Looooong Exposures

[Pawlowski6132]

So, I've always been meaning to ask this so...here goes: I often see images where the photographer indicated he used a, say, a 30 min shutter speed. How did he know he needed that long of an exposure. Who's meter goes up to 30 min? Not mine. Would I need a new one if I ever wanted to get out of the studio?

I know, a duh question I'm sure.

Joe

:o

[Richard Wasserman]

There are no duh questions! It's called "Reciprocity Failure". See: http://silvergrain.org/Photo-Tech/reciprocity.html

[bigdog]

Who's meter goes up to 30 min? Not mine.

I'll bet it goes to a minute or two. If you meter an exposure for 1 minute at f/2, what would the exposure be at f/64? Not even counting reciprocity (which you must count). ;)

For the record, my Sekonic spot meter, Minolta IVF and my Luna Pro SBC all go to 30 minutes. I didn't even know that - I had to look.

[Vaughn]

My Pentax Digital Spot meter goes to 4 minutes -- does not take many stops to stretch that out to an hour or more -- with or without reciprocity figured in!

The dials for the Luna Pros go up to 8 hours...LOL!

Vaughn

[Brian Vuillemenot]

The long exposures are all just trial and error- no metering involoved, just previous experience and intuition. If the "correct" exposure is 30 minutes, ten minutes off in either direction is less than half a stop. And it's hard to know what it's going to look like, due to reciprocity failure.

[jimmyp]

Hi Joe.

I think it comes from experience. I do a lot of night exposures and I've come to recognize how long I might have to expose something under a full moon, or with some reflected street lights etc. I use NPL and it's forgiving, and I've made plenty of mistakes. I think meters lie at night anyway. :)

Troy Paiva has some how-to tips on his website
http://www.lostamerica.com/technique.html

What are you trying to shoot? Maybe we can give you some starting points.

jimmy

[Brian C. Miller]

I just did a ridiculously long exposure last night. I think I left the lens open for, oh, 1-1/2 hours? Maybe two or more? I took a nap.

Take a look at the manufactuer's film data. I used Kodak Plus-X Pan, and it indicates that for an exposure of 100 seconds, the adjusted exposure time for reciprocity is 1200 seconds (20 minutes), and then develop -30% time.

For me, at f32 under my bathroom light, the meter read 4 minutes, and that was before compensation for bellows extension. So I left the lens open for a *long* time, and then today I developed the sheet in Ilford Ilfosol-3, 1:14, 70F, for four minutes. And it came out pretty good! Not shabby for film that expired before I went into the Army.

[Brian C. Miller]

OK, I attached a quick scan of the negative.

Dessicated Lemon in a Box.

[tenderobject]

was looking for some info about this as well especially with film and largeformat photography.. i have a question as well.. where do you usually meter in this situation.. low light (long exposure photography).. newbie as well :P

[Eric Woodbury]

Sometimes it is a matter of wanting a long exposure. If the meter says 1 sec at f/22 and I'm adding a 10 stop ND filter, then the exposure is easy to calc. Add the 10 stops, which is about a factor of 1000x and then add the recip. failure and you got it. Meters don't have much need to go to long exposure because it is all in the recip. failure area anyway.

[Brian C. Miller]

You can measure the incident light, or if the light is way too low, I use my spot meter to measure a white object, and then I know the value of the highlights, and I go from there.

When I photographed the lemon, I knew I was going to have to factor in bellows extension falloff, since the bellows were at their max. I first measured the value of the room light on a grey card. Then I measured, at infinity focus and wide open, the grey card on the ground glass. Then I extended the bellows to their max, and measured the amount of light falloff. Then I calculated the time, before factoring for reciprocity. Then I looked at the film chart, and made a guess.

The thing about it is that as the exposure gets really long, then the film has to have "pull" development. This means that the film is given a shorter development time to keep the grey scale values approximately where they should be.

[al olson]

This is an example of a nine and a half hour (from 7:30 pm to 5:00 am in November) exposure. Camera was Technika IV with Schneider 150mm lens at f/11 on Portra 160NC.

Tried a little too much rise to keep the verticals parallel. Hence the vignetting.

The camera was set up in my back yard so that the houses behind were part of the scene. The exposure recorded neighborhood activities including my neighbor parking a car in the drive and traffic going by on the street in front.

http://www.photo-artiste.com/images/night/startrails.jpg

Surprisingly, most of the specular lights were not badly blown out.

After this experiment I decided that 15 minute to half hour exposures are better. It is easier to identify the stars when there is a short streak instead of a long arc. And the scene is just as effective.

[Brian Ellis]

The long exposures are all just trial and error- no metering involoved, just previous experience and intuition. If the "correct" exposure is 30 minutes, ten minutes off in either direction is less than half a stop. And it's hard to know what it's going to look like, due to reciprocity failure.

Maybe you use trial and error and if it works for you that's great but I meter and use reciprocity tables to calculate the effect of reciprocity failure.

[tenderobject]

You can measure the incident light, or if the light is way too low, I use my spot meter to measure a white object, and then I know the value of the highlights, and I go from there.

