Screen size advice

[Quark]

2 hours ago, Scotttj said:

I've been playing with the Projector Central Calculator and to achieve a 130" CinemaScope screen, i need the projector to be at least 4.26m from the screen. At this distance the image brightness will be 34fL so it's not a whole lot difference to the 31fL level when mounted 5.4m back. 

  

Will this brightness level be enough for 4k hdr?

 

 

Despite our resident naysayer (same person who was never, ever, ever getting a projector when he was dribbling over his Sony LCOS TV some years ago) 34fL will be enough for the way HDR is implemented on current projectors. Saying that, more lumens are better and you should still consider a 1.26 gain screen to reduce the risk of needing to replace lamps before their nominal end of life.

[Owen]

Since the projector only provides about 75% of it rated output in actual use with accurate colour the calculators results are way off. If it says 34fL you will get about 26fL with a new lamp and its down hill from here. Drop in the wide gamut filter and you are down to something like 23fL.

 

I have owned projectors continuosly for the last 18 years, starting with triple gun CRT, and JVC's for the last 7 years.

Edited November 16, 2018 by Owen

[IMDave]

3 hours ago, Scotttj said:

 

I've been playing with the Projector Central Calculator and to achieve a 130" CinemaScope screen, i need the projector to be at least 4.26m from the screen. At this distance the image brightness will be 34fL so it's not a whole lot difference to the 31fL level when mounted 5.4m back. 

 

Will this brightness level be enough for 4k hdr?

 

I'll put a disclaimer in here that like @:) al and @Quark I have an X7000, but as previously stated my lens is 3.95m from the screen, so I'm not sure the PJ Central calculator is correct for the 4.26m

Pt#2 : despite what Owen says ( he may be technically correct by the strictest letter of the law about re-mapping SDR to 100Nits, BUT IT DOESN'T MATTER. IT IS HOW HDR WORKS IN 2018 !!! ) 30ftL is plenty for 4k/UHD/HDR.

 

I've taken a couple of photos of my ceiling to show you the box my X7000 sits in. Obviously the phone flash has blown it out to make my ceiling considerably lighter in colour than it actually , but hopefully it gives you an idea. ( Actually, now that the photos are uploaded it looks way more obtrusive than it does in real life. Trust me, you can walk into the room, and you wouldn't know there was a projector on the ceiling until you walked around the front to be able to see it)

 

[Owen]

4 hours ago, IMDave said:

BUT IT DOESN'T MATTER. IT IS HOW HDR WORKS IN 2018 !!! ) 30ftL is plenty for 4k/UHD/HDR.

I never said it doesn't look good, the point is 30fL (100 nits) is NOT HDA. Thats not what people want to here but its a fact. If 30fL is HDR a 40 year old CRT TV is a HDR display, they could do 30fL or more. In fact, that old CRT had a greater dynamic range than any digital projector because it could do absolute black.

 

If  the gamma of SDR and HDR video is setup to give the same on screen gamma and the same peak light output, lets say 30fL, the resulting picture is effectively identical. Same black point, same white point and same video levels in between.

Once you understand how to adjust gamma you can make the picture look however you want it to look, you have almost compete control and thats very valuable.

[Primare Knob]

You will have found out by now that everything in a HT room is competing for space.

You want the viewing angle to be right, to make sure the eyes can be relaxed without having to jump all over the screen to take in the whole picture.

You don't want to sit to close to the screen to be able to indentify pixels. You don't want to sit to far away from it for the resolution to become pointless, as your eyes might not be able to pick out the details. 4K alles you to sit closer to the screen

You don't want the screen to bright so that it strains your eyes and watching a movie becomes an exercise. You want to keep the brightness down in order to keep the maximum dynamic range. A darker room allows you to display the maximum dynamic range of an image, a lighter room compromises this and you will need more light output the prevent the highlights from washing out, but you will lose some in the shadows.

Move the projector closer, move the screen closer, go with a smaller size screen will increase screen light output.

Projector central uses the manufacturer rated light output, but I believe it does use the rated eco values. The real values are less than this, but you will have to dig them up out of reviews to find them.

