sensable Lux

George Beck · April 19th, 2004, 06:28 PM

hey.. next time you have no excuse! =)
(you have a DV cam now)

Frank Granovski · April 19th, 2004, 06:56 PM

I'll have to wait for old age dementia to set in. It won't be long now. :-))

George Beck · April 19th, 2004, 07:09 PM

hehe.. looking for other excuses, ey? ;-)

you start the fire now, I'm coming over with marshmallows in a few min. :)

Frank Granovski · April 19th, 2004, 07:36 PM

I do have one other excuse: no fire insurance. :-((

Rob Belics · April 19th, 2004, 08:39 PM

George, since you have the cam why can't you test it yourself?

BTW, you tell people I'm wrong and, as a professional trying to help you understand, I'm insulted. You don't seem to be able to comprehend what you are being told and want others to do your work for you.

George Beck · April 19th, 2004, 09:36 PM

I'm between cams right now. I'm waiting for Gs400 to come out this Jul. So I can't test it. If I could I would have done it. =/

The problem is that is not correct.

The CCD of GS400 will be different, and will not produce the same results as dv953. When I get the cam I'll test it, and maybe post pics if I don't forget.

It's not the wide angle, it's the extra mm of the lens that will make a difference.

The error you make comes from the fact that you thing of the extra lens only in turms of providing wider angle. This would be right if the wide angle lense you put on the cam is the same size as your original lens (like Frank had done with the 37mm wide angle). In this case you would be right, but we are not, and never talked about this case. We are talking for lens with larger surface area.

Frank Granovski · April 19th, 2004, 09:43 PM

When I mentioned 37mm threads, I meant 37mm threaded wides with my 37mm threads on my 2 cams; and 43mm threaded wides for my 1 43mm threaded cam.

George Beck · April 19th, 2004, 09:48 PM

oh... ok

excuse my mouse-drawing:
http://www.alienminds.ca/extra-lens.jpg
(very simplified)

case2:
http://www.alienminds.ca/extra-lens2.jpg
(wide-angle same size, same amount of light from apple, but focused on smaller surface)

Justin Boyle · April 20th, 2004, 12:28 AM

George i had the same belief as you and i still dont know if i understand fully. A lot of the posts on here clearly show that people haven't really read what each other are saying they just keep on saying the same thing all along. I don't think anything has been gained from all this C!@p. anyways can anyone read my post on the first page and explain to me why i am wrong. and i think the arguement is that with bigger lens you catch more light like the bucket. so more light means more energy and therefore since that light is being focused on the ccd the same size no matter what then wouldn't/shouldn't it help. why and why not,. lets forget what has been said and the tension that has built and start fresh from this. Thanks. It just seems logic from my explanation of a 2x converter.

Thanks

Justin

Andre De Clercq · April 20th, 2004, 04:54 AM

Convertor lenses are not designed to change lux ratings. I think in this thread, there is a lot of confusion between what we all learned at school about (simple) lenses and complex optical systems on the other hand . In practical terms, one should know that a convertor "lens" is an a-focal optical piece of glass which only changes the angle of the incoming light on the main camera lens. The amount of light hitting the CCD remains determined by the main optics. The convertor lens gradually "prebends" the incoming light, just like mirrors which can bend the light. The larger front area is needed for redirecting the light without vignetting. Because the convertor lens is a-focal ((=infinite focal lenght ) the captured light isn't concentrated into the main optics, so the larger area doesnt make any difference. Only powerfull raytracing programs can show exactly what happens in detail.

George Beck · April 20th, 2004, 08:51 AM

Justin, I agree... I'm tired of repeating myself.

Andre, you are saying that if you put 37mm wide angle lens on 37mm cam there will be no change. how about 54mm wide angle..
how about 250mm?
you are saying that there will be no difference between having those different lens.

arguments like "Only powerfull raytracing programs can show exactly what happens " or "Convertor lenses are not designed to change lux ratings."
no one said they are designed for that, that doesn't mean it does not happen either....

Andre De Clercq · April 20th, 2004, 02:42 PM

Yes George, once the convertor lens is "large enough", this means just shows no vignetting at the wide position of yr camera optics, the lens diameter doesn't make any difference. So you can put a 250mm diameter convertor in front of yr 37 mm camera optics... only a small central part of the convertor will be "seen" by the CCD(s). By "not designed for.." I mean that the optical challenges for convertor design are avoiding field distortion and field curvature while keeping good resolution specs. Most of the time this ends up in some lightloss. With raytracing programs one can verify and optimize those parameters. One could also easely verify how much light would be wasted with the 250 mm lens on a 37 mm cam.

