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Problem with Tokina 12-24 on IRmod D70

Discussion in 'Night, InfraRed, and UltraViolet Photography' started by SilverEagle, Oct 2, 2005.

  1. After seeing Wilk's IR shots I had Life Pixel mod my D70. Images look fine with 18-70mm Nikon and 10.5mm lenses, but not with the Tokina 12-24 f/4. I get a light double spot in the center of the image, which is more pronounced by stopping down. I suspect there is an IR light leak in the way the shutter opens, since I see a brighter small dot in the center of a light spot. This lens has a round flare spot by design( not pentagonal, hexagonal, etc.) These are in the very center of the image. Has anyone else encounterd this with any lens? particularly the Tokina 12-24mm. By the way, when I try this on my 'regular' D70s using an 89b filter over the front of the lens, there is no light spot. Also, I stand in the shade for my test shots to avoid flare.

  2. nfoto

    nfoto Guest

    Welcome to the mad world of IR photography. Hot-spots are a fairly common and certainly very annoying issue. It occurs not because the shutter leaks IR, but results from stray light being bounced back and forth inside the mirror box of the camera. The lens coating is ineffective in IR thus you see this more easily when an IR filter is put over the lens to block visible light. However, it would be very misleading to associate hot-spots with lens coatings per se, since the issue really is stray light inside the camera!

    In my experience the hot-spot issue is slightly unpredictable as far as its occurrence is concerned, since some combinations of lenses, IR filters, and cameras show hot-spots, while another combination using the same lens may not have a problem. However, some lenses do consistently develop hot-spots and there is an emerging pattern of wide-angle zoom lenses with hot-spot issues. Another lens with frequent hot-spots is the AF Nikkor 50 mm f/1.8 D.

    If you have gone to the effort of having an IR-modified camera, why not go the whole way and add an IR-dedicated lens to it? The top candidate for this is the non-AI 28 mm f/3.5 Nikkor, which is a fantastic performer in IR (it is superb for ordinary use as well, but really shines in IR). I never have had any hot-spot issues with this lens on any camera for IR. The 28/3.5 can be had dirt cheap on the second-hand market and obviously must be AI-modified to mount on modern cameras, but many of the lenses floating around these days have already been modified. Some quite crudely, in fact, but that doesn't matter since you are not going to meter with this lens, that it mounts on the camera entirely suffices.

    Most of my IR work is done with the 28/3.5.
  3. Bjørn,
    This is most helpful. And I really appreciate the recommendation for the non-AI 28 f/3.5. I will have to find one. In fact, I may have one among my old equipment. Also, in my web search since my original post, I found a site ( http://www.nickgallery.com ) that offers a number of free photoshop actions, including Color-to-IR.
    Thanks again,
  4. Wilk


    Jul 28, 2005
    Interesting... I've not faced the problem yet. I have all Nikkor except for two sigma primes, which I don't think I've tried yet, will have to do that. So far, I've mosty used my 12-24 Nikkor (which seems to have no discernable problems so far) the kit which does work great for me as well, a few with my 85 1.4 and many with my 135 F/2 DC which all seem to be fine, but have not post processed a lot of these. Although a non AI lens won't function on the D70 (assuming it will with the mod, but it's an area I'm sorely lacking in knowledge wise) I could shoot the D70 all day long in manual, as it's pretty easy to zone in with a manual test or two - I've been doing most of my brackets in manual anyhow.

    Hope your trip is going well, otherwise.

    Bjørn, I SO appreciate your amazing expertise in this arena!
  5. nfoto

    nfoto Guest

    A number of people report bad issues with the 12-24 DX Nikkor and IR hot-spots. I can vouch for the reality of those issues, since the 12-24 on certain cameras exhibits the worst IR hot-spots I've ever encountered.

    All this underscores the need for testing the combination of lens, filter(s), and camera before embarking on any serious IR shooting.
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