Does anyone know of a simple formula to record the minimum ammount of light required to show density on Tri-x and T-max films? I am looking for something along the lines of 1/500 at f/3.5 ten feet from 60watt bulb or other similar, simple way of pre-exposing these films. thanks!!

-- Justin Fullmer (provo.jfullmer@state.ut.us), July 27, 2001

Answers

The Zone I exposure from your zone system film speed test gives you the info you need to make your pre-exposure. Pre-exposure is most easily done in-camera.

Without knowing your own film speed, you can't really account for variables, such as shutter efficiency and accuracy.

-- Charlie Strack (charlie_strack@sti.com), July 27, 2001.

I used to preflash color slides by shooting a white card, after stopping down 3.5 stops from what my light meter called the correct exposure. Since I was usually using strobes, and small f stops were called for, I had to put enough neutral-density filter in front of the lens to provide the exposure reduction my diaphragm couldn't manage. I was trying to get a 10% preflash. I never tried this with b&w film, but it seemed to cut contrast a little in color.

-- Keith Nichols (knichols1@mindspring.com), July 27, 2001.

I've had some luck with using a grey card. I would stop down 3 stops from what my meter said was the correct exposure for the grey card. I'd set the lens at infinity and hold the grey card 18 inches from the lens.

-- Ed Buffaloe (edb@unblinkingeye.com), July 27, 2001.

Justin et al:

In any field of technology, simplicity is the ultimate sophistication.

Shoot regularly, then use a lowwer contrast filter in printing, or scan it and use photoshop or other software to cut the contrast.

If it is colour slides you are making, then Fuji's new Frontier print system solves the problem of excessive contrast that only a dye transfer print could handle. Thse too are obsolete.

Again, pre-flashing was used in the "old days" before the photo industry spent m(b)illlions on research just to overcome the need for such techniques.

K.I.S.S. & cheers

-- RICHARD ILOMAKI (richardjx@hotmail.com), July 28, 2001.

Ed has the proper method here. Zone one (grey card minus 3-3 1/2 stops) will give you a good 1/2 to one stop more latitude in black and white film. The old ways are still the correct way that is used by professional photographers all over the world. If there is no shadow detail in the negative, Photo Shop won't put it there.

-- james (james_mickelson@hotmail.com), July 29, 2001.