Guessing long exposure reciprocity failure!

[marciofs]

Can you photograph long exposure without mesuring the light but just guessing by intuition, and get good results?

Or is it a mith?

 

[bdial]

You can but you should probably expect a lot of failures during the learning experience. Bracketing a lot will help insure you end up with something usable.

 

[marciofs]

I may try.

 

[jimjm]

It also depends on which film you're using. Some manufacturers have specific recommendations for long exposures up to several minutes. Check the datasheet for the film you're using.

Longer than that - like 1/2 hour and more, trial and error is how many folks learn. When I started doing night photography, I realized that it's better to err on the side of overexposure.

If I estimate a scene needs a 2 min exposure, I'll also shoot one at 3 mins and one at 4 mins. It's easy to underexpose a shot, but much harder to overexpose at night.

Fuji Neopan Acros 100 needs no adjustment for reciprocity up to 3 minutes. Up to 15 mins, open up by 1/2 stop or add 50% more exposure time than the meter indicates (if you're metering the scene).

The Noctures web site has some good info at http://www.thenocturnes.com/resources.html

 

[MrBrowning]

You can but like bdial said be prepared for a lot for failures and bracket. The way I have done it in the past is to guess the exposure then half it and double it.

 

[Michael W]

I guess ... one hour. Give it a shot and report back with your results.

 

[RalphLambrecht]

Can you photograph long exposure without mesuring the light but just guessing by intuition, and get good results?

Or is it a mith?

Yes, with some experience.Also,you can find estimatingtables with suggestions for many conditions on the web.

 

[marciofs]

I don't plan to do night photographs (now) but to photograph indoors and dark days with pinhole camera, which can easy reach the 30min/1h exposure + reciprocity failure.

Fiji across is expensive on 4x5 so I am fist using Delta 100 and later on Fomapan 200 and 400.

 

[Doremus Scudder]

Marcio,

Are you using a light meter? If you are, then there is really no reason not to do the adjustments for reciprocity failure. Just find the table for the film you are using somewhere (the manufacturer's data sheet is a good place to start!) and make the appropriate adjustment for the time indicated on your meter. Example: the meter says 8 seconds, you look at the table and it says give 25 seconds, so you give 25 seconds. The Delta 100 data sheet is here: http://www.ilfordphoto.com/Webfiles/201062894918374.pdf

If you are guessing at exposures without a meter, then good luck. It will take time and experience and some failures till you develop a real feeling for how much to expose.

FWIW, it's much better to err on the side of overexposure than underexposure in these situations. And, keep in mind that a one-stop increase in exposure is a doubling of the exposure time. That means that in order to overexpose a 10-minute exposure by one stop, you will need 20 minutes. One stop of overexposure is fairly easy to deal with. Even two stops isn't much of a problem with larger film (that would be a 40 minute exposure in our example). And, to get three stops of overexposure, you are into the hour-and-a-half range... So, when in doubt, longer is going to be safer.

Best,

Doremus

 

[Jim Jones]

. . . FWIW, it's much better to err on the side of overexposure than underexposure in these situations. And, keep in mind that a one-stop increase in exposure is a doubling of the exposure time. That means that in order to overexpose a 10-minute exposure by one stop, you will need 20 minutes. One stop of overexposure is fairly easy to deal with. Even two stops isn't much of a problem with larger film (that would be a 40 minute exposure in our example). And, to get three stops of overexposure, you are into the hour-and-a-half range... So, when in doubt, longer is going to be safer.

Best,

Doremus

Doubling the time to double the exposure doesn't always work that way in long exposures. Reciprocity failure may require more than double the time to double the exposure. With some films, there is a quite significant increase in required time when doubling the exposure.

 

[Thomas Bertilsson]

If you continue to use the same film over and over and over again, you will learn how to expose by experience.

For example, I use mostly Tri-X and HP5+ film, and for moonlit scenes I know that about 10 minutes at f/5.6 is going to do the job the way I want it. Street lit scenes is more like 3-4 seconds at f/5.6, but I bracket those, and sometimes I meter for the shadows on those.

Just start using the camera and film in darker and darker situations, and bracket your exposures. Eventually you will learn.
But, you will save time and money by using published information, such as Howard Bond's extremely well executed test and you can use manufacturer's published times as starting points.

Good luck!

 

[marciofs]

I am actually using light meter but since the data sheet shows only up to 30sec, I will have to guess longer exposures anyway.

 

[summicron1]

I don't plan to do night photographs (now) but to photograph indoors and dark days with pinhole camera, which can easy reach the 30min/1h exposure + reciprocity failure.

Fiji across is expensive on 4x5 so I am fist using Delta 100 and later on Fomapan 200 and 400.

I've found that pinhole is pretty forgiving on long exposures, but some films react better to reciprocity than others -- When in doubt, give it longer exposure, I've taken exposures where I doubled the length of time and didn't notice much difference.

