4x5 ISO 100 long exposure

Need some enlightment or at least an educated guess! :confused:

I want to start doing some long exposures (5 minutes +).

In the past I have use a 3.0 ND filter which gives me a well exposed negative at about 5 minutes which a 6.0 ND the exposure times start at over 1 hour.

The exposure assumes ISO 100 on a bright day, shutter on T.

Any ideas or advise for a 5-7 minutes exposure, or what do I need to add to my ND 3.0 to get there.

Thanks

Hugh

well, I am not sure how much neutral density you need, but be aware of reciprocity failure, and also be aware that your normal developing time may result in a great deal more contrast than you expect, depending on what film you are using.

What film are you using, and are you accounting for reciprocity?

Normally TMAX 100, not sure how to account for reciprocity on the exposure or development time

Check the data sheet for starting points. You can download data sheets from the film manufacturers' websites. TMX has unusually good reciprocity characteristics, so if you want really long exposures, you might want to shoot a film that has more normal reciprocity failure, like FP4+ or Plus-X. There's usually a graph or a table on the datasheet, so you can start out with your desired exposure length, and work backward to find the meter reading you want to get that amount of exposure after adding in reciprocity failure.

Thanks David, any idea about how to calculate the ND factor?

Tmax100 handles long exposures exceptionally well, just needing a little extra exposure, but no change in development. The shadow detail in very low light levels are exceptional.

My only problem is keeping count - I don't own or wear a watch, but walking round in circles counting out loud has always worked well

The ND factors are ND2 - 1 stop, ND4 2 stops. ND8 - 3 stops

Ian

4x5 ISO long exposure

Reciprocity for Tmax-100 starts at about a 4 sec. exp.=increase to 5 sec.
8 sec.=increase to 12 sec.
15 sec.=increase to 25 sec.
30 sec.=increase to 55 sec.
60 sec.=increase to 2 min.
2 min.=increase to 5 min.
4 min.=increase to 12 min.

This from John Sexton's workbook.

I have attached in PDF form, Kodaks' Bulletin F-4016 of October '07. This is I think the most recent information on all things TMAX.

ND guidance

Like others have said - reciprocity is an issue here. I presume that you are going with neutral denisty to get moving objects removed from the static scene you wnat to capture.

I would suggest you read up on the Ultimate Exposure Computer by Fred Parker on the Web. You will learn that EV's are nothing to be afraid of, and there are a couple of great tables worth printing off.

Say you want to shoot a brightly lit nightime street. That maps usually to EV 7. You are using TMAX100. You are 4x5, so I guess we want something like f/11. 4 minutes at f/11 100asa is EV -1.

So between EV 7 and EV -1 is 8 stops - no direct hit for a simple single filter ND filtration. I here would suggest ND 1.8 plus ND 0.6 to get 8 stops of light loss, and then f/11, for a 4 minute base exposure, before reciprocity should get you a good exposure.

below is a clip from the wiki page on ND filters.

Attenuation Factor Filter Optical Density f-Stop Reduction % transmittance
attenuation 2 0 d0.3 1 stop 50%
4 0.6 2 25%
8 0.9 3 12.5%
64 1.8 6 1.5625%
1,000 3.0 10 <0.1%
10,000 4.0 13
1,000,000 6.0 20

Thanks everybody for taking the time, I will start experimenting this weekend.

Hugh

Hughjb said:

Need some enlightment or at least an educated guess! :confused:

I want to start doing some long exposures (5 minutes +).


Any ideas or advise for a 5-7 minutes exposure, or what do I need to add to my ND 3.0 to get there.

Thanks

Hugh

Click to expand...

To paraphrase an old photo-journalist quote "f256, and be there".
That's 10 stops from f8 (3.0 ND).
For tiny film (4x5), your lens should handle f32 without much diffraction, so with a 1.4 reciprocity factor a 5 min. exposure should require that you stack a 0.6 ND and a 3.0 ND and shoot at f32.3. As David points out, any other film than T-Max will require a more heroic reciprocity factor, up to 2.0--that would be 5 min. at f22.6 down to f22.

Fuji Neopan also has excellent maintenance of reciprocity during long exposures. So does Provia, if you want a color film.

The first thing you do, in lieu of doing your own tests, is to look at the film's data sheet. Read the section on reciprocity characteristics. Look for the exposure which you need to expose 5 minutes to replicate. For sake of this example, let us say that your data sheet says to expose 5 minutes when your desired exposure calls for a 4 minute shutter speed. So you want to calculate your effective f/stop based on a 4 minute shutter speed (in this hypothetical example). When aiming for a particular shutter speed, you come at it backwards like this, because the desired shutter speed of 5 minutes is your fixed factor.

Assuming a bright, sunny day, you would use this film at approx. f/16-2/3 at '60, assuming that box speed matches your personal EI, which it probably does not. To get '60 down to 4 minutes, you need to go, let's see...'30, '15, '8, '4, '2, 1, 2, 4, 8, 15, 30 sec., 1 min., 2, 4. So you need to cut 14 stops from your BDE (basic daylight exposure, AKA sunny 16 rule). Go to f/32-2/3 and you only need to cut 12 stops, or add 3.60 total ND. So, you need to stack a 0.60 ND filter on top of your 3.0 ND filter, assuming shots in bright sun on a clear day.

Of course, you can use wider apertures by using more ND. If I was going to make a pastime out of this, I would have 6.0, 3.0, 1.20, a few 0.60s, and a few 0.30s.

In this case, you may, in fact, be better off using a film that suffers from bad reciprocity loss during long exposures. You just need to test for it first to get a handle on things.

2F/2F