Long exposures with film

[Compaq]

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?

 

[tyqre]

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.

 

[ann]

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.

 

[Compaq]

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)

 

[ann]

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.

 

[Compaq]

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!

 

[timor]

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.

 

[ann]

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.

 

[Compaq]

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!!!

 

[ann]

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.

 

[Josh66]

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!

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...

 

[gsgary]

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

 

[Light Guru]

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

 

[ann]

:thumbup: good idea

 

[BrianV]

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.