When I photographed the lemon, I knew I was going to have to factor in bellows extension falloff, since the bellows were at their max. I first measured the value of the room light on a grey card. Then I measured, at infinity focus and wide open, the grey card on the ground glass. Then I extended the bellows to their max, and measured the amount of light falloff. Then I calculated the time, before factoring for reciprocity. Then I looked at the film chart, and made a guess.

The thing about it is that as the exposure gets really long, then the film has to have "pull" development. This means that the film is given a shorter development time to keep the grey scale values approximately where they should be.

thanks for sharing. any other techniques/style we should know when doing long exposures? thanks again!

[ki6mf]

thanks for sharing. any other techniques/style we should know when doing long exposures? thanks again!

For night photography, B&W and color, its best to use trial and error and keep an accurate log of what your exposure is. Try and develop a sense for how bright the ambient light is for a given situation and then use that as a starting point. Bracket by taking multiple exposures varying times. For HP5 and D 76 i use 5 minutes at f22 for many urban scenes as a starting point. Normally compensating developer ( I recommend very gentle agitation too but this is my opinion) is needed because you need less highlight development.

The most important piece of equipment outside of cameras: a folding camp chair to sit on for the long times between exposures!

[tenderobject]

For night photography, B&W and color, its best to use trial and error and keep an accurate log of what your exposure is. Try and develop a sense for how bright the ambient light is for a given situation and then use that as a starting point. Bracket by taking multiple exposures varying times. For HP5 and D 76 i use 5 minutes at f22 for many urban scenes as a starting point. Normally compensating developer ( I recommend very gentle agitation too but this is my opinion) is needed because you need less highlight development.

The most important piece of equipment outside of cameras: a folding camp chair to sit on for the long times between exposures!


thanks ki6mf. i might try this first using paper negs.

[Jon Shiu]

thanks ki6mf. i might try this first using paper negs.
I would suggest a standard film and developer, because paper negs are too slow, and you need to get a feel for your materials (film & developer and printing paper) respond to the low light situation.

Jon

[tenderobject]

I would suggest a standard film and developer, because paper negs are too slow, and you need to get a feel for your materials (film & developer and printing paper) respond to the low light situation.

Jon

thanks jon, actually i will try both. its would be a practise to me as well. :)

[J. E. Brown]

Interesting stuff.

Another question to pose:

If one where to use a digital camera for night exposure, and determine that a 20 min. exposure at f22 was desired, would you directly transfer that to your film camera? Or would you take 20:00 @ f22 simply as a 'meter' reading and compensate for reciprocity for your given film (I am using TMY-2)? I assume that is what you must do, as the digital camera has no interaction with film.

As always, insightful and interesting discussing.

Thank you.


Kind regards,

-JB

[Robert Hall]

OK, I attached a quick scan of the negative.

Dessicated Lemon in a Box.

It started out as a fresh lemon! ;)

[Jack Dahlgren]

Interesting stuff.

Another question to pose:

If one where to use a digital camera for night exposure, and determine that a 20 min. exposure at f22 was desired, would you directly transfer that to your film camera? Or would you take 20:00 @ f22 simply as a 'meter' reading and compensate for reciprocity for your given film (I am using TMY-2)? I assume that is what you must do, as the digital camera has no interaction with film.

As always, insightful and interesting discussing.

Thank you.


Kind regards,

-JB

Yes, you would take it as a reading and apply reciprocity factor and film speed into account.

[ki6mf]

Interesting stuff.

Another question to pose:

If one where to use a digital camera for night exposure, and determine that a 20 min. exposure at f22 was desired, would you directly transfer that to your film camera? Or would you take 20:00 @ f22 simply as a 'meter' reading and compensate for reciprocity for your given film (I am using TMY-2)? I assume that is what you must do, as the digital camera has no interaction with film.

As always, insightful and interesting discussing.

Thank you.


Kind regards,

-JB

You would test film and digital separately. One would not necessarily transfer. I tried doing this at a dawn shoot with a digital and a large format camera. I kept altering the manual settings on the digital then used the final setting on the film camera. My sky was blown out on film and the darker areas were to dense making the color film unusable! Best to test each separately!

[kev curry]

Reciprocity tables have never failed me...the ones I use on (HP5) are from Steve Simmons's book ''Using the View camera and there bang on for that film.

[Robert Hughes]

Do digital sensors experience reciprocity failure? :confused:

[BetterSense]

In a sense, digital sensors experience the opposite of reciprocity failure; the dark pixels will increment even in total darkness due to thermal 'dark current'. If you put a camera in a lead box with the shutter closed but the sensor somehow active (like film behind a shutter) the sensor would eventually be completely "exposed" and the image would be all white. In reality this would never happen of course because the cameras only 'activate' the sensor before exposure and the sensor would overheat or the battery would go dead before this point was reached. This effect of dark current can be removed from overall exposure with balancing resistors but then it manifests itself as mere noise. Who knows how digital sensors are actually designed; unlike film manufacturers who publish good datasheets on their film, digital photographers are expected to be happy while being kept in the dark about the actual tools they use.