Go Back   Steve's Digicams Forums > Digicam Help > General Discussion

Reply
 
Thread Tools Search this Thread
Old Jan 16, 2009, 10:04 PM   #1
Junior Member
 
Join Date: Jan 2009
Posts: 2
Default

Hi,

I am trying to capture images in different bands of the visible spectrum.

So, instead of the RGB bands, I want to use a filter to split the R band into two, G band into two, etc.

Essentially, the result will be six identical images but each taken with only exposure to certain wavelengths. So.. image the visible spectrum below

| R | G | B |

|<-->| <- this is what I want in one photo, without half of the R, and without G and B.

I am completely new to photography, and am wondering if there is anything like that out there?

Thanks

vegetable is offline   Reply With Quote
Sponsored Links
Old Jan 16, 2009, 10:52 PM   #2
Senior Member
 
TCav's Avatar
 
Join Date: Sep 2005
Location: Washington, DC, Metro Area, Maryland
Posts: 13,572
Default

I think you can do some of what you want with filters, but I think it would be easier in post processing. You might be interested in Tiffen's Dfx Digital Filter Software.
TCav is offline   Reply With Quote
Old Jan 17, 2009, 12:12 AM   #3
Junior Member
 
Join Date: Jan 2009
Posts: 2
Default

the software looks intriguing, but I think i'd rather go with the filters because I'll be losing data if i do post processing, right?

essentially I want to run some algorithms on the images, using the different filters to obtain more data per spectrum-block, if you will.

what would these filters be called? I don't have an slr and only a canon point/shoot camera, but I'm hoping to place it in front of the camera as close as possible to obtain the desired effect. Any opinions?

thanks for your help!
vegetable is offline   Reply With Quote
Old Jan 17, 2009, 8:14 AM   #4
Senior Member
 
TCav's Avatar
 
Join Date: Sep 2005
Location: Washington, DC, Metro Area, Maryland
Posts: 13,572
Default

Take a look at Adorama's selection of Black & White Contrast Filters. Also, take a look at the Cokin Filter System.
TCav is offline   Reply With Quote
Old Jan 17, 2009, 5:38 PM   #5
Senior Member
 
BillDrew's Avatar
 
Join Date: Jun 2002
Location: Hay River Township, WI
Posts: 2,512
Default

vegetable wrote:
Quote:
the software looks intriguing, but I think i'd rather go with the filters because I'll be losing data if i do post processing, right?

essentially I want to run some algorithms on the images, using the different filters to obtain more data per spectrum-block, if you will.

what would these filters be called? I don't have an slr and only a canon point/shoot camera, but I'm hoping to place it in front of the camera as close as possible to obtain the desired effect. Any opinions?

thanks for your help!
True, you will lose data by doing post processing. But the data you should consider is the light coming to your camera. By putting filters in front of the lens you are losing data - much the same data you will lose with post processing.

Your example of trying to capture just above the infrared, you will only be looking at the output of only those sensors with red filter in front of them. Doubt there is any realistic way to split the red into the finer segments you want, but I would suggest that you look at software to see what the results are before spending a bunch on several high quality filters.

Take a look at the info on the Bayer (sp?) filter system used ahead of the sensor. They allow some very specific frequency ranges through - if you use a filter ahead of the lens that only allows a very narrow band through it could have some very strange results with the interaction of the Bayer filter.

Take a look at various RAW converters for your camera - you might find one that allows you to pull out just the specific sensor signals (RGB). That with some knowledge of the bandwidth of the filter you could put in front of the lens should get you near to figuring out if you can do what you want.
BillDrew is offline   Reply With Quote
Old Jan 17, 2009, 5:47 PM   #6
Senior Member
 
TCav's Avatar
 
Join Date: Sep 2005
Location: Washington, DC, Metro Area, Maryland
Posts: 13,572
Default

BillDrew makes several good points. The Bayer filter limits the light that gets through to each photoreceptor, and putting another narrow bandwidth filter may severely affect what you're trying to do.

But here's another idea. digital cameras designed for astrophotography don't have Bayer filters, and so are much more sensitive to light (they just don't detect color.) You might be able to use one of these for your project. The problem is that these don't have lenses of their own, and are designed to be attached to another optical instrument. You might be able to use one of them with a spotting scope to do what you want, however.
TCav is offline   Reply With Quote
 
Reply


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 Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 8:24 PM.