Help: Printing with Graflarger on 12x16 Paper

[tenderobject]

Thanks Tim. Let's wait for the folks in EU/US!

I forgot to try F8. Will try this next time! I run out of papers! I should've bought a lot of 12x16! It's soo nice size wise!

At F16. Exposure times varies from 16-22 seconds. Is this bad?

This is my first time printing 4x5 negs and printing at 12x16. I usually enlarge 5x7 / 8x10 from small negs or contact printing.

My Graflarger i think is a Cold Light.. I had a big transformers in our bathroom just to be able to use this! Hahaha

I Don't know. Once the experts in Europe and America wake up I'm sure you will get more helpful answers.

At f16, don't you have really long exposure times? Try f8 and see if that makes a difference, maybe.

11x14 is not much smaller, but I have replaced my cold light with an enlarger bulb (I plugged the original light into a 220v outlet and blew it up!)

[tenderobject]

Yay.. I should've done this! Will get paper soon!

According to the "Enlarging" article on Wikipedia "The lens is set to its working aperture. Enlarging lenses have an optimum range of apertures which yield a sharp image from corner to corner, often around f8."

So give that a try!

[David A. Goldfarb]

The more you stop down, the more even the illumination should be, so I wouldn't expect an improvement in illumination by enlarging at f:8, though you may improve sharpness by enlarging at the optimal aperture, if it happens to be f:8.

I also don't see why you should be getting light corners with a Graflarger, which isn't too different from other kinds of cold light heads, unless the bulb is simply old (which it is, if it hasn't been replaced) and not as bright at the ends of the tube as it is in the center.

It's not an issue with the taking lens, because falloff with the taking lens would produce dark corners, rather than light ones, unless you're doing something strange like using a center filter where it isn't needed.

A mystery.

[ic-racer]

That is probably as good as you are going to get with the light source. Some things others have tried:
1) make sure you are stopping down at least to f11 (see below)
2) gray paint under the light grid near the center
3) make a center filter
4) just burn the edges as a routine
5) give up and get a better enlarger


f8 and f11 for the 150mm lens at your magnification are represented by the highest dotted red lines. At f8 the illumination falls off near the edge of the projected image.

This is a center filter made from inkjet transparency film. It goes between the light source and the negative.

[tenderobject]

GUys thanks! This is a mystery indeed. It looks like i have problem with the diffuser with the Graflarger i have.
Anyone has any idea of the Graflarger diffuser? I checked it a while ago and i noticed that the diffuser has 2 different illumination when checking directly from a light source.
The diffuser when i was using it was flipped at the dark side of it. I just flipped the diffuser and have the bright side directly to lens. I think this would illuminate the light evenly.
I will try to have a test asap. I'm gonna check the other Graflarger that i have with broken bulb but perfect diffuser..

Hopefully this would fix the problem. I'm loving the print size of 12x16!!!

[tenderobject]

Yo guys.. Testing the Graflarger again.. I did try using an incident meter to check the illumination of the graflarger. It seems like that the center of the bulb is 1stop + from the corners! Looks like my light has something to do with this.. Any solution on this? Or burning the edges for now is the better solution for me to continue printing! Yikes!

[Tim Meisburger]

I think you should make a center filter like that recommended by IC-RACER above. Just print that image on transparency film the same size as the diffusion glass and lay it on top of the glass, then repeat your checks and see what you have. Light will be decreases but should be more even across the 12x16 sheet.

[ic-racer]

Also, as I mentioned, you can experiment with painting the center area behind the tube gray, instead of white. Again, experimentation is the only way to solve it.