How to take long exposures on film
This is the fifth chapter of the series Long Exposure Photography. A new post is published every Wednesday.
Taking long exposures on film can be trickier than doing it with a digital camera.
Don't be afraid, though! After getting familiar with a couple of gotchas, you'll find the process pretty straightforward.
And I actually like the results much more than the ones I get with digital!
In this week's chapter of the Long Exposure Photography Series we will talk about what's different, the downsides and the advantages of using film for long exposures.
Pacific Ocean, somewhere in Oregon.
Your light meter is lying
In chapter 3, How to take a long exposure, we talked about how to calculate the exposure time.
If you are shooting film, that value is no longer valid!
We are going to need much longer exposure times than the one indicated by the light meter.
Why? Enter reciprocity failure.
Chicago Skyline.
Reciprocity failure
Experts (and the Internet) say that film is made of really tiny silver crystals that react to light, and I believe them. Those crystals can only react for a limited time while keeping their original properties, though.
This means that you don't have to worry if your exposure time is that of half a second or faster. But things start to get more complicated the longer your exposure gets.
We have to expose the film for a longer time than the meter indicates. How much longer, you ask? It depends on the film stock.
The now extinct Fuji Acros had virtually no reciprocity failure and needed an adjustment of just 1/2 stop for exposure times of >2min.
Other films like my beloved HP5+ do need more dramatic adjustments.
Trillium Lake, Mt Hood National Forest, Oregon.
Adjusting our exposure times
Ilford recommends to use a reciprocity factor, but if you don't want to do the math, this is the table I've been using for more than a year (it also works for FP4+):
Indicated exposure is the shutter speed that the light meter is giving us. Adjusted exposure is the time we actually need to expose the film for to get the right exposure.
As you can see, it's not linear: the longer the exposure, the bigger the adjustments you need to make.
You will need to have this table with you, either printed or on your phone.
Mendocino, California.
Taking the long exposure
I know, all of that sounded very complicated. But believe me, we are done here!
Use that table (you should be able to find the one for your film stock on the manufacturer's website, or somewhere on the internet) and you are good to go.
Everything we've talked about long exposures still applies here.
Well, there is one "small" difference.
Bandon, Oregon.
Embrace the contrast
Film can dramatically increase the contrast when taking a long exposure. Highlights and shadows have different reciprocity failures, meaning that the brighter parts of the image will get recorded much faster than the darker ones.
It gets "worse" the longer the exposure.
I quoted worse because I like contrast, so it depends on what you are looking for.
If you don't want increased contrast, you can try pulling the development.
Night sky, Valley of Fire, Nevada.
Why film is so much better for long exposures
Increased contrast and adjustment of exposure times are the two big differences, and depending on how you look at it, the two downsides of using film for long exposures.
There are advantages, though.
One depends on your camera. If you use a mechanical camera, or one that allows you to capture long exposures without using battery, then the doors are wide open to you for extreme long exposure photography.
Digital doesn't do well with very long exposures.
First, there's the battery issue. You will need an external battery, if your camera supports it.
But even then, digital sensors heat up and can create a lot of noise on your long exposures - and it's not the kind of noise I like, the ugly, digital noise no one wants.
The solution is to use LENR: Long Exposure Noise Reduction. Using this mode, the camera will take a second long exposure of the same length after you are done. It will be a black exposure, with just the noise, that the camera will use to eliminate it from the original exposure.
In the end, it looks like digital has its own reciprocity failure, doesn't it?
Moonrise over Mt St Helens, Washington. Example of a extreme long exposure, 3.5 hours.
Conclusion
Making a long exposure image with film can be challenging at first, but it gets easier as you make more and more.
It also comes with some other oddities, like the increased contrast.
Everything else is good, though.
Extreme long exposures are much easier with film, using mechanical cameras that don't drain the battery.
Digital cameras also have some problems, like the noise created when the sensor heats up.
In the end, the tool doesn't matter as long as you achieve the image you were looking for, and that represents your vision.
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