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» Film-Tech Forum   » Operations   » Digital Cinema Forum   » 2K DCP in 2K Projector vs 2K DCP in 4K projector

   
Author Topic: 2K DCP in 2K Projector vs 2K DCP in 4K projector
Nastia Motovilova
Film Handler

Posts: 30
From: Nicosia, Nicosia, Cyprus
Registered: Sep 2012


 - posted 01-22-2013 05:51 AM      Profile for Nastia Motovilova     Send New Private Message       Edit/Delete Post 
Hi to all,

As I understand, upgrading a 2K projector/chip to a 4K projector, bears the cost of the actual upgrade + the cost of changing the lens.

I've read in a couple of articles however, that even when watching a 2K film projected by a 4K projector, the image is more clear, sharp and with added brightness. Does this hold any truth?

Also if with 4K projector we get a reduction in pixel size (compared to 2K), what would the effect be when watching a 2K film on a 4K projector? Is there a reduction in pixel size again?

There's a lot of confusion in my mind that I need to clear [Smile]

Thanks!

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Antti Nayha
Master Film Handler

Posts: 259
From: Helsinki, Finland
Registered: Oct 2008


 - posted 01-22-2013 10:09 AM      Profile for Antti Nayha   Email Antti Nayha   Send New Private Message       Edit/Delete Post 
2K DCI material viewed on a 4K DCI projector won’t be any sharper or brighter. However, the pixel grid is twice as dense and thus much less visible. This can be a real advantage, particularly if the screen is viewed from a very close distance.

I understand that the DCI spec only allows simple pixel doubling when displaying 2K material on a 4K chip. There is no ”smart” upsampling involved so the actual resolution is not increased – each pixel simply becomes four pixels, and the physical size of the image on the screen remains the same. Perhaps an illustration will make this clearer:

 -

Regarding a 2K to 4K upgrade, it tends to be prohibitely expensive as of today. Note that 4K also requires an IMB, so you will have to include that in the cost if your existing 2K system doesn’t already have one.

Has anyone here ever actually upgraded a 2K DLP projector – instead of just buying a new 4K machine and moving the old one to another booth (or selling it)?

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Nastia Motovilova
Film Handler

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From: Nicosia, Nicosia, Cyprus
Registered: Sep 2012


 - posted 01-22-2013 02:17 PM      Profile for Nastia Motovilova     Send New Private Message       Edit/Delete Post 
That's some really great info Annti! Did you make those graphs by your self? If they were part of a publication I would love to have a read of the whole article.

I found this article (p19):

http://www.arri.de/fileadmin/media/arri.com/downloads/Camera/Tutorials/SystemsTechnologyBrochure.pdf

which was the reason why I asked about the sharpness. I don't know much it would apply regarding the sharpness with a digital w

So as I understand there's no up-sampling of the image. If for example a pixel is 4 millimeters, then that same pixel becomes 4X5 smaller pixels which can't be detected that easily, if ofcourse sitting close enough to the screen? Is this correct?

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Antti Nayha
Master Film Handler

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From: Helsinki, Finland
Registered: Oct 2008


 - posted 01-22-2013 02:26 PM      Profile for Antti Nayha   Email Antti Nayha   Send New Private Message       Edit/Delete Post 
I made the picture for some training material a while ago.

As you can see, the four smaller ”4K pixels” will form one larger ”2K pixel”, which is just as much visible as a pixel in a normal 2K image. It’s just that the screen-door pattern becomes harder to notice.

