A Useful Replacement Bulb For The Elwood 5x7

<p>I'm setting up a newly acquired Elwood SP-2 ("Special") 5x7 Enlarger. The enlarger has the original glass diffusion plate and stack of three sheets of heat absorbing glass installed.<br>

The enlarger bulb that I found in it was a #302 "Photo Enlarger" lamp, 500watts(!). This bulb has an S30 glass envelope which is 8 1/4 inches long with a 3 3/4 inch diameter spherical portion. The Elwood manual for the SP-2 cautions that it particularly important to use the correct diameter bulb (the S30 type) in order to have even illumination. I did try a (smaller) PH211bulb and, indeed, the illumination was visually quite uneven. <br>

The S30 enlarger bulbs appear to be extinct; there are, however, several frosted 200W S30 bulbs available from mail order light bulbs suppliers. Phillips seems to be the manufacturer.<br>

I found a readily available alternative that seems to work well. This is the GE G40 Soft white bulb (GE PC49781). It is a spherical bulb about 4 1/2 diameter and the coating appears very similar to the opal coating on a PH211 enlarger bulb; it even has the bulb label printed on the stem rather than on the spherical portion. These go for about $5 at Home Depot and local hardware stores.<br>

I installed the G40 in the Elwood using a pair of socket extenders to bring the overall length (extenders plus bulb) to 8 inches, the same as the bulb that I found in the enlarger.<br>

I've tested this by enlarging 5x7 negatives to 11x14. The prints show no evidence of a central hot spot or light fall off at the edges. The 100 watt output won't be an issue for me. Exposure times are typically 30 seconds at f8 or f11 with a #3 polycontrast filter on Ilford Multigrade.<br>

The Ektanon Enlarging lens that came with my Elwood isn't too shabby either.<br>

FWIW</p>

<p>You do know how to adjust the light position in the reflector, right? Best bet to ensure no hot spot is to expose a piece of paper to a medium gray and process as normal, should you need to adjust slightly, there is an Elwood user's manual on either the Camera Eccentric site or Mike Butkus', well worth the few mins. to download</p>

<p>Thank you for the information.<br>

As it happens, the manual on Camera Eccentric is the same as the one that came with the enlarger, along with several boxes of wedding negatives from the early 1950's. I printed a few of these out of curiosity and so far, I find at least two different brides.<br>

Some of the negatives that I printed had a region of constant gray scale across the long dimension of negative, I based my judgement of even illumination on the constant density of this region in my prints. Your suggestion is a more rigorous test.<br>

I used the socket extensions to bring the center of the G40 bulb spherical section to the same position in the reflectpr dome that was occupied by the center of the S30 bulb sphere - I'm presuming, of course, that the enlarger was adjusted properly for the 500W bulb by its previous owner. As I can't see evidence of uneven illumination problems, I'll leave things be. Other Elwood owners might well need to make a centering adjustment and your suggestion is valuable.</p>

<p>Wendell, some printers prefer to leave a bit of fall-off in the enlarger to compensate for any vignetting on the negative. This is especially true if a wideangle camera lens is used. In any case the enlarger lens will always contribute some slight vignetting of its own, so you'll never get a perfectly even exposure.</p>