I was wondering if there is any way to increase the exposure time whilst enlarging. I find that when making 7x5 prints, even at the lens' smallest apperture I can only expose the paper for 4 seconds.

-- Mark Engers (paul.engers@tesco.net), November 18, 1999

Answers

Spontaneously I can think of a few things (although I'm surprised you get only 4 seconds at the enlarger lens smallest -and probably worst- aperture):

First: a bulb of a lower wattage than what you have now is the obvious first step to take.

* Fibre paper is slower than rc-paper * Some graded papers in the higher contrast grades, 3 or higher, require longer exposure times than softer papers (about twice as long) * chloro-bromide papers are slower (about twice as slow) * a heat resistand neutral density filter in the filter drawer would prolong exposure time * a longer focal length of the enlarger lens will increase exposure time (especially if you don't use your enlargers "devoted" diffusion box for the smaller format but instead uses the diffusion box that matches the enlarging lens of the longer focal length)

Underexposed film will of course also force you to have shorter exposure times than you would with correctly exposed film.

-- Peter Olsson (peter.olsson@lulebo.se), November 18, 1999.

A slower bulb or an ND filter are probably the best ways. I would not recommend using the smallest aperture of your lens, because diffraction may reduce the image sharpness there.

You might also try to attach two polarizers below the lens. Adjusting their polarizing planes should give you any reduction in light intensity between one f-stop and complete extinction. This means four more glass surfaces under the lens, but if you use high-quality polarizers, the loss in sharpness might be less than that from stopping down the lens beyond its optimum.

If your enlarger is one with a conventional tungsten bulb, one might also think of using a dimmer to reduce light intensity. Beware, however, as this also shifts the colour of the light towards red when the voltage is reduced. This will affect VC papers. For graded papers, I would expect a general loss in speed as the blue is reduced in the light.

It is not generally true that FB paper is slower than RC paper. On Monday, I made a speed test of all the papers I presently have in my stock, using a gray step wedge. With Ilford MG IV RC as the reference, about half of the FB papers were in fact faster, and the other half were slower. The fastest FB paper was almost one f-stop faster than the reference RC paper, both being VC papers tested at the same grade, i.e. with the same filter.

-- Thomas Wollstein (thomas_wollstein@web.de), November 19, 1999.

If your enlarger uses a conventional tungsten bulb, use a variable transformer (Variac, Staco, etc) to cut the voltage down. A dimmer will work, but they aren't stable with line voltage and noise, and will suddenly change intensity. The bulb will shift towards the red as the voltage is reduced, but I've actually tested and measured this, and the shift is less than half a paper grade for any reasonable reduction. Your bulb life will increase by an unbelievable factor, and your ability to dodge and burn will be improved by having time to do it. You'll also get less negative "pop" as the wattage dumped into the negative will go down. Finally, you'll be able to print somewhere near the optimum lens aperture- about two stops down from wide open. Oh yeah, if you use a mechanical timer, your exposre accuracy will increase by a bunch. That should be enough to get you interested!

-- Conrad Hoffman (choffman@rpa.net), November 19, 1999.

Thanks for the advice - I'll put it into practice

-- Mark Engers (paul.engers@tesco.net), November 25, 1999.