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-   -   Some GrayHawk Pics (http://www.avsforum.com/forum/23-screens/19314-some-grayhawk-pics.html)

Carey P 01-04-2001 08:06 PM

For anyone interested. I posted a few pics here. The screen is non-perf. You can see the projector in one of the shots.

Note the brightness with ambient lighting in the wide shots. Close-ups were in total darkness. Enjoy.

Carey

DanHouck 01-05-2001 05:49 AM

Sweet!

Could you describe the setup? Projector, screen size, feed, etc.?

Thanks!

Dan

Federico 01-05-2001 06:19 AM

Nice pics!
I would like to see a picture with white reference over the grey screen.
Federico

Carey P 01-05-2001 07:21 AM

My reviews are elsewhere. I just decided to post some pics, as I needed to use up a roll the other day. These were scanned from 4x6 prints (used real film) at 150 ppi with histograms set to match the print as best possible.

The setup is described in the page title. Though I neglected to point out that these are all 480p DVD images from a Toshiba 6200 player. I don't have HDTV yet and I'm still waiting for my HTPC. I expect to take more pics when the Panamorph arrives too.

I didn't take any pictures when I was doing the testing and comparisons with white fields, etc. Note, however, that a white field shot would simply look white to the eye or the camera without a pure white reference right next to it. Even then, it would take careful exposure close up to see the difference.

Carey


Dean McManis 01-05-2001 12:48 PM

Carey,

My screen's picture looks different than these pictures, but there are many variables here with a different projector, and DVD player. As well as the camera used for the pictures, and scanner/software.

Your white level looks a bit high, but that could be from any one of the factors mentioned above.

By the way, you HT room looks great!

-Dean.

kelliot 01-05-2001 01:00 PM

How about a photo of just the screen with no projection with ambient lighting?

Carey P 01-05-2001 02:53 PM

Dean,
You're right. There are a lot of variables to consider. Basically it was just set up for the way it looked best. If it looked overly bright, it was due to the camera exposure setting more than anything else. On the wide shots I was trying to get a balance of ambient and screen lighting so it metered the same. That way I wouldn't over or underexpose too much on the picture and still get the room. 28mm for the wide angles and 50mm for the close-ups. I used standard Kodak 200 ASA Print film and a snapscan 1212p scanner. Nothing special. FWIW, I keep the projector Gamma at standard setting now. There's not much else to adjust but color, brightness and contrast with 480p setting.

Ken,
I'll be glad to take that photo with my next roll, or when I borrow a digital camera from work. However, I don't think this will do it justice, since I would need a very balanced white ambient lighting and need the white walls in the background to see any difference. The gray isn't really dark enough to show up on film very well.

Carey

kelliot 01-05-2001 07:35 PM

Such a photo (digital or film) would give people an idea of the gray level. Ideally a Kodak gray card with it and anything white (the back side of Kodak cards is calibrated 90% white) gives one a pretty good idea of how gray it is.


As an example, here is my DIY gray screen with Kodak 90% and 18% cards up against it.
http://home1.gte.net/kelliot/avsforum/HTsmall.jpg

[This message has been edited by kelliot (edited 01-05-2001).]

Carey P 01-05-2001 08:09 PM

I agree that without some sort of reference it wouldn't make much sense. I don't have those cards, but I'll see what I can do.
-Carey

KBK 01-06-2001 04:04 PM

What you should do is go to a photo shop and pick up the 'Kodak Grey Scale' card, which should be about $10, and it can be placed in front of the screen, for a close up shot, and then one further back. There is a LARGER one out there, that is about 14" long, not the 9" one. The larger one is only a couple of bucks more, and is much better for these purposes.

The card has, 20 f stops of grey level, from completely white to completely black.

This allows us to calibrate our understanding according to what we know of the grey-scale card, and allows us to compensate for irregularities and inconsistencies with the software encoding, decoding, our display at our end, etc. If the twenty gradations are truncated in some fashion by encoding and other such considerations, it will show to a certain extent when using this card.


I am going to send this card in (two different versions, but both identical -one older, and the other newer) to a place that will calibrate it to the grey % numbers instead of f stops, and to the same level and standards as the National Bureau of Standards. The gentleman involved is doing it to help us out here (nobody knows who it is, or where it is being done, and it has to stay that way,.... shhh......)

Carey P 01-08-2001 08:44 PM

Alright. I happened to get my hands on a digital camera today, but I still don't have Kodak cards. For now, I put up a bright white (96+ inkjet) paper and the DaLite HC DaMat sample (one of the original ones). This may tell you something. Then again...

I had to use a flash to get any consistancy and I didn't want to take it straight on to avoid hot-spotting. Anyway, here they are (These are the small versions). Enjoy. -Carey
http://home.earthlink.net/~prometheus5/grayh1.jpg
http://home.earthlink.net/~prometheus5/grayh2.jpg
http://home.earthlink.net/~prometheus5/grayh3.jpg

kelliot 01-08-2001 10:35 PM

Great job Carey,
The Stewart looks very similar in tone to my fabric screen. If the texture is good and it has some gain, then I may be in business. If it were just an itsy bitsy bit darker...

kelliot 01-08-2001 11:16 PM

After taking a look at your photos, KBK's photos, my screen and samples, etc., I think that the HC-DaMat is closer to a 35% gray. I think I like something closer to a 63% gray (density =.2 on the Kodak gray scale) with some compensating reflective gain.

Carey P 01-09-2001 07:35 AM

Maybe I've got it reversed, but it seems like 63% gray would be way too dark. You must have plenty of lumens to spare. For me, with supposedly 1000 lumens, I think the picture is acceptable, even with some ambient light. However, I find that with the Sharp, I can certainly make the image much brighter, but then I don't have any more contrast control to compensate for it, so the picture gets more washed out.

So for this projector at 1000 lumens, this screen is perfect. If it were any darker, I don't think the improved (if any) contrast will compensate for the required increase in the brightness setting.

It may be that once I get my HTPC, I may have more control over these things from the DVD end, I don't know. Of course, the Panamorph will help, but I'm trying not to think about that any more until it someday shows up at my door.

kelliot 01-09-2001 08:12 AM

I have 1300 lumens and 24 ft^2 screen.


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