gelatin filters for EtBr photography

gustilo at pobox.upenn.edu gustilo at pobox.upenn.edu
Fri Nov 18 09:51:49 EST 1994


In article <n1427018700.44804 at starbase1.caltech.edu>,
frohlichm at STARBASE1.CALTECH.EDU ("FrohlichM") wrote:

> >Paul Hengen wrote:
> >
> >This is nothing more than a Kodak Wratten Gelatin filter No. 15 yellow
> >(catalog number 149 6648) that you can get for $6.95 US from your local
> >camera shop.
> >
> >I wonder if filters for regular EtBr-UV photography are available at a 
> >similarly low price from a camera shop.  Our camera rig has two filters
> >in it - I'm not sure what they are - but they're so old scratched and
> >smudged that image quality suffers.  Any suggestions?  Paul?
> >
> >Thanks
> >
> > Al McGraw
> >       Univ. of Ga.
> 
> Many filters will effectively block the UV for photography of EtBr
> fluorescence.  Unfortunatley, the filters typically also fluoresce, which
> adds a diffuse glow to the picture.  You can avoid the problem by using two
> filters; the bottom filter blocks UV but emitts a yellowish fluorescence,
> while the top filter blocks the fluorescence from the filter below.  Gelatin
> filters work well.  I recommend Kodak Wratten 8 (yellow) for the lower filter
> and Wratten 25 (red) for the upper one.  Most good camera stores should stock
> the Wratten 25, but the 8 will probably be a special order.  I find it works
> significantly better than other yellow filters, so it's worth the wait to get
> it.  Exposure times will be longer because the red filter blocks some EtBr
> fluroescence, but contrast (the thing that matters) will be much improved.

If you are using this on a Polaroid MP system, Fisher sells a kit that has
glass filters. There are filters for EtBr, Commassie (sp?) Blue and Silver
Stain and a screw on adapter for the camera. You don't have to swing out
the filter to focus.

We used to use Wratten filters but like Paul's the filters eventually
cracked and glazed over making our EtBr pictures hard to read and out of
focus.

I doubt that the glass filters will be affected too much by the UV light

--

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    I am not responsible for comments that I make after 3:00 A.M. or after 5 cups of double espresso, whichever comes first.

gustilo at pobox.upenn.edu



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