Unrealistic expectations

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A huge screen has great initail impact. People say WOW! look at the size of that image! After 1/2 hr I would think that would wear off if the image is poor.

You go to the store and look at the big screen tvs and see mostly $3000 for about 60" Even for that money the picture isnt great. I have a 60" wide screen projector I made with much better image. Why not blow it up bigger?!? Gorge on the huge floor to ceiling movie! Thats like buying a gallon tub of the cheapest ice cream and stuffing your face with crap till your sick. :dead:

Do you really think a $50 lens is going to give you anything but a muddy image at that size? Give your head a shake. :whazzat:

Unless your ready to pay for the optics don't go into the project with stupid expectations.
 
No. My point is dont think you will get a great massive picture.

Simple reality check. 90" screen is 6x magnification on a 15" lcd. Take a 6x magnifier and look at a LCD monitor. If you do everything perfect that is as good as your screen can look. Put it a bit out of focus and that is probably what you will get. If its not too big it will look OK.

Try the same with a 10x magnifier.
 
With most lenses that are available to the diy community you can achieve excellent results with screen sizes up to 100 inch diagonal. Some people have 120 inch diagonal screens and they are happy with the results. By excellent results I mean to sit down and watch TV, enjoy a movie or play a video game. I am not referring to trying to read an 8 point font in the upper right hand corner. That is another issue in itself. While projecting a "floor to ceiling" (8 feet by 10.5 feet) screen may make a len's short comings more noitceable, another issue is the insufficient light output of a 400 watt bulb to cover such a large screen.
 
Me2! said:
No. My point is dont think you will get a great massive picture.

Simple reality check. 90" screen is 6x magnification on a 15" lcd. Take a 6x magnifier and look at a LCD monitor. If you do everything perfect that is as good as your screen can look. Put it a bit out of focus and that is probably what you will get. If its not too big it will look OK.

Try the same with a 10x magnifier.


I'm also sitting about 10 inches from my lcd, so magnify that 6x and i'm sitting 5 feet from the projected 90" image and i should have about the same quality as the unmagnified image from 10 inches
 
Me2! said:
No. My point is dont think you will get a great massive picture.

Simple reality check. 90" screen is 6x magnification on a 15" lcd. Take a 6x magnifier and look at a LCD monitor. If you do everything perfect that is as good as your screen can look. Put it a bit out of focus and that is probably what you will get. If its not too big it will look OK.

Try the same with a 10x magnifier.

i think you are quite innacurate with your post ...

first off, the differnce between a 90" screen coming from a 15" lcd, is much larger than 6 times magnification, you would need to find the square area in order to calculate the magnification factor.

Secondly, what matters is how close you sit to the screen. yeah blowing the image up reduces the quality if you dont sit further away from the screen. Hell the 15" monitor would look like crap if you get close enough to it.

the projection lens and the fresnels are designed to be more optimal than looking at an LCD through a generic magnifier (granted alot of people use the cruddy fresnels that can be had for $5 at an office surplus store, but im speaking of people that use a higher quality fresnel lens)

I dont know what your basing your experience with, but I get very good focus with my projector, maybe its slightly more primative, but Ive also taken the tame to make an adjustment system to all of my lenses/bulbs/reflector so that I can find the exact focal point of each component. A fresnel lens may have a focus rated at 220mm, but I find that there is a natural tolderance curve that alot focus within a 10mm range around that 220mm rating. My adjustment system allows me to tweak untill I find that spot exactly

the projected screen size plays nothing on its focus, since the projection lens throws from a single point. granted if its out of focus then regardless of projected size it will be out of focus. But if you calculate your throw ratio, place the projector at the correct distance from the screen, then the focus will be at a fixed point. You can calculate these parameters for a throw of any feasible length and find the exact focal point to set to.

your correlation of image size to quality of focus, especially when dealing with a larger 15" is wrong. If that were the case, then the Expensive $10,000 projectors, that project a large size using only a 1" square DLP source would be producing some awfull quality going by your assumptions.

Are PJ compare to the entry level units, and if you think that they use a $500 projection lens or something that expensive then your crazy ..... They use similar quality projection lenses, in fact I can guarentee you that they use a Lower quality then the long throw lenses that both LL and DIYPC sells.
 
Hot button topic. :)

your correlation of image size to quality of focus, especially when dealing with a larger 15" is wrong. If that were the case, then the Expensive $10,000 projectors, that project a large size using only a 1" square DLP source would be producing some awfull quality going by your assumptions.

Im not making any such correlation. Im saying the quality of the image cannot get better than the original and in many cases would be worse. Blowing that up by a large amount takes you beyond the optimum of that system. Unless you are quite far from the image you see the pixels if you blow it up too much.

The only system I see that could handle the big screens (well) is Minoten with his WUXGA. The higher resolution means he doesnt run into the graininess. He's limited by other parts of the system however. Eventually i'd like to build a unit like his. Then I would goto a bigger screen. I find 60"wide a good resolution for 1024x768 at 12ft. It is bright and crisp. When I get closer to the screen to see what a bigger image would be like [back wall is in the way of pulling the system back] I see graininess that is distracting.

