Uneven illumination

[Wolfeye]

My enlarger prints one area consistently lighter than other sections. What should I be looking for? It's a Beseler Printmaker 35 which I also use with the medium format kit.

[Sirius Glass]

It sounds like you need to align your enlarger.

Steve

[Christopher Walrath]

Wirelessly posted (BlackBerry9000/4.6.0.167 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/102 UP.Link/6.3.0.0.0)

Are you using the right lens? MF requires something in the 75-80 range. The wrong lens could cause falloff. Also, what aperture and enlarger height?

[Sirius Glass]

It sounds like you need to align your enlarger.

Steve

Or adjust the condenser/diffuser.

Steve

[Nicholas Lindan]

I am assuming you have the condenser version.

You don't mention the location of the lighter/darker sections: is the problem vignetting, is one side lighter or darker, is it an offset patch that is darker (prints lighter)?

It it is adjustable, try moving the lightbulb's position. Sometimes the light bulb itself is to blame and changing the bulb can resolve the problem. Try unscrewing the light bulb a tad just to see if the uneven pattern rotates with the bulb - if it does then the bulb is the culprit. Check that the condensers are clean. Don't use the lens wide-open, most need to be closed down 2 stops to cure vignetting.

A good enlarging meter is a great aid to troubleshooting illumination problems.

[MattKing]

1) check the light path to make sure that there isn't something blocking the light, and that the condensors and internal filter holder (if there is one) are seated correctly.

2) Make sure that the bulb is in the correct location.

3) Contact Beseler for help.

Where is the problem in the image - at the edges, or nearer the centre?

Matt

[Wolfeye]

I bought the enlarger second-hand. It's my first, so be gentle with me. No instructions came with it, nor with the medium format conversion kit that I bought new from B&H. Beseler ignores all emails and there is no manual online on their website. I will doublecheck everything I can when I am home tonight. No idea how to "align" the enlarger. It seems fairly well lined up to me, but I don't know what I'm doing. I'll check the lens... I know I have a 50 and an 80. One is a Beseler and the other a Rodenstock. They both seem capable of sharp prints up to 11x14

Oh - the actual problem seems to reoccur in just one corner. It's not getting enough light on that spot, which happens to be the righthand corner closest to the enlarger.

[DLawson]

According to http://www.beselerphoto.com/parts.html#printmaker you can order the Instruction Model from Beseler (phone number on that page). I don't know whether the manual has useful detail or just basic "here's the switch" instructions.

[ic-racer]

There is optical alignment and there is vertical alignment of the light source, negative and lens. Frequently these adjustments involve tweaking the little bit of play that exists in light boxes, and negative carriers to get things lined up.

The steps involved would be like using a laser alignment device to see the diffraction pattern off the lens and get the optical center of the lens. Then make a big X centered on that spot on the baseboard. Then take the negative carrier out and see that the projection of the light source borders are the same distance from the center of the X. If not then shift the head, lightbox or the lensboard to get them aligned. Then put the negative carrier in and see that the projected corners are all the same distance from the center of the X. Even high-end large format enlargers can have very little leeway when using them for full-frame printing of the the maximum negative size. This is just one method. Like optical alignment, there are a lot of ways to get the job done.

I have shop manuals and service manuals for all my enlargers and this type of alignment is not discussed in those manuals. (Some manuals do cover it in brief ie the Chromega-D manual).