# Long exposures with film



## Compaq (Jan 10, 2013)

I've been wanting to shoot star trails with my analog setup. However, I'm not sure how to set the exposure.

The long exposure diagram for the Ilford black and white film series go to 35 seconds, but that's not enough for what I'm intending. The graph is exponential in its growth, and exposures such as 20 minutes seem impossible - that would take hours. I'm not sure if the piece of film is even capable of that. It's the silver halide that's the limiting factor here, not time 

So, are there any films specifically made for this purpose? Does anyone have experience with this?


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## tyqre (Jan 10, 2013)

I'm guessing film with more silver will be able to be exposed for a linger amount of time. You could just leave it open for a long time and see what happens, tthen go from there.


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## ann (Jan 10, 2013)

You just need to figure out the reciprocity failure rate for the film your using. Put the camera on a tripod, use bulb mode and a cable release. Find a stool and sit down with a watch.

The reciprocity number should be given on the spec sheet of the film your using.


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## Compaq (Jan 10, 2013)

Ann, I know. I've read Ilford's tech sheets. 35 seconds "light meter exposure" needs 200 seconds ~ 3,3 minutes for Delta 100 Pro. The same goes for D400Pro and D3200Pro.

Yes, I can try and see what happens. 

I looked on the graph on Ilford's site, wrote down the apprx coordinates of light meter exposure time (seconds): 0,5,10,15,20,25,30,35 and their corresponding "necessary" exposure time (due to reciprocity failure). I plotted these on my graphical calculator, and extrapolated the curve to 1200 seconds light meter time. "Necessary exposure time" is then given to be apprx 155100 seconds = 43,08 hours. I don't expect this to be very accurate when extrapolating this far, but at least it serves for the argument's sake: If the light meter would suggest 20 minutes, I would need several hours.

I hope I explained my situation here. I'm wondering if, at all, I can expect to see clear star trails with Ilford's Delta pro range films. If no one has tried, I will of course just try and see what happens  I was merely hoping someone might have done that before, so that I wouldn't have to (if I can be so rude)


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## ann (Jan 10, 2013)

Your not being rude, I think you are over thinking this; you didn't say which ilford film but for instance HP5 at 30 secs would mean a correct time of 2 minutes and 35 sec.  Oops I see Ilford delta pro mentioned here. 

I don't understand these plotted times.Even if you were using ND filters in the middle of the day you  might get up to a few hours, but bot 43.  If you use the correct exposure you will see star trails, they really aren't hard.


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## Compaq (Jan 10, 2013)

I see. But then my question is " how do I figure out the correct exposure?".

My point with the line was this: imagine the long exposure graph ilford provides in their tech sheets extends further: does not abruptly stop. I can only assume that Ilford has done several measurements of times between 5 and 35 seconds, as that is how far the x-axis goes. Extrapolating, or assuming the graph follows the same growth as it does in the investigated interval, may not be accurate at all. 

Anyway, I'll do some test shots with different exposure times and see what I get.

Another question that arises is: for how long do I develop the film, when I'm not sure at which ISO I'm shooting? I'm just guessing the exposure! Should I maybe keep the development constant during the test, and see if I'm able to make a workable development strategy for such night shots?

Thanks for the help!


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## timor (Jan 10, 2013)

Anders, what do you want to include in the frame ? Some landscape ? Or just sky and stars ? How long star trails do you want to record ? 20 min gonna give you speck-long line, remember, you in Norway, stars turn there slower then in most of American states, especially if you gonna point your camera north. I think you can forget about reciprocity failure, you will deal only with black and white and nothing in-between so who cares.


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## ann (Jan 10, 2013)

If the meter says 30 secs. then the exposure becomes 2minutes and 35 secs.

Development times will depend on which developer you using. Basically your over exposing so you will need to under develop. Why don't you know what ISO your using? You have to set the meter for an ISO.


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## Compaq (Jan 10, 2013)

I just don't reckon my old meter on my Olympus 35 SP is able to meter EVs that low. It stops at 3, I think. If I point my meter on the sky, the bar won't move.

I could bring my digital SLR just to see if that one is able to give me something. I want to include some landscape. I was hoping I could manually flash the ground or something just to see if I'm able to light up some foreground. Now I start to see how easy everything was with digital!!!


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## ann (Jan 10, 2013)

Well, with digital one doesn't have recp. failure to worry about.

YOu could do a bit of painting with light on the foreground with a flashlight.

with night photography there are no failures, just difference  go give it a try. Take a flashlight , a note pad and keep notes so you repeat the "look" you want.


