|
As this forum is rarely used anymore, we've locked it. Feel free to browse and read. Questions? Please reach out to us directly. Cheers! |
|
 |
|
|
| Author |
Message |
cmjohnson
Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s
|
| Posted: Wed Dec 21, 2016 6:49 am Post subject: |
|
|
OK, the RS45 is now sitting on a shelf mounted under the Marquee, levelled, image centered up, etc.
Don't say anything about having it at the same distance as the Marquee because I have NO CHOICE. The Marquee
is backed up to the back wall. I't's not that big a room and I barely got my 120 inch throw distance for an 8 foot wide image.
If I have to replace any card in the card cage on the Marquee, I have to take it down off the mount. It's that close to the back wall.
In fact it's a bit of a challenge just to plug cables into it.
The JVC only gets the benefit of a few more inches of throw distance. But the image covers the same area.
I spent a few hours tonight not only doing the basic setup, but also used this setup as a guide to setting up the screen geometry
on the Marquee as perfectly as possible, by using all geometry and convergence controls to overlap test patterns as perfectly as I am able to do.
But trying to watch both PJs running at the same time is really not workable due to the video processing time delay difference.
The JVC is much slower than the Marquee with a Moome card. I have not found any way to speed up the JVC's image processing speed yet.
Next step: Drag out the calibrator and let it do its thing with both projectors.
|
|
| Back to top |
|
 |
ecrabb
Forum Moderator
Joined: 13 Mar 2006
Posts: 15909
Location: Utah
TV/Projector: JVC RS40, Epson 5010
|
| Posted: Wed Dec 21, 2016 7:17 am Post subject: |
|
|
| cmjohnson wrote: | | garyfritz wrote: | | kal wrote: | | Install the digital as FAR from the screen as you can to maximize contrast ratio (but still keeping the light output you need - the farther back you install the greater the contrast ratio but the lower the lumens). |
How does throw distance affect contrast, or even lumens (or, more likely, ftL)? Ignoring the negligible light loss from "more air in the way," I would think a digital would produce the same ftL on an X" screen regardless of the distance. You have Y lumens coming off the panel, regardless of distance, and the ftL should be the same (for a constant zoomed screen size) regardless of distance -- ftL = lumens / square feet. What am I missing? |
The larger the displayed image, the greater the light fall-off but only because the projected image is getting bigger.
But distance alone should not have anything to do with it.
It's screen size, not projector to screen distance, that affects luminosity.
If you go to a larger projected image, yes, you will get better black levels but your white levels will fall off as well. |
Sorry, that's not correct, CJ. With a fixed-focal length lens like CRT, you'd be right. But, most consumer digital projectors have variable focal length (zoom) lenses, and most of those also vary light output with focal length.
Screen brightness is indeed a function of projector lamp output, screen size, and screen gain, but depending on the lens design, effective light output often varies with focal length.
At the widest zoom setting (shortest focal length), you're using more of the glass. Because you're using more of the glass at the shorter focal length, the lens passes more light, resolution (sharpness) is typically a little better, but uniformity and focus suffer a little, and contrast is reduced.
At the most telephoto end of the zoom range (longest focal length), you're using less of the glass so passing less light, resolution is negatively impacted, but uniformity and focus are better, and more importantly contrast is better.
For instance, a zoom lens might be a 50-75mm (1-1.5x zoom), f2.0 - 2.5. f/2 to f/2.5 is about 2/3 of a stop difference, or about 1.5x difference in brightness. So, let's say you've calibrated your projector, and you're getting 20fL at the longest telephoto setting. You should get almost 30fL at the widest setting, at the expense of some ANSI contrast.
The differences aren't typically quite that big, but they do exist in most projectors, JVC included. The difference is usually enough, that for guys who use lens memory (servo shift/focus/zoom with memory) to run 16:9 and scope on a scope screen, most of the difference between the larger scope image and the smaller 1.78:1 image are negated by the lens.
Cheers,
SC
|
|
| Back to top |
|
|
cmjohnson
Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s
|
| Posted: Wed Dec 21, 2016 2:53 pm Post subject: |
|
|
Yeah, that's different from CRT because we don't have zoom lenses on CRT projectors. (Imagine the cost of a set of zoom HD-10GT17s!) Being something of a photographer I understand F stops, apertures, and so on, so of course I get what you're
saying there. But it's irrelevant in my own particular situation as the room places certain limitations on how I can set up this
projector. The relatively short throw and relatively wide screen demands that I'm running the RS45 with the zoom lens pushed
close to its wide angle limit. That's not something that I can turn into a variable in this room. It's got to be there, and
ti's got to be set like that unless I want to set this up for a screen that is smaller than I want.
