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Author Topic: Deciphering projector stats  (Read 5152 times)

Gerry Seymour

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Deciphering projector stats
« on: January 27, 2013, 10:08:23 pm »

Long time away, and now I'm posting in the AV section instead of the Lounge...

I've been digging through the myriad available portable projectors for conference room-style training use (follow-along computer demonstrations, PowerPoint, etc.), and I can't figure out what I should really be looking for. I have a loaner for now, but it's pretty low-end, and doesn't look good under normal lighting in those places.

I've visited websites to look for answers, but I've seen info I can't believe is true (some say 5,000 lumens or more if ANY ambient light, for example), as well as a large amount of info I don't really know the importance of (contrast ratio, which I understand is probably more determined by ambient lighting than the projector).

So, to the experts out there, if you were choosing a portable (will have to be able to carry on planes at times) projector, what would you look for. Ideally, I'd like to get answers in two categories: relatively low-cost (to replace the loaner pretty quickly) and what you'd prefer if cost weren't really much of a concern.

Follow-up: It looks like LED isn't anywhere near ready for this kind of application (the brightest I could find was 700 lumens, I think). Is there any expectation of higher-output portable LED projectors in the next few years?
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Gerry Seymour

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Jordan Wolf

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Re: Deciphering projector stats
« Reply #1 on: January 27, 2013, 10:33:39 pm »

Gerry,

I know you didn't ask for a particular product, but this one has worked well for us for the types of meetings you seem to be doing

The NEC NP-M311W works very well in "typical" ambient light conditions of most meeting spaces that would require (from my experience) no more than a 7ft. wide screen for the types of material you're presenting.

It's native widescreen (16:10 @ 1280x800) and has an HDMI input for futureproofness™.  The built-in speaker is admirable for what it is…if you need more output for the room, you probably also need a larger screen and projector.  Make sure to turn the auto-keystoning "feature" OFF.  One of my favorite features is the lens cover - it knocks down the lamp output when used as a shutter, so you're not left with just digital black on the screen.
« Last Edit: January 27, 2013, 10:36:43 pm by Jordan Wolf »
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Gerry Seymour

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Re: Deciphering projector stats
« Reply #2 on: January 27, 2013, 11:58:38 pm »

Gerry,

I know you didn't ask for a particular product, but this one has worked well for us for the types of meetings you seem to be doing

The NEC NP-M311W works very well in "typical" ambient light conditions of most meeting spaces that would require (from my experience) no more than a 7ft. wide screen for the types of material you're presenting.

It's native widescreen (16:10 @ 1280x800) and has an HDMI input for futureproofness™.  The built-in speaker is admirable for what it is…if you need more output for the room, you probably also need a larger screen and projector.  Make sure to turn the auto-keystoning "feature" OFF.  One of my favorite features is the lens cover - it knocks down the lamp output when used as a shutter, so you're not left with just digital black on the screen.

I'll take a look at that one. I guess I wasn't clear - I actually do want to hear some actual recommendations like this, as well as advice on what stats really matter (and at what level).

Yes, in my experience, a 7'-wide screen is about as large as one can expect to go with a portable projector, and as large as one would need in a situation using portable equipment.

A side note: it makes complete sense that projectors should follow the computer display trend and go to widescreen resolutions. However, in my experience, that's a sub-optimal setup for most presentation uses. If I have to use PowerPoint (or similar), I rarely have long enough bullet points to use the additional width wisely. If I'm demonstrating software, a similar issue exists (unless it's software with lots of tool docks, like illustration software). The issue is that I'm still working with 7' of width, regardless of the ratio. With 16:9 (and other wide formats) that means my screen is much "shorter" than if I use 4:3 resolutions.

So, I usually end up going dual-display, setting the projector as the second monitor at a 4:3 resolution, and getting a bit more real estate on my screen.
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Gerry Seymour

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Brad Weber

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Re: Deciphering projector stats
« Reply #3 on: January 28, 2013, 09:29:19 am »

It is really all application driven and some factors may be:
 
Format/Resolution - What type of content will be displayed?  Do the potential applications involve HD content?  Will the use be primarily video or computer graphics or some mix?  These kind of factors may indicate what format (4:3, 16:10, 16:9, etc.) and resolution (1024x768, 1280x800, 1920x1080, 1920x1200, etc.) are most appropriate.
 
