Just a basic question about exposure, please don't flame me.

[rpavich]

I'm trying to reconcile something in my mind. I'm not a veteran film shooter, I've only taken up shooting film for less than a year but as I progress, a question has come to my mind.

I had assumed that whatever conditions I shoot in, dark house vs outside on a sunny day, that exposure is exposure. That is, as long as the shutter lets in enough light, then all is equal the results should be equal.

What I have noticed is that there is an amount of light, a threshold of sorts where my images start to look very grainy with milky blacks. Above that threshold the exposure equality that I mentioned pretty much is in effect but at some reduced light level, it just doesn't work. I could leave the shutter open for twice as long and the images just don't hold up.

I hope I explained it correctly. I'm just wondering about it, that's all.

 

[BrianShaw]

At some point in long exposure time most film experiences "reciprocity failure". Are you experiencing this phenomenon you describe at the long exposure times versus shorter times? The film data sheet often gives information for correction.

https://en.m.wikipedia.org/wiki/Reciprocity_(photography)

 

[rpavich]

At some point in long exposure time most film experiences "reciprocity failure". Are you experiencing this phenomenon you describe at the long exposure times versus shorter times? The film data sheet often gives information for correction.

https://en.m.wikipedia.org/wiki/Reciprocity_(photography)

You know, I don't know.
The exposure times I'm talking about are f/2, ISO 400, 1/4 second ss. That sort of ballpark. Not minutes or anything...just a pretty dark house. Example. I can take a shot right under the kitchen table of some object and the exposure is f/2 for 1/30 or 1/60...something like that. When I do, though not optimum, I can get an image that's expected.
If I swing the camera around and shoot something away from the light I get 1/2 second or 1/4 second for SS and that's when things fall apart. I've thought that maybe I'm inadvertently underexposing so I've purposefully shot an extra stop of shutter speed and that didn't help.
The shots look underexposed even though the meter says "one stop over"

 

[Kirks518]

Could be your camera's shutter has issues with the slower speeds, and not staying open for the proper length of time. What camera is it?

 

[BrianShaw]

What film? The reciprocity failure characteristic is somewhat unique. Look up the data sheet and see what the manufacturer says.

Or, what Kirk and Chan suggests

 

[Chan Tran]

That could still be that you are underexposing if you determine the exposure via the camera meter. Your camera meter may be at fault and is not accurate in low light.

 

[greg zinselmeier]

my experience with reciprocity failure- it is different with each film, in most instances, I have to over expose and reduce development time, for long exposures. The only "good way", I know of, is to test the film.

 

[rwreich]

You might be bumping up against the effective range of your camera's meter. Have you tried using an electronic hand held meter in the same situation?

 

[BrianShaw]

... Or you may have an "averaging" meter that isn't seeing a "normal" scene when you are metering. Unfortunately there could be several issues to consider, even if the equipment is working normally.

 

[rpavich]

Could be your camera's shutter has issues with the slower speeds, and not staying open for the proper length of time. What camera is it?

It's happened with all of my cameras and all of my film. If I thought it was a mechanical failure than I'd not wonder about it but it seems like I've run into "Bob's law" or something (My name is Bob)

 

[rpavich]

You might be bumping up against the effective range of your camera's meter. Have you tried using an electronic hand held meter in the same situation?

Yes, I have, and I get the same result. At some point things get murky.
Now, I will say that it SEEMS to be dependent on the strength of light in the scene, that is a scene with LOTS of contrast (think dark but with bright lamp or something is different. If I was shooting a band with stage lights and most of the frame was pitch dark but there were spot lights on a face then it would be different, I hope that makes sense.

 

[Vaughn]

Expose at your meter reading as usual, then take additional shots -- adding twice as much light each time (double the exposure time) -- try three or five more times and see when you get better negatives (or transparencies).

 

[rpavich]

my experience with reciprocity failure- it is different with each film, in most instances, I have to over expose and reduce development time, for long exposures. The only "good way", I know of, is to test the film.

So If I wanted to test this...then all I'd have to do is to shoot in that lighting situation and take exposures that are increasingly long and longer...right? 1 sec, 2 sec, 4 sec, 8 sec...etc.

 

[rpavich]

Expose at your meter reading as usual, then take additional shots -- adding twice as much light each time (double the exposure time) -- try three or five more times and see when you get better negatives (or transparencies).

That's what I'm thinking, I'm going to do that and see.

 

[greg zinselmeier]

Oh! I forgot to add, twilight is the most difficult to test. after the sun has completely gone down, is easier to test, because the light source is usually putting out the same amount lumens ( street light)night after night. inclement weather is difficult ( rain/fog) to test . . . . sometimes fog is more dense then other nights. use only one film for RF work.

 

[Vaughn]

That's what I'm thinking, I'm going to do that and see.

Great! That will give you a base of real-world information to build on.

 

[greg zinselmeier]

it depends, so say. . . your light meter says 15 seconds, using the same aperture take additional exposures at 30 secs, 1 min, 2 min, 4 min, etc. however remember your highlights might not be effected by Reciprocity failure, therefor you may have to subtract development time, so your highlights do not build up too quickly. its better if you have sheet film for your tests not roll film.

 

[rpavich]

Thanks everyone. I'm going to test this week. I appreciate the timely help.

 

[BrianShaw]

Thanks everyone. I'm going to test this week. I appreciate the timely help.

But you might get more definitive help if you'd answer two questions previously asked: what film and what camera?? "All" and "every" would make little sense.

 

[rpavich]

But you might get more definitive help if you'd sewer two questions previously asked: what film and what camera??

I answered that above; all cameras all film. It's a constant of location and light, not equipment. It's happened with color film, black and white film, HP5+, Portra 400, Kentmere 400, Kodak 5219, Fuji 800, Color Plus 200, I can't remember them all.

Leica M6, Zorki 4, Nikon FM2, Pentax K1000, Minolta SRT101...

 

[BrianShaw]

Makes no sense to me then. Not all should have that kind of issue due to reciprocity, and some have averaging meters but others should be able to handle less average lighting. It might be that you aren't metering correctly for the conditions if you are the only constant.

 

[Old-N-Feeble]

Your problem might be metering technique. If you're pointing your meter at the overall scene with bright light coming through windows, the meter reading will underexpose the interior details.

 

[rpavich]

Makes no sense to me then. Not all should have that kind of issue due to reciprocity, and some have averaging meters but others should be able to handle less average lighting. It might be that you aren't metering correctly for the conditions if you are the only constant.

That's a possibility

 

[rpavich]

Your problem might be metering technique. If you're pointing your meter at the overall scene with bright light coming through windows, the meter reading will underexpose the interior details.

It might be, my testing might expose that.

 

[Ricardo Miranda]

Leica M6, Zorki 4, Nikon FM2, Pentax K1000, Minolta SRT101...

These are all mechanical and if they haven't been checked for precision of the shutter speeds recently, they can go out of spec, especially as some of your cameras can be over 40 years old.