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Carsten Kurz
Film God

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From: Cologne, NRW, Germany
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 - posted 01-22-2013 02:50 PM      Profile for Carsten Kurz   Email Carsten Kurz   Send New Private Message       Edit/Delete Post 
Upsampling is not prohibited by DCI - but only straight 2:1 is allowed - that is not necessarily pixel-repeating:

'8.2.2.7. Spatial Resolution Conversion
The projector is required to display either a native resolution of 4096x2160 or 2048x1080. If the projector's native resolution is 4096x2160, and the incoming spatial resolution of the content is 2048x1080, then the projection system is required to perform the up-conversion of 2048x1080 content to 4096x2160. All spatial conversions are required to be done at an exact ratio of 2:1 in each axis, i.e., a projector with a horizontal pixel count of slightly higher than the image container is required to not convert the projected image beyond the image container to fill the array, nor is an image to be converted to something less than the 4096x2160 or 2048x1080 image container size.
Should electronic image resizing or scaling be used to support a constant height projection or constant width projection theater environment, then it is required that the image resizing or scaling does not introduce visible image artifacts. It is intended that the projector project the full horizontal pixel count or the full vertical pixel count of the image container.'

Regarding 4k vs 2k: I recently inquired for 4k machines vs 2k vs upgrade.
For a Christie, 4k vs 2k was about 18.000US$. The new Dolby IMB is quoted to include 4k at no additional cost. For the Doremi, the 4k firmware upgrade has a list price of 3600US$. So the initial added cost for 4k could be around 15.000US$ -20.000US$ for real deals. That's still huge.

Another quote from Kinoton: 17.000US$ for 4k vs 2k on all machines, 34.000US$ for a later upgrade (light engine swap) from 2k to 4k. Projector only, so potential added IMB upgrade cost as above.

Lens I don't know. Most manufacturers have lists of standard and high-contrast lenses, But I heard that hardly any hc lenses are actually available currently.

It is certainly not strictly necessary to swap to a higher contrast lens, I think for most theaters the reduced pixel count alone is a nice to have (yet at a price).

However, 4k DLPs are 1.38", 2k are 1.2". That means, your throw ratio will change with the 4k upgrade. Depending on where you were with your 2k zoom lens, a different focal range zoom lens may be needed after the upgrade, be it high contrast or not, to fit both flat and scope to your screen.

The new Sony SRX-R515P at 55.000US$ (incl. HFR capable server/IMB, UPS and lens) seems to be the more attractive choice for a 4k machine - if 15.000 lumens peak is enough.

- Carsten

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Marco Giustini
Film God

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From: Reading, UK
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 - posted 01-22-2013 02:52 PM      Profile for Marco Giustini   Email Marco Giustini   Send New Private Message       Edit/Delete Post 
Nastia, the document you linked shows the benefit of a 4K digital process in post production. When it comes to 2K through a 4K projector, there is no difference, but maybe a more smooth general picture because your pixels will be smaller. But in D-Cinema there is no creative scaling of the picture, it's as Antti says.

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Antti Nayha
Master Film Handler

Posts: 259
From: Helsinki, Finland
Registered: Oct 2008


 - posted 01-22-2013 03:09 PM      Profile for Antti Nayha   Email Antti Nayha   Send New Private Message       Edit/Delete Post 
quote:
Upsampling is not prohibited by DCI - but only straight 2:1 is allowed - that is not necessarily pixel-repeating:
It looks like you’re right, Carsten. I was just going through the spec again myself, and I think I have just misread section 8.2.2.7 before. Thanks for the correction.

So presumably one could use a more advanced upsampling algorithm to smooth out the 2K jaggies a bit for 4K projection. Although you still wouldn’t gain any actual resolution (as in resolved detail), of course.

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Nastia Motovilova
Film Handler

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From: Nicosia, Nicosia, Cyprus
Registered: Sep 2012


 - posted 01-23-2013 09:05 AM      Profile for Nastia Motovilova     Send New Private Message       Edit/Delete Post 
Annti, if possible I would still like to read your presentation, if it's in English and available in pdf/video of course. [Smile]

Is there a formula for calculating the throw ratio/changing the lens when using 4K vs 2K?

Also if we calculate size of a pixel in millimeters (or the ppi), how can we determine how close a person needs to sit to the screen to be able to detect the pixels? Is there a formula that we can use to calculate the min/max distance we need to sit from the screen to be able to appreciate 4K?

