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Discussion Starter #1
Hi all,

I'm relatively new here. Harpmaker has been helping me in another thread (I mixed Black Widow with a new AAA-F batch) but I thought that my questions or complications should now be put into a new thread for all to maybe learn from and because I wanted to get specific.

Room - a living room with pretty good dark curtains and white walls and ceiling.
Projector is the Panasonic PT-AE8000 or as Panasonic likes to do a PT-AT6000 over here.
I watch both TV and Movies but would prefer this time to set up a 2.35 aspect ratio screen. Being able to see and eat while watching is important sometimes.

I want to set the projector at around 15 feet or (4.6m) and the screen size I have painted has a diagonal of 115 inches (2.9m). I just wanted to start big and work down to a size I prefer.

I understand also from the review of the Panasonic PT-AT8000 from projector central that the brightness of the projector is as follows.

Mode - Lumens
Cinema 1 - 822
Cinema 2 - 1612
Game - 1673
Normal - 1752
Dynamic - 2471
Rec. 709 - 821
D-Cinema - 872

I don't fully understand the calculator (I dont know which brightness setting this is on.) and I have read here some are not a fan of it or them generally, but it says that the Panasonic will produce around 17 fL. This I have also read is acceptable.

It now also seems I have access to both the old and new AAA-f (i have to buy some more and now from a new source which has both old and new). Thus I now have paint with NCS S 0907 Y70R or the Bermuda Beige. I also have paint with RAL 7038 (N7.9).

So my questions;

Are my calculations above with the projector central calculator correct?
I know screen size and brightness at the end of the day are subjective but please give me your opinion, given my situation?
In your opinion should I be using Black Widow (ie. BB and AAA-F) or Black Widow Ultra (ie. RAL 7038 (N7.9) and AAA-F)?

Any other tips or pointers would be helpful.
 

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It now also seems I have access to both the old and new AAA-f (i have to buy some more and now from a new source which has both old and new). Thus I now have paint with NCS S 0907 Y70R or the Bermuda Beige. I also have paint with RAL 7038 (N7.9).
I am very interessed to locate the old formula of AAA-F. Can you tell me where did you find it?

How big is your screen? How many hours on the lamp? Are you going to calibrate your projector or not?
 

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Discussion Starter #3
I am very interessed to locate the old formula of AAA-F. Can you tell me where did you find it?
I'm in Munich. I have not got it yet but on the phone it sounded like he had 1 or 2 old bottles of 120ml. They don't have an online shop.

How big is your screen? How many hours on the lamp? Are you going to calibrate your projector or not?
Projector is brand new. In fact not even out of the box. I am flexible with the screen size, you can read above the maximum or starting screen size.
 

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Footlamberts (fL) = Foot-Candles x Gain

Foot-Candles = Lumens per square foot of screen surface

To calculate the footlamberts you will get, first calculate the screen surface area in square feet:

Your example was 115" diagonal (106" wide x 44" high) so the width if feet is 106/12, and height is 44/12, or
8.83 ft x 3.67ft. Therefore the area is 32.39 square feet

Say you choose to run in the lowest setting to get a good image for movies, you would have 821 lumens available (Rec. 709). So, your foot-candles would be 821/32.39 or 25.3.

Assuming you use a screen with a Gain of 1.0, calculate the Footlamberts as 25.3 x 1.0 which is still 25.3 fL.

Now, you need to consider that your lamp will age and decrease in brightness to 50% of the new lamp value.

So take half of 821 and re-calculate the fL:

821/2 = 410.5

410.5 lumens / 32.39 square feet = 12.7 foot-candles

With a 1.0 gain screen, its still 12.7 fL.

12.7 might be a little low for some and may force you to change settings towards the end of the lamp life.

The Projectorcentral.com calculator does something like this but they don't tell you what initial lumens setting they pick, nor what they assume the lumens will be when the lamp gets old.

If you follow the calculation above you can do it all on your own! Good Luck!
 

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Now, you need to consider that your lamp will age and decrease in brightness to 50% of the new lamp value.

Can i ask how you came up with such percentage?

Most of the times, brightness drop is due to dust in the wheel or in the panels. As a matter of fact, my two projectors have a drop of 20-30% after 800 - 1500 hours caused by my lamp only.
 

