# Why is my 2 second long exposure shot overexposed?

I have the Olympus PEN Lite E-PL5 and I’m kind of getting frustrated because whenever I try to do a long exposure shot it’s always blown out.

I put the ISO to 200 because that’s the lowest I can go, I have it on f.22, I also used a ND filter, and the time was set for 2 seconds. But it’s still always blown out and white everywhere. I can’t see a single thing! It’s set on manual on a tripod so no shakiness.

• What value of ND filter are you using, for what level of scene lighting? Those settings, using only a 1-stop filter could still produce blown out pictures in bright directly sunlit scenes. Feb 9, 2018 at 0:53
• "What is an effective exposure strategy?": photo.stackexchange.com/questions/4285/…
– Rob
Feb 9, 2018 at 2:31
• Did you take a frame at a regular (shorter) exposure time? If so - what was that exposure? If not, why not? Always start with a decent exposure before calculating longer exposures. Feb 9, 2018 at 16:19
• Why did you choose the settings of f22 and 2 seconds? Did you take a meter reading with the ND filter and the iso set to 200 and get a reading of f22 for 2 seconds? You have to meter the scene and use the appropriate settings. Feb 9, 2018 at 21:06

We have no idea of the brightness of the scene you are photographing. Are you on a Mediterranean beach? In a forest at night? Put the camera on automatic, take a photo, and see what iso, aperture and shutter speed the camera chooses. You should aim for the same exposure, but just adjust other exposure settings (including choice of ND filter) so that you can use a longer shutter speed.

Photography is the art for mathematicians. You need to do some calculations. You can't just randomly lengthen your shutter speed and hope for the best. If you want to double your shutter speed, you must halve something else. If you can't halve something else, then it's no wonder your result is blown out.
(I suspect that you need to halve the light in the scene (and halve it again and again...) by using a stronger ND filter, or wait until light levels are naturally lower - but like I said, you must do it mathematically.)

• Long exposure photography as an art for mathematicians, I like how it rolls of the tongue! Feb 9, 2018 at 9:50
• Personally, I upvoted @scottbb's answer - read it in conjuction with mine. Feb 10, 2018 at 10:58
• @osullic Ditto. =)
– scottbb
Feb 11, 2018 at 2:36

Without knowing what strength of ND filter you were using, or under what lighting conditions, I can't give a specific answer. However, a little bit of back-of-the-envelope math can help give you an idea of the magnitude of the problem.

Assuming you were shooting a brightly-lit scene under bright midday sun, without any ND filters, the Sunny 16 rule states that at ƒ/16, a correctly-exposed shot requires a shutter time that is the reciprocal of your ISO. With an ISO of 200, the shutter speed should be 1/200.

Again, assuming you were shooting under Sunny 16 conditions, your shutter speed was overexposed by log2(2 / (1/200) = 8.6 stops. Because you were using ƒ/22, we can reduce that overexposure by one stop, down to 7.6 stops of overexposure.

Subtract from 7.6 the strength of your ND filter (I'm guessing 1 or 2 stops, probably). That is how much your long exposure shot was overexposed (again, for typical Sunny 16 exposure conditions).

If you were shooting a snow-covered landscape on a bright sunny day, you'd actually be overexposed even further, because of the light reflected from the large area of landscape. On the other hand, if there was some partial clouds, slight haze, or you subject was partially shaded, then your scene might not have been quite so overexposed by the amount calculated.

However, this gives you a rough idea of what to expect when trying to shoot long exposure shots in midday sun. You tend to need a lot of ND filter to keep the shutter open for 2 seconds. In your case, a minimum of a 6-stop ND filter: ND1.8 in Lee/Tiffen nomenclature; ND64 in Hoya/B+W/Cokin nomenclature. See also: How to read ND filter description?

For a particular scene, an easy way to figure out how much ND filter you need is set up your camera in aperture priority mode, select your aperture (in this case, ƒ/22) and ISO (200), and without an ND filter on your lens, let the camera meter the scene and determine the shutter speed. Whatever the camera meters for the scene, count the number of times you need to double the shutter speed until you get to your desired long-exposure duration.

For instance, say the camera determined that 1/125 seconds was properly exposed, and you want a 4 second long exposure to smooth some moving water and slightly blur fast moving clouds. Starting from 1/125, start doubling it:

Shutter speed:  1/125 -> 1/64 -> 1/32 -> 1/16 -> 1/8 -> 1/4 -> 1/2 -> 1 -> 2 -> 4
# of doublings:    0       1       2       3      4      5      6     7    8    9


Thus, this would require a 9 stop ND filter. But you only have a 10 stop ND filter (such as a Lee Big Stopper), either increase the ISO to 400, or open up the aperture one stop to ƒ/16. Either way, you will have the right combination of exposure settings and ND filter to correctly expose a 4 second shot in this particular scene.