George Beck · April 20th, 2004, 03:39 PM

Andre, I didn't want to go into this but.... see.. the light collected by a lens is determined by it's surface area (the higher the angle - the more surface, the higher the diameter - the more surface again)
if the lens is doing what it is supposed to do then that light will be transfered to the original lens.

maybe 250mm was a bit too much, but this (85mm) can and was used by someone, on dv953:
http://www.fortvir.net/albums/tom-s-photo-album/deep_curvature.sized.jpg

and I was wondering IF the extra collected light by the lens was enough to make a difference after considering the light loss of aditional light-direction correction trough the extra lens(es).

the fact of the increased (amount of) light collected is beyond contestation, I was wondering how much after the additional loss is left and if it makes visible difference.
anyway... we are going no where like this.
when I get my cam, I'll make the tests and post the results.

Frank Granovski · April 20th, 2004, 03:50 PM

Quote:

we are going no where like this. when I get my cam, I'll make the tests and post the results.

Why not do it with your PV-DV953 now? So we can see your scientific results sooner (I'm assuming your background is broadcast engineering like Andre). The GS400 may be many months away. :-))

I might just have to reconsider a 37mm and 43mm wide angle for that extra LUX.

George Beck · April 20th, 2004, 04:01 PM

Frank I think I answered this question some time ago =)
The only miniDV cam I have available now is not my personal cam and it's canon XL1.
If I could I would have done it and not even talked about that in a forum.
Maybe Andre can use the "raytracing programs" and tell us the results when we use this:

http://www.fortvir.net/albums/tom-s-...ture.sized.jpg

on dv953

ps. do you want to know my background too?

ps2.how about considering the 85mm?
http://www.fortvir.net/albums/tom-s-...ture.sized.jpg

April 20th, 2004, 12:28 AM	#39
Justin Boyle Major Player Join Date: Dec 2003 Location: Australia Posts: 207	George i had the same belief as you and i still dont know if i understand fully. A lot of the posts on here clearly show that people haven't really read what each other are saying they just keep on saying the same thing all along. I don't think anything has been gained from all this C!@p. anyways can anyone read my post on the first page and explain to me why i am wrong. and i think the arguement is that with bigger lens you catch more light like the bucket. so more light means more energy and therefore since that light is being focused on the ccd the same size no matter what then wouldn't/shouldn't it help. why and why not,. lets forget what has been said and the tension that has built and start fresh from this. Thanks. It just seems logic from my explanation of a 2x converter. Thanks Justin __________________ jlboyle

April 19th, 2004, 06:28 PM	#31
George Beck Major Player Join Date: Apr 2004 Location: Toronto, ON Posts: 244	hey.. next time you have no excuse! =) (you have a DV cam now)

April 19th, 2004, 06:56 PM	#32
Frank Granovski Outer Circle Join Date: May 2002 Location: Hope, BC Posts: 7,524	I'll have to wait for old age dementia to set in. It won't be long now. :-))

April 19th, 2004, 07:09 PM	#33
George Beck Major Player Join Date: Apr 2004 Location: Toronto, ON Posts: 244	hehe.. looking for other excuses, ey? ;-) you start the fire now, I'm coming over with marshmallows in a few min. :)

April 19th, 2004, 07:36 PM	#34
Frank Granovski Outer Circle Join Date: May 2002 Location: Hope, BC Posts: 7,524	I do have one other excuse: no fire insurance. :-((

April 19th, 2004, 08:39 PM	#35
Rob Belics Major Player Join Date: Apr 2003 Location: St. Louis, MO Posts: 581	George, since you have the cam why can't you test it yourself? BTW, you tell people I'm wrong and, as a professional trying to help you understand, I'm insulted. You don't seem to be able to comprehend what you are being told and want others to do your work for you.

April 19th, 2004, 09:36 PM	#36
George Beck Major Player Join Date: Apr 2004 Location: Toronto, ON Posts: 244	I'm between cams right now. I'm waiting for Gs400 to come out this Jul. So I can't test it. If I could I would have done it. =/ The problem is that is not correct. The CCD of GS400 will be different, and will not produce the same results as dv953. When I get the cam I'll test it, and maybe post pics if I don't forget. It's not the wide angle, it's the extra mm of the lens that will make a difference. The error you make comes from the fact that you thing of the extra lens only in turms of providing wider angle. This would be right if the wide angle lense you put on the cam is the same size as your original lens (like Frank had done with the 37mm wide angle). In this case you would be right, but we are not, and never talked about this case. We are talking for lens with larger surface area.

