Anyone had this problem? the centre of my print is in focus, but towards the edges the print is slightly out of focus. On the contact sheet the focus is uniform. My enlarger is ancient - my Dad bought it second hand in the sixties - it doesn't have a name I can find on it. Has anyone had this problem with a newer, decent enlarger? (I want to check other factors before saving pennies for new equipment) Thanks

-- Greg Brosnan (gbrosnan@infosel.net.mx), April 26, 1999

Answers

check to see if your negative is flat and you might need to stop down some more.

-- mark lindsey (lindseygraves@msn.com), April 26, 1999.

A good, properly aligned enlarger, with a good lens, should produce prints that are equally sharp all over, right up to the corners. If you use a grainy film such as T-Max 3200 or Delta 3200 you should see sharp grain all over a 10x8.

There's nothing inherently wrong with using an old enlarger, they can be fine. If the alignment is slightly out, then stopping down will help.

Similar remarks apply to the lens. However, this is most likely to be the problem. See if you can borrow a really good lens (such as the Schneider Componon-S, El-Nikkor, or something) and see if that makes a difference.

-- Alan Gibson (Alan.Gibson@technologist.com), April 27, 1999.

Don't look at the contact sheet, examine the negatives with a loupe of some type to see if the edges are truly sharp.

You might also see if there is a glass negative carrier for the enlarger to ensure that the negative is held flat.

Good luck.

-- James D. Steele (jdsteele@erols.com), April 27, 1999.

On the enlarger side: are the neg stage/lens board/easel all parallel? Assuming the enlarger is capable of alignment, Dela makes a special tool for this for about $30 (US.) Is the negative sagging so that the center is focused, but edges are not? If you're using 35 mm, this will not be a factor. Are you using a condenser enlarger without a heat absorbing glass? The high temps from condensers will cause a negative to 'pop.' (Yet another reason to use cold light.)

Concerning your lens. A cheap, four-element enlarging lens isn't worth the gunpowder to blow it up! Get a good lens. You can still use it when you get a new enlarger. I recommend a slightly longer focal lenth than 'normal.' This way, you are using the center of the lens even at wide apertures. I use a 65 mm for 35 mm, and 80 mm for 6X6, a 105 mm for 6X7 & 6X9, and 150 mm for 4X5. The price of a Rodenstock Rodagon is cheap considering the waste of time and materials.

-- Michael D Fraser (mdfraser@earthlink.net), May 02, 1999.

Try focusing on one of the edges. If all the edges are now in focus but the center isn't, it's probably a film flatness problem. If some of the other edges are out of focus, it's probably alignment. Of course, it could be a combination.

By the way, I think Michael Frasier is engaging in a good bit of hyperbole when he writes about the value of four-element lenses. When I switched from a Rodenstock 4-element to a 6-element Rodagon, I found the difference subtle at best (at least for the 4-6X magnifications at which I generally print).

-- Chris Patti (cmpatti@ucop.edu), May 02, 1999.

Another suggestion is to get a enlarging magnifier that allows you to oberve the edges of the negative before printing. I have two, one a high magnification grain focuser for the center and a lower power wide field focuser to check the edges. With my set up, I've learned in making large prints, I first will get the center focused, and then slightly defocus the center by racking the lens up toward the negative. Stopping down 2 to 3 stops gets every thing in focus without having to resort to glass carriers and all the additional spotting.

As far a 4 vs 6 element lenses, for B&W, I've compared a 4 element 50mm f4 El-nikkor with a 6 element 50mm f2.8 El-nikkor and can see no difference at the edges in 16x20 prints stopped down at least f-8.

-- Gene Crumpler (nikonguy@worldnet.att.net), May 27, 1999.