Archived posting to the Leica Users Group, 2006/11/15
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Mark, You're right. I just tested the hot mirror with a gray card. There is no visible light loss with this filter. I was going by my experience shooting UV images with black light. I use a B+H 403 UV pass filter and a hot mirror. When I add the hot mirror I need to increase exposure. My light source must have a high IR component as well as UV. Len On Nov 15, 2006, at 4:57 PM, MARK DAVISON wrote: > Leonard, > > I didn't notice any light loss with the IR cut filter (the Tiffen > hot-mirror filter). These filters are listed in the manufacturers > catalogs as having a filter factor of 1. > > Mark > > > >> From: Leonard Taupier <len-1@comcast.net> >> Reply-To: Leica Users Group <lug@leica-users.org> >> To: Leica Users Group <lug@leica-users.org> >> Subject: Re: [Leica] Some IR filtration experiments >> Date: Wed, 15 Nov 2006 16:25:37 -0500 >> >> Mark, >> >> Great work. Your results are especially interesting to me as I >> want the kind of sensitivity to IR that the M8 has. I shoot a lot >> of IR photos. That's just the opposite of everybody else. I'm >> very familiar with the IR sensitivity of the D200 (none), the D2H >> (little more than average), D2X (a little less than the D2H), and >> D1X ( more sensitive than the D2H). The hot mirror IR filter >> approach may be fine in the short term but that's slowing down >> all your lenses by 1 to 2 stops. Since your experiment with the >> Phase One profile has only limited success, you're right. Leica >> will have to fix it. That may not be too easy as Leica has >> already suggested that adding an IR filter over the sensor may >> (my interpretation) mess up their edge performance they went so >> hard to develop). Your new Heliopan filter experiment will be >> interesting but I think the UV contribution to the problem is >> very minor compared to IR. Most modern lenses roll off UV fairly >> well. I have to use enlarging lenses for UV images. And your >> D200 also has absolutely no sensitivity to UV. It looks like a >> winner right now. While I want the IR sensitivity of the M8, not >> at the expense of color cast problems. For now I'll just wait and >> see how the M8 evolves and continue to buy more film for my M6 >> and M7s. >> >> Thanks and keep us informed on your future experiments. >> Len >> >> >> On Nov 15, 2006, at 1:45 PM, MARK DAVISON wrote: >> >>> I have been conducting some experiments to understand the issue >>> of IR contamination and filtration in digital cameras. I have >>> posted some results at >>> >>> http://gallery.leica-users.org/v/MarkEDavison/M8infrared/ >>> >>> to show some comparative examples of IR filtration. I have >>> included a Leica M8 shot where the filtration was done by >>> applying a modified Phase One profile which is supposed to >>> correct blacks under tungsten light. My conclusion is that the >>> software filtration works surprising well on the blacks that are >>> IR contaminated, but hardly affects the other contaminated >>> colors at all, but you should look and come to your own conclusion. >>> >>> (Note: this is a cross post. There is an on-going discussion of >>> software profile methods for IR filtration at >>> http://www.leica-camera-user.com/digital-forum/9178-magenta-work- >>> around-capture-one-workflow.html >>> >>> or >>> >>> http://tinyurl.com/y6cjx2 >>> >>> which gives more detail on the origins of the modified profile I >>> used on the Leica M8 image.) >>> >>> Here's a description of the shots: >>> >>> The scene was shot with incandescent illumination from ordinary >>> lightbulbs. The camera white balances were set to 2800 K except >>> for the Epson R-D1, which was set to incandescent. (The Epson R- >>> D1 does not allow you to set white balance in Kelvin.) >>> >>> The first example is the D200, which is very insensitive to IR. >>> The colors in the first D200 photograph are a very accurate >>> rendition of the way the scene appears to my eye. Take special >>> note of the maroon and green pile blankets, the black Leica M >>> lens, and the black pile jacket at the bottom of the photograph. >>> The second photograph shows the D200 with IR cut filtration (via >>> a Tiffen standard hot mirror filter). There is hardly any >>> visible change in the