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Author Topic: High-res projection question  (Read 12587 times)
John Camp
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« on: December 17, 2008, 11:16:25 AM »
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I want to project a photograph of an object on a much larger screen so that it can be manually traced on the screen. The problem is, using a D3 at 12mp, when the projection gets large enough (~6 feet/2 meters) in the long dimension, the edges become obscure. They're clear enough when you stand back, but if you're right on the screen, trying to follow an edge with a pencil, an edge may be a quarter-inch wide. I don't believe that changing to a higher resolution camera would help, because the resolution here is dependent on the resolution of the LCD in the projector, correct? Is it possible to break the image into several pieces and project them separately, essentially doing a kind of manual "stitch?" While you still run into some edge problems when projecting at more than 100%, they wouldn't be as severe as just projecting a whole frame at the LCD resolution, would they?

I'm beginning to think that I should just find a digital-to-slide film service and project a film slide...

Any help on this would be appreciated.


JC
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Ray
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« Reply #1 on: December 18, 2008, 04:49:27 PM »
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John,
I imagine that doing a manual stitch would be very troublesome unless you had a way of precisely adjusting the position of the projector, from side to side and up and down. In principle it could be done. You could crop the 12mp D3 image into a number of, say, 2mp overlapping sections. Move the projector much closer to the screen; project the first full resolution image, say bottom left corner; make the tracing; project the second full-rez image and move the projector carefully to the right to a position whereby the overlap of the second image precisely matched the tracing previously made from the first image; repeat the process with each crop.

Perhaps you could place the projector on a computer chair with adjustable height.
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keithrsmith
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« Reply #2 on: December 19, 2008, 05:40:37 AM »
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why not try with an "Find Edges" version of the image?

Keith
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bjanes
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« Reply #3 on: December 19, 2008, 06:21:23 AM »
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Quote from: John Camp
I want to project a photograph of an object on a much larger screen so that it can be manually traced on the screen. The problem is, using a D3 at 12mp, when the projection gets large enough (~6 feet/2 meters) in the long dimension, the edges become obscure. They're clear enough when you stand back, but if you're right on the screen, trying to follow an edge with a pencil, an edge may be a quarter-inch wide. I don't believe that changing to a higher resolution camera would help, because the resolution here is dependent on the resolution of the LCD in the projector, correct? Is it possible to break the image into several pieces and project them separately, essentially doing a kind of manual "stitch?" While you still run into some edge problems when projecting at more than 100%, they wouldn't be as severe as just projecting a whole frame at the LCD resolution, would they?

I'm beginning to think that I should just find a digital-to-slide film service and project a film slide...

Any help on this would be appreciated.


JC

Why do you need to project the image? I presume some type of analysis. The freeware program ImageJ has quite a few analysis features.

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bill t.
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« Reply #4 on: December 22, 2008, 10:24:38 PM »
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Not sure what your goal is, but it might be useful to process the image in various ways to enhance the visibility of edges, lines, whatever you're interested in.

Some of the edge and posterization effects available in the Photoshop Filters menu are possibilities.  Nice thing about digital projection is you can have exact registration from image to image, you can browse through a set of differently processed versions of the image to find the one most useful for a particular feature you are tracing or measuring.  An image reduced to black outlines with a white background should be quite easy to trace for gross shapes.

If you are seeing fading towards the edges, it may be that you have the lens at a rather wide setting.  It may be helpful to zoom towards the telephoto range with the projector as far away as practical.
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AJSJones
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« Reply #5 on: December 25, 2008, 02:31:39 PM »
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I think we are puzzled by the fact that your desired precision is so fine (the 1/4" edge being your "limitation")  Seems like you need a very accurate large scale hard copy of the object in question.  Even with a 1920x1080 HD projector, you'll not have true accuracy without stitching.  The computer tricks already suggested could let you transfer that outline as a single pixel line to its own layer in Photoshop.  Then find a printing service to make a large b/w bitmap print at whatever resolution your project requires (possibly several strips to be taped later to make the full-scale hard copy?  I've done something similar with my Epson 7600 onto cheap paper to make fabric patterns for my wife   (although the required precision was not that tight!!!)
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jani
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« Reply #6 on: December 27, 2008, 04:41:40 PM »
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Quote from: John Camp
I want to project a photograph of an object on a much larger screen so that it can be manually traced on the screen. The problem is, using a D3 at 12mp, when the projection gets large enough (~6 feet/2 meters) in the long dimension, the edges become obscure. They're clear enough when you stand back, but if you're right on the screen, trying to follow an edge with a pencil, an edge may be a quarter-inch wide. I don't believe that changing to a higher resolution camera would help, because the resolution here is dependent on the resolution of the LCD in the projector, correct? Is it possible to break the image into several pieces and project them separately, essentially doing a kind of manual "stitch?" While you still run into some edge problems when projecting at more than 100%, they wouldn't be as severe as just projecting a whole frame at the LCD resolution, would they?
As others have pointed out, the resolution you get from a projector is fairly low compared to what you get from your D3.