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## Josh66 (Jan 10, 2013)

Compaq said:


> I see. But then my question is " how do I figure out the correct exposure?".
> 
> My point with the line was this: imagine the long exposure graph ilford provides in their tech sheets extends further: does not abruptly stop. I can only assume that Ilford has done several measurements of times between 5 and 35 seconds, as that is how far the x-axis goes. Extrapolating, or assuming the graph follows the same growth as it does in the investigated interval, may not be accurate at all.
> 
> ...



The answer to both questions is - trial and error.  

For development, I would start out as if it were exposed normally at the box speed - and make adjustments from there.


Try Fuji Acros - it has absolutely the best reciprocity characteristics there are.  No correction needed till 120 seconds.  Between 120 and 1000 (16.6 minutes) seconds, you only need +1/2 a stop of correction.  Longer than that, it's going to be trial and error...


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## gsgary (Jan 10, 2013)

For developement personally i would use (b+W) i would use Rodinal 1+100 agitate for first minute and leave it stand for 1hour


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## Light Guru (Jan 10, 2013)

there are several iPhone apps that calculate reciprocity for you, you select the film type and your metered exposure and it calculates the reciprocity for you


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## ann (Jan 10, 2013)

:thumbup: good idea


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## BrianV (Jan 10, 2013)

We never tried to figure out exposure. Just left the camera open. With a stationary camera, the stars will move across the film- and that will limit how many show up. If you put it on a telescope and guide the camera, long-exposure means getting fainter stars. 

One way to combat reciprocity failure is to cool the film. Cold winter nights help, but my friend in High School made a dry-ice back for his camera.


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## Compaq (Jan 11, 2013)

O|||||||O said:


> The answer to both questions is - trial and error.
> 
> For development, I would start out as if it were exposed normally at the box speed - and make adjustments from there.
> 
> ...




Hehe, thanks! I just checked, and the main site for analog photography products in Norway is stocked up on that film! Maybe I'll get one or two someday. I will start with Delta 100 Pro, and see what happens. This should be exciting.

One, maybe silly, question: When I note down my camera settings for each frame, do I number my notes according to the counter on the camera?  How does that counter work? Fair enough, when I advance the film the counter wheel turns, but how does it compensate for any "dead advances" in the beginning of the film? I've noticed it starts on "1" after three advances after I've shut the compartment door shut.


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## Josh66 (Jan 11, 2013)

As long as you number them (in your notes) in the same order you shoot them, it should be easy to figure out which shot is which.  Maybe shoot something different in the middle somewhere if the whole roll is mostly the same thing - just to have a good spot to count from.


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## molested_cow (Jan 11, 2013)

From my experience with night shots, even taking notes won't mean much unless you are taking the shots at the same place, same time of the month, same weather and same atmospheric conditions. That's not going to happen.

Different times of the day matters. Position of the moon matters. Humidity matters. Air pollution matters. Light pollution matters. There are tons of factor affecting your shots, and most of these factors aren't detectable with the naked eye, only picked up when your film has been exposed long enough.

Which means, it's trial and error. I am not a fussy person so I never think too much about this. Also, I suck at Math. I basically go out there and shoot at F5.6 with ISO400 film. I play with 20min, 30min and 40min exposures. It depends on how long you want the trails to be.

Honestly, the exposure difference between 20, 30 and 40min isn't very great because when you get to that time length, one stop more is A LOT. 40min is like one stop more than 20min. In day light, that's a big difference. In total darkness, you will have enough room for adjust in post processing(digital wise). You should be more worried about clouds moving in or some jerk driving up to you with his high-beam on to see what you are doing, half way into your shots.

Dress warm! Once I was all alone on the beach in total darkness. It was really creepy because I hear the sound of the waves but I could see nothing. I kept turning around thinking there's someone around. So I left the camera on the beach, went back to do my laundry and came back 45min later to pick it up. Of course the camera was still there. You couldn't see a thing!


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## bsinmich (Jan 12, 2013)

With the stars constantly moving the exposure to one small trail of lght  is not the entire 2 min. or whatever time you choose. The actual time amounts to only the time that particular star was in the line of your camera lens.


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## Jhorneva (Jan 13, 2013)

Try looking at the info on this website:
Night Sky Photo Tips

Dennis Mammana is recognized as one of the best night sky photographers working today.  I really doubt you need to worry about reciprocity when doing star trail imagery.  The exposures are going to be many minutes long and will be more influenced by sky brightness from artificial lights unless you are photographing from a very dark sky site.


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