What issues should I expect with a multi-hour exposure using a 9-stop ND filter?
Asked 5/21/2012
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2 answers
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I’m considering an experiment with a zone plate/zone sieve setup (around f/50 to f/100) and adding an ND400 filter, which is about 9 stops. If my exposure is about 30 seconds without the ND filter, would adding 9 stops make it roughly 30 × 512 seconds, or about 4 hours?
If I attempt a multi-hour exposure like this, what practical or image-quality problems should I expect? I’m especially wondering about sensor overheating, noise, and whether powering the camera externally would be enough to make it feasible.
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
14y ago
2 Answers
4
I really like the idea but in my opinion anything can go wrong with a 4 hour exposure.
Firstly, you may be right about the sensor. It might overheat, although opinions are divided on this issue. CMOS sensors are really energy efficient and I've never experienced sensor overheating while taking pictures or recording videos. However, my longest exposures were 3 consecutive 30min exposures, captured with a Nikon D7000. Some people claim that the reason why you can only capture 20min videos on most DSLR cameras relates to sensor overheating. I personally believe that this isn't really a problem. Most advanced DSLR cameras are probably equipped with a thermal cut-off system that simply turns the sensor off when it reaches critical temperatures (please don't quote me on that). Besides, overheating also depends on a variety of outside factors like the weather.
Secondly, with a 4 hour exposure it would be difficult to determine the light conditions and calculate other settings such as ISO and aperture. I realise that you want to use the zone sieve so the aperture is already determined. However, with such 'extreme' setup, your built-in light meter will become inaccurate or even unusable. Therefore, if you are wrong with your calculations, your pictures can be either overexposed or underexposed. I personally think that a 4 hour exposure is just like a stab in the dark. You never know what to expect as the light conditions can drastically change in 4 hours.
Next, the images may be completely unusable due to the amount of noise. My experience is limited to APS-C sensors but I can tell you that a 30min exposure I took was very noisy. It took me a long time and effort to reduce the noise and the image quality wasn't great.
Finally, you have to think about image stabilisation. Like I said, anything can happen during 4 hours so you have to stabilise your tripod and protect it from outside influences such as a strong wind or even rain.
I hope I managed to answer your question and I'm looking forward to seeing your 4 hour exposure soon.
Best Greg
Originally by user1440. Source · Licensed CC BY-SA 4.0
user1440
14y ago
0
Generated from our catalog & community — verify before relying on it.
Yes—adding 9 stops multiplies exposure time by 2^9, so 30 seconds becomes about 15,360 seconds, or roughly 4.3 hours.
The main risks with a multi-hour digital exposure are usually image quality and reliability rather than catastrophic sensor damage. Based on community experience, likely issues include:
- increased noise and hot pixels from the very long exposure
- possible thermal buildup, though many cameras handle this reasonably well
- battery/power limits unless you use external power
- environmental changes during the exposure (light level, temperature, weather, movement)
- camera stability over several hours
Sensor overheating is possible, but it’s not universally a major problem; some users report long exposures without serious overheating. If heat does build up, the more obvious effect is usually extra noise rather than permanent harm.
A few practical notes: cover the viewfinder to prevent stray light leaks, use a very stable tripod, disable anything that interrupts the exposure, and expect sunset light to change so much that reciprocity from a simple “multiply by 512” may not match the final result visually.
In short: it’s feasible, but expect noise, hot pixels, and changing scene conditions to be bigger concerns than outright sensor failure.
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AI14y ago
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