Re: UV photography & Tiffen makes 87 IR filter

[ANDPPH@xxxxxxxxxxxxxxxxxx]

> If you use an 18A UV passing filter (only allows medium and long UV
> rays to pass through it  and no visible light)  are you limited to
> using B&W films, or can you use color films? Furthermore what is a
> good B&W or a good color film to use?  One web page said that high
> speed B&W films were good while another web page said to use slow
> speed B&W films?   

First, note that a 3" square of Kodak Wratten 18A costs in the $200-300 range I
believe. Some other brands in screw-in format may be cheaper. If you will be
using the filter over light (as for fluorescence photography) you will not need
optically clear and polished filters and some scientific glass houses may have
lower cost alternatives. 

Actually the 18A transmits not only long wave UV but also a bit of near IR. But
since you would not be using IR senstive film that is of no consequence.

You can use any film you want. If you use color film the pictures will simply
be various shades of blue since you will only be exposing the top layer due to
the presence of a yellow filter below that layer to prevent blue from exposing
the bottom two layers which are also blue sensitive.

> I saw a few UV pictures in an old Kodak publication
> that showed skin damage, fingerprints, and altered documents using
> reflected UV techniques. Although they were technically good images,
> it's not what I'm interested in photographing.  How do people and
> landscapes generally look using an 18A filter and reflective UV
> techniques? From my reading, I have a feeling that B&W reflective UV
> photography looks very similar to "normal" visible light B&W
> photography.  Most B&W IR images are drastically different than a
> normal B&W images, is the same true for most B&W UV images.  Any web
> pages with UV images?

This is typically the case ... unless you happen to find a subject whose UV
reflectance is different than its light repflectance! Same as in IR. IR does
not necessarily look different than visible ... it is that we tend to point our
cameras at subjects whose IR reflectance characteristics differ widely from
their visible reflectances. The fact is, that if reflected UV photography shows
skin lesions, etc. better than visible, well, then right there you have a
significant difference. But the point is that we generally don't find bruises
the most interesting thing to photograph.

> If B&W UV photography does indeed look very similar to visible light
> B&W photography, I will probably be more interested in doing
> flourescent UV photography.  Again, what's a good color film to use?
> Any difference between slide and color negative film?  

Generally you can again use any color film but the higher speed ones will tend
to make the process practical, while the slower films will provide better
"looking" pictures in terms of sharpness, probably also saturation and color
fidelity ... but they will require greater exposure which will result in longer
times or larger apertures.

Using color print film is somewhat inadvisable as the colors are subject to the
whims of the printer. Other than this I have not experienced much difficulty
using either.

> Since I use Nikon equipment, I was wondering if the Nikon SB-26 & SB-28
> speedlights have any nasty UV coatings/filters in them that causes a
> lack of UV emissions?  

Probably. Most flashes these days are equipped with a pale yellow coating or
filter built into the head. Just look for flashes that have a clear flashtube
instead of a yellowish one. 

> Any cheap UV passing filter that I can use over the flash heads.

I mentioned this earlier ... that a 18A over the flash does not have to be
optically perfect ... but I don't know a ready source of such material. Corning
or PPG or Schott come to mind.

> Will unexposed E-6 slide film work?  

No. It transmits IR but not UV.

> Also what's so
> special about the UV-Nikkor 105mm lens?  What range of UV light does
> it allow transmission of?  I'm guessing that I will only need to use
> this special lens if I want to capture short & medium length UV light?
> According to a web page, my current lenses should allow me to
> photograph long UV rays.

I don't know. Your normal camera lenses in most cases will be quite adequate if
you want to do reflected UV photography with the 18A filter over the camera
lens. However, I heard that some camera lenses are coated to attempt to exclude
UV but I have not myself seen any that completely eliminated it. That is why
you use UV filters (UV blocking filters) over the lens. Of course, for fUV
excited fluorescence any lens will do but be sure to place a pale yellow UV
blocking filter that itself does not fluoresce over the camer lens.
 
> Recommended development times and ISO settings anyone?  Lastly, is
> there a UV FAQ somewhere?

I can't help with development times except to say that you probably want to
increase development time about 15% or so for the reflected UV. No changes for
fluorescent. ISO ... hmmmm .. sticky wicket this! However, what I can say on
this is that the darkness of the filter has significantly less effect on proper
exposure than one might think. In fact, in daylight, if memory serves me right 
I have used only a 3 or 4 stop compensation when using T-Max 400 film. Lastly
don't forget that for tack sharp photos you will _probably_ want to rack the
lens out a bit ... in same direction as you would for IR. Most lenses require
this but a few do not.

You can see a bunch of IR and UV articles off my page at:

       http:/www.rit.edu/~andpph/articles.html

regards,

Andy

 o o  0 0 o ' o  Andrew Davidhazy, Imaging and Photo Tech - High Speed Photo
  \/\/\/\/\/\/   andpph@xxxxxxx,  http://www.rit.edu/~andpph,   716-475-2592  
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