If you have a reasonably affordable projector, or even a moderately expensive one, the best you can hope for in a 3:2 frame is 1620 x 1080 pixels with a "full HD" capable projector.

1620 pixels over 6 feet => 22.5 PPI

If you don't have a "full HD" capable projector, but merely one that agrees with 720p/i, your display will suffer even more.

1280 x 800 projector => 1200 pixels => 16.7 PPI

Since you want to avoid adjusting your projection size and viewing distance, you're left with adjusting the projection resolution.

As mentioned by others, stitching several projections is fiddly work at best, and you'll have a nightmarish job aligning the focus properly for four or more projectors. It may work for operation centers and suchlike, but I doubt that it will work well for art.

The alternative is to purchase or rent a more expensive projector, specifically one that is capable of displaying 4K (number of vertical lines, or horizontal resolution; 2K and "full HD" are very close); this will double your resolution to 45-50 PPI, and comes reasonably close (7-8.5 megapixels) to your native resolution.

Both JVC and Sony make such projectors (the quite expensive SXRD series can be had, JVC's better-resolving DLA-SH4K is about to get there), and I'm sure that there are competitors.

JVC has created an 8K (8192 x 4320) LCD projector chip, yielding more resolution than you or 1Ds MkIII, A900, and D3x owners need for single-shot images.

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I'm beginning to think that I should just find a digital-to-slide film service and project a film slide...
That is certainly an option, provided that you can get a service that will provide you with the necessary resolution and quality. It's probably significantly cheaper than purchasing a 4K projector.
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Doug Peterson
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« Reply #7 on: December 30, 2008, 09:08:10 AM »
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(mistake post)
« Last Edit: December 30, 2008, 09:08:34 AM by dougpetersonci » Logged

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Jonathan Wienke
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« Reply #8 on: January 01, 2009, 03:05:40 PM »
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Quote from: jani
If you have a reasonably affordable projector, or even a moderately expensive one, the best you can hope for in a 3:2 frame is 1620 x 1080 pixels with a "full HD" capable projector.

1620 pixels over 6 feet => 22.5 PPI

That actually should be 1920x1080, not 1620.
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jani
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« Reply #9 on: January 01, 2009, 04:39:18 PM »
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Quote from: Jonathan Wienke
That actually should be 1920x1080, not 1620.
No, because you won't be able to take advantage of the 1920 wide resolution with a 3:2 format; that translates to a picture height of 1280 pixels. The widest 3:2 format image you can have at a height of 1080 pixels is 1620.
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Dan Wells
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« Reply #10 on: January 04, 2009, 09:38:33 AM »
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Wow- that 8k chip will display a full-resolution image (barely) from a 24+mp camera - assuming that the color and tonal range are there as well, that is the best projection (digital or analog) EVER available, with the possible exception of IMAX film projection and a few machines that could project a 4x5 transparency (nobody ever invented one with a changer, though - they were all quite tricky manual advance requiring many seconds to change images). This has a lot of potential for extremely high-quality slide shows (think of a really good presentation at a National Park, or Frans Lanting's amazing Life: A Journey Through Time), although I don't even want to THINK about the computer power required to dissolve 24 mp!.  Hopefully, the 8k chip will find its way into an under $10,000 projector in the next few years.


                                                          -Dan
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Jonathan Wienke
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« Reply #11 on: February 16, 2009, 04:26:54 PM »
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Quote from: jani
No, because you won't be able to take advantage of the 1920 wide resolution with a 3:2 format; that translates to a picture height of 1280 pixels.

Yes, because not every image shot with a 3:2 aspect camera is displayed uncropped...
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