But, it's very nearly a straight-on shot from the projector to the screen. My keystone correction is 2. Just 2 points of keystone to
match up the edges.
I don't actually know where the lens shift "zero" setting is but I have to be close to it. That shift has INSANE range, incidentally.
Not seeing any significant focus or brightness uniformity issues. Meaning, I haven't noticed any yet.
The video processing delay is not only visible when both PJs run at the same time, it's enough to be distracting as audio happens
before the events that cause them and it can be kind of noticeable. I have no way to delay the audio path and no way I know
of to reduce the video processing delay in the RS45.
|
|
| Back to top |
|
|
AnalogRocks
Forum Moderator
Joined: 08 Mar 2006
Posts: 26706
Location: Toronto, Ontario, Canada
TV/Projector: Sony 1252Q, AMPRO 4000G
|
| Posted: Wed Dec 21, 2016 4:47 pm Post subject: |
|
|
| cmjohnson wrote: |
The video processing delay is not only visible when both PJs run at the same time, it's enough to be distracting as audio happens
before the events that cause them and it can be kind of noticeable. I have no way to delay the audio path and no way I know
of to reduce the video processing delay in the RS45. |
CM, check this out: http://www.felston.com/dd740/
_________________
Tech support for nothing
CRT.
HD done right!
|
|
| Back to top |
|
|
Jeremy112
Joined: 28 Sep 2006
Posts: 2649
Location: Fond du Lac, WI
|
| Posted: Wed Dec 21, 2016 4:50 pm Post subject: |
|
|
| AnalogRocks wrote: | | cmjohnson wrote: |
The video processing delay is not only visible when both PJs run at the same time, it's enough to be distracting as audio happens
before the events that cause them and it can be kind of noticeable. I have no way to delay the audio path and no way I know
of to reduce the video processing delay in the RS45. |
CM, check this out: http://www.felston.com/dd740/ |
LOL, I was just going to suggest the DD740 (there's an Ad for it on the right of the screen at this moment  )
_________________
When I'm asking for a Model number, that doesn't mean I'm asking for a nude photo with your number on it 
|
|
| Back to top |
|
|
kal
Forum Administrator
Joined: 06 Mar 2006
Posts: 18114
Location: Ottawa, Canada
TV/Projector: JVC DLA-NZ7
|
|
| Back to top |
|
|
cmjohnson
Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s
|
| Posted: Wed Dec 21, 2016 9:49 pm Post subject: |
|
|
|
Seems reasonable, and a bit easier than making up a 100 ms delay line coaxial cable. Which would have to be about 50 million meters in length.
|
|
| Back to top |
|
|
garyfritz
Joined: 08 Apr 2006
Posts: 12088
Location: Fort Collins, CO
|
| Posted: Thu Dec 22, 2016 1:44 am Post subject: |
|
|
| ecrabb wrote: | | At the widest zoom setting (shortest focal length), you're using more of the glass. Because you're using more of the glass at the shorter focal length, the lens passes more light, resolution (sharpness) is typically a little better, but uniformity and focus suffer a little, and contrast is reduced. |
I still don't understand. If I have a light source that emits X lumens, and I shine it through a plate of glass, the SIZE of the light beam going through the glass is irrelevant. You've still got X lumens passing through the glass. Why would lenses be different?
Are you talking about a different aperture at different zoom levels? If so, that would make sense. If the widest zoom setting has a larger aperture, that would indeed let more light through (vs. blocking it at the smaller aperture), focal depth would suffer, etc.
I guess then my question would be, why would wider zooms have larger aperture? Is it just a property of the zoom lenses?
|
|
| Back to top |
|
|
cmjohnson
Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s
|
| Posted: Thu Dec 22, 2016 2:20 am Post subject: |
|
|
My experience in photography can help explain that. As I zoom in on a distant object, the camera sensor sees less light, and the image becomes darker. With a telescope, the higher your magnification, the darker the image becomes.
A projector is nothing other than a camera optic system used in the reverse direction. So it works the same.
As you zoom in, the image on the sensor becomes LARGER. So there is less light on the image sensor because the incoming
image is now spreading out past the limits of the sensor.
Now imagine that the image sensor is, instead, the illuminated image generator. (LCD, LCOS, or DLP panel, or CRT face)
|
|
| Back to top |
|
|
jbltecnicspro
Joined: 23 Apr 2016
Posts: 512
|
| Posted: Thu Dec 22, 2016 3:06 am Post subject: |
|
|
| cmjohnson wrote: |
But trying to watch both PJs running at the same time is really not workable due to the video processing time delay difference.
The JVC is much slower than the Marquee with a Moome card. I have not found any way to speed up the JVC's image processing speed yet.
