Easy Long Exposure Calculation
Long Exposures look great but can be a little tricky to get the correct exposure. Sure there are Apps and Charts to help out, but, what if there was an Easy Way?
A way that doesn’t require an App, doesn’t require a Chart and most importantly, doesn’t require taking your filters off to calculate the exposure length.
There is a simple way to perfectly calculate the Exposure for your Long Exposures every time!
Let’s get into it.
- Frame up your shot.
- Place the filters you wish to use into your filter holder and onto the camera, ready to shoot.
- Set your ISO to 6400.
- Test shoot at ISO 6400 until you have the perfect Histogram.
- Once you have the perfect histogram, take note of the exposure length.
- Set your camera back to ISO 100.
- However many seconds exposure at ISO 6400 now equal minutes at ISO 100.
Basically, with all your filters in place and your camera set to ISO 6400, if the perfect exposure was 1 second, once you switch back to ISO 100, your perfect Exposure will be 1 minute.
2.5 secs = 2.5 minutes
10 secs = 10 minutes
Once you have the perfect exposure at ISO 6400, you have the perfect exposure time at ISO 100
ISO 6400 Seconds = ISO 100 Minutes
Why? Basically, it comes down to ratios.
60 seconds in 1 minute = 64 ISO 100s in ISO 6400. Roughly the same ratio’s.
I guarantee this technique works perfectly in constant light. Go out at midday with your 10 stop filter and try out the ISO 6400 technique. I bet it works every time!
Just make sure you remember to switch back to ISO 100 before taking the Long Exposure!
Oh and remember to calculate the ISO 6400 seconds with your filters in place.
Long Exposure Tips
- Make sure when you are shooting LE’s that you cover up your rear view finder. A little light can sneak in there and ruin your Long Exposures.
- LE’s can be really tricky when the light is rapidly changing, like Sunset/Sunrise. My rule of thumb here is if you are shooting LE’s as the light is changing, you need to 1/2 your exposure time as the light is increasing at Sunrise and Double it as the light fades at Sunset.
- Use Bulb Mode to shoot LE’s longer than 30 seconds.
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Feel free to email me at adam@easywayphotography.com if you have any questions.
Take care,
Adam
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That’s a great tip. Thank you.