
 

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Quote:
Originally Posted by K-Spaz /forum/post/16931000


Thanks guys, I know it seems a stupid question, but, it's sorta like asking if a HT receiver with HDMI Input will accept audio via HDMI. Well, it would seem that yes, this thing does audio, and basically that's all it does, and this IS the input, so, therefore of course it will play audio via that HDMI/ But alas, that's not the truth unless you specifically ask that question before purchasing. You may just end up with a receiver with a whole bunch of hdmi in's that still requires an additional optical cable for each sources audio.

I hear you. My cousin just recently bought a Sony AV system with HDMI build in. He was under the impression that all HDMI AVR nowadays will be able to do either True HD and DTS MA decoding for all the BD. Guess what it can't, just LPCM for those Sony receivers... Of course a lot of people will debate the LPCM verus True HD/DTS MA, that will be another story.
 

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Discussion Starter · #7 ·

Quote:
Originally Posted by stanger89 /forum/post/16931251


It should be noted that if the projector has a constant aperture, ie constant light output across it's zoom range, that since the zoomed area for the wider 2.35:1 image would be approximately 80% larger, and thus 80% dimmer, vs only 1/3 or so with the lens. But as noted in the last paragraph, most projectors aren't like this.

I think this last paragraph describes my situation with my Infocus X10. I don't get an aperture change with my zoom so in my situation the image would then get slightly dimmer. I don't think that would be a problem for me in my room but that's what I wanted to know. Probably (knowing me) one fine day I'll get a wild hair up ___ and there'll be a lens on the way. I just want to feel as if I'd made all my shopping decisions ahead of time and have some idea what the end result will be before pulling the trigger. I like having my mind made up, sitting with the cash and then finding the deal that gives me the warm fuzzy feeling so I can just grab and go.


Thanks again for all the info. I had to read that twice to take it all in. Thankfully, I had the right idea to begin with so I don't feel so bad now.
 

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There is a common misconception that if you increase image area by a certain percentage (say 33%) then the resulting brightness will be 100% minus the same percentage. This is not correct. The decrease in brightness is the inverse of the increase in area. Hence, a 4/3 increase in image size will present an image that is 3/4 times as bright (75%) as the original starting image, not 2/3 times (67%).

Zooming

You are increasing your image size by 4/3 in both directions. Thus, the area of the image on screen is 4/3 x 4/3 = 16/9 times the pre-zoom image size. With a perfect optical system, the relative brightness of the zoomed image to the starting image is the inverse of this, 9/16, or about 56%.

But, because the aperture is more efficient when you zoom larger, add about 5-15% of extra brightness dividend, depending on make of lens, its zoom ratio, and the "from" and "to" zoom positions (as the increase in aperture efficiency is not linear through the zoom range).


Final result: the zoomed image is from about 61% to 71% as bright as the original non-zoomed image, depending on projector optics and the "from" and "to" zoom positions.

Anamorphic Lens

You digitally stretch the letterboxed image in the vertical direction. No loss of brightness so far.


You place a 4/3 expansion lens in the light path, which widens the image optically, increasing its area by 4/3 in one direction only... horizontally. Thus, the brightness of the widened image is, once again, the inverse of the increase in area: 3/4, or 75% as bright as your starting image/


But we have to take 5% (assuming anti-reflection coatings on all lens elements) off for light loss through the lens.


Final result for anamorphic lenses: about 70% as bright as the pre-lens image.

Comparison

In some cases the anamorphically expanded image is appreciably brighter than the zoomed image of the same size. As the brightness of the anamorphically expanded image is relatively constant, this comparison can best be expressed using "Worst Case Zoom" and "Best Case Zoom" situations:

Worst Case Zoom

70% (anamorphic) divided by 61% (worst case zoom) shows the anamorphic image to be about a 16% brighter than the zoomed image.


In some cases the anamorphically expanded image has little or no brightness dividend.

Best Case Zoom

70% (anamorphic) divided by 71% (best case zoom) shows the anamorphic image to be about the same brightness or slightly less in brightness than the zoomed image.

Observation

In my personal experience (which is likely different to other Forum members with different setups) with a range of projectors at the same throw and screen size, I have found that with a 2:1 zoom projector lens, projecting an image at a throw ratio of about 2.0, the anamorphic image is about 15% brighter than the equivalent zoomed image... i.e. close to the "worst case zoom" example above. This combination - 2:1 zoom at a 2.0 throw ratio - seems to be a sweet spot for anamorphic lenses.
 
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