Acros doesn't seem to need much, if any, adjustment. Rather than just guess, I would look up Delta 100, or whatever film you use, and see what the data sheet says.

If you are using 4 by 5, why not go faster, since grain isn't a problem? Indoors even Ilford's HP5 requires you to double or even quadruple, so with slower film the exposures can easily extend into lengths so far you almost wonder why you bothered.

take a magazine and a chair.

 

[wy2l]

What great idea - read the film's technical data to get reciprocity failure information!

 

[Richard S. (rich815)]

What great idea - read the film's technical data to get reciprocity failure information!

No, then sites like this would have like 90% less postings!

 

[davidmasek]

Maybe the Pinholedesigner software could be helpful for you? http://www.pinhole.cz/en/pinholedesigner/
Reciprocity failure calculations is one of the things it does.

 

[marciofs]

As I have read in several places, the data sheet about reciprocity failure is not very acurate.

I read somewhere about a guy who made a test on Delta 100 and he explained the line is not curve but straight. According to what I read, if I well understood, it only needed to ad 1/3 stop for each stop after 4sec exposure.


I am not good in math. I am actually very bad. But based on it I came to this list:

4s =4s
8s = 11s
16s = 21s
32s = 42s
1m = 1m20s
2m = 2m40s
4m = 5m10s
8m = 11m30s
17m = 22m75s
34m = 46m
1h8m = 1h31m

Very different from the data sheet but as I said I am not good at all in math or I may not have understood well the article.


Edited...
Ok, I just saw my mistake.

 

[Terry Breedlove]

I don't plan to do night photographs (now) but to photograph indoors and dark days with pinhole camera, which can easy reach the 30min/1h exposure + reciprocity failure.

Fiji across is expensive on 4x5 so I am fist using Delta 100 and later on Fomapan 200 and 400.

What I did with my pinhole camera was to to shoot some film at high noon. Found the best exposure and then for every stop of light below that I doubled my time. Works perfectly and is super easy to calculate in the field.

For example let's say at high noon the exposure was 4 seconds that is your base.

Minus one stop of light = 8 seconds
Minus two stops of light = 16 seconds
Minus three stops of light = 32 seconds
Minus four stops of light = 64 seconds

I was making perfect exposures at four stops under my base this way. You really need to test with your film and find that base exposure to build from.

 

[marciofs]

Maybe the Pinholedesigner software could be helpful for you? http://www.pinhole.cz/en/pinholedesigner/
Reciprocity failure calculations is one of the things it does.

Thank you a lot.

 

[marciofs]

What I did with my pinhole camera was to to shoot some film at high noon. Found the best exposure and then for every stop of light below that I doubled my time. Works perfectly and is super easy to calculate in the field.

For example let's say at high noon the exposure was 4 seconds that is your base.

Minus one stop of light = 8 seconds
Minus two stops of light = 16 seconds
Minus three stops of light = 32 seconds
Minus four stops of light = 64 seconds

I was making perfect exposures at four stops under my base this way. You really need to test with your film and find that base exposure to build from.

I will try.

 

[summicron1]

What I did with my pinhole camera was to to shoot some film at high noon. Found the best exposure and then for every stop of light below that I doubled my time. Works perfectly and is super easy to calculate in the field.

For example let's say at high noon the exposure was 4 seconds that is your base.

Minus one stop of light = 8 seconds
Minus two stops of light = 16 seconds
Minus three stops of light = 32 seconds
Minus four stops of light = 64 seconds

I was making perfect exposures at four stops under my base this way. You really need to test with your film and find that base exposure to build from.

it is impossible to make firm rules for pinhole OR for reciprocity failure -- you can study data sheets all you want, and even experiment, but it will all come down to educated guessing.

Every film is different and, as I understand it, when the light is dim enough it has so little energy that there are some films it simply isn't powerful enough to nudge those little silver halide atoms around to create silver. In those situations, you can wait until the cows come home and the image will still suck.

So use everything as a guide, wet your finger and test the wind, ponder light direction, light color, film speed and the phase of the moon. Did you sleep well last night? Check the weather in Saigon?

Then guess. And bracket like hell.

 

[Thomas Bertilsson]

http://phototechmag.com/black-and-white-reciprocity-departure-revisited-by-howard-bond/

Everything you need to know. His numbers work really really well.

 

[Thomas Bertilsson]

What great idea - read the film's technical data to get reciprocity failure information!

The problem with that is that the information isn't even remotely accurate.

 

[marciofs]

http://phototechmag.com/black-and-white-reciprocity-departure-revisited-by-howard-bond/

Everything you need to know. His numbers work really really well.

I find hard to understend.

 

[Xmas]

I find hard to understend.

Perfect post by normal web standards...

But for OP

use uncoated lens
widest aperture for depth of field
Lunasix or other meter good for moonlight
Bracket in 10x exposure time steps!

email film supplier for detail