Go Back   Steve's Digicams Forums >

LinkBack Thread Tools Search this Thread
Old Feb 17, 2016, 2:32 PM   #21
Senior Member
VTphotog's Avatar
Join Date: Mar 2005
Location: Extreme Northeastern Vermont, USA
Posts: 4,309

John, I think you may be overly complicating this. If you remove the IR blocking filter, and the Bayer filter, then place the IR pass filter in front of the lens, the only thing the pixels on the sensor will see is IR levels.
If you leave the Bayer filter in place, it will block some of the IR to those pixels which are under the blue (the most), green (partly), and red (least) parts of the filter. If you view this as a color image, it would show up with a strong red cast, as that is where most of the light is. If you remove the Bayer filter, all pixels will get the same illumination (assuming you're aiming at a blank wall), but if you view this as a color image, it will tend to look blue because of how the camera software interprets the pixel values. It is because the Bayer filter has twice as many green pixels as red or blue, so those pixels have to be given greater weight when mixing colors. Since the sensor itself is more sensitive to red light than blue, the blue pixels get a bit more weight than the red. Switching your camera to monochrome will be more correct.
VTphotog is offline   Reply With Quote
Old Feb 18, 2016, 11:06 AM   #22
Senior Member
Shinnen's Avatar
Join Date: Jan 2013
Posts: 399

Hi Conor,
Yes, I understand. It's just the term 'unexposed' I find odd. How can one unexpose what hasn't been exposed. Never mind, I'm just being anal.
.... john
Shinnen is offline   Reply With Quote
Old Feb 18, 2016, 11:41 AM   #23
Senior Member
Shinnen's Avatar
Join Date: Jan 2013
Posts: 399

Hi VTphotog/Tcav,
Right, OK. That makes it quite clear. I think that Tcav was trying to tell me the same thing, but I just didn't get it.
So, where is the Bayer filter, and is it easily removed?
I finally received the film, from the film club. (They're in California. It's VERY good of them to do this for me.) They sent me three strips, a very dark and a very light (kind of orangish/brown). I'm assuming that these are exposed and unexposed, respectively. The exposed seems to remove all colour from the IR/colour image. The unexposed doesn't seem to remove much. Most the the write ups say to use 2 or 3 layers, so I may try this. The images produced are heavily red/blue(?) Have a look here
I believe that I can remove this cast by doing a RGB switcharoo.
Tcav. Yes, getting the proper filter would be the easiest (and probably best) way, but what fun would there be in that.
Just a side note. Removing the IR block filter has left me with a camera that can be used for both visible and infrared, after some minor processing. This flexibility is interesting. If I remove the Bayer filter now, I loose the option of taking colour.
..... john
Shinnen is offline   Reply With Quote
Old Feb 18, 2016, 12:49 PM   #24
Senior Member
TCav's Avatar
Join Date: Sep 2005
Location: Washington, DC, Metro Area, Maryland
Posts: 13,826

You've got a camera without an IR Blocking filter. Any photos you take will be tinted red depending on the amount of IR in the scene, because the IR won't pass through the blue and green microfilters in the Bayer Filter, but will pass through the red microfilters, so the camera will think the IR is red.

If you install an IR Blocking filter, like a B+W 486, you can capture conventional color photos without the red tint from any IR.

If you install an IR Passing filter instead, like a B+W 093, you can capture IR photos where the IR will appear as red.

Anything else, and there's no way to know what you'll be capturing.
  • The lens is the thing.
  • 'Full Frame' is the new 'Medium Format'.
  • "One good test is worth a thousand expert opinions." - Tex Johnston, Boeing 707 test pilot.

Last edited by TCav; Feb 18, 2016 at 12:51 PM.
TCav is offline   Reply With Quote
Old Feb 19, 2016, 11:23 AM   #25
Senior Member
Shinnen's Avatar
Join Date: Jan 2013
Posts: 399

Hi Tcav,
Alright. Sounds good. I'll look into it.
... john
Shinnen is offline   Reply With Quote

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

All times are GMT -5. The time now is 8:16 AM.