Then when you think you have found the right screen, you will probably find out that this screen doesn't work with the ideal speaker placement, bugger.

HT is also about compromising your desires in order to make the details work. Because if you get the details right, the whole experience will feel right and much enjoyable for everyone, and will get more use.

Keep planing and tweaking until you have found the right balance. Watching a move should not be hard work, by that time the hard work should be behind you.

[betty boop]

I am not sure its all that complicated though.

 

as I mentioned before for myself I found THX spec for immersion which works on 41.5 deg seems to match well with the 2/3rd room length for viewing distance/main listening position. the THX spec seems to be pretty optimum for screen size., gentle enough for fta does over resolve 1080p and for that reason does give gains for 4k. also 2/3rd room length for listening./ viewing position good audio wise for speaker placements mains and surrounds. 

 

as to screen brightness the below chart from Jvc seems to be a good guide I think as to what might be a good choice to borderline or not enough..... do note that this is a 16:9 screen size and 1.3 gain. so if using scope convert back to the equivalent 16:9 image you are zooming out .... so a 130" scope is really zooming a 140" 16:9 image for instance. 

 

[Primare Knob]

The minimum width of your speakers (center of speaker) at 400cm at 22 degree is 55cm from the side walls. The max of 30 degree will be beyond the width of your room.

Your projector would need to output 700 real ANSI lumens for a 16fl screen light output which will be good for a complete dark room. For a slightly light room you would like to have 22fl or a bit more which requires an light output from your projector of 930 real ANSI lumen. These numbers aren't very difficult to achieve for a modern projector.

At 400cm viewing distance you are actually not getting the full benefit of 4k, as you are sitting to far away from the screen for your eyes to pick out the differences in detail. To get the full benefit of 4k you could go up to 180" screen size, or a viewing distance of roughly 3 meter.

You could also move a 130" screen a meter closer to decrease the viewing distance. This would also allow you to put your speaker behind the screen.

A 150" screen at 350cm viewing distance with 930 real ANSI lumen would be ideal with 16fl for a dark room and 4k viewing.

I wouldn't pay touch attention to HDR, as in the end it is all about the dynamic range between light and more importantly dark. There is way more information in the shadows than in the highlights, and a to bright an image will make watching a movie tiresome for your eyes and unpleasant.

Your speakers would still be within range as they are pushed to the side of the screen and you might have the ability to build a baffel wall. I would personally choose an AT screen and move the speakers behind the screen for that clean look.

At 400cm you are sitting at 2/3 the way which makes it a more or less ideal position for even bas response, but since we use a subwoofer ideally 2 subwoofers this doesn't matter as much as it does with full range speakers.

One question, why do you go for a white ceiling if this is a dedicated room? The ceiling is going to reflect a lot of light into the room and compromise your dynamic range. You might want to take that into consideration when choosing your screen material. One that can cancel out a lot of indirect lighting might be helpful.

[Primare Knob]

Just as a quick guide.

A HDR image requires at least 2 full stops more (peak) light output. This roughly translates in 64fl of screen light output.

If we take the THX 16fl as our base; 16 X 2 X 2 = 64. Every stop is a doubling of light.

[betty boop]

8 minutes ago, Primare Knob said:

Just as a quick guide.

A HDR image requires at least 2 full stops more (peak) light output. This roughly translates in 64fl of screen light output.

If we take the THX 16fl as our base; 16 X 2 X 2 = 64. Every stop is a doubling of light.

I think you will find if you do your research SDR is 12-16FL (this is well defined)

 

and the accepted minimum required for projectors HDR is 100nits or 34 FL. if you want to gain any further that is totally your choice and to work out how to do that. but can tell you since the launch of HDR uhd material this is what people have been doing and to great end result. are you running a projector for 64 FL and HDR ? 

[Primare Knob]

I think you will find if you do your research SDR is 12-16FL (this is well defined)
 
and the accepted minimum required for projectors HDR is 100nits or 34 FL. if you want to gain any further that is totally your choice and to work out how to do that. but can tell you since the launch of HDR uhd material this is what people have been doing and to great end result. are you running a projector for 64 FL and HDR ? 