Brightness and Contrast - As you mentioned, what really matters is the image contrast ratio, how black and white in the projected image relate to one another with the black level often set by the ambient light in the room rather than by the projector.  There is actually a Standard for recommended image contrast ratios for several general applications but that is much more establishing goals than defining what may be acceptable, ironically recommended image contrast information is often presented using projected images with contrast ratios lower than what are being suggested.  But basically, the larger the image and brighter the room, the brighter the projector required to maintain a usable contrast ratio for a given type of content or application.  And with modern projectors the contrast ratio for the projector itself is rarely a significant factor except in the darkest environments and most critical applications.
 
Throw Distance and Lens - How far can the projector be from the screen to create a certain size image or what size image can be created from a certain location?  If you have typical image sizes and/or screen and projector locations then you want to make sure the projector supports those.  And where you don't have known conditions you may want a projector and lens that are as flexible as possible in the locations and image sizes supported.
 
Inputs - What signals (composite video, VGA/RGBHV, HDMI, DVI, SDI and so on) do you need or want the projector to support?
 
Lens Shift/Keystoning - It can often be necessary to locate the projector at something other than the ideal location relative to the projected image, what variation from the ideal vertical and horizontal location needs to be accommodated or how much value does supporting a larger variation offer?  Lens shift is actually using the optics to allow moving the projected image up and down or left and right while keystoning with digital projectors is usually digitally manipulating the image to compensate for keystoning that occurs.
 
Noise Level - In some applications the noise level from the projector can be a factor.
 
Multiple Lamp Operation - Some projectors use a multiple lamp system and many of those allow that to be employed to provide redundancy or longer life at a lower output.  I like these in situations where a show might stop with a dead lamp but could continue with a slightly dimmer image.
 
Lamp Life - How long do lamps typically last?  What is often misunderstood is that the values quoted are typical useful lives with the OEM lamps and aren't necessarily when lamp failure is expected, however some projectors start putting up messages, etc. when the lamps reach the end of their expected life.
 
Filters - Most projectors have filters that need to be kept clean for proper operation and longest life.  Some projectors have self-cleaning filters or filter cartridges that automatically change the portion exposed.  If there are filters, how they are accessed, etc. can become a factor depending on the location and accessibility of the projector.
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Jordan Wolf

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Re: Deciphering projector stats
« Reply #4 on: January 28, 2013, 09:54:37 am »

I'm going to go alongside Brad's post, point-by-point, to demonstrate how I feel the NEC projector I mentioned, and any similarly-spec'd unit, would rate for the OP's use.

Format/Resolution - Yes, the unit is 16:10 native, but you can certainly change some settings to show a 4:3 A.R.  There will be digital black on the sides, which may or may not be an issue.
 
Brightness and Contrast - My first-hand experience with this projector has been in meeting rooms that max out at around 40ft. deep by 32ft. wide.  With house lights at 100%, all text and lines/outlines were sharp and well-defined from at least 2/3 of the way back into the space on a 7ft. tripod screen in 4:3 format.  Most meeting rooms have space in the back for luggage, water stations, etc., so it's not unlikely that seating would be closer to the front than that.
 
Throw Distance and Lens - Since the OP seems to be knowledgeable, I would assume that - like me - he would want to arrange for optimal placement of the projector (not usually an issue for small- to medium-sized spaces.  For a 7ft. screen, 12ft. of throw gets you in the middle of the lens' zoom range.
 
Inputs - Adding HDMI, as well as having 2 VGA inputs, allows for a more-futureproof unit.  A USB Wifi transceiver can also be added, allowing for remote control and networking.
 
Lens Shift/Keystoning - There is only vertical keystoning, and no cornerstoning ability.  However, the two rear feet are fully adjustable, and the front main foot, centered, allows for small changes in height.  With
 
Noise Level - 35dB is what the manual claims (what freq. range, weighting, etc. I'm not sure…maybe there's a spec. for those things, I just don't know).
 
Multiple Lamp Operation - Only 1 lamp necessary, and they're compatible from the older models of the projector.
 
Lamp Life - That depends on how long you run it - in my previous post, I mentioned how sliding the lens cover dims the lamp brightness, which helps increase lamp life when you don't want an image up, but need immediate access to use the projector if needed.
 
