[JapanDave]

Ok, I am getting closer to figuring all this CIH stuff, but I don't know how long throw distances should be for an anamorphic Lens? I have a room that may only allow a 16' throw distance, so is there any way of calculating what throw distance I will need for a "X" sized screen with an anamorphic Lens?


I got this off the net ,but it is not helping me much at all.

1.78:1 screen width = 1.78 * (2.35:1 screen width/2.35)


This calculates out as 0.757 * 2.35:1 screen width


Specifically I am still looking at a JVC HD350 PJ for its 2X zoom feature amoung other things BTW.


Any help is appreciated.

 

[Widlarizer]

Mark told me once, that the minimal throw ratio for the MKIII is 2.0. Otherwise you get vignetting.

 

[JapanDave]



Quote:
Originally Posted by Widlarizer /forum/post/16900165


Mark told me once, that the minimal throw ratio for the MKIII is 2.0. Otherwise you get vignetting.

So that would mean that the widest screen I could get is 8'? I am not liking having limited throw distance at all!

 

[CAVX]

Most anamorphic adapters will require long throws simply due to the fact that the light beam now has to travel through a box on its way to the screen. The rear optic on the MK3 is actually the largest on the market at 100mm x 90mm however, the fact remains, as the TR decreases, the beam angles expand. This expansion will further increase pincushion (which many complain about).

If you would like a very simple way to know if the lens will suit your need, take the room length and divide it by 4.5 to find the ideal screen height for the room.

Disclaimer: The 4.5 figure applies to the MK3 to ensure long enough throws and no vignetting.

 

[Jason Turk]



Quote:
Originally Posted by JapanDave /forum/post/16900192


So that would mean that the widest screen I could get is 8'? I am not liking having limited throw distance at all!

No. That is the widest 16:9 you can get (works out to 54"x96"). But with an HE lens, you can get up to 54"x127".


Key thing with that projector is maintain a 2x TR or longer with any anamorphic lens...partly because of what Mark said and partly because the recessed lens on the JVC.

 

[JapanDave]



Quote:
Originally Posted by CAVX /forum/post/16900228


Most anamorphic adapters will require long throws simply due to the fact that the light beam now has to travel through a “box” on its way to the screen. The rear optic on the MK3 is actually the largest on the market at 100mm x 90mm however, the fact remains, as the TR decreases, the beam angles expand. This expansion will further increase pincushion (which many complain about).

If you would like a very simple way to know if the lens will suit your need, take the room length and divide it by 4.5 to find the ideal screen height for the room.

Disclaimer: The 4.5 figure applies to the MK3 to ensure long enough throws and no vignetting.

Thank you very much for the info. BTW I gave you guys an e-mail the other day and spoke to you guys on the phone.

(I am obviously the guy from Japan)

Quote:
Originally Posted by Jason Turk /forum/post/16901530


No. That is the widest 16:9 you can get (works out to 54"x96"). But with an HE lens, you can get up to 54"x127".


Key thing with that projector is maintain a 2x TR or longer with any anamorphic lens...partly because of what Mark said and partly because the recessed lens on the JVC.

With the 2X TR, is that calculation based on a 16:9 screen or a 2.35:1 screen? And how did you get a screen height of 54", with the divide by 4.5 rule I could only get a 40" high screen? BTW, I have not been able to give you a call due to work commitments, but I will try to do so next week.

 

[Aussie Bob]

Jason, did you remember to measue the depth of that lens recess on the RS-20?

 

[CAVX]



Quote:
Originally Posted by JapanDave /forum/post/16904312


Thank you very much for the info. BTW I gave you guys an e-mail the other day and spoke to you guys on the phone.

(I am obviously the guy from Japan)


With the 2X TR, is that calculation based on a 16:9 screen or a 2.35:1 screen? And how did you get a screen height of 54", with the divide by 4.5 rule I could only get a 40" high screen? BTW, I have not been able to give you a call due to work commitments, but I will try to do so next week.

TRs for HE lenses are typically based on the native 16:9 image width of the projector.


Example: if the 16:9 image width is 8 feet [96"], then the TR of 2.0 = 16 feet [192"]. This is the distance needed between the projectors lens and the screen fabric. This method is fine if the room length is not an issue and if you already have a screen. If you need to find a screen height for a given room, then our 4.5 rule is based on the following:


Example:


Room Length 225" / 4.5 = a screen height of 50".

You would sit no closer then 2x or 100" and no further back than 4x or 200" with 3x or 150" being preferred.


This assumes the projector is mounted as far back as possible. If this is done, generally the beam is small enough and should not vignet with our anamorphic adaptor.

 

[JapanDave]



Quote:
Originally Posted by CAVX /forum/post/16906191


TRs for HE lenses are typically based on the native 16:9 image width of the projector.


