jon_witt

<p>Joe you may have already found your answer, but for the community, I will chime in.<br>

According to Lord Rayleigh constant from the Pinhole Designer calculator, the optimal focal length for .24mm is approximately 29mm and the optimal pinhole for a focal length of 70mm would be .373mm. Film coverage isn't really an issue, however when a pinhole is too small, the light rays diffract, causing image blur.<br>

Putting technical info aside, if you already have the aperture made, give it a try anyway!</p>

<p>Oh I see Nicholas. I have been concerned with this as well using step-up rings instead of the correct adapter rings with the Cokin X Pro system. I have not had this problem yet, being that I have not tried this with the 72 SA XL. <br>

Well assuming a perfectly flat, rectilinear world....<br>

Taking the 77mm lens diameter of the Fujinon SW 105, with a 100 degree angle of view, it seems as though you can add up to 32.3mm of filter thread, before interfering with the sight of the lens. I came up with this by doing the calculations, but I imagine this needs to be validated for each lens. Interesting enough, I come up with 31.8mm for the 72 SA XL.<br>

Thank you Nicholas as I was unaware that there were EW filters designed for this dilemma.<br>

Cheers!</p>

<p>Nicholas, I would say that you probably don't need to get a filter right away, unless your shots are demanding one. I was considering the Center Filter for the Schneider 72mm Super Angulon XL, but after I saw the results from shooting without, I realized that my typical outdor landscape shots didn't <em>require</em> the filter. Matter of fact, the subtle falloff can sometimes be delightful. </p>

<p>Take a look at Schneider's Center Filter explanation as well as the write up by Ken Rockwell.</p>

<p><a href="https://www.schneideroptics.com/ecommerce/CatalogSubCategoryDisplay.aspx?CID=182">https://www.schneideroptics.com/ecommerce/CatalogSubCategoryDisplay.aspx?CID=182</a><br>

<a href="http://www.kenrockwell.com/tech/center-filters.htm">http://www.kenrockwell.com/tech/center-filters.htm</a></p>

<p>Hope this helps.<br>

Good luck!</p>

<p>To my understanding the 75mm and 127mm are capable of covering a fair amount of a 4x5 as their image circles actually exceed that of Polaroid 3 1/4 x 4 1/4. I think this project would be worth pursuing just being the fact that 4x5 film is easier to handle in the darkroom, as well as handling post-darkroom processing.<br>

Reference:</p>

<ul>

<li><a href="http://members.cox.net/gmhsint/75mmlens.html">http://members.cox.net/gmhsint/75mmlens.html</a></li>

<li><a href="http://members.cox.net/gmhsint/127mmlens.html">http://members.cox.net/gmhsint/127mmlens.html</a></li>

</ul>