I don't run HDR as I am still on 1080p. Whatever people find acceptable is their own choice.

I simple stated that an HDR image needs a minimum of 2 full stops more in highlights compared to a SDR image.

If the SDR image requires 16fl than a HDR image requires 64fl.

16fl is the THX reference for SDR images in a dark room, as mentioned. 12fl is the bare minimum but isn't very comfortable for everyone as the dim image can strain the eyes. And in the end, it is about comfort as watching a movie should not be an exercise.

I personally would prefer more details in shadows and clipped highlights, as stated before, so 34fl would probably suite me fine.

This was just intended to put perspective in the HDR requirements and that there are other ways of increasing the dynamic range, or loose it.

[betty boop]

11 minutes ago, Primare Knob said:

I don't run HDR as I am still on 1080p. Whatever people find acceptable is their own choice.

I simple stated that an HDR image needs a minimum of 2 full stops more in highlights compared to a SDR image.

If the SDR image requires 16fl than a HDR image requires 64fl.

16fl is the THX reference for SDR images in a dark room, as mentioned. 12fl is the bare minimum but isn't very comfortable for everyone as the dim image can strain the eyes. And in the end, it is about comfort as watching a movie should not be an exercise.

I personally would prefer more details in shadows and clipped highlights, as stated before, so 34fl would probably suite me fine.

This was just intended to put perspective in the HDR requirements and that there are other ways of increasing the dynamic range, or loose it.
 

the smpte standard for screen luminance requires nominal 16fl allowing minimum of 12FL to upto 22 FL

 

http://cdn-docs.av-iq.com/dataSheet//Screen Luminance Datasheet.pdf

 

it is an incorrect assumption of needing 64 FL as a minimum. as I said before 34 FL or 100 nits is the accepted minimum. actually even 30FL yields good gains over SDR. if you planning to explore most definitely do so. I think will find as you are thinking that 34 FL will suite just fine

[Owen]

Domestic SDR video, which is what we have on 1080 Bluray, is mastered for 30fl (100 nits), how many times do I have to point his out?????     30fl IS the SDR statndard.

The target display device is a TV operating in a non dark environment and a high average picture level is desirable for domestic viewing environments so a display gamma of 2.2 is the calibration target.

 

Cinemas could not provide 30fL so the standard for cinemas is about 15fL, which was generally achievable but not always. HOWEVER the video mastered for cinemas is mastered for about 15fl NOT 30fL like domestic video AND the system gamma is different to domestic video as well. Put simply, the cinema standard is LESS THAN SDR, in fact a cinema has about half the dynamic range of a 40 year old CRT TV that the SDR standard was designed for.

 

We typically have displayed 1080 Bluary source at about the same brightness as a commercial cinema even though the video was not mastered for that application. A display gamma of 2.2 suitable for TV use is not ideal and tends to provide an image thats lacking in depth and "pop" so a display gamma of 2.4 or even 2.6 is often preferred. Altering gamma does not affect the black level or the peak white level at all, it simply lowers the levels in between black and white which in turn makes the average picture level dimmer and looks more HDR like.

 

The HDR "standard" is 1000 nits plus with some video already being mastered for 4000 nits. Again its designed for TV's not projectors and the target display gamma is VERY, VERY different due to the VERY high display brightness intended to be used.

HDR is mastered for displays running at 10 to 40 times the peak brightness of SDR, thats more than 3 to 5 stops brighter. Now if we say that 15fL is notionally "SDR" on a projector HDR is required to be 10 to 40 times brighter, or 150 to 600fL, to give the same effective result. Thats VASTLY different to the sort of light output we can expect from a domestic projector, so calling anything we view on a projector "HDR" is simple ridiculous, it's so far off its silly.

 

Now people say, "but HDR looks so good on my projector" even though they are looking at maybe 30fL, thats because we don't need a lot of brightness to get a fantastic picture on a big screen in a dark room, we never did. The quality of the image is dominated by image gamma which must be matched to the peak brightness of the display, and since a projector has only a fraction of the brightness of a HDR TV that the video was mastered for gamma MUST be heavily remapped. 