colors. The third photograph is with the >>> D200 and the IR pass filter (a Hoya R72), taken at the same >>> exposure as the first two photographs. There is no visble IR at >>> all at this exposure. >>> >>> The photographs continue in sequence for 3 more cameras: the >>> Leica M8, the Epson R-D1 and the Nikon D2h. For each camera I >>> show an image with no filtration, with IR cut, and IR pass, all >>> at the same exposure. Note how much IR is recorded by the M8--it >>> is the most IR sensitive of all the cameras. Note also how the >>> IR contamination has completely bleached the green out of the >>> green pile blanket, how the maroon blanket has shifted color, >>> how there is a purple sheen on the barrel of the Leica lens, and >>> how the black pile jacket has turned dark purple. The shot with >>> IR cut filtration knocks down the purple sheen on the lens >>> barrel, improves color saturation and contrast overall, but >>> doesn't quite return the green pile blanket to the correct >>> color. Note also that there was a glowing IR reflection from the >>> "black" pile jacket on the bottom of the apple which is taken >>> out by the IR filtration. >>> >>> Similar comments apply to the Nikon D2h, but the infrared >>> sensitivity is weaker and the corrections with the IR cut filter >>> look better to my eye. >>> >>> The Leica M8 shot which has been filtered by application of the >>> profile Jamie Roberts supplied does have better blacks in the >>> anodized aluminum objects, but the green of the pile blanket at >>> the top has not been restored, and in general the colors of the >>> pile fabrics look faded. More subtly, the IR reflection on the >>> bottom of the apple has not been removed. >>> >>> My point is that IR contamination doesn't just affect synthetic >>> black objects and dark anodized aluminum--it contaminates >>> practially all synthetic pile fabrics that I can find in my >>> house. So you can't just hunt down dark purple things and change >>> their color. (By the way, if you shoot social events and >>> students in classrooms in Seattle in the winter, you are going >>> to encounter a lot of pile jackets and incandescent light, so >>> this is not some obscure rare combination, at least for my use.) >>> >>> The Tiffen hot mirror filter which I used in these experiments >>> is obviously too weak to restore all the colors (especially for >>> the green pile fabric), so I have a better UV/IR cut filter on >>> order--a Heliopan 8152. >>> >>> Some philosophical notes: >>> >>> I have been using these other cameras for some time now, and I >>> always had more trouble getting indoor shots from the R-D1 and >>> D2h to look "right". There was some indescernible purpleness >>> about these photographs that reminded me of faded advertising >>> posters. In comparison the D200 photographs looked rich and >>> vibrant. Now I understand the source of the problem. I'll be >>> using the IR cut filters on the other cameras when the situation >>> warrants. I have also noticed that foliage never looks right in >>> the IR sensitive cameras--it's always a funny spring green. I >>> will wager anything that this comes from high IR reflections in >>> plant leaves, even under daylight. >>> >>> One huge difference between a film and digital camera is that >>> the spectral sensitivity functions of the digital camera R, G, >>> and B channels are fixed forever. You can't change the >>> spectral sensitivities by simply loading a different brand or >>> type of film. Since this is the case, I think it would make life >>> easier for serious photographers if digital camera manufacturers >>> would measure the spectral sensitivity functions of their >>> cameras and publish them, just as Kodak does with their films. >>> With such a graph you can tell at a glance if the camera has >>> significant IR or UV sensitivity, and you can pick your lens >>> filters accordingly. >>> >>> >>> >>> >>> >>> >>> Mark Davison >>> >>> >>> >>> _______________________________________________ >>> Leica Users Group. >>> See http://leica-users.org/mailman/listinfo/lug for more information >> >> >> _______________________________________________ >> Leica Users Group. >> See http://leica-users.org/mailman/listinfo/lug for more information > > > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information