Filters - All the NEC portable projectors I have used have filters that are easily accessed and cleaned.  The alerts can also be reset from the menu without digging through too many submenus.
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Jordan Wolf
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Brad Weber

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Re: Deciphering projector stats
« Reply #5 on: January 28, 2013, 03:31:10 pm »

A side note: it makes complete sense that projectors should follow the computer display trend and go to widescreen resolutions. However, in my experience, that's a sub-optimal setup for most presentation uses. If I have to use PowerPoint (or similar), I rarely have long enough bullet points to use the additional width wisely. If I'm demonstrating software, a similar issue exists (unless it's software with lots of tool docks, like illustration software. The issue is that I'm still working with 7' of width, regardless of the ratio. With 16:9 (and other wide formats) that means my screen is much "shorter" than if I use 4:3 resolutions.
 
So, I usually end up going dual-display, setting the projector as the second monitor at a 4:3 resolution, and getting a bit more real estate on my screen.
You note some good points in relation to your content and your level of knowledge, however my experience in general is that with new laptops and monitors being almost all widescreen formats, most presenters now tend to create content using those widescreen formats.  Adding to that, presentations seem to increaingly be incorporating other media that is sometimes in widescreen format.  And many of those same people do not know how to deal with extended desktops, changing the resolution for the second output, etc.
 
It seems that your situation may be a good example of one where your specific needs and knowledge suggest a different approach than what might work best for many others in similar situations.
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Gerry Seymour

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Re: Deciphering projector stats
« Reply #6 on: January 28, 2013, 10:14:06 pm »

I'm going to go alongside Brad's post, point-by-point, to demonstrate how I feel the NEC projector I mentioned, and any similarly-spec'd unit, would rate for the OP's use.

...

Jordan has addressed most of this for me, but I'll clarify on a few points.

I'll have some control of throw distance. In seminars of this sort, there's considerable flexibility up front, so off-angle (sideways) placements won't be an issue. Of course, keystoning is an issue in almost all situations, and pretty much all projectors do a reasonable job with this.

As for the dual-lamp offerings, I do like the concept of them, as this also (usually) means no downtime if a lamp goes out. However, I've not yet come across one that was as portable and inexpensive as comparable single-lamp offerings. I'll likely resort to just carrying a spare lamp.

Noise level has never been much of an issue with any of the portable projectors I've encountered. I've even had to speak over some with failing fan motors - which about doubles the perceived noise level - without any real issue. As my wife can attest, I"m pretty loud. :)

As for other points, I actually covered many of them in my first two posts (type of material, 4:3 ratio, etc.). What I didn't cover was source format. Currently, every computer I'd likely use is capable of VGA (one of them via Displayport adapter), and those cables (and the Displayport adapters) are easy to find, so that's my preference. Of course, it would be nice if it had HDMI or other newer-format input, as well.
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Gerry Seymour

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Re: Deciphering projector stats
« Reply #7 on: January 28, 2013, 10:20:18 pm »

You note some good points in relation to your content and your level of knowledge, however my experience in general is that with new laptops and monitors being almost all widescreen formats, most presenters now tend to create content using those widescreen formats.  Adding to that, presentations seem to increaingly be incorporating other media that is sometimes in widescreen format.  And many of those same people do not know how to deal with extended desktops, changing the resolution for the second output, etc.
 
It seems that your situation may be a good example of one where your specific needs and knowledge suggest a different approach than what might work best for many others in similar situations.

I understand those points, and that some of the adjustments I make are difficult for some. I still maintain that 4:3 is a more universally useful ratio for these situations (different in other situations). The fact is that the limiting factor is usually the width of the screen. Thus, widescreen material letterboxed into 4:3 will be exactly the same size it would be on a 16:9 presentation. The PowerPoint slides (and similar material), however, will be significantly larger in 4:3 than in widescreen formats.
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Gerry Seymour

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Rob Spence

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Deciphering projector stats
« Reply #8 on: January 29, 2013, 01:17:17 am »

This is very useful to me.

I am also looking at projectors.

What I find hard to decipher is how to figure out what size image I can get at what distance. For example, determining if a particular unit will be suitable for
6' wide screen at 14' or
10' wide at 30'

I know I need 3000 to 4000 lumens for my applications.

Thanks


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Brad Weber

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Re: Deciphering projector stats
« Reply #9 on: January 29, 2013, 07:12:35 am »

This is very useful to me.