Next step: Drag out the calibrator and let it do its thing with both projectors. |
That's incredible that there would be so much delay. This is one of the reasons why there are still a small group of CRT hold-outs when it comes to computer gaming. I hope that as we continue things in this realm get better. It seems that for digital displays, input lag is all over the map.
|
|
| Back to top |
|
|
cmjohnson
Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s
|
| Posted: Thu Dec 22, 2016 3:26 am Post subject: |
|
|
Yeah, isn't it funny that the lag involved in converting HDMI to analog via the Moome card is trivial, while
the time it takes to process HDMI and KEEP it in the digital domain and send it on to the LCOS panels is several times longer?
That's....counterintuitive. You'd figure that translating from one mode to the other (Digital, analog) would take more time.
But then again, the projector does have to do a lot of image manipulation before sending the image to the LCOS panels.
Geometry adjustments, color temperature, etc...
I just had a question come up. Anybody who can answer or explain, please feel free to chime in.
The RS45 is 1080p native. 1920x1080.
My source outputs 1080p.
I'd expect that the 1080p formatted video will be mapped to the projector's pixels "1 for 1".
But there's an anamorphic mode for use when you have an anamorphic lens handy. Gives you a wider picture
by using more vertical height on the LCOS panels.
By using more height on the panels. More pixels.
So if it's doing that, how many pixels is it ACTUALLY using when not in anamorphic mode?
Am I getting the full 1920x1080 or is it scaling the image back when not in anamorphic mode?
|
|
| Back to top |
|
|
Jeremy112
Joined: 28 Sep 2006
Posts: 2649
Location: Fond du Lac, WI
|
| Posted: Thu Dec 22, 2016 3:39 am Post subject: |
|
|
All anamorphic mode does is stretch the image for 2.35:1 material. You enable that mode when you put a cinemascope move on, disable it when you intend to use the PJ for say gaming at 1080p.
You are still using all the pixels either way. The anamorphic mode just compensates for cinemascope aspect ratio when cinemascope is used 
If you leave anamorphic mode off while watching cinemascope, then the black bars on top and bottom should still be present.
This is how anamorphic mode works on a couple PJs I have here anyway.
_________________
When I'm asking for a Model number, that doesn't mean I'm asking for a nude photo with your number on it
|
|
| Back to top |
|
|
garyfritz
Joined: 08 Apr 2006
Posts: 12088
Location: Fort Collins, CO
|
| Posted: Thu Dec 22, 2016 4:48 am Post subject: |
|
|
| cmjohnson wrote: | My experience in photography can help explain that. As I zoom in on a distant object, the camera sensor sees less light, and the image becomes darker. With a telescope, the higher your magnification, the darker the image becomes.
A projector is nothing other than a camera optic system used in the reverse direction. So it works the same. |
No it doesn't. As you said, with the camera you're zooming in on the distant object, so there is less area in the field of view, and therefore less light reflecting off that area. That makes total sense.
But with the digital projector, you are projecting the SAME area. And in the example I think we're talking about, you're projecting that constant area onto a constant-sized screen. So you're projecting the panel with its 1920x1080 or whatever pixels onto the same size screen at different distances. Whether you project it onto a 100" screen at 10' or a 100" at 20', you're still projecting the same pixels onto the same size screen. Brightness/etc shouldn't change.
Going back to your camera example, it's analogous to zooming while you change distance. Say you're taking a picture of the side of a building from 50' away, and you zoom so the building fills the frame. Now go out to 500' and zoom so the building fills the frame again. The different zoom will affect things like depth of field &etc, but not brightness/contrast. Unless I'm really confused.
|
|
| Back to top |
|
|
garyfritz
Joined: 08 Apr 2006
Posts: 12088
Location: Fort Collins, CO
|
| Posted: Thu Dec 22, 2016 5:01 am Post subject: |
|
|
| cmjohnson wrote: | But there's an anamorphic mode for use when you have an anamorphic lens handy. Gives you a wider picture by using more vertical height on the LCOS panels.
By using more height on the panels. More pixels.
So if it's doing that, how many pixels is it ACTUALLY using when not in anamorphic mode?
Am I getting the full 1920x1080 or is it scaling the image back when not in anamorphic mode? |
The 1080p panel is a 1.78:1 aspect ratio: 1920/1080 = 1.78.
Scope movies are 2.35:1 or thereabouts.
If you display a scope movie WITHOUT the anamorphic lens, you don't use the full panel. The "2.35 dimension" fills up the full 1920 pixels of width, but the "1 dimension" fills only 1920 / 2.35 = 817 pixels. 1920 / 817 = 2.35, so the aspect ratio on the panel (and thus on the screen) is correct. But you've got black bars above & below the image. You're not getting the lumens or the vertical resolution you'd have with the full panel. And unless you zoom out, the image will be the same width as a standard HDTV image, which doesn't give the "widescreen" effect people like with scope films.