If we choose to display HDR via a projector at say 15fL, as many people do for SDR video, we need to remap HDR back to the same effective on screen gamma as we would use for SDR at 15 fL, and when we do that, guess what, SDR and HDR  look THE SAME. Same black level, same white level and the same at every level in between.

 

Modern projectors often have more brightness than is required so people often don't run them at full output as it looks too bright with SDR video using the standard gamma the projector comes setup with by default.

To get some sort of HDR "look" with HDR video the projector must run flat out to be as bright as possible, and may be able to provide 30 to 40fL on a relatively small screen. The projector then re maps HDR video to look as good as possible, or what the manufacturer thought the average punter would like, at the brightness level available. Yes it looks different - better than SDR looks by default at 15fL and so it should, 15fL is only HALF SDR.

 

Now comes the part no one seems to talk about, why I don't know. We can run the projector flat out for SDR video source and get the exact same black level,  peak white level AND DYNAMIC RANGE we get with "so called" HDR on a projector. When we do that we can and should remap the gamma of SDR to match what HDR is remapped to when it is displayed at the same brightness, if we don't the image will be too bright, lack depth and overall look very different to HDR.

 

So when people say HDR looks "better" than SDR on their projector they are comparing apples to oranges. The mastering of the video source is different, the display brightness is different, the system gamma is very different, the colour calibration is different. Pretty much all the major influencing factors that affect  what we see on screen are different so its no surprise they don't look the same. With so many fundamental difference its amazing they look so similar.

 

When we setup a projector so that SDR and HDR are properly matched on screen its no surprise that the visible differences disappear. On a title by title basis is possible to get the HDR and SDR disk visions of a movie to look effectively identical, if I get it right I simply can't tell which is which. Not only that, I can make either look however I want it to look.

 

For optimal results with SDR and HDR a range of gamma presets is required, this is especially important with HDR as its inconsistent from title to title, much more so than SDR. Therefore a single HDR setup is always going to be a compromise and unfortunately projectors don't have enough programable modes to allow more than a couple of gamma setups. I use a PC as a video source and can call up an appropriate gamma map in a moment. I can make an individual map for every individual movie title if need be, there is no limit.

 

Can we please accept that there is no such thing as HDR on a projector, we only have approximately SDR or less.

Projectors are HDR "compatible" but NOT HDR "capable", both  Sony and JVC admit this because its a fact so lets get past the HDR BS please. We don't have it and don't need it for a fantastic picture that blows any HDR TV into the weeds.

 

 

 

 

[Primare Knob]

Domestic SDR video, which is what we have on 1080 Bluray, is mastered for 30fl (100 nits), how many times do I have to point his out?????     30fl IS the SDR statndard.
The target display device is a TV operating in a non dark environment and a high average picture level is desirable for domestic viewing environments so a display gamma of 2.2 is the calibration target.
 
Cinemas could not provide 30fL so the standard for cinemas is about 15fL, which was generally achievable but not always. HOWEVER the video mastered for cinemas is mastered for about 15fl NOT 30fL like domestic video AND the system gamma is different to domestic video as well. Put simply, the cinema standard is LESS THAN SDR, in fact a cinema has about half the dynamic range of a 40 year old CRT TV that the SDR standard was designed for.
 
We typically have displayed 1080 Bluary source at about the same brightness as a commercial cinema even though the video was not mastered for that application. A display gamma of 2.2 suitable for TV use is not ideal and tends to provide an image thats lacking in depth and "pop" so a display gamma of 2.4 or even 2.6 is often preferred. Altering gamma does not affect the black level or the peak white level at all, it simply lowers the levels in between black and white which in turn makes the average picture level dimmer and looks more HDR like.
 
The HDR "standard" is 1000 nits plus with some video already being mastered for 4000 nits. Again its designed for TV's not projectors and the target display gamma is VERY, VERY different due to the VERY high display brightness intended to be used.
HDR is mastered for displays running at 10 to 40 times the peak brightness of SDR, thats more than 3 to 5 stops brighter. Now if we say that 15fL is notionally "SDR" on a projector HDR is required to be 10 to 40 times brighter, or 150 to 600fL, to give the same effective result. Thats VASTLY different to the sort of light output we can expect from a domestic projector, so calling anything we view on a projector "HDR" is simple ridiculous, it's so far off its silly.
 