I am also looking at projectors.

What I find hard to decipher is how to figure out what size image I can get at what distance. For example, determining if a particular unit will be suitable for
6' wide screen at 14' or
10' wide at 30'

I know I need 3000 to 4000 lumens for my applications.
Rob, most projector manuals are available online and most of those include a chart or calculation for throw distance and image size.  Many projector manufacturers also have some form of projection calculator on their web sites that where you enter certain pieces of information and it calculates the results, often showing some graphical representation of those results.  There is also http://www.projectorcentral.com/projection-calculator-pro.cfm that can calculate throw distances, image sizes and image brightness for most current and many discontinued projector models.
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Jordan Wolf

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Re: Deciphering projector stats
« Reply #10 on: January 29, 2013, 10:27:27 pm »

What I find hard to decipher is how to figure out what size image I can get at what distance. For example, determining if a particular unit will be suitable for
6' wide screen at 14' or
10' wide at 30'

I know I need 3000 to 4000 lumens for my applications.
We routinely use 5500 lumen projectors to throw about 55ft.-60ft. for 9x12 screens, and with the house lights at 100%, I feel that the brightness level is acceptable.  I, however, would prefer them to be brighter - I think a 7500 lumen projector is a better fit, personally…but I'll take what I'm given if it works well enough.

In your case, I'd say 35ft.-40ft. would be the max I'd want to throw for a 4000 lumen projector - and I'd aim for a 9ft. x 16ft. screen if possible…or a 9ft. x 12ft. screen if you need to stick with 4:3 AR.  If you have total control of the ambient lighting, those limits may be exceeded by a good bit, but you will always have the most brightness when the projector is as close to the surface as the lens will allow.

The 3500 lumen projectors at my job have 1.8-2.2 lenses - others are available, those are what we have in-house, so we're stuck with them.  Multiplying those numbers by the screen width gives me the minimum and maximum distances I can be from the screen surface.

I find that the 3500 lumen units are fine for a 7.5x10 screen with house lights at 100%, but find them lacking for a 9x12 with the same ambient lighting.  This "lacking" is both a decrease in apparent brightness on the screen surface (judged by my eyes), and also a graininess/lack of clean lines from needing to magnify the LCD pixels so  much to adequately fill the surface.

Hope that helps some…
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Jordan Wolf
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Gerry Seymour

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Re: Deciphering projector stats
« Reply #11 on: January 30, 2013, 09:23:10 pm »

Jordan, I think his question was more a matter of what size he can produce at a given distance, rather than how large and how far away.

I, however, have learned something I didn't expect. I didn't think a 4,000 lumen projector was capable of an image that size under full ambient lighting. I'm starting to wonder just how badly my current projector sucks.
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Gerry Seymour

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Brad Weber

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Re: Deciphering projector stats
« Reply #12 on: January 31, 2013, 08:23:51 am »

I, however, have learned something I didn't expect. I didn't think a 4,000 lumen projector was capable of an image that size under full ambient lighting. I'm starting to wonder just how badly my current projector sucks.
This seems to possibly get into an area that I questioned when a 10:1 image contrast ratio was being taught and that was how that number was determined.  One reason that was asked is that InfoComm itself was routinely making presentation with lower contrats images than they were teaching were required yet people found those image quite usable.
 
The fairly recent InfoComm/ANSI Standard for image contrast ratio apparently had a number of subject matter experts assess different types of images at different image contrast ratios and determine the minimum contrast ratio deemed to provide an acceptable (in their assessment) result for each type of image.  My concern there is that while the people making that assessment are well trained in viewing, they may also have greater expectations than many real world users.  That is why I tend to use that information as a goal but to temper it with the reality that in many cases a lower image contrast ratio may be acceptable.
 
This is a long way of saying that there are some guidelines for image brightness based on the associated image contrast ratio but in the end it is a subjective determination that may vary.  Adding to that are potential variations in what terms such as "full ambient light" and "house lights at 100%" actually represent as far as the light levels on the screen.
 
