adan Posted November 2, 2009 Share #1 Posted November 2, 2009 Advertisement (gone after registration) Answer: about 1/4000th as sensitive to IR as it is to visible light Two shots - straight daylight, and with Hoya 092 IR-pass filter. (pardon my finger in the IR shot holding the filter in place) ISO 1600 (required to get the IR image at a hand-holdable 1/8th second). Exposure for straight color shot: 1/4000th @ f/8 Exposure for IR shot with filter: 1/8th @ f/2.8 (= 1 second @ f/8) The effective "Infrared ISO" of the M9 is thus about ISO 0.25 when set to 1600, and about 0.025 when set to ISO 160..based on the "sunny 16" rule. Or on average, 1 IR photon contributing to the image for every 3999 visible light photons. or a little less, since the 092 filter "leaks" a tiny amount of visible red light as well. Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/102314-so-ir-sensitive-is-the-m9/?do=findComment&comment=1099539'>More sharing options...
Advertisement Posted November 2, 2009 Posted November 2, 2009 Hi adan, Take a look here So IR-sensitive IS the M9....?. I'm sure you'll find what you were looking for!
carstenw Posted November 2, 2009 Share #2 Posted November 2, 2009 It is an interesting test, but I am not sure that it fully captures the problem, since we don't know how much IR light is in that photo. The place where IR light is usually a problem for the M8 is indoors, in tungsten light, with skin and artificial textiles. Care to re-test in that scenario? Link to post Share on other sites More sharing options...
t024484 Posted November 4, 2009 Share #3 Posted November 4, 2009 Adan, Nice test. It would be informative to have the same test done with an M8 with and without IR filter and in both cases with your Hoya filter on top. This will show how much the M9 has improved in IR suppression. Are you in the possession of an M8 ? Hans Link to post Share on other sites More sharing options...
adan Posted November 4, 2009 Author Share #4 Posted November 4, 2009 Carsten - will try, once I can get an IR-pass filter and tungsten light in the same place at the same time (I borrowed that filter off a camera-store used table, and my own 39mm Leitz IR-pass filter has crawled into hiding somewhere). t0...- No longer have an M8, but I do have M8-IR shots under similar lighting, so I could get a fair measure of its daylight-ISO-equivalent for IR fromthose, when I get time. Link to post Share on other sites More sharing options...
rice twigs charlie Posted November 8, 2009 Share #5 Posted November 8, 2009 Thanks for the pictures and advice. My M8 allows generally good IR B&W images at f 5'6 and 1/30th at ISO 640 and MID DAY light. I use the old Dark Red Leica IR filters, It appears that this won't be possible with the M9:( Link to post Share on other sites More sharing options...
johnbuckley Posted November 9, 2009 Share #6 Posted November 9, 2009 Good Lord, Andy, you have that much snow ALREADY in Colorado! Going to be a long winter... Link to post Share on other sites More sharing options...
brill64 Posted November 10, 2009 Share #7 Posted November 10, 2009 Advertisement (gone after registration) thanks for doing this test, andy. i am for one, happy to see that the ir effect is achievable as with the m8 Link to post Share on other sites More sharing options...
adan Posted November 13, 2009 Author Share #8 Posted November 13, 2009 Ok, Carsten, here's a similar comparison under tungsten light. The difference in exposures is 1/350 second for visible light and 1/4 sec for IR-only, or 90:1 ratio (6.5 stops more or less) ISO 1600, f/1.4, Leitz IR filter (which passes a bit more visible red than the Hoya used for the daylight scene above - i.e. it is slightly lighter black/red) I've realized what I should do next time is shoot the same shutter speed for both IR and visible light, to see if the IR even registers at a "normal" tungsten full color exposure. I'd guess it should, since my shirtcuff DR test for the M9 was 8-9 stops, but we'll see.... Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/102314-so-ir-sensitive-is-the-m9/?do=findComment&comment=1114912'>More sharing options...
sean_reid Posted November 13, 2009 Share #9 Posted November 13, 2009 Ok, Carsten, here's a similar comparison under tungsten light. The difference in exposures is 1/350 second for visible light and 1/4 sec for IR-only, or 90:1 ratio (6.5 stops more or less) ISO 1600, f/1.4, Leitz IR filter (which passes a bit more visible red than the Hoya used for the daylight scene above - i.e. it is slightly lighter black/red) I've realized what I should do next time is shoot the same shutter speed for both IR and visible light, to see if the IR even registers at a "normal" tungsten full color exposure. I'd guess it should, since my shirtcuff DR test for the M9 was 8-9 stops, but we'll see.... Hi Andy, Interesting tests. That last one looks like tungsten/daylight mix perhaps? Try pure tungsten as well if you get a chance (ie: night or no other light sources). Cheers, Sean Link to post Share on other sites More sharing options...
adan Posted December 16, 2009 Author Share #10 Posted December 16, 2009 Sorry - a month later.... Shot under pure household tungsten lights - 6 x 60 watts top image is straight M9, bottom image is SAME exposure (shutter speed/aperture) with IR-pass filter mounted - i.e. it shows how much the IR light (+ a tiny amount of visible red) contributes to a color M9 image under tungsten light. Exact same raw conversion, too. Yes, there is some exposure there, believe it or not. If you look hard you can just make out the brightest highlight on the towel rail (actual RGB value 4R/0G/1B) as a speck center right. White photo matte is 4R/0G/0B. If you download this jpeg and do some major curve or level adjustments to brighten it, you can bring up the IR image, just to see for yourself that it is there. Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/102314-so-ir-sensitive-is-the-m9/?do=findComment&comment=1153468'>More sharing options...
lct Posted December 16, 2009 Share #11 Posted December 16, 2009 ...bottom image is SAME exposure (shutter speed/aperture) with IR-pass filter mounted... Sounds like you forgot to remove your lens cap, Andy. Link to post Share on other sites More sharing options...
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