Researching likely 35mm adaptor use on SI2K.

Bob Hart · September 15th, 2010, 10:14 PM

Dennis and Hien, if you are around, here is a theortical query for you.

Have you been told any experiences relating to infra-red contamination of images when deep ND filtering is used with groundglass devices?

Mixed visible and IR sources have a very significant negative effect on tube-based night-vision as far as image clarity is concerned. My imagining is that the same might apply over the much longer optical path via adaptors and that maybe IR light-loss through the adaptor path may be also less than for visible light.

Dennis Wood · September 16th, 2010, 01:05 PM

Bob, I've observed some very strange things with regard to ND filters and IR, particularly on our EX1 (another CMOS camera!). With the SI-2K, and Ari's advise regarding IR, I'm guessing there's a very good chance that something interesting is going on outdoors.

The chart looks good.

Cheers,
Dennis.

Bob Hart · September 28th, 2010, 08:30 AM

Now the flu is done and dusted and I am only half-dead, I thought I'd get one of the hard bits over first and try the relay in low light in a less well lit corner of the Armadale Retail dragstrip.

The relay was wide-open to provoke any softness it might have. The lenses were Noct-Nikkor 58mm f1.2 and Nikon 28mm f1.4, both backed off into a sweeter spot than wide-open. Camera gain was set to 0db. It is all about not being a fair test. I only shot 0db. I was getting some unwelcome attention from some people in a car across the road out of the shot. So I did not shoot at higher gains but packed up and left. It is a bit of a crimmy neighbourhood. I think they thought I might have been running a speed-camera, something I have been confronted with previously.

Here are a few grabs, two standard, two pushed in post. In the pushed grabs, I dropped the blue channel quite a lot. The camera white-balance was set to 3200K.

Given the hostile conditions, it seems to be resolving quite well.

Bob Hart · October 28th, 2010, 01:56 PM

I have just received the True-cut IR filter so will resume my tests with the Cinevate varifocal relay. I will also try it with the anti-aliasing filter removed as it is expected that the groundglass itself, with a notional 5 micron "grain" over an approx 27,000 micron groundglass screen width will perform that function.

September 15th, 2010, 10:14 PM	#16
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,476	Dennis and Hien, if you are around, here is a theortical query for you. Have you been told any experiences relating to infra-red contamination of images when deep ND filtering is used with groundglass devices? Mixed visible and IR sources have a very significant negative effect on tube-based night-vision as far as image clarity is concerned. My imagining is that the same might apply over the much longer optical path via adaptors and that maybe IR light-loss through the adaptor path may be also less than for visible light. Last edited by Bob Hart; September 15th, 2010 at 10:14 PM. Reason: error

September 28th, 2010, 08:30 AM	#18
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,476	Now the flu is done and dusted and I am only half-dead, I thought I'd get one of the hard bits over first and try the relay in low light in a less well lit corner of the Armadale Retail dragstrip. The relay was wide-open to provoke any softness it might have. The lenses were Noct-Nikkor 58mm f1.2 and Nikon 28mm f1.4, both backed off into a sweeter spot than wide-open. Camera gain was set to 0db. It is all about not being a fair test. I only shot 0db. I was getting some unwelcome attention from some people in a car across the road out of the shot. So I did not shoot at higher gains but packed up and left. It is a bit of a crimmy neighbourhood. I think they thought I might have been running a speed-camera, something I have been confronted with previously. Here are a few grabs, two standard, two pushed in post. In the pushed grabs, I dropped the blue channel quite a lot. The camera white-balance was set to 3200K. Given the hostile conditions, it seems to be resolving quite well. Attached Thumbnails Last edited by Bob Hart; September 28th, 2010 at 08:53 AM. Reason: added grabs

September 16th, 2010, 01:05 PM	#17
Dennis Wood Major Player Join Date: Mar 2005 Location: Ontario, Canada Posts: 916	Bob, I've observed some very strange things with regard to ND filters and IR, particularly on our EX1 (another CMOS camera!). With the SI-2K, and Ari's advise regarding IR, I'm guessing there's a very good chance that something interesting is going on outdoors. The chart looks good. Cheers, Dennis.

October 28th, 2010, 01:56 PM	#19
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,476	I have just received the True-cut IR filter so will resume my tests with the Cinevate varifocal relay. I will also try it with the anti-aliasing filter removed as it is expected that the groundglass itself, with a notional 5 micron "grain" over an approx 27,000 micron groundglass screen width will perform that function.