Concerning long exposure photography for a beginner

[Neil Kelly]

Hi all,

I'll be going away for a long weekend to Oslo this coming weekend, and I'd like to try and do some long exposures of the city/water/sky etc. I've not done this before so I'm trying to wrap my head around the calculations and where reciprocity failure comes into things

If for example, I have a metered exposure time of say 1/10th second, and I want to use a 6 stop ND filter (ND64) - giving an exposure time of 6.4 seconds according to this page - http://www.vassilistangoulis.com/gr/?p=4958

Do I then count this extended time as the psuedo metered time for calculating reciprocity failure correction?

In this example, if I were using Ilford Delta 100, this would then give a corrected exposure time of 10.4 seconds (per the document on the Ilford website here (https://www.ilfordphoto.com/wp/wp-content/uploads/2017/06/Reciprocity-Failure-Compensation.pdf)

Does this workflow and method of working make sense? I can find information on reciprocity failure corrections and on using ND filters separately but I can't seem to find much on both together (if I'm being a bit simple, I apologise!)

I know this might seem very simple, but I just wanted to double check with the gurus here before I go off and make a fool of myself (and waste film!)

All replies and advice greatly appreciated

 

[Sirius Glass]

I have used this since the 1960's. http://f-sunny.com/night-exposures-in-a-jiffy/ Enjoy your trip.

 

[MattKing]

Do I then count this extended time as the psuedo metered time for calculating reciprocity failure correction?

Yes.
One thing to remember when you start working with materials that suffer from reciprocity failure is that although we often talk about that failure in terms of long exposure times, the cause of that failure is actually due to the intensity of the light hitting the film being too low to cause the film to respond "normally". Anything that reduces that intensity of light at the film - small apertures, bellows extension, ND filters - can force you into making reciprocity failure adjustments.
Of course, this only applies to the sort of reciprocity failure that occurs with long, dim exposures. There are different considerations with the sort of reciprocity failure that occurs with very short, very intense exposures (like high power electronic flashes).

 

[jonasfj]

There is a smartphone app called Reciprocity Timer for $1.99. It contains a database of the most common films and I have used it with pretty good results. I always bracket my shots with additonal -30% and +30% exposure times.

 

[bernard_L]

Your first reference is just a long write-up of the equation 10ND. The real tricky part, reciprocity failure, is not addressed.
If you use Ilford film, just use the extra correction as per Ilford recommendation. They should know. Other films: Foma films are worse (larger corrections). Acros is better (smaller correction).

Something else: in night shots, quite often, the light sources are in the field of view, like metering by pointing the meter at the sun. In that respect, the table indicated by Sirius Glass might be more reliable than a light meter. But, your OP mentions long exposures, not night shots.

Finally, IMHO, +/-30% bracket is virtually insignificant for b/w negative You would not see the difference between two frames on the negative. If your don't believe me, just try. In your situation, I would just shoot nominal and +2 stops. Negative b/w (except slow films like PanF) is extremely tolerant of overexposure.

 

[jonasfj]

Finally, IMHO, +/-30% bracket is virtually insignificant for b/w negative You would not see the difference between two frames on the negative. If your don't believe me, just try. In your situation, I would just shoot nominal and +2 stops. Negative b/w (except slow films like PanF) is extremely tolerant of overexposure.

I have tried many times and the 30% bracketing works very well for me and I see a significant difference:

https://www.flickr.com/photos/jonas_fjellstedt/28945704312/in/dateposted-public/

 

[howardpan]

If you have access to Fuji Acros, it requires no exposure correction for up to 2 minutes, and I believe half a stop correction up to 1000 seconds.

Simplifies life for a newbie.

https://www.fujifilmusa.com/shared/bin/NeopanAcros100.pdf

 

[Ste_S]

I wouldn't worry too much about being spot on - as others have said modern film has a very forgiving latitude.
I've just started going out myself at night with a tripod, cable release and Mamiya C330. I measure my exposure times from Lightmeter Pro iPhone app and anything less than 10secs I'll count in my head, otherwise I'll use the timer on my phone.
So for the results have been good, although I'm started experimenting with 5min+ exposures so will see how those turn out..

 

[bernard_L]

I have tried many times and the 30% bracketing works very well for me and I see a significant difference:
https://www.flickr.com/photos/jonas_fjellstedt/28945704312/in/dateposted-public/

Congratulations for the really nice pictures. However, I cannot see how they support the statement that +30% exposure makes a visible difference on a b/w negative.

 

[MrBrowning]

Here is a chart I made up for most Ilford films based on the new reciprocity numbers they provide for night photography. It's easier to carry the chart than to have to pull my phone out to do the math on a cold night. So far It's worked well for me. Delta 3200 should have been grouped with Pan F and I forgot to add SFX on there when I made it up. At some point I'll make those correction.

Edit: If you are using a filter the Metered time in the chart would be the actual metered time + your filter. As said I made this with night photography in mind.

 

[jonasfj]

Congratulations for the really nice pictures. However, I cannot see how they support the statement that +30% exposure makes a visible difference on a b/w negative.

You just have to take my word for it. I'm bothering scanning and processing the lesser negatives. Obviously, if I did not see a benefit from my way of bracketing.