Sorry for all the questions, as you figured I'm totally new to digital cinema tech.

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Carsten Kurz
Film God

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From: Cologne, NRW, Germany
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 - posted 01-23-2013 11:42 AM      Profile for Carsten Kurz   Email Carsten Kurz   Send New Private Message       Edit/Delete Post 
quote: Nastia Motovilova
Is there a formula for calculating the throw ratio/changing the lens when using 4K vs 2K?
It's the same as the difference in diagonal: 1:38 vs. 1.24, so a factor of roughly 1.112. A 2k 1.45-2.05 zoom becomes a 1.31-1.85 zoom with a 4k imager.

With the same lens and setting, the IMAGER becomes larger at 4k, and so does the image on the screen. You need to get it smaller again. It's the higher value of the projection ratio, and it is essential for the flat image. If you have been at 1:1.95 in flat with your 1.45-2.05 lens, after the 4k upgrade you can not bring the full image on the screen, as your highest zoom setting is then 1:1.85.

quote: Nastia Motovilova

Also if we calculate size of a pixel in millimeters (or the ppi), how can we determine how close a person needs to sit to the screen to be able to detect the pixels? Is there a formula that we can use to calculate the min/max distance we need to sit from the screen to be able to appreciate 4K?

There is a formula, but it makes basic asumptions on 'average' visual acuity, which is similiar to high frequency hearing capabilities. It varies a lot betweens humans, depending on individual factors.

http://en.wikipedia.org/wiki/Visual_acuity
http://pro.sony.com/bbsccms/static/files/mkt/digitalcinema/Why_4K_WP_Final.pdf

- Carsten

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Lyle Romer
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From: Davie, FL, USA
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 - posted 01-24-2013 06:20 AM      Profile for Lyle Romer   Email Lyle Romer   Send New Private Message       Edit/Delete Post 
Sony at least must do something to upscale when their 4k projectors play 2k content. The jaggies are much less noticeable.

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Nastia Motovilova
Film Handler

Posts: 30
From: Nicosia, Nicosia, Cyprus
Registered: Sep 2012


 - posted 01-25-2013 08:21 AM      Profile for Nastia Motovilova     Send New Private Message       Edit/Delete Post 
Would the feature mentioned here upscale a 2K film or do they mean something entirely different?

http://www.doremilabs.com/products/cinema-products/showvault-imb/#

The sony document provides some excellent info. If we were to adopt a relaxed vs a conservative reference to get to an average, can we determine the minimum distance a person must sit to avoid seeing any artifacts? I found the following though I can't make the connection between the formula below and the document.

http://en.wikipedia.org/wiki/Optimum_HDTV_viewing_distance#Factors_influencing_the_calculations

In the document it doesn't make a reference to the screen dimensions used in the wiki link above. It only refers to PH.

As a side note, are there any books that explain all these subjects?

I really appreciate all the replies!

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Tom Bert
Expert Film Handler

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From: Belgium
Registered: Apr 2010


 - posted 02-05-2013 10:19 AM      Profile for Tom Bert   Email Tom Bert   Send New Private Message       Edit/Delete Post 
I'd like to comment that the image in the 2nd post is not correct: when showing 2K content on 4K DLP, we do more intelligent interpolation than what is depicted.

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Antti Nayha
Master Film Handler

Posts: 259
From: Helsinki, Finland
Registered: Oct 2008


 - posted 02-05-2013 10:46 AM      Profile for Antti Nayha   Email Antti Nayha   Send New Private Message       Edit/Delete Post 
Tom, thanks for clearing that up. I suppose that the interpolation is handled by the TI software?

Also, this Sony brochure (pages 7–9) confirms that they use an interpolation-based upscaling algorithm which they call ”Intelligent Smoothing”.

So I stand humbly corrected! It’s good that the issue was brought up, though, since it seems to be a fairly common misconception.

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