CurtPalme.com Home Theater Forum

km987654 · Posted: Mon Aug 18, 2008 9:32 pm Post subject:

Thanks for all the input. I am looking at applying lens flapping to my PJ which currently does not have this feature. There seems to be a bit of work to make this happen so it seems reasonable to ask the question. I work mostly in Information Technology and over the years I seen many technical upgrades and on paper then would seem to make considerable difference in reality they don't have a great effect because there are many real world factors that influence the performance of any technology. This why I will ususally ask for real comparisons. Some obviouly felt this was going too far. I would note though that those same complainants spents considerable time explaining there positions on this matter (Lens Flapping) with great detail for which I thank them.

People are always free to not respond to any given request for information.

The information provided by some Forum members is very detailed and shows they are passionate about CRT projectors and that is why this is best place to be.

Thanks Again

PJMoore · Joined: 05 Oct 2006 Posts: 99

km - From my perspective, I would never alter my flapping to perform a test simply because it takes so much time and patience to get flapping right. Changing it to satisfy a point of curiousity just wouldn't make sense. Yes - that leaves you in the "trust me" mode (which I dislike a lot) but when everyone says the same thing the same way, I tend to trust the input. I know it is very easy to mod a Sony. I don't know about other PJs. It is worth it, however.

km987654 · Posted: Mon Aug 18, 2008 10:38 pm Post subject:

My system is a Barco 1100. I have Tanks and lens setup from a Ampro 4000 which has Lens Flapping so I though a transplant would be in order. The other driver here is that most of the tubes I have are attached to Ampro tanks and while they are easy to remove I can't say the same for the Barco ones these are almost impossible to remove. So using the Ampro tanks solves two problems.

rabies_70 · Posted: Mon Aug 18, 2008 11:11 pm Post subject:

Last night I finally got to adjust my flapping for the first time where I had a sense of what I was doing. I finally "got it". It actually made sense to me doing the adjustments and watching the image on the screen. I can say without reservation that my test patterns are sharper than they have EVER been in my setup. I'm not exactly sure why I didn't get it before because once I started doing it I was like, Oh, I see. The little sony tool for the G70 made it way easy to go back and forth

ecrabb · Posted: Mon Aug 18, 2008 11:43 pm Post subject:

I'd like to point out that there are certain installations which won't require Scheimpflug. My old 1271 was apparently installed at or near the ideal throw angle and screen sizer for the installed spacers, because I never had a problem with dissimilar sharpness across the screen. The side-to-side and top-to-bottom focus was almost identical. So, if a particular setup's focus is similar across the screen (i.e. the top-bottom and left-right focus as are similar or identical), then adding a flapping mod won't gain you much - if anything.

On the other hand, I installed a friend's 1272 that had "rear" spacers installed - that is to say rear projection zero-degree throw angle spacers. When we set it up as a floor-mount with a fair amount of throw angle, we found out it wouldn't focus worth a crap at the top or bottom of the screen. If it was sharp in the center, the top and bottom were soft. If we focused at the top, the bottom was horrible (and vice-versa). I went through a box of hardware and found some various-sized washers. By trial and error, I found a washer about 1mm in thickness, that when used to shim the top of the lens out, brought the entire screen into focus perfectly. That's flapping.

Nobody wants to screw up their setup to illustrate the effect, but I'll attach a JPG that shows exactly what it will look like if the plane of focus isn't parallel to the screen. This isn't much worse than the 1272 looked before I put the 1mm shims in place. It doesn't take much!

SC

km987654 · Posted: Tue Aug 19, 2008 12:34 am Post subject:

A picture paints a thousand words and shows what 1mm can do!!

Tom.W · Joined: 09 Mar 2006 Posts: 6635

I've been using view cameras for 25 years now and the principle is much easier to see on the large ground glass of an 8X10 camera with multiple swings and tilts.

Depth of field is a big problem with CRT projectors and also 8X10 view cameras as the standard lens is 360mm (just to cover the large negative). You have the same depth of field with an 8X10 view camera using a 360mm lens as a 360mm lens on a 35mm camera.Nil to none so you learn to adjust the focal plane.

At least you can close down the iris and increase the DOF with a camera but with a CRT your stuck wide open. Even very small changes make a very big difference.

I wish you luck with the Barco 1100 !

MikeEby · Joined: 24 Jun 2007 Posts: 5237 Location: Osceola, Indiana

Focus may not be great but damn that geometry is perfect. Mr. Green

Mike

Tom.W · Joined: 09 Mar 2006 Posts: 6635

I was thinking the same thing... Wink

ecrabb · Posted: Tue Aug 19, 2008 4:42 am Post subject:

km987654 · Posted: Tue Aug 19, 2008 6:44 am Post subject:

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

ecrabb · Posted: Tue Aug 19, 2008 6:06 pm Post subject:

Correct, Gary... Unless the projector is specifically set up for zero-throw angle projection, of course. In that case you'd need no vertical flapping at all. Regardless, you're right, though. Unless you have a machine with stepless scheimpflug, your projector will have some default amount of flapping built in. If your install matches or closely matches that built-in compensation, you're good to go. If not, to get optimal focus across the screen, you'll have to adjust flapping by whatever means you have available.

SC

larryk · Joined: 23 Aug 2007 Posts: 106 Location: Edmonton Alberta

I have been conducting some experiments with my XG regarding lens flapping. these units have rings that step from one setting to the next. I have built a prototype lens mount that convert these units to infinate adjustment. I have also built a prototype of a precision focus lever for mechanical focus adjustments. I have not been able to test them properly yet because of other problems with the PJ but when it's all up and running I believe it will help to sharpen things up considerably. I don't know what possibilities there are for other makes of PJ's as I have never seen anything other than a PG and XG series. If there is enough interest I may build a number of these sets.

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

The Marquees already have continuous adjustment, even though they are a massive PITA to adjust. I'm not sure what you'd gain with this.

larryk · Joined: 23 Aug 2007 Posts: 106 Location: Edmonton Alberta

I will have some pics once I have the final version done. I started talking about doing this quite a while ago but it has been so busy this year with project after project that I haven't been able to complete the next level prototype yet. I don't know how this would fit to the adaptor plates or if they would help with the Marquee.