In your case, I'd say 35ft.-40ft. would be the max I'd want to throw for a 4000 lumen projector - and I'd aim for a 9ft. x 16ft. screen if possible…or a 9ft. x 12ft. screen if you need to stick with 4:3 AR.  If you have total control of the ambient lighting, those limits may be exceeded by a good bit, but you will always have the most brightness when the projector is as close to the surface as the lens will allow.
Just so others don't get confused, it is the image size rather then the throw distance that directly affects the image brghtness.  Theoretically, a projector producing a certain size image will produce the same image brightness regardless of how far it is located from that image as it is still providing the same total brightness over the same image area.
 
There can be an indirect effect of throw distance in that different lenses, and different points along the zoom range of a zoom lens, incur different losses in the optics themselves which can thus affect the actual brightness provided by the projector.  It is a generalization but for lenses of comparable quality long throw lenses often incur greater losses.
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Jordan Wolf

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Re: Deciphering projector stats
« Reply #13 on: January 31, 2013, 08:49:24 pm »

...potential variations in what terms such as "full ambient light" and "house lights at 100%" actually represent as far as the light levels on the screen.
Yes, and I can't say that I have any objective measurements to provide...we don't have a light meter - thus the lack of lux/footcandle data from the ambient lighting.

Quote
Just so others don't get confused, it is the image size rather then the throw distance that directly affects the image brghtness.  Theoretically, a projector producing a certain size image will produce the same image brightness regardless of how far it is located from that image as it is still providing the same total brightness over the same image area.
I think that most people would agree that getting the projector as close as possible to the screen surface is best practice.  Even if using a zoom lens, there is still noticeable dropoff in the image brightness when compared to a screen that has a projector mounted closer to it...isn't that why a projector with a higher lumen rating would be desired for a greater throw distance?

I still don't know hardly as much as I'd like about the industry standards for brightness, etc., and I will gladly defer to your knowledge and expertise on the subject.  If I've said anything incorrect, or that needs clarification, please fix my mistake(s) - I'd love to learn more (and I certainly don't want to confuse others who are reading along).
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Bojan Bajsic

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Re: Deciphering projector stats
« Reply #14 on: February 01, 2013, 05:39:55 am »

I think that most people would agree that getting the projector as close as possible to the screen surface is best practice.  Even if using a zoom lens, there is still noticeable dropoff in the image brightness when compared to a screen that has a projector mounted closer to it...isn't that why a projector with a higher lumen rating would be desired for a greater throw distance?

In short. No.

The projector with a higher lumen rating would be desired for greater screen width and for better contrast in non-dark conditions.

The projected light doesnt loose enough energy on a ie. 50ft journey to be considered detrimental to the image.
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Brad Weber

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Re: Deciphering projector stats
« Reply #15 on: February 01, 2013, 07:37:00 am »

I think that most people would agree that getting the projector as close as possible to the screen surface is best practice.  Even if using a zoom lens, there is still noticeable dropoff in the image brightness when compared to a screen that has a projector mounted closer to it...isn't that why a projector with a higher lumen rating would be desired for a greater throw distance?
The simple concept is that image brightness is a factor of having a certain number of lumens from the projector spread over a certain image area and if the projector brightness and image area remain constant then then the throw distance is not a factor.  Throw distance can become a factor if it changing causes the image area or projector output to change.
 
So say you had a 4,000 lumen projector creating a 9' wide by 12' high image, that's 4,000/(9x12) or just over 37 ftL (footLamberts).  It doesn't matter where the projector is, if the image size and projector brightness remain the same you get the same result.
 
The other factor in image brightness is screen gain or how the screen affects the light hitting it.  However, you do not really have to consider that in assessing the image contrast as screen gain tends to affect both the projector output and ambient light about the same.
 
What can happen in some cases is that a different lens or different point in the zoom range may resulting in a reduction in the projector output.  Obviously most projector manufacturers are going to rate their products based on the most favorable condition and it is possible that a long throw lens or a lens zoomed in tight may actually reduce the projector output.
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Gerry Seymour

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Re: Deciphering projector stats
« Reply #16 on: February 01, 2013, 01:50:18 pm »

The simple concept is that image brightness is a factor of having a certain number of lumens from the projector spread over a certain image area and if the projector brightness and image area remain constant then then the throw distance is not a factor.  Throw distance can become a factor if it changing causes the image area or projector output to change.
 
So say you had a 4,000 lumen projector creating a 9' wide by 12' high image, that's 4,000/(9x12) or just over 37 ftL (footLamberts).  It doesn't matter where the projector is, if the image size and projector brightness remain the same you get the same result.
 
