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Is anybody with the RS40/50 or 60 using a wide zoom setting of over 1.5 X up to 1.75 X zoom? How is your image? Anybody with an older gen or other model JVC RS or HD projector using a wide angle zoom?


After figuring a few things out, I realized that I can mount my RS40 (not here yet) with little or no horizontal lens shift, and not much vertical lens shift, probably less than 15% in each case.


While this is good, I recently downloaded the owners manual for the X3/X7/X9 and have figured out that with my approximately 100" diagonal 16:9 screen and 12.5 foot throw distance, I will be looking at what I believe is roughly a 1.75 X zoom ratio (if I understand the zoom properly).

Bottom line is that for a 100" screen size, the JVC manual shows a range of distance from 3.0 m to 6.13 m and my projector lens will be at 3.76 m. I will be 75% closer to the screen than the longest throw distance.


This is a fairly wide zoom and certainly not ideal. I would have prefered something in between 1.00 and 1.5 X zoom, or not much more than 1.5 X zoom. Probably 1.25 X would have been good. With the HD250, I would have gotten away with about a 1.60 X zoom. With the Mitsubishi HC7000 I was looking at around 1.3 X zoom (out of a total of a possible 1.6 so about 1.5 X of available zoom).


So, I am wondering how will this 1.75 X zoom affect my projected image? From what I understand, the contrast is higher, black levels lower and image geometry better at the longer tele end of the zoom. Should I be concerned with this setup? I may be willing to reduce the size of my screen to reduce zoom, but it seems like it would take a large decrease in screen size to reduce zoom a significant amount.
 

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Discussion Starter · #2 ·
Is there anybody with a new or previous gen JVC using a wide zoom similar to using 1.75 X of the zoom range? How is your image?
 

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Actually what is ideal or not is not clear. Keeping the lens toward the widest angle end of its zoom range (shortest projector to screen throw distance) will provide a brighter image and this can be very useful if using a large and/or low gain screen, especially for the 3D mode on these new projectors. I have seen not definitive test data to indicate that the JVC lens has better resolution, lower chromatic aberration or any specific optical advantage when used at one end of the zoom range vs. the other or a a mid-zoom setting. However, the measured contrast ratio of these projectors will be somewhat higher when the lens is stopped down and this can done by using the lens iris and, to a lesser degree, by zooming the lens for max. throw distance (which provides a numerically higher F-Stop).
 

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Discussion Starter · #4 ·

Quote:
Originally Posted by Ron Jones /forum/post/19637545


Actually what is ideal or not is not clear. Keeping the lens toward the widest angle end of its zoom range (shortest projector to screen throw distance) will provide a brighter image and this can be very useful if using a large and/or low gain screen, especially for the 3D mode on these new projectors. I have seen not definitive test data to indicate that the JVC lens has better resolution, lower chromatic aberration or any specific optical advantage when used at one end of the zoom range vs. the other or a a mid-zoom setting. However, the measured contrast ratio of these projectors will be somewhat higher when the lens is stopped down and this can done by using the lens iris and, to a lesser degree, by zooming the lens for max. throw distance (which provides a numerically higher F-Stop).

True, at this point, for the RS40/50 and 60, I don't think it is clear what is best in terms of zoom. In many cases with other projectors it is shown that a longer throw and tele zoom gives better geometry and higher contrast, lower black levels. What isn't clear, is how things work with the RS40 and other JVC projectors, such as the older RS25 etc and the newer HD250. I am pretty sure cine4home did some testing, or has done some testing with throw/zoom and contrast. Perhaps there was another person or tester/reviewer who did such a test.


My bigger concern would be sharpness/convergence and chromatic aberration, and it is not clear how this new lens behaves. I guess I am hoping people can try different amounts of zoom out. My screen will be relatively small and in a dark, light-controlled room, so I am not longing for brightness (pardon the pun). In the end, I may get the projector and just try it out with the setup I have and see how it does. I am also aware that I can stop down the iris to reduce brightness and lower black levels.


thanks for the feedback,

 

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Quote:
Originally Posted by cpc /forum/post/19638260


True, at this point, for the RS40/50 and 60, I don't think it is clear what is best in terms of zoom. In many cases with other projectors it is shown that a longer throw and tele zoom gives better geometry and higher contrast, lower black levels. What isn't clear, is how things work with the RS40 and other JVC projectors, such as the older RS25 etc and the newer HD250. I am pretty sure cine4home did some testing, or has done some testing with throw/zoom and contrast. Perhaps there was another person or tester/reviewer who did such a test.


