Having Problems with ND Filters and Long Exposures

sbannon

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Hello Everyone,

I am brand new to photography (a few months out of auto) and even newer to this forum (first post). Before I knew anything about photography I decided to purchase a DSLR and purchased the Nikon D3000. I understand this is a very entry level DSLR and I plan to upgrade at some point soon.

I am preparing for a vacation that I am taking later on this year and I have been fooling around with some ND filters for long exposure photography. I ordered a set of ND filters on amazon which included the following filters: ND2, ND4, ND8 as well as the same in grad. I also have a 10-stop filter that I also ordered that hasn't showed up yet.

I understand that ND2 (1-stop), ND4 (2-stops) and ND8 (3-stops) are often not sufficient to allow for long enough exposures in broad daylight but I wanted to give long exposure a try.

I went out and set up my tripod and took a neutral exposure photo of a waterfall with autofocus. I turned off autofocus and then proceeded to use the three filters in series to effectively achieve 6-stops and attempt to obtain a long exposure. I understand this is not ideal but I was working with what I had.

What I found was that the long exposure photograph that came through was very washed out and blurry. I expected a subpar photo using the setup I had but the result was far worse than I expected. I have some suspect reasons why it has happened but being a new photographer I want some opinions.

Here are some of the reasons why I think that it is happening:

1. Limitations of the D3000
1. Limitations of the 18-55 f3.5-5.6 kit lens
2. Not covering the viewfinder (but I didn't expect this to be a huge factor at only a 2sec exposure)
3. Dirty Filters or Lenses (Although this did not appear to be the case upon inspection)
4. High humidity (it was hot and humid that day)
5. Filter stacking
6. Shite (cheap) filters.
7. Combination of all of the above.

Can someone give me an idea of what might be causing this? I have included the photos below with some general metadata.

Both exposures were taken with a Nikon D3000 with the 18-55mm kit lens.

Neutral.jpg

(ISO 100, 46 mm, f/8, 1/30)
LE.jpg
(ISO 100, 46 mm, f/8, 2 sec)
 
- Looks like the 2nd one is out of focus. Would it be focus changed while installing the filters?
- The wash out look .... possible is the filter itself. Are the filters have any coating on it? If not, when the photo was taken, was there any chance that the sun light were shined on the filter? (without lens hood)
 
Take a series of test shots.

Start with a well-lit subject that's in consistent lighting. Take a shot with no NDs. That's the Benchmark image.

Then take one with the ND2. Another with the ND2 plus the ND4. Finally, one with all 3 filters.

If you want, take two more, one each with just the ND4 and one with just the ND8.

Make sure you keep track of which imaged has which filter(s). Then bring them all up on the computer to compare them.

If an image with one filter is fine, but the one with two is worse and you end up with the same result with the three filters, then the issue is the filters.

Take two more shots, one with the viewfinder uncovered and one with. If you see the difference, light leakage is the issue.
 
Looks to me like you've knocked the lens out of focus when putting the filters on but I'd still expect the exposure to be better (indeed the same as the first as your shutter speed calculations seem correct). You can expect a bit of a colour cast using cheap filters but I suspect Dao is right that there may have been a bit of light shining between your filters as well.

After a lot of research I ordered Kood filters as a decent but budget option and have been quite impressed with them for their price point.
 
I'd always get the best filters that you can afford, as they will be the weak link on your images. Mind you some of them are more expensive than some lenses - Lee just released a 4 stop that is 30% more expensive than the big stopper. Stacking multiple ND filters can cause quite a lot of colour cast, and unless they have the backing of them that Lee filters have are at risk of letting light in.

If you are stacking them, keep the strongest one at the back. Ideally, shoot with just one at dawn or twilight... You can also lengthen the exposure time by using a smaller (higher number) aperture. Yes you will get diffraction at some point, but generally, flowing water tends to soften the shot on a long exposure...
 
The test shots are a good idea. If I had this problem I'd look at the filters themselves since the camera took a perfectly good shot without the filters installed. Also, even for 2 seconds you need a rock solid tripod on a rock solid base and also use a remote trigger.
 
I am fairly certain of at least these two things :

1)You altered the focus when screwing on the filters.

2)When you stack three filters, you've added three more surfaces for light to bounce around on. This is in my opinion almost certainly the cause for the washed out look. It's just a lot of flare.
 
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- The wash out look .... possible is the filter itself. Are the filters have any coating on it? If not, when the photo was taken, was there any chance that the sun light were shined on the filter? (without lens hood)

Does look similar to loss of contrast due to flare - as when using a teleconverter. Multiple filters in combination maybe is an issue. Shade the filters/lens with your hand. You could also stop down to f11 and lose another stop.
 

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