Now people say, "but HDR looks so good on my projector" even though they are looking at maybe 30fL, thats because we don't need a lot of brightness to get a fantastic picture on a big screen in a dark room, we never did. The quality of the image is dominated by image gamma which must be matched to the peak brightness of the display, and since a projector has only a fraction of the brightness of a HDR TV that the video was mastered for gamma MUST be heavily remapped. 
If we choose to display HDR via a projector at say 15fL, as many people do for SDR video, we need to remap HDR back to the same effective on screen gamma as we would use for SDR at 15 fL, and when we do that, guess what, SDR and HDR  look THE SAME. Same black level, same white level and the same at every level in between.
 
Modern projectors often have more brightness than is required so people often don't run them at full output as it looks too bright with SDR video using the standard gamma the projector comes setup with by default.
To get some sort of HDR "look" with HDR video the projector must run flat out to be as bright as possible, and may be able to provide 30 to 40fL on a relatively small screen. The projector then re maps HDR video to look as good as possible, or what the manufacturer thought the average punter would like, at the brightness level available. Yes it looks different - better than SDR looks by default at 15fL and so it should, 15fL is only HALF SDR.
 
Now comes the part no one seems to talk about, why I don't know. We can run the projector flat out for SDR video source and get the exact same black level,  peak white level AND DYNAMIC RANGE we get with "so called" HDR on a projector. When we do that we can and should remap the gamma of SDR to match what HDR is remapped to when it is displayed at the same brightness, if we don't the image will be too bright, lack depth and overall look very different to HDR.
 
So when people say HDR looks "better" than SDR on their projector they are comparing apples to oranges. The mastering of the video source is different, the display brightness is different, the system gamma is very different, the colour calibration is different. Pretty much all the major influencing factors that affect  what we see on screen are different so its no surprise they don't look the same. With so many fundamental difference its amazing they look so similar.
 
When we setup a projector so that SDR and HDR are properly matched on screen its no surprise that the visible differences disappear. On a title by title basis is possible to get the HDR and SDR disk visions of a movie to look effectively identical, if I get it right I simply can't tell which is which. Not only that, I can make either look however I want it to look.
 
For optimal results with SDR and HDR a range of gamma presets is required, this is especially important with HDR as its inconsistent from title to title, much more so than SDR. Therefore a single HDR setup is always going to be a compromise and unfortunately projectors don't have enough programable modes to allow more than a couple of gamma setups. I use a PC as a video source and can call up an appropriate gamma map in a moment. I can make an individual map for every individual movie title if need be, there is no limit.
 
Can we please accept that there is no such thing as HDR on a projector, we only have approximately SDR or less.
Projectors are HDR "compatible" but NOT HDR "capable", both  Sony and JVC admit this because its a fact so lets get past the HDR BS please. We don't have it and don't need it for a fantastic picture that blows any HDR TV into the weeds.
 
 
 
 

You really like to hear yourself talk, don't you?
No-one is saying that HDR on a projector is possible. Simply mapping the limitations.

[Owen]

3 hours ago, Primare Knob said:

No-one is saying that HDR on a projector is possible.

Actually people do. According to them, if we can get 30-35fL on screen we can get a great "HDR" picture. Now people no doubt get a picture they are delighted with BUT there is nothing "HDR" about the picture they see,  the same image can easily be created with SDR video source if they setup thier projector to do it. Projector manufactures could easily provide a preset mode to do just that, but it would blow the lid of the HDR myth and be a bad marketing move.

How do your get people to buy a new projector if they find out they can get the same result with SDR video on the projector they already own?

 

3 hours ago, Primare Knob said:

Simply mapping the limitations.

The "limitation" is that projectors are standard dynamic range display devices, and with many projector - screen combinations less than SDR, feeding them HDR video doesn't change that.

Edited November 18, 2018 by Owen