April 19th, 2004, 09:43 PM	#37
Frank Granovski Outer Circle Join Date: May 2002 Location: Hope, BC Posts: 7,524	When I mentioned 37mm threads, I meant 37mm threaded wides with my 37mm threads on my 2 cams; and 43mm threaded wides for my 1 43mm threaded cam.

April 19th, 2004, 09:48 PM	#38
George Beck Major Player Join Date: Apr 2004 Location: Toronto, ON Posts: 244	oh... ok excuse my mouse-drawing: http://www.alienminds.ca/extra-lens.jpg (very simplified) case2: http://www.alienminds.ca/extra-lens2.jpg (wide-angle same size, same amount of light from apple, but focused on smaller surface)

April 20th, 2004, 04:54 AM	#40
Andre De Clercq Major Player Join Date: Sep 2002 Location: Belgium Posts: 804	Convertor lenses are not designed to change lux ratings. I think in this thread, there is a lot of confusion between what we all learned at school about (simple) lenses and complex optical systems on the other hand . In practical terms, one should know that a convertor "lens" is an a-focal optical piece of glass which only changes the angle of the incoming light on the main camera lens. The amount of light hitting the CCD remains determined by the main optics. The convertor lens gradually "prebends" the incoming light, just like mirrors which can bend the light. The larger front area is needed for redirecting the light without vignetting. Because the convertor lens is a-focal ((=infinite focal lenght ) the captured light isn't concentrated into the main optics, so the larger area doesnt make any difference. Only powerfull raytracing programs can show exactly what happens in detail.

April 20th, 2004, 08:51 AM	#41
George Beck Major Player Join Date: Apr 2004 Location: Toronto, ON Posts: 244	Justin, I agree... I'm tired of repeating myself. Andre, you are saying that if you put 37mm wide angle lens on 37mm cam there will be no change. how about 54mm wide angle.. how about 250mm? you are saying that there will be no difference between having those different lens. arguments like "Only powerfull raytracing programs can show exactly what happens " or "Convertor lenses are not designed to change lux ratings." no one said they are designed for that, that doesn't mean it does not happen either....

April 20th, 2004, 02:42 PM	#42
Andre De Clercq Major Player Join Date: Sep 2002 Location: Belgium Posts: 804	Yes George, once the convertor lens is "large enough", this means just shows no vignetting at the wide position of yr camera optics, the lens diameter doesn't make any difference. So you can put a 250mm diameter convertor in front of yr 37 mm camera optics... only a small central part of the convertor will be "seen" by the CCD(s). By "not designed for.." I mean that the optical challenges for convertor design are avoiding field distortion and field curvature while keeping good resolution specs. Most of the time this ends up in some lightloss. With raytracing programs one can verify and optimize those parameters. One could also easely verify how much light would be wasted with the 250 mm lens on a 37 mm cam.

April 20th, 2004, 03:39 PM	#43
George Beck Major Player Join Date: Apr 2004 Location: Toronto, ON Posts: 244	Andre, I didn't want to go into this but.... see.. the light collected by a lens is determined by it's surface area (the higher the angle - the more surface, the higher the diameter - the more surface again) if the lens is doing what it is supposed to do then that light will be transfered to the original lens. maybe 250mm was a bit too much, but this (85mm) can and was used by someone, on dv953: http://www.fortvir.net/albums/tom-s-photo-album/deep_curvature.sized.jpg and I was wondering IF the extra collected light by the lens was enough to make a difference after considering the light loss of aditional light-direction correction trough the extra lens(es). the fact of the increased (amount of) light collected is beyond contestation, I was wondering how much after the additional loss is left and if it makes visible difference. anyway... we are going no where like this. when I get my cam, I'll make the tests and post the results.

April 20th, 2004, 04:01 PM	#45
George Beck Major Player Join Date: Apr 2004 Location: Toronto, ON Posts: 244	Frank I think I answered this question some time ago =) The only miniDV cam I have available now is not my personal cam and it's canon XL1. If I could I would have done it and not even talked about that in a forum. Maybe Andre can use the "raytracing programs" and tell us the results when we use this: http://www.fortvir.net/albums/tom-s-...ture.sized.jpg on dv953 ps. do you want to know my background too? ps2.how about considering the 85mm? http://www.fortvir.net/albums/tom-s-...ture.sized.jpg