Example: if the 16:9 image width is 8 feet [96"], then the TR of 2.0 = 16 feet [192"]. This is the distance needed between the projectors lens and the screen fabric. This method is fine if the room length is not an issue and if you already have a screen. If you need to find a screen height for a given room, then our 4.5 rule is based on the following:


Example:


Room Length 225" / 4.5 = a screen height of 50".

You would sit no closer then 2x or 100" and no further back than 4x or 200" with 3x or 150" being preferred.


This assumes the projector is mounted as far back as possible. If this is done, generally the beam is small enough and should not vignet with our anamorphic adaptor.

Thank you so much for your help. I am am thinking of every possible way to be able to use your lens.

I may have found a way to get a throw distance of 245" to get my desired screen height of 55", the only thing is I need to have the PJ (I think I will go with JVC HD350 for now which has ±34% horizontal lens shift ) offset about 8"-12" off center horizontaly. My question is, will that be possible while using the MKIII? And if so will that offset have a noticable affect on image quality?


Again thanks so much to everyone who has helped me, I am so very greatful.

 

[Franin]



Quote:
Originally Posted by JapanDave /forum/post/16906248


Thank you so much for your help. I am am thinking of every possible way to be able to use your lens.

I may have found a way to get a throw distance of 245" to get my desired screen height of 55", the only thing is I need to have the PJ (I think I will go with JVC HD350 for now which has ±34% horizontal lens shift ) offset about 8" off center horizontaly. My question is, will that be possible while using the MKIII? And if so will that offset have a noticable affect on image quality?


Again thanks so much to everyone who has helped me, I am so very greatful.

I have one and I love it. I also have the JVC HD350 and it compliments the lens well

 

[JapanDave]



Quote:
Originally Posted by Franin /forum/post/16906259


I have one and I love it. I also have the JVC HD350 and it compliments the lens well

Thanks for boost of confidence. Do you know if the lens can be used when the PJ is off center by 8-12" and if so does it affect IQ? Cheers.

 

[Franin]



Quote:
Originally Posted by JapanDave /forum/post/16906266


Thanks for boost of confidence. Do you know if the lens can be used when the PJ is off center by 8-12" and if so does it affect IQ? Cheers.

I got mine professionally installed and im not full bottle in this anamorphic as yet, still learning.

Cavx should be able to have all the answers for you.

 

[CAVX]



Quote:
Originally Posted by JapanDave /forum/post/16906248


My question is, will that be possible while using the MKIII? And if so will that offset have a noticable affect on image quality?

I'll do some testing and get back to you.

 

[JapanDave]



Quote:
Originally Posted by CAVX /forum/post/16909752


I'll do some testing and get back to you.

Thanks you.

 

[littlerabbit]

I will wait for thr consequence.

 

[JapanDave]



Quote:
Originally Posted by CAVX /forum/post/16909752


I'll do some testing and get back to you.

How did you get on with the testing?

 

[CAVX]



Quote:
Originally Posted by JapanDave /forum/post/16933108


How did you get on with the testing?

You can have a limited amount of H offset, then you will need to tilt the lens horizontally as well. Unless you really don't have any choice, I am recommending you keep the projector/lens as straigh as possible.

 

[JapanDave]



Quote:
Originally Posted by CAVX /forum/post/16937047


You can have a limited amount of H offset, then you will need to tilt the lens horizontally as well. Unless you really don't have any choice, I am recommending you keep the projector/lens as straigh as possible.

Thanks, at the moment, I can get away with 5-6" off ceter horizontaly on a 130" wide screen. I not sure how the calculations work, but from the way I worked it out that is about a 5% shift. Will that work without having too much loss of PQ?

 

[CAVX]



Quote:
Originally Posted by JapanDave /forum/post/16937257


Thanks, at the moment, I can get away with 5-6' off ceter horizontaly on a 130" wide screen. I not sure how the calculations work, but from the way I worked it out that is about a 5% shift. Will that work without having too much loss of PQ?

If you using H shift in the projector, all you have to do is move the lens in the same direction so it doesn't vignette. The prolems occur when you go past the projector's allowed H shift and have to rotate the projector. Then you introduce keystone and then you have problems. If your image can be kept straight, then happy days

 

[JapanDave]



Quote:
Originally Posted by CAVX /forum/post/16937279


If you using H shift in the projector, all you have to do is move the lens in the same direction so it doesn't vignette. The prolems occur when you go past the projector's allowed H shift and have to rotate the projector. Then you introduce keystone and then you have problems. If your image can be kept straight, then happy days

Exellent, it is well within the PJ horizontal lens shift.

Would this still mean I would have to rotate the lens? (I guess it would)


Edit , that number was suposed to be 5-6 inches not ft BTW