D100 Infrared and old AI lenses

[Mike Richards]

I've just about decided to get a D100 and have it converted to infrared http://www.irdigital.net/. I have a 20+ year old Nikon F3 and a number of AI lenses. Can the AI lenses be used on the D100? If so, with what limitations? Tried to get this info on the Nikon web site, but could not sort it out. Appreciate any help on this.

[sfaust]

From the top of my head, you will loose the all auto exposure modes and metering. It will become a fully manual camera as far as those items go. However, being digital, you can preview your shots on the LCD with histograms to find the correct exposure, so that point is fairly moot. As long as you don't have the need to shoot quickly, and can take the time to setup your shot, it won't hamper your style much. And thats pretty much a given when shooting infared based on the long exposures. You won't be running around hand held at 4 fps! :)

[brianvsweeney]

I looked at the irdigital.net homepage and reading the desription, it "sounds" like the camera would be sensitive in the IR only. You can do that with a digital camera by putting a filter, like a Kodak Wratten 88a, over the CCD. I guess the advantage is that you would not get a dim or black viewfinder, and the image would be IR only.

I would think that leaving all filters off and using the CCD array like infrared film, which is sensitive in visible and IR, would have advantages though. Use a Red filter when you want mostly IR and use a Hot Mirror filter when you want visible only.

Does anyone know what the conversion involves? I've got an OLD Kodak DCS200IR that does not use a cut-off filter so that it is sensitive from visible to IR. It's N8008s body works with all AI and most AF lenses, does not provide power for the "Internal motor " lenses. I could put a Wratten filter over the array, but I think I will stick to putting filters over the lens.

Without the Hot Mirror filter long exposures are not necessary. You get about the same sensitivity on the CCD in IR as you do in Visible. You do have to compensate for exposure as the Meter's photo diodes are sensitive to visible, not IR. We found that you had to use a -1ev compensation when shooting without filters.

[Mike Richards]

The whole point of the conversion on the D100 is normal hand held exposures. I have a Leica D1 which takes neat IR photos with an 092 or 093 filter attached. But the IR reduction or cutoff filter within the camera limits one to time exposures and tripods. I had the conversion done on my D100, and I understand the IR reduction filter within the camera was removed and replaced with an IR pass filter. (this can't be done on the Leica). Anyway, I now have reasonable handheld shots. I also found my best results have been obtained with my old AI lenses and manual mode. The lenses have a redline mark for IR, and in manual mode, I'm able to open up the aperture and use reasonable shutter speeds for handheld. My favorite is the 28mm AI Nikkor. The new autofocus lenses need to be stopped down to f8 or f11 for good results, which means large DOF and slower shutter speeds.

[brianvsweeney]

Mike,

Does the converted camera still work in visible if you do not have a red filter on it? If they put an IR pass filter, like a Wratten 88a, it will stop all visible light. It sounds like that is what they did. If you look at the array with the shutter open the filter appears as "jet black". The exposure is going to be way off from what the camera's meter indicates; it is metering visible light and the CCD array is picking up just the IR. What I need to do is put some Silicon Photovoltaic Cells in place of the old Selenium cells of an old meter and put a IR pass filter in front of it.

My DCS200ir does not have any filter in front of the CCD array; any filtration is done like a film camera. I have a Hot Mirror filter in 52mm and 62mm and Red filters, so I will be trying it out. I managed to find some drivers, a version of photoshop, and a SCSI card that actually worked!

[Mike Richards]

The irdigital conversion is permanent. The IR filtering is now inside the camera, and it's not necessary to attach a filter to the lens. Trying to get the right IR exposure by measuring visible light is a guessing game no matter what -- film or digital sensor. I've found a +2 EV exposure compensation is usually a good starting point. Beyond that, bracketing and checking the histogram can ensure at least one good exposure. I'm still experimenting, but found that I like manual mode and my old AI lenses the best. This means an additional step or two when setting up the exposure, but it's not really that difficult.
One other thing. I have a 600mm mirror lens that I haven't tried yet. In theory, it would seem that no focus compensation would be required to capture IR with a mirror lens. Can anyone verify this?

[brianvsweeney]

The mirror lens should not need IR focus correction. I can test this with my Nikkor 500mm F8 and Vivitar 600mm F8 Solid Cat. The latter has a lot of glass in it, so it will be a good experiment.

I bought ED series lenses for the DCS200IR for this reason; refocussing was not required. I also have a Pentax 85mm F4.5 Super-Achromat in M42 mount. I will be looking for a Nikon F adapter for it.

[brianvsweeney]

Badly burned out, but this is the 500mm F8 Reflex-Nikkor with an R60 filter, exposure was about 1/250th at F8 and Back set for ASA200. I will play with it, but you can see that the focus does not shift with this lens.

Also used it later with a Hot Mirror filter and 70-210 AF-Nikkor, exposures match the meter on the N8008s in that mode. IR will need about a 4 stop correction, ie reduction over what the meter claims. I think I will get an old Silicon Cell Optical Power Meter.

Jorge, I'll get the 1952 RF Nikkor 25cm f4 on it soon, do not worry.

[brianvsweeney]

Again with the Reflex-Nikkor 500mm F8 and R60 filter. Camera set for ASA100 and underexposed 4 F-Stops of what the meter claimed.

[brianvsweeney]

So the effective spectral range is 6000 to 11,000 Angstroms. Not bad for a 12 year old Digital camera; I count a few hot pixels.

I did not try the Vivitar Solid Cat on the camera; the T-mount on it will hang on the AF contacts of the camera. Ask me how I know... If I want to use it, I will need to get a new T-Mount adapter specifically for Nikon AF cameras. It clears the electrical contacts. With that said, the Vivitar lens does not have an IR focus index mark, which indicates that focus correction IS NOT required. It should work just fine in IR. It is a very compact lens, much smaller than my 1970 vintage Nikkor used for these shots. The Vivitar is a mid 70's lens, made in the US by Perkin+Elmer.

[brianvsweeney]

Kodak manuals have an appendix for the Infrared cameras, the DCS200IR and DCS420IR. They recommend the use of Micro-Nikkor lenses as the color shift is minimal. I have been trying the 55mm F2.8 AIS nikkor (not AF varient) with the DCS200IR and have had good results. Even at F2.8 I and close-up, did not notice much of a focus shift.