With the anamorph, the 2.35:1 content fills the ENTIRE panel, top to bottom. If you projected it WITHOUT the anamorph, it would be a 1.78:1 image but everything would be stretched vertically (or squeezed horizontally). Add the anamorph, and it optically stretches the image horizontally to the correct 2.35:1 aspect ratio. And that 2.35:1 image has 1920x1080 pixels.
Make sense?
|
|
| Back to top |
|
|
cmjohnson
Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s
|
| Posted: Thu Dec 22, 2016 5:26 am Post subject: |
|
|
|
Got it. Short version: Some letterboxing is built into most titles. In anamorphic mode, that letterboxing is expanded out of the picture vertically. (Most of it, anyway.)
|
|
| Back to top |
|
|
Jeremy112
Joined: 28 Sep 2006
Posts: 2649
Location: Fond du Lac, WI
|
| Posted: Thu Dec 22, 2016 6:01 am Post subject: |
|
|
Basically, yep
_________________
When I'm asking for a Model number, that doesn't mean I'm asking for a nude photo with your number on it
|
|
| Back to top |
|
|
cmjohnson
Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s
|
| Posted: Thu Dec 22, 2016 4:09 pm Post subject: |
|
|
Now that I have this RS45 I got curious about anamorphic lenses, searched, and found the price range.
Just for fun I then tried to figure out if there is any anamorphic lens ouit there that even MIGHT be usable on a CRT projector,
knowing you'd need three of them.
Nope. Nothing that big in a cinema anamorphic lens seems to exist!
So the cost of that would be...goat-chokingly expensive. Maybe with NASA's budget.....
|
|
| Back to top |
|
|
garyfritz
Joined: 08 Apr 2006
Posts: 12088
Location: Fort Collins, CO
|
| Posted: Thu Dec 22, 2016 10:16 pm Post subject: |
|
|
That's why people play with blends instead. 
|
|
| Back to top |
|
|
ecrabb
Forum Moderator
Joined: 13 Mar 2006
Posts: 15909
Location: Utah
TV/Projector: JVC RS40, Epson 5010
|
| Posted: Thu Dec 22, 2016 11:59 pm Post subject: |
|
|
| garyfritz wrote: | | ecrabb wrote: | | At the widest zoom setting (shortest focal length), you're using more of the glass. Because you're using more of the glass at the shorter focal length, the lens passes more light, resolution (sharpness) is typically a little better, but uniformity and focus suffer a little, and contrast is reduced. |
I still don't understand. If I have a light source that emits X lumens, and I shine it through a plate of glass, the SIZE of the light beam going through the glass is irrelevant. You've still got X lumens passing through the glass. Why would lenses be different?
Are you talking about a different aperture at different zoom levels? If so, that would make sense. If the widest zoom setting has a larger aperture, that would indeed let more light through (vs. blocking it at the smaller aperture), focal depth would suffer, etc.
I guess then my question would be, why would wider zooms have larger aperture? Is it just a property of the zoom lenses? |
Yes, Gary - Most zoom lenses have a variable aperture, and yes it's a property of the zoom lens. Obviously, projector lenses don't have a physical aperture (like a camera lens does to vary the light passed by the lens), but it does have an effective aperture, and that effective aperture changes when the lens is adjusted from one focal length to another.
Constant aperture zoom lenses are available for higher-end photography lenses, but they're big, heavy, and expensive. For instance, the Nikon 70-300 f/4-5.6 lens I have for my DSLR is $500. The Nikon 70-200 fixed-aperture f/4 professional lens is $1400. It's a pro lens, so it isn't just the lens design, but it's bigger (longer) and heavier in spite of being a shorter focal length lens. So, size, weight, and cost make fixed-aperture zoom lenses impractical for most projection applications. That's why most projector zoom lenses (and even most camera zoom lenses), are variable aperture.
SC
|
|
| Back to top |
|
|
cmjohnson
Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s
|
| Posted: Fri Dec 23, 2016 12:39 am Post subject: |
|
|
When you point a zoom lens at a light source and vary the zoom, the image it projects on the target (sensor or film in the case of a camera) changes as you vary the zoom. Thus, with a fixed amount of light coming into the zoom lens, the light coming out of it
varies in intensity as the size of the projected image varies. The projected image is largest when zoom is full out, giving maximum effective magnification. Since the projected image is largest, the light from it is spread out over a wider area.
It's the same exact thing in principle with a zoom lens on a projector. But reversed, obviously.
|
|
| Back to top |
|
|
|
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
|
Forum powered by phpBB © phpBB Group
|
|