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I'm not answering for Pyrometman, but I have always seen the 50% drop-off value used for lumens during the life of a normal PJ lamp. I have never read anything documenting that "fact" though. :ponder: This is yet another very good reason to purchase an inexpensive light meter that measures in Lux or Foot-Lamberts. They can be had online for $20 or less and are as accurate in measuring light as photographic meters costing hundreds of dollars. :nerd:
 

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Can i ask how you came up with such percentage?

Most of the times, brightness drop is due to dust in the wheel or in the panels. As a matter of fact, my two projectors have a drop of 20-30% after 800 - 1500 hours caused by my lamp only.

A lot of lamp manufacturers don't give a rating to final lamp failure, they give a life rating (in hours) to 50% lamp brightness.
 

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Yes, Don, i don't question the percentage of the drop. The thing is that many many people hardly ever go in service for cleaning after 1000 or so hours, and i can assure you that a great percentage of brightness drop is due to dust in the internal parts and especially the light path. Of course, the majority ''blames'' the lamp's poor performance but this is only the half truth.
 

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Yes, Don, i don't question the percentage of the drop. The thing is that many many people hardly ever go in service for cleaning after 1000 or so hours, and i can assure you that a great percentage of brightness drop is due to dust in the internal parts and especially the light path. Of course, the majority ''blames'' the lamp's poor performance but this is only the half truth.
Yes, that is also true...and some projectors are designed better than others to keep dust out of the light path...but it's always a good idea to keep it clean.
 

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Discussion Starter #10
Thank you Pyrometman for your formula that sounds good. There is one variable that I don't see in your calculation and that is the distance to the screen? Am I missing something here?

Also I have a burning question or decision to make and that is what paint to use or would be suitable and I am hoping to get opinions. As I wrote above it appears I have access to both old and new AAA-F and I have already bought two different base paints so what in you opinion is the best course of action?
 

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Thank you Pyrometman for your formula that sounds good. There is one variable that I don't see in your calculation and that is the distance to the screen? Am I missing something here?

Also I have a burning question or decision to make and that is what paint to use or would be suitable and I am hoping to get opinions. As I wrote above it appears I have access to both old and new AAA-F and I have already bought two different base paints so what in you opinion is the best course of action?
darbid,

The throw distance isn't necessary for calculation of the Footlamberts. It is only needed to calculate how wide your image will be, based on the throw ratio range of your projector.

However, it is in your interest to have as long a throw as possible. Based on what you have stated for your room/ambient lighting conditions, you may want to choose a light gray screen, maybe N9 that has some specular reflectivity as well to bring the gain back to around 1.0. The long throw distance helps because the use of screens that have some specular reflectivity will not direct light back to you if the throw distance is very short. The reason for that is because the angles become greater, particularly to the bottom corners (ceiling mounted setup). The light in the corners is not reflected back to you as much as in the center and you start to see less brightness uniformity across the screen. You may want to research the Cream&Sugar DIY solution found here in this forum. You should also get input from others as well as someone may have a better solution. More input is always helpful to weigh the positives and negatives.
 

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Ok thank you. This is all new to me.

So I have bought already (about N7.9) (RAL7038) - I was thinking I would need something darker. I also have the old Black Widow base paint. I can add AAA-F to both to increase the reflectivity that you talk about. So is the Original Black Widow base paint going to be more than N7.9?

PS. Actually I am surprised that you are suggesting something so light. On my reading N7.9 is around the Veil grey which is what is suggested in most cases.
 

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Ok thank you. This is all new to me.

So I have bought already (about N7.9) (RAL7038) - I was thinking I would need something darker. I also have the old Black Widow base paint. I can add AAA-F to both to increase the reflectivity that you talk about. So is the Original Black Widow base paint going to be more than N7.9?

PS. Actually I am surprised that you are suggesting something so light. On my reading N7.9 is around the Veil grey which is what is suggested in most cases.
I think the original Black Widow was around N7.5 but with a gain of 0.88. It might be a bit dim for the screen size you wanted to achieve...assuming you set your projector on one of the lower lumen settings to get a better image and longer lamp life. If you choose to use a different setting (higher output), then perhaps you can recalculate your expected Footlamberts and use a darker gray paint. I think most people like to achieve 15 or greater Footlamberts.
 
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