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HDTV Display Devices, Recorders and Programming In here you can discuss subjects on Plasma TV's, LCD TV's, Projectors and more high definition displays. Also discuss HDTV hardware, receivers and programs for Satellite, Over-the-Air, Cable, and FIOS



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Old 09-08-2006   #1 (permalink)
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HD Pictures for a Projector?

Can anyone tell me is there a digital camera available that I can take HD picture fro my Panasonic HD 720p 900 projector?
I use a Canon Powershoot A80 and the pictures on the screen are just not good enough!
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Old 09-08-2006   #2 (permalink)
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Re: HD Pictures for a Projector?

I have a Panasonic PT-AE500E HD projector and have tried several digital cameras to take a photo; all giving the same issue. From my experience, the contrast goes so strong that anything dark turns black, anything bright becomes washed out and the picture looks a mixture of green, cyan and blue like if the red contrast was turned way down. In fact, no matter what I tried adjusting on my camera, there was no way I could take the shot such that both the highlights and shadows came out in the picture. The following photo shows an example of the issue I have with the projector's default adjustment, set to 'Normal':



As taking digital photographs was my only means of capturing HD screenshots for the last few reviews I carried out on HD upscaling DVD players, I had to resort to adjusting the actual projector's brightness, contrast and RGB settings in order for me to capture a decent (but not perfect) screenshot. Luckily my camera does not pick up moiré from the picture like it does from LCD monitors and TV sets.

To calibrate your projector for picture taking, first you will need to set your camera to a totally manual mode if your camera has this setting. This is important if you need to take screenshots of both bright and dark scenes, however you will probably get away with aperture priority if you don't have a full combined manual aperture & shutter speed adjustment mode. Next, set your camera's ISO to as low as it goes, set the white balance to cloudy and set the camera on something stable, such as a tripod.

Now get hold of a colour calibration chart with red, green and blue bars ranging from their darkest shade to their brightest shade. For my calibration chart, I simply drew a sequence of red, green and blue squares ranging from values of 0 to 255 in steps of 16. I did one final bar in shades of grey to check its white balance from the darkest shade of grey to its brightest shade. As you can see in the following photo, this is the issue I had:



The first thing I done is set the camera to manual, set its aperture as wide as it could go and then manually adjusted the shutter speed on the camera until the saturated part was roughly on par with the blackened out part of the bars. Unfortunately, if I tried adjusting the camera such that it picked up the brightest shades fine, I completely lost everything from midway down and if I adjusted the shutter such that it picked up the darkest shades, the camera was running into seconds of exposure. So, I adjusted the brightness of the projector until the darkest shades of blue & green started showing on-screen on the camera and then began decreasing the contrast until the brightest shades could all be made out.

At this point, it is possible to take photos with the full range of green & blue. In order to get the red, I began increasing the red's brightness on the projector until its darkest shade started showing. Finally, I took a photo to check the colour rendering on the computer using a photo editing software's dropper tool (in my case I use the GIMP). As you can see in the following photo, I got a more accurate reproduction of the colours, however it is still not perfect due to the red and blue saturating at their brightest shades:



So this time I began adjusting the individual RGB brightness levels by lowering and increasing them down by a few levels, taking a photo and repeating this process several times. I would then view the photos on the PC and check at which point did the individual colours stop turning black (where the RGB values are about identical) at their darkest shade. I repeated the process for the RGB contrast levels to find at which point did the individual RGB levels stop maxing out (>250) at their brightest shades. Unfortunately, I have found an issue in that there is quite a bit of leakage between the colours, at least on my camera. For example, if I adjust the blue such that it is around 220, I end up with a green value of 40, however this is likely an issue with the colour filtering in the camera’s sensors. Once you get the levels all adjusted, you should be able to start taking photos of your projected image. Here is an example of the first screenshot after doing some quick RGB adjustments using this technique:



Assuming you have not used up the setting memories on your projector, I would recommend storing this as a memory such that you can easily change to this memory to capture a photo and then switch back to the default for regular viewing. In fact, just to give an example of how differently my camera sees the projector screen compared with the eye, the above photo looks extremely weak in contrast and rather red when looking at it directly, yet the above is how my camera picks it as. Unfortunately the above screenshot still does not look anywhere near like what the default setting looks to the eye, however it is still much better than the first photo shown at the top of this post before any adjustment was made.

Good luck with your adjustments.
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