I dont buy the idea that people cant resolve the grain with those big screens hence the hand loupe analogy. If I can almost see it at 60" It doesnt matter how your system is designed it's going to be very visible at 120" [unless its fuzzed out]. Either way you are beyond the optimum for 1024x768. You would have to go to a higher res. lcd.

A commercial projector using a very fine lcd would need more precise optics to get a good image. The lens may not be more expensive for the company but it's probably better designed than the average DIY lens.

Thanks for the reply with explained reasoning behind your perspective.
 
sorry if I sounded sort of aggitated in my response, after reading 2 or three of your post I got the feeling that you were another DIY basher that really has no experience to back up his opinon ....

I see your point, and its a good one, but that problem holds true with any type of LCD projector.

Its not a flaw that lyes in belly of DIY. Hell at school we have one of the entry level X1's or something like that ... and even at roughtly 80" the screen door is very apparent(havnt measured, just guessing by looking at it),

When dealing with anythng other than CRT or film your going to have a pixelating effect when blown up, that will get worse. The idea is to be at a good distance from the screen.

About 4 years back I worked for a hi-fi A/V shop, and we sold some of the first widescreen DLP projectors that were made, and even then it was noticeable, but when you sat at an appropriate distance it was very tolerable.

You cant every expect your image to be without some sort of flaw, the technology of LCD/DLP is limiting in that nature, and unless we use a 36" LCD panel at about 9000x12000 resolution we are going to notice screen door effect when blown up. in fact Minoten is using a great panel, but he too will see screen door also ....
 
DIY basher lol h3ll no!

I didn't really explain well at the beginning. I'm recharging batteries for my camera right now... if i can find the cable for the comp i will send a pic.

I modified the focus of my system a bit. I used to see the box of each pixel. It least it looked like a box. Now i see 3 coloured stripes inside each pixel. blue, green, red, The blue looked like a vertical pixel boundary from further away.

Like I said at 60" the image is real crisp. the pixels look like a faint grid from the sofa - mostly vertical stripes. I cant see going bigger.
 
Me2! said:
DIY basher lol h3ll no!

I didn't really explain well at the beginning. I'm recharging batteries for my camera right now... if i can find the cable for the comp i will send a pic.

I modified the focus of my system a bit. I used to see the box of each pixel. It least it looked like a box. Now i see 3 coloured stripes inside each pixel. blue, green, red, The blue looked like a vertical pixel boundary from further away.

Like I said at 60" the image is real crisp. the pixels look like a faint grid from the sofa - mostly vertical stripes. I cant see going bigger.

That sounds really odd to me .... Ive projected fairly small, and fairly large and have never had color isolation like that .... I think it may be an issue with some of your optics ...
 
I can see the same vertical stripes in the pixels of my projection.

I remember seeing a post by Guy Grotke where he described the same thing. I wonder if it has something to do with the LCD structure or if the optics are separting the colours?

I'm currently using an SGI 1600SW LCD sitting on top of a 3M 9200 ohp.
 
I was being cheeky in my last post. The stripes are supposed to be there. If you can see them thats as good as it gets. You can't invent resolution within the pixels.

I see what you guys mean about digital cameras and projections. Holycr@p! Thats a bad shot! Wonder why it does that?! Besides my finger over the flash...I'll borrow an SLR and scan the picture.
 
Decided to paste the shot anyway for the people that are losing faith in the lack of pictures posted. Its horid but you can see the stripes of the pixels. Yes the whole screen at 60"wide shows these stripes if you get close. Can't imagine wanting to see them at 120".

pic attached. It was cropped but untouched otherwise. I have no idea why the camera has these awful colours. The whole image on the screen is good. Camera was about 1 ft away from the screen at a slight angle.

The pic is of the corner of your display properties, settings with azul( comes with windows XP) as wallpaper. The troubleshoot and advanced buttons are shown.


I will redo with an SLR later.
 

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Hi all,

I understand Me2!'s point about needing a higher resolution to get a bigger image, but by way of comparison have any of you been to the cinema recently?

Their screens are pretty big, so the resolution must be huge, right? What do you think the resolution of cinema film is? 10,000 pixels across? 5,000 pixels?? No, the resolution of film is only somewhere around 3,000 by 2,000 pixels for cinemascope, less for widescreen because it uses less of the frame than 'scope. (BTW, cinema widescreen is not the same as home entertainment widescreen. Cinema widescreen has an aspect ratio of 1.85 to 1, whereas home entertainment widescreen has an aspect ratio of 1.78 to 1, so is slightly narrower. Oh, cinemascope has an aspect ratio of 2.2 to 1)

If you want the best image you can get, should definitely invest in good lenses. And invest is the right word, as the best lenses aren't cheap. A widescreen lens (basically two coated glass lenses in a brass tube) for my cinema projector at work would cost about 400 UK pounds, and a cinemascope lens would cost around 1000 to 1500 pounds!
 
Sorry, but cinema film does have pixels, well sort of anyway. Many movies nowadays are duplicated using machines which use a high resolution CRT or laser to project the movie onto the film stock. Have a look at http://www.celco.com/Technology.asp for an explanation. I underestimated the resolution though. Celco's Fury can print films at a staggering 4096x3072 onto 35mm film!!!

You are getting cinema film confused with photographic film. Conventional photographs are an optical/chemical process and they don't have a 'resolution' in the same way that digital photos do.
 
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