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#11
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Infrared photography
"nospam" wrote in message
... In article , bino wrote: The problem is that you won't see an IR picture per se, as the image requires post processing to be anything but a dark red image. If your camera has a B&W mode, that would be helpful, but the image will still require post processing. false. You got some facts jackass? Experience? I've shot IR film and IR digital. The red filter makes the color sensor see red. Period. |
#12
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Infrared photography
In article , bino
wrote: The problem is that you won't see an IR picture per se, as the image requires post processing to be anything but a dark red image. If your camera has a B&W mode, that would be helpful, but the image will still require post processing. false. You got some facts jackass? Experience? I've shot IR film and IR digital. The red filter makes the color sensor see red. Period. except that the blue pixels also pass infrared light and depending on the camera, the white balance, the strength of the infrared filter and the raw processing, the results can be virtually anything. i've used a couple of digital cameras for infrared and modified one of them myself. none of them produce red images out of the camera. on the camera's lcd screen and the jpegs they produce, the result is b/w. if anything, there's a mild greenish cast, perhaps because the camera is boosting green due to the weak response of the green pixels with infrared light. the very same image when shot raw and processed via adobe camera raw has an entirely different appearance than with nikon or canon's software. saying that it will always be red is simply false. |
#13
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Infrared photography
In rec.photo.digital bino wrote:
| "nospam" wrote in message | ... | In article , bino | wrote: | | The problem is that you won't see an IR picture per se, as the image | requires post processing to be anything but a dark red image. If your | camera has a B&W mode, that would be helpful, but the image will still | require post processing. | | false. | | | You got some facts jackass? Experience? I've shot IR film and IR digital. | The red filter makes the color sensor see red. Period. Who said anything about a red filter ... in this thread? Actually, I would recommend a IR-passing filter (e.g. type 89) on the lens after the IR-blocking filter is removed. The sensor (with a replacement all-passing filter to keep the optics consistent) will pick up IR in other colors. This is because the color separation of the sensor is not designed to discriminate IR (and hence why an IR-blocking filter needs to be added in the normal case). The red channel will get the most IR. The blue channel will get a lot. The green channel will get some. And these will vary by what IR wavelength is involved. So you will get some false color effects. Directly viewing the image on the camera screen will give some funny reddish colors for sure. Post processing can then give you the effets you want if you were using the correct lens-front filter to begin with (type 29 for some effects, type 89 for others, and type 87 for yet others). In some cases the desired effect is achieved by making everything monochrome. In other cases the desired affect is a color product derived from adding or subtracting the various color channels. Additionally, multiple shooting of a stationary subject with different lens-front filters (the above plus 25, 23, 15, 12, and none at all) can give you multi-channel info to even be able to derive the original visual image unaffected by infrared (with the correct formula). -- |WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance | | by the abuse department, bellsouth.net is blocked. If you post to | | Usenet from these places, find another Usenet provider ASAP. | | Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) | |
#14
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Infrared photography
In rec.photo.digital Pat wrote:
| There are some good step-by-step instruction out there for removing | the filter. You can leave the filter off, but IIRC you need to | replace it with small shims to keep everything in place. | | If you use a IR filter, you then have to have extraordinary long | exposures because you still have the IR filter in place taking out | most of the IR. | | The other option is to just buy the right camera, something like the | old Canon EOS 20Da. The "a" designates it as a astronomy camera and | it doesn't have the filter. I think it's been discontinued but you | can probably find one if you sniff around. | | If you go IR, you might also want to buy an older lens. Some of the | older ones had an IR mark on the focus ring so you could adjust the IR | focus (which isn't the same as the visible light focus). Or you can pay someone else to do the conversion for you: http://www.lifepixel.com/ http://www.spencerscamera.com/ -- |WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance | | by the abuse department, bellsouth.net is blocked. If you post to | | Usenet from these places, find another Usenet provider ASAP. | | Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) | |
