BillB,

I don't think this problem is caused by focusing, but rather by vignetting from the filter holder. If that is the case you should also have this problem with the holder without any filter in it and should get worse for shorter focal lengths settings of the lens(es). Are you sure that this filter holder is suitable for the lens(es) you are using.

Frans Waterlander
pixographer

What Frans says translates to using a larger filter adapter than the front filter size of the lens. Use a step up ring to connect them. Or purchase an oversize infrared filter and hold it in front of the lens with the camera on a tripod.

[url=http://www.bermangraphics.com/digicam/d70-infrared.
htm]The D70 seems to do OK with infrared.[/url]

Bill and Larry,

For the Nikon D50, D70 or D70s with a lens of 18mm or longer focal length, you don't have to buy an oversized screw-in type IR filter. You won't get vignetting with this setup. You can buy a filter of the same size as the lens with the largest thread and use a step-up adapter for the lenses with a smaller filter thread.

Frans Waterlander
pixographer

I'm not sure I understand. I have been using the D70 kit lens that has a 67mm thread on which I have attached a step down ring (Tiffen 67mm to 62mm) which then allows me to screw on the Kenko 62mm filter holder that holds a 3"x3" 87C gel filter. If this increased length causes vignetting, is there any way with this rig that I can eliminate the problem? Could you explain the solution a little more clearly for me? Thanks for the prompt reply. BillB

BillB,

Using a step-down ring causes vignetting as it prevents light rays that make up the outer edges of your image from reaching your camera's sensor. This is worst at the shortest focal length of your lens and may still be a problem at the longest focal length. So this is a no-no. The Kenko filter holder worsens these problems.

I'm not sure if a 67mm filter holder would not cause vignetting at the shorter focal lengths, because the cylindrical part of it seems rather long and may show in your images. I know that a 67mm screw-in type IR filter will work for sure, as it does a great job on my Nikon D70.

Frans Waterlander
pixographer

I use a 72mm IR filter on my D70. I use a step up adapter from 67mm to 72mm which eliminates vignetting. But if I were to do it over again, I'd probably get a 77mm IR filter and a 67mm to 77mm step up adapter. Most of Nikon's better lenses have a 77mm filter size.

Both of you have been very helpful. Finally, I understand what is going on. Frans, would you send me the proper identification for the 67mm screw in IR filter you use and possibly a good source for it so that I may order one. I like the effect the 87C gives rather than those that admit some visible light so would also appreciate if you know the identification for an 87C type 67mm screw-in filter. My reason for going the Kenko filter holder route was economics but it looks like it was wasted money. Once again, thanks to both of you. BillB

BillB,

I'm using the Hoya 67mm RM72 IR filter. I bought mine from baehrmall on Ebay for $58 + $5 shipping. This filter is not as far into the infrared as the 87C filter, but lets very, very little visible light through. The advantage is that the D70 can still autofocus with this filter and exposure times are shorter. Some people prefer the IR effect of this filter, others prefer the 87C. I use a 62 to 67mm step up ring for use of this filter with my 70-210mm telezoom that has a 62mm filter thread. I bought that from B&H (www.bhphotovideo.com) for $6.95 (SKU# GBSUR6267).

This webaddress http://wrotniak.net/photo/infrared/ gives useful information on the various IR filters available in case you want to use one different from the Hoya RM72.

Here is my advise on how to use the Hoya RM72 IR filter with the Nikon D70:

Workflow for infrared non-panorama images for the Nikon D70 and Hoya R72 IR filter

Making the shots
1 Mount the camera on a tripod and set it to auto white balance, auto focus and auto exposure
2 Compose without the IR filter on, then put the filter on
2 Cover the viewfinder and make the shot

Importing and editing in Photoshop
1 In the RAW converter: use White Balance As Shot for best results (increasing Temperature emphasizes the red channel and IR effects, but causes loss of definition and sharpness, contributed by the green and blue channels; decreasing Temperature reduces the IR effects)
2 In the RAW converter, tweak Exposure and Shadows to maximize the tonal range
3 Desaturate (keeps RGB mode)
4 Apply

Thanks Frans. Your information and proceedures have helped enormously. I'll probably go ahead and buy an RM72 filter as suggested. Yesterday, I tried to find ways to stop the vignetting with my setup and I found that with my 18-70mm lens set on manual for 2 & 5 seconds, the problem exists at the low end. Aroung 50mm up it doesn't show up. Also I get a lot of noise with the longer exposures. So, you're way of shorter exposures and autofocus sounds good to me. Thanks again. BillB