The other factor in image brightness is screen gain or how the screen affects the light hitting it.  However, you do not really have to consider that in assessing the image contrast as screen gain tends to affect both the projector output and ambient light about the same.
 
What can happen in some cases is that a different lens or different point in the zoom range may resulting in a reduction in the projector output.  Obviously most projector manufacturers are going to rate their products based on the most favorable condition and it is possible that a long throw lens or a lens zoomed in tight may actually reduce the projector output.

Hmm...since we all (myself included...in fact, I may have started it) have long since hijacked this thread, let the festivities continue!

What about screen selection? I know the screen has an effect upon brightness, but are some screen types better than others in high ambient lighting? Is it just a matter of highest gain (since a given % loss has a much higher impact on the brighter projection source than the dimmer ambient light)?
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Gerry Seymour

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Re: Deciphering projector stats
« Reply #17 on: February 02, 2013, 02:33:58 am »

In my experience, i would sooner go with the opposite! A gain screen will help the projected light, sure. But it remains a highly reflecting white screen and it will reflect ambient light at the same rate.

In ambient light conditions, if given the chance i would either go for:
 - high contrast grey screen (to get better blacks and improve contrast. But be careful as these are usually 0.5-0.9 gain screens, so one needs a proportionally higher output projector)
 - rear projection (but this depends on space and the viewing angle of presenters, usually not easy to implement if you don't know ahead of time what kind of place you will come to. Really unsuitable for wide viewing angles/auditoria)
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Brad Weber

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Re: Deciphering projector stats
« Reply #18 on: February 02, 2013, 07:46:05 am »

What about screen selection? I know the screen has an effect upon brightness, but are some screen types better than others in high ambient lighting? Is it just a matter of highest gain (since a given % loss has a much higher impact on the brighter projection source than the dimmer ambient light)?
The gain affects both the projected and ambient light the same thus if the ambient light is setting the black level it has no effect on the resulting image contrast ratio.

There are 'high contrast' screen surfaces that can help reduce the apparent black level and some of these are very effective, actually making the image appear brighter due to the greater image contrast ratio.  However, I have found many churches do not like the typically gray color of the high contrast screens when they are not in use.

Also consider the viewing angle or half gain angle of the screen surfaces as that indicates how the reflected light falls off as the viewers get off-axis of the screen.

Rear projection is often a very good option as it addresses several issues but it can be more expensive and you have to have the space for it.
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Gerry Seymour

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Re: Deciphering projector stats
« Reply #19 on: February 02, 2013, 11:36:46 am »

So, that's two recommendations (with qualifications) for the high-contrast screens. I have never really looked at these. Since the main issue I've seen in high-ambient light conditions is the contrast (blacks), this might be well worth it. I'll have to look around and see if I can rent one in the area for one run, just to try it out before I buy.
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Gerry Seymour

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Brad Weber

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Re: Deciphering projector stats
« Reply #20 on: February 02, 2013, 02:32:56 pm »

So, that's two recommendations (with qualifications) for the high-contrast screens. I have never really looked at these. Since the main issue I've seen in high-ambient light conditions is the contrast (blacks), this might be well worth it. I'll have to look around and see if I can rent one in the area for one run, just to try it out before I buy.
Stewart Filmscreen used to have a demo at trade shows with a small 'room' with one half of the screen a standard matte finish and the other a high contrast surface of slightly lower gain.  The high contrast screen had not only lower black levels but colors against a dark background appeared brighter.  The downside was that white was not as white, so not necessarily as beneficial for viewing Word documents or Excel spreadsheets.
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Gerry Seymour

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Re: Deciphering projector stats
« Reply #21 on: February 02, 2013, 03:02:55 pm »

Stewart Filmscreen used to have a demo at trade shows with a small 'room' with one half of the screen a standard matte finish and the other a high contrast surface of slightly lower gain.  The high contrast screen had not only lower black levels but colors against a dark background appeared brighter.  The downside was that white was not as white, so not necessarily as beneficial for viewing Word documents or Excel spreadsheets.

Not as beneficial, bt was it detrimental? Was the overall readability about the same as the standard, or was readability higher on the standard side?
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Gerry Seymour

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Re: Deciphering projector stats
« Reply #21 on: February 02, 2013, 03:02:55 pm »


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