</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Ed Sukach @ Apr 10 2003, 02:21 PM)</td></tr><tr><td id='QUOTE'>"Poco" described the filter in question to be "on the diffuser box", which would indicate to me that it had, in fact, a heat attenuation purpose.&nbsp; I don&#39;t infer any "adjustablilty" from the original post.&nbsp; </td></tr></table><span class='postcolor'>
Ed,

I thought you were arguing that the dichroic filters inside the color head work like infrared filters, too. I must have misunderstood you.

Thermal radiation is usually not a problem within an enlarger and a simple piece of glass would stop it (that&#39;s why a Greenhouse functions in practice). The dedicated IR filters within an enlarger head are used to eleminate near IR which might lead to an unsharp overlay on color papers.

The IR filters usually used within enlarger heads are dichroic (inference) filters, too.