Long ND exposure question

Are you using a DSLR? Those are subject to light leaks through the viewfinder. You should be able to get a cover for the viewfinder eyepiece to eliminate this problem.

If you don't have a DSLR, I have no idea what's happening.

Serge Soucy said:

I've been having issues with my B+W ND 3.0 filter, which is obvious to see in the images included. There must be a specific name for this kind of problem and is there a solution to it? Is it with the filter itself or am I somehow using it incorrectly?

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"Light leakage". You don't mention what kind of camera you are using, but it is likely it is a DSLR. Unless it is covered, the viewfinder allows a small amount of light to enter and get past the raised mirror into the mirror box, where it can reach the sensor. In a normal exposure, this amount of light is insignificant compared to the light reaching the sensor through the lens, and thus has not visible effect on the image. But when you are using a very strong ND filter, the amount of light through the lens is dramatically reduced and the viewfinder-leaked light becomes significant and visible in the image.

The solution is to cover the view finder. Your camera probably came with a little rubber thing attached to the camera strap, the purpose of which may not be self-evident. This is what it's for: to slip over the viewfinder during long exposures. You can also cover the viewfinder with a cloth or anything else that mostly prevents light from entering.

Serge Soucy said:

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Dave

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As the others have said, light leakage is the obvious cause. EXIF says you use a D610 so there's no doubt about it being a DSLR.

EXIF also says ISO800 on one shot. Why use high ISO when you want a long exposure?

Yes, that looks like light is leaking past the mirror. Gotta cover the viewfinder.

f/29 is rather borderline. Even on full frame, you are likely to get some diffraction softness. I would say no smaller than f/22.

Given the great responses so far, I wouldn't have normally responded, but this problem brings back some memories - so decided to pitch in anyway.

Many moons ago, in the days before forums and the interweb, it took me months to work out what was going on when I first came across this in my own images... How things have changed.

I would confirm that this is a light leak from the viewfinder. From what I've seen, it always seems to exhibit itself as a bright band about 1/4 of the way up from the bottom of an image with further unpleasantness above. As everyone else has said, very simple to remedy (a dark cloth or a high tech Nikon DK5 widget), but near impossible get get rid of in PP so don't waste too much time trying...

R

I thought some dSLR's had a "switch-lever" to close an internal door inside the viewfinder ??? Am I wrong ???

PhotoTeach2 said:

I thought some dSLR's had a "switch-lever" to close an internal door inside the viewfinder ??? Am I wrong ???

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Some, maybe, and some DSLRs seal out the light completely when mirror is up, so no cover is needed. Apparently, OP's model is not one of those some.

PhotoTeach2 said:

I thought some dSLR's had a "switch-lever" to close an internal door inside the viewfinder ??? Am I wrong ???

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That's usually only the higher end dSLRs...the lower ones usually came with a plastic/rubber cover in the box like what's shown below (this one is unusual in that it stays attached to the strap so you don't lose it):

scorrpio said:

some DSLRs seal out the light completely when mirror is up, so no cover is needed.

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It's not just light leakage, although that's the problem we see in the image. With dSLRs the sensor for the light meter is usually located in the viewfinder area, on this camera you can see the lens above the viewfinder to focus the light onto the light sensor:

scorrpio said:

Apparently, OP's model is not one of those some.

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Or more likely, the OP doesn't know what they have since they have the light leakage problem to begin with and don't know how to solve with.

Thanks you everyone for the replies, I'll take all the feedback with me when I go shooting again. As somebody pointed out by observing the metadata, I was using a D610 DSLR.