Long Exposure

Hello-
I am sure this has been asked millions of times, so please excuse me. I am newbie with long exposure and I am wondering how to go about them. I would like to take some long 30 second shots with a roll of TRI-X 400, but I don't know what to aperature to use. I am guessing a slower film would be better? I have a cable release and a tripod. I really don't know how to go about asking this question. Is there any good resource online that I could look at. I am planning to go off to shoot today and it is a somwhat rainy new england afternoon....Thanks for any advice you can give me.

Good Morning, Ektagraphic,

Are you thinking of long exposures as in twilight/night shots or long exposures as in 1/15 to several seconds, as in flowing-water shots? Your post seems to indicate something like the latter. The Tri-X should work out, although I'd lean toward TMY myself.

If you plan night shots (many seconds or minutes), I'd ditch the Tri-X and go to a film with better reciprocity characteristics, such as T-100 or Acros. Since you indicate tripod usage, the slower film should cause no problems and would give less-grainy results, especially if the "roll of TRI-X 400" happens to be 35mm.

Konical

Different films have different reciprocity characteristics, just as Konical states. You should go to Kodak's web page and download the pdf for Tri-X. It will have a reciprocity curve that you can follow.

Kodak's reciprocity adjustment recommendations for traditional emulsion B&W films (even in the tech bulletins for specific films) are generic, and haven't changed since the 1970's. Tri-X has changed multiple times since then.

For experimentally confirmed times for Tri-X from 2003 look for the Tri-X data in Howard Bond's article:

http://www.phototechmag.com/articles/articles/200705/0403Bond_Reciprocity2.pdf

This is discussed many other places on APUG.

So if you want a 30 second exposure, look at the chart on the last page of Bond's article on the line for the adjusted times for Tri-X and find 30 seconds. There's an entry for 29 seconds, which is more than close enough. Look at the metered time that corresponds to, which is 15 seconds, find the aperture (or combination of aperture and neutral density filter) that gives you a meter reading indicating 15 seconds. Use that aperture (or aperture + filter) and expose for 30 seconds (or 29 if you're a strict constructionist).

Lee

Ektagraphic,
Basically yes, use a slower film or even filter.
Use of a polarizer will give you about a two stop reduction in exposure.
Neutral Density(ND) filters can be had in a variety of strengths, The ND's are log values though so one stop=.3 two=.6 and three=.9 whereas factors for standard filters are geometric and one stop=2X,
two stops=4X, three stops=8X.
For what it's worth I think THIS is the best source online for photographic information. As you've seen above people can provide the best available sites if the info isn't at hand.

I would highly recommend getting a B+W ND110 filter. This will reduce the amount of light by 10 stops! Twin this with Fuji Acros, and forget about reciprocity ajustments.
This will give you shutter speeds around 15 seconds to 2mins, during the day.
I shoot with a hand held meter that gives readings in EV's which makes working out filter factors easy.
1 stop = 1 EV.

There's a group on Flickr called ND110, will give you some idea of the look.
A search for FLUX on flickr will also bring up a photographer who is a master of this technique.
I've just started shooting like this, and love the results i'm getting.

I decided to go pack light today on my walk, but I will read up and try some long exposures next weekend. I am going to go up to my cabin in the woods of Maine. Maybe I will try for some shots of the stars. There are also some great water falls up that that may be interesting subjects for longer exposure. I'll let you all know how I make out.