My bigger concern would be sharpness/convergence and chromatic aberration, and it is not clear how this new lens behaves. I guess I am hoping people can try different amounts of zoom out. My screen will be relatively small and in a dark, light-controlled room, so I am not longing for brightness (pardon the pun). In the end, I may get the projector and just try it out with the setup I have and see how it does. I am also aware that I can stop down the iris to reduce brightness and lower black levels.


thanks for the feedback,


I guess the real question that I haven't seen addressed in any JVC review is will the black level or contrast ratio (dynamic and ANSI) be any better in - Case 1 of using the lens zoomed for longest throw vs. in - Case 2 of having the lens zoomed for shortest throw plus using the iris to stop down the lens to produce the same F-Stop as with the first case. Let's face it, the JVC claimed dynamic CR is only achieved at the longest throw and with the light output of the projector set to produce the dimmest image (iris stopped down as far as it goes and usually with the lamp in econo mode), but ANSI CR may be worse with this setting. Very few HT owners would really want to use their projectors in this mode as the image would be too dim unless they were using a small and/or really high gain screen.
 

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Discussion Starter · #6 ·

Quote:
Originally Posted by Ron Jones /forum/post/19638462


I guess the real question that I haven't seen addressed in any JVC review is will the black level or contrast ratio (dynamic and ANSI) be any better in - Case 1 of using the lens zoomed for longest throw vs. in - Case 2 of having the lens zoomed for shortest throw plus using the iris to stop down the lens to produce the same F-Stop as with the first case. Let's face it, the JVC claimed dynamic CR is only achieved at the longest throw and with the light output of the projector set to produce the dimmest image (iris stopped down as far as it goes and usually with the lamp in econo mode), but ANSI CR may be worse with this setting. Very few HT owners would really want to use their projectors in this mode as the image would be too dim unless they were using a small and/or really high gain screen.

I guess it is what it is. I was just worried that I was more towards the worse end of things, but, I'm not too far towards the one extreme. I can make some mods to make sure I'm a little farther away, or, possibly much farther away. I will try to experiment.


I thought I saw some reports from cine4home regarding throw, zoom and iris settings for native contrast of the JVC's....but perhaps it was another projector. I'll take another look.
 

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Quote:
Originally Posted by cpc /forum/post/19642741


I thought I saw some reports from cine4home regarding throw, zoom and iris settings for native contrast of the JVC's....but perhaps it was another projector. I'll take another look.

It doesn't really look like they are updating the English version of their site, but if you got to cine4home.com and look at the review of the HD550/HD950 you can find a table with some of these values.


As I've mentioned in other threads, by eye the pixels in the center of the screen were sharpest on the focus pattern for an RS20 and RS50 when the projectors were closest to the screen for the screen size we had. With longer throw ratio the pixels there looked less sharp. This was all standing up by the screen and looking at things up close.


--Darin
 

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Discussion Starter · #8 ·

Quote:
Originally Posted by darinp2 /forum/post/19642837


It doesn't really look like they are updating the English version of their site, but if you got to cine4home.com and look at the review of the HD550/HD950 you can find a table with some of these values.


As I've mentioned in other threads, by eye the pixels in the center of the screen were sharpest on the focus pattern for an RS20 and RS50 when the projectors were closest to the screen for the screen size we had. With longer throw ratio the pixels there looked less sharp. This was all standing up by the screen and looking at things up close.


--Darin

Fair enough. So you compared the old RS20 and new RS50 JVC projectors for zoom and focus? I haven't followed your posts in any of the new JVC threads.


Being a sharpness guy myself, the experience you describe would be preferable if it means my image will be sharp at the wider setting. I could have sworn that longer throw and zoom meant better sharpness and convergence, but I guess that is more for image geometry, like less pincusion and/or barrel distortion or something. Perhaps I am thinking too much along the lines of making anamorphic lens work, which, I can't make use of in my setup.
 
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