#15
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Infrared photography
sure. generally it's 2mm thick optical glass that's typically a 2" or
3" square piece and you'll need to cut it to fit the camera. Seems straightforward (notice the absence of the term "simple"). Can you give a URL for such a piece? The proper thickness of the replacement glass should be...? Should it be the same thickness as the filter removed from the imager? Thanks, -- DaveC This is an invalid return address Please reply in the news group |
#16
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Infrared photography
On Thu, 25 Sep 2008 07:44:25 -0700, DaveC wrote:
I want to photograph and video in infrared mode. I understand that some point-and-shoot cameras provide this style of photography/videography. Alternately, some people have "hacked" a camera by removing the IR filter from in front of the imaging element. There are instructions on-line to DIY this, or to send in your P&S to have it done. Basically, the IR filter is removed and replaced with another (not a procedure for the faint at heart). The replacement filter is $$$. My question is this: is this replacement filter that passes rather than blocks IR available as a gelatin or other commonly available filter that I can source elsewhere other than from these camera-mod services? Or can I just strip off the existing filter and not replace it with anything? I'm looking for quantitative data (the existence of IR) not qualitative data (a pretty picture). What function does the replacement filter provide (other than passing IR data)? To clarify, I want to "see" IR images real-time in the viewfinder, not post-process the image data to reveal the IR. If there's another forum you suggest I should ask this question in, please let me know. You could try picking up a Sony F707 or others of that ilk. If my memory serves me right they do have IR capabilities. Eric Stevens |
#17
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Infrared photography
In article .net,
DaveC wrote: sure. generally it's 2mm thick optical glass that's typically a 2" or 3" square piece and you'll need to cut it to fit the camera. Seems straightforward (notice the absence of the term "simple"). if you know how to cut glass it should be fairly easy. however, opening up the camera to replace the filter is usually not easy at all. Can you give a URL for such a piece? here's a few: http://www.alpineastro.com/filters/filters.htm http://www.controloptics.com/product_colorglassfilters.htm http://www.edmundoptics.com/onlineca...cfm?productID= 1918 The proper thickness of the replacement glass should be...? Should it be the same thickness as the filter removed from the imager? it should. if it's not that close, you might lose either infinity focus or close-up focus, but stopping down should compensate for that. depending on the camera, the autofocus might need adjusting. the other problem is the only way to know how thick a filter to get is open up the camera and measure it. it varies depending on the camera, and sometimes it varies with the *same* camera, depending on the revision. i've also heard of using microscope slides to match the thickness. |
#18
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Infrared photography
On Fri, 26 Sep 2008 17:11:35 +1200, Eric Stevens wrote:
On Thu, 25 Sep 2008 07:44:25 -0700, DaveC wrote: I want to photograph and video in infrared mode. I understand that some point-and-shoot cameras provide this style of photography/videography. Alternately, some people have "hacked" a camera by removing the IR filter from in front of the imaging element. There are instructions on-line to DIY this, or to send in your P&S to have it done. Basically, the IR filter is removed and replaced with another (not a procedure for the faint at heart). The replacement filter is $$$. My question is this: is this replacement filter that passes rather than blocks IR available as a gelatin or other commonly available filter that I can source elsewhere other than from these camera-mod services? Or can I just strip off the existing filter and not replace it with anything? I'm looking for quantitative data (the existence of IR) not qualitative data (a pretty picture). What function does the replacement filter provide (other than passing IR data)? To clarify, I want to "see" IR images real-time in the viewfinder, not post-process the image data to reveal the IR. If there's another forum you suggest I should ask this question in, please let me know. You could try picking up a Sony F707 or others of that ilk. If my memory serves me right they do have IR capabilities. Correct, the Sony F707, F717, F818, H3(?), and H9 all have this capability, and they all do it very well. Real-time hand-held IR photography and videos are a feature of all of them. No need to hack or alter any camera, just flip a switch to their "Night-Shot" mode. According to my add-on lenses and things, I would have to go with a 62mm filter size to make it the most adaptable to the most situations (including for use with my 35mm film gear). When looking at IR filters I was shocked at the prices so I went in search of an affordable alternative. The Kodak Wratten Gel Filters come in 3"x3" sizes. I could cut one of those up into a circle and put it inside of an inexpensive filter-ring holder. But they're prone to water-damage, humidity, etc. And they're still about $25-$30 depending where you get them, that's probably not worth the hassle and care for the few dollars savings. Then I found some 3"x3", Lee Polyester IR filters at B&H for only $14. Durable, worth the cost for an experiment. I didn't want near-infrared, I wanted infrared only, so I opted to go with the Wratten #87. $14 for the filter, and $10-$15 for a cheap skylight filter (to dismantle for the mount, I couldn't find a source of empty filter-ring holders), and I'd be good to go for under $30. If you have an old filter that you can dismantle for the filter-ring, more power to you, then you can get into IR photography for only $14. Here's those Lee filters at B&H Photo & Video if anyone else wants to go this route: http://www.bhphotovideo.com/bh4.sph/...=F 5261AD1470 Normally a decent IR filter of the size needed can run you upwards of $70-$130, you can see the kind of savings attained by doing it this way. A problem with all these Sony cameras is that Sony stupidly listened to some sexually-insecure puritanical idiots at one point and crippled the shutter speeds and apertures that may be used in their Night-Shot mode. They were concerned that some people were using them to shoot through certain swim-wear fabrics at the beach, fabrics transparent to IR. For daylight IR photography you have to lower the IR levels to those required for shooting in the dark. I experimented and found out that a Wratten Green filter (for b/w photography) lowered the levels just right. I found an inexpensive Hoya G (XI). In total you are using a two filter stack, IR + Wratten Green. One other thing, you have to make a rubber gasket to cover up Sony's own IR emitters in the lens housing, that the camera uses to take photos in complete darkness. Otherwise the IR from those bounces off the back of the filter stack and into your lens, ruining your shots with nasty light reflection artifacts in the glass layers. Here's a quick sample of a hand-held daylight IR shot from one of these cameras http://farm4.static.flickr.com/3085/...e6058929_o.jpg |
#19
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Infrared photography
DaveC wrote:
I want to photograph and video in infrared mode. I understand that some point-and-shoot cameras provide this style of photography/videography. Alternately, some people have "hacked" a camera by removing the IR filter from in front of the imaging element. There are instructions on-line to DIY this, or to send in your P&S to have it done. Basically, the IR filter is removed and replaced with another (not a procedure for the faint at heart). The replacement filter is $$$. My question is this: is this replacement filter that passes rather than blocks IR available as a gelatin or other commonly available filter that I can source elsewhere other than from these camera-mod services? Or can I just strip off the existing filter and not replace it with anything? I'm looking for quantitative data (the existence of IR) not qualitative data (a pretty picture). What function does the replacement filter provide (other than passing IR data)? To clarify, I want to "see" IR images real-time in the viewfinder, not post-process the image data to reveal the IR. If there's another forum you suggest I should ask this question in, please let me know. Thanks, You will not SEE the IR regardless of whether the filter allows a live preview. A filter only allows or blocks a given wavelength- it does not CONVERT it from one wavelength to another. In effect, the digital camera does a conversion, but provides three channels of color info. The read channel does not maintain spectral information. All reds are the same. What the result is is a "false color" picture. You are not viewing real infrared radiation when you view a print or a viewfinder image taken with an IR-enabled camera. |
#20
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Infrared photography
You are not viewing real infrared radiation when you
view a print or a viewfinder image taken with an IR-enabled camera. Ah, yes, of course you're correct. Isn't language a trip-up? "No, you misunderstood what I meant to say"... :-) Thanks, -- DaveC